GOST for the determination of ochratoxin a. Ochratoxins. Checking the acceptability of the results of parallel determinations

INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION

INTERSTATE COUNCIL FOR STANDARDIZATION, METROLOGY AND CERTIFICATION


INTERSTATE

STANDARD

WINE AND WINE MATERIALS

Determination of ochratoxin A content by high performance liquid chromatography

Official edition

Standartinform


Foreword

The goals, basic principles and basic procedure for carrying out work on interstate standardization are established by GOST 1.0-92 “Interstate standardization system. Basic Provisions” and GOST 1.2-2009 “Interstate Standardization System. Interstate standards, rules and recommendations for interstate standardization. Rules for the development, adoption, application, updating and cancellation "

About the standard

1 DEVELOPED by the Limited Liability Company "Lumex-Marketing" (LLC "Lumex Marketing")

2 INTRODUCED by the Federal Agency for technical regulation and metrology (Rosstaidart)

3 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 47 dated June 18, 2015)

4 By order of the Federal Agency for Technical Regulation and Metrology dated July 21, 2015 No. 948-st, the interstate standard GOST 33287-2015 was put into effect as a national standard Russian Federation from January 1, 2017

5 INTRODUCED FOR THE FIRST TIME

Information about changes to this standard is published in the annual information index "National Standards", and the text of changes and amendments - in the monthly information index "National Standards". In case of revision (replacement) or cancellation of this standard, a corresponding notice will be published in the monthly information index to the National Standards. Relevant information, notification and texts are also posted in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet

© Standartinform. 2016

In the Russian Federation, this standard cannot be fully or partially reproduced, replicated and distributed as an official publication without the permission of the Federal Agency for Technical Regulation and Metrology

INTERSTATE STANDARD

WINE AND WINE MATERIALS

Determination of ochratoxic A content by high performance liquid chromatography

Wine and wine materials.

Determination of ochratoxin A content by high performance liquid chromatography

Introduction date - 2017-01-01

1 area of ​​use

This International Standard applies to wine and wine materials and specifies a method for determining the mass concentration of ochratoxin A using high performance liquid chromatography (HPLC).

The measurement range of the mass concentration of ochratoxin A is from 0.001 to 0.1 mg/dm 3 .

8 of this standard uses normative references to the following standards:

GOST 12.1.004-91 Occupational safety standards system. Fire safety. General requirements

GOST 12.1.007-76 Occupational safety standards system. Classification and general safety requirements

GOST 12.1.010-76 Occupational safety standards system. Explosion-proof. General requirements

GOST 12.1.019-79 Occupational safety standards system. Electrical safety. General requirements and nomenclature of types of protection

GOST 61-75 Acetic acid. Specifications

GOST 1770-74 (ISO 1042-63. ISO 4788-60) Measuring laboratory glassware. Cylinders, beakers, flasks, test tubes. General specifications

GOST ISO 3696-2013 Water for laboratory analysis. Technical requirements and control methods

GOST 4233-77 Reagents. Sodium chloride. Specifications GOST 4204-77 Reagents. Sulfuric acid. Specifications

GOST ISO 5725*6-2003° Accuracy (correctness and precision) of measurement methods and results. Part 6. Use of accuracy values ​​in practice GOST 6709-72 Distilled water. Specifications GOST 9293-74 (ISO 2435-73) Gaseous and liquid nitrogen. Specifications GOST 16317-87 Household electric refrigeration appliances. General specifications GOST ISO/IEC 17025-2009 General requirements for the competence of testing and calibration laboratories

GOST 25336-82 Glassware and laboratory equipment. Types. Basic parameters and dimensions GOST 29227-91 (ISO 835*1-61) Laboratory glassware. Pipettes graduated. Part 1. General requirements

GOST 31730-2012 Wine products. Acceptance rules and sampling methods GOST OIML R 76-1-2011 State system for ensuring the uniformity of measurements. Non-automatic scales. Part 1. Metrological and technical requirements. Tests

Note - When using this standard, it is advisable to check the validity of reference standards in the public information system - on the official website of the Federal Agency for Technical Regulation and Metrology on the Internet or according to the annual information

"" In the Russian Federation there is GOST R ISO 5725-6-2002 "Accuracy (correctness and precision) of measurement methods and results. Part 6. Using precision values ​​in practice.

the index "National Standards", which was published as of January 1 of the current year, and according to the issues of the monthly information index "National Standards)" for the current year. If the reference standard is replaced (modified), then when using this standard, you should be guided by the replacing (modified) standard. If the referenced standard is canceled without replacement, the provision in which the reference to it is given applies to the extent that this reference is not affected.

3 Sampling and preparation of a sample for testing

Sampling according to GOST 31730.

Wines from high content carbon dioxide is pre-degassed. To do this, 50 ml of the product is placed in a flask with a 100 ml tube (see 6.22), shaken and connected to a vacuum pump (see 6.6). Degas for 10-15 minutes until the foam disappears and large bubbles appear on the surface of the liquid.

4 Safety requirements

When carrying out measurements, the following requirements must be observed:

Electrical safety in accordance with GOST 12.1.019 and technical documentation for the chromatograph:

Eeryesafety in accordance with GOST 12.1.010;

Fire safety in accordance with GOST 12.1.004;

Safety when working with harmful substances in accordance with GOST 12.1.007.

WARNING - Ochratoxin A causes kidney and liver damage and

presumably a carcinogen. All work related to sample preparation and preparation of ochratoxin A solutions should be carried out in a fume hood using protective clothing, gloves and goggles. Decontamination of glassware that has been in contact with ochratoxin A is carried out with a 4% solution of sodium hypochlorite.

5 Essence of the method

The method is based on extraction of ochratoxin A from a sample with acidified methylene chloride, concentration of the resulting extract, screening of samples and determination of the mass concentration of ochratoxin A using HPLC on a reverse column with fluorimetric detection.

6 Measuring instruments, auxiliary equipment, reference materials, reagents, glassware and materials

6.1 Liquid chromatograph with a fluorimetric or spsktrofluorimstrich detector providing excitation of fluorescence in the spectral region (330 ± 20) nm and registration of fluorescence intensity in the spectral region (465 ± 20) nm. The applied detector should provide the limit of detection of ochratoxin A not more than 5 ng/cm 3 .

6.2 Non-automatic scales according to GOST OIML R 76-1 with limits of permissible absolute error not more than ± 0.01 g.

6.3 Analytical chromatographic column, filled with a reversed phase sorbent with a particle size of 5 µm. having an efficiency of at least 5000 theoretical plates for the peak of ochratoxin A "\

6.4 Guard column of the same internal diameter and filled with the same reversed phase sorbent as the analytical column.

6.5 Rotary evaporator, equipped with a water bath with a temperature regulator in the range from 20 °C to 50 °C.

6.6 Laboratory vacuum, diaphragm or water jet pump according to GOST 25336, providing vacuum from 2.5 to 10 kPa.

0 An example of a commercial product that meets the specified requirements. - chromatographic column with an internal diameter of 2.1 mm and a length of 120 mm. filled with reverse-faed sorbent Kromasil S-18. Alltfcna C18 and others with a particle size of 5 μm. equipped with a 25 mm long pre-cup. This information is given for the convenience of users of this International Standard and does not constitute an endorsement of the specified product.

6.7 Drying cabinet, providing temperature up to 200 C.

6.8 Household refrigerator according to GOST 16317.

6.9 Laboratory centrifuge with a speed of at least 5000 rpm.

6.10 Interstate or metrologically secured in the national measurement system of the state that adopted the standard, state standard sample 1 "of the composition of a solution of ochratoxin A in acetonitrile mass concentration of 50 μg / cm 3 with an error of the certified value of not more than ± 2.5 μg / cm 3. The use of standard samples of the composition is allowed solution of ochratoxin A in other solvents, which must be taken into account when preparing the initial solution according to 7.3.1.

6.11 distilled water in accordance with GOST 6709 or water for laboratory analysis of purity 1 in accordance with GOST ISO 3696.

6.12 Acetic acid according to GOST 61. glacial.

6.13 Acetonitrile for liquid chromatography, optical density relative to distilled water at 200 nm, not more than 0.025, mass fraction of water, not more than 0.03%.

6.14 Methylene chloride for high performance liquid chromatography according to regulatory documents operating in the territory of the state that adopted the standard.

6.15 Sulfuric acid according to GOST 4204, x. h or h.

8.16 Sodium chloride according to GOST 4233. x. h.

6.17 Pipettes, graduated 1-2-2-1. 1-2-2-2. 1-2*2*5, 1-2-2-10 or other types and designs according to GOST 29227.

6.18 Measuring cylinders 1-25-2.1-50-2.1-250-2 or other designs according to GOST 1770.

6.19 Volumetric flasks 2-25-2. 2-50-2.2-100-2. 2-500-2 according to GOST 1770.

6.20 Pointed-bottom flasks 0-10-14/23 and 0-50-14/23 according to GOST 25336.

6.21 Flat-bottom flasks P-1-50-29/32, P-1-10O-29/32. P-1-20O-29/32. P-1-250-29/32 or Kn-1-50-29/32. Kn-1-100-29/32. Kn-1 -250-29/32 according to GOST 25336.

6.22 Flasks with a tube 2-100-19/26.2-250-29/32 according to GOST 25336.

6.23 Dividing funnels, type VD, versions 1 or 3, with a capacity of 50 cm 3 according to GOST 25336.

6.24 Laboratory funnels type B according to GOST 25336.

6.25 Paper filters "red tape" according to the regulatory documents in force in the territory of the state that adopted the standard.

6.26 Glass containers with a capacity of 25.50.250, 1000 cm 3 with ground glass, fluoroplastic or polyethylene stoppers according to the regulatory documents in force on the territory of the state that adopted the standard.

6.27 Hourglass or timer according to the regulations in force in the territory of the state that adopted the standard.

It is allowed to use other measuring instruments with metrological characteristics not worse than the above and auxiliary equipment, reagents and materials with technical characteristics not worse than the above.

7 Preparation for the test

7.1 Preparing glassware

Vessels for the preparation and storage of the mobile phase are treated only with sulfuric acid according to 6.15 without the use of other detergents, washed thoroughly with tap water and rinsed with distilled water.

The rest of the glassware is treated with hot water and detergent, rinsed thoroughly with distilled water and dried in an oven at a temperature of 105°C.

7.2 Preparation of auxiliary solutions

7.2.1 Mobile phase preparation

8 a pre-prepared glass container with a capacity of 1000 cm 3 with a tightly closed ground glass, fluoroplastic or polyethylene stopper is placed 5 cm 3 of glacial acetic acid (see 6.12), 215 cm 3 of acetonitrile (see 6.13) and 280 cm 3 of distilled water. The mixture is thoroughly mixed. When storing the mobile phase, the use of rubber or cork stoppers is unacceptable.

Shelf life of the mixture at room temperature - no more than 1 month.

Before use, the mobile phase is degassed and filtered according to the chromatograph manufacturer's recommendations.

"In the Russian Federation - a standard sample of an approved type.

7.2.2 Preparation of a mixture of methylene chloride and acetic acid in a volume ratio of 200:1

Place 200 ml of methylene chloride (6.14) and 1.0 ml of glacial acetic acid (6.12) in a 250 ml flat-bottomed flask.

The shelf life of the mixture at room temperature in a glass container with a ground glass, fluoroplastic or polyethylene stopper is not more than 1 month.

7.2.3 Preparation of a solution of sodium chloride with a mass fraction of 20%.

Place 20 g of sodium chloride (see 6.16) into a flat-bottomed flask with a capacity of 200 cm 3, add 80 cm 3 of distilled water, mix thoroughly.

Shelf life of the solution at room temperature - no more than 3 months.

7.3 Preparation of ochratoxin A solutions

7.3.1 Preparation of stock solution of ochratoxin A c nominal value mass concentration 1 μg / cm 3

Pipette 1 cm 3 of a standard sample of the composition of a solution of ochratoxin A in acetonitrile with a mass concentration of 50 µg/cm 3 (see 6.10). place in a 50 ml volumetric flask and dilute to the mark with acetonitrile (6.13).

The shelf life of the prepared solution in the refrigerator at a temperature of 2 ° C to 6 * C - no more than 6 months.

The actual value of the mass concentration of ochratoxin A in the initial solution (Cm, μg / cm 3) is calculated by the formula




where Cco is the certified value of the mass concentration of ochratoxin A in the standard sample according to the passport, µg/cm 3 ;

Vco - the volume of the standard sample of the composition of the solution of ochratoxin A. selected for the preparation of the initial solution, cm 3 (1 cm 3);

V^, - the volume of the volumetric flask used to prepare the initial solution, cm 3 (50 cm 3).

Note - When using a standard sample of the composition of a solution of ochratoxin A in other solvents, an aliquot (1 cm 3) is evaporated to a dry residue in vacuum at a water bath temperature from 40 "C to 45 * C or in a stream of nitrogen. The dry residue is dissolved in 2 cm 1 of acetonitrile and stirred for 1 minute Then the resulting solution is quantitatively transferred into a volumetric flask with a capacity of 50 cm 3 and diluted to the mark with acetonitrile.

7.3.2 Preparation of a mobile phase solution of ochratoxin A with a nominal mass concentration of 50 ng/cm

In a volumetric flask with a capacity of 50 cm 3, place 2.5 cm 3 of the initial solution of ochratoxin A according to 7.3.1 and bring the volume to the mark with the mobile phase according to 7.2.1.

The shelf life of the resulting solution in a refrigerator at a temperature of 2 to 6 and C - no more than 3 months.

The actual value of the mass concentration of ochratoxin A in solution (Co, ng / cm 3) is calculated by the formula

С„ = r ~, ; v ~ -10QQ. (2)

where Cm is the actual value of the mass concentration of ochratoxin A in the initial solution (see 7.3.1), µg/cm 3 ;

The volume of the initial solution according to 7.3.1. selected for the preparation of this solution. cm 3 (2.5 cm 3);

Vo is the volume of the volumetric flask used to prepare the initial solution, cm 3 (50 cm 3);

1000 - the coefficient of coordination of the dimensions of units of mass.

7.3.3 Preparation of ochratoxin A calibration solutions

The initial solution of ochratoxin A in acetonitrile according to 7.3.1 is placed in a volumetric flask with a capacity of 50 cm 3 . The volume of ochratoxin A solution must meet the requirements of Table 1.

Table 1

The contents of the flask are diluted to the mark with the mobile phase according to 7.2.1 in accordance with Table 1.

The shelf life of calibration solutions in a refrigerator at a temperature of 2 °C to 6 °C is no more than seven days.

NOTE If necessary, for example to add ochragoxin A to the sample (see 8.2). it is allowed to prepare solutions of ochratoxin A of other concentrations in a similar way.

The actual value of the mass concentration of ochratoxin A in the calibration solutions is calculated by formula (2). based on the values ​​of the volumes of the initial solution according to table 1.

Before use, the solutions are kept until room temperature is reached.

7.4 Preparing the chromatograph

Preparation of the chromatograph for measurements is carried out in accordance with the manual (instruction) for operation.

Set the operating wavelengths for excitation and detection of fluorescence (see 6.1). The volumetric flow rate of the mobile phase and the dosing volume of the sample are set depending on the column sizes, guided by the instructions of the chromatograph and column manufacturer. For example, for the chromatographic column given in 6.3. the value of the space velocity of 200 mm 3 / min and the volume of the loop of the dosing valve from 10 to 20 mm are recommended. If there is a column thermostat, the temperature is set to (25 ± 1) ° С.

7.5 Chromatograph calibration

The linearity range of the calibration characteristic is from 5 to 100 ng/cm*. As samples for calibration of the chromatograph, calibration solutions of ochratoxin A no 7.3.3 are used.

Two chromatograms of each calibration solution are recorded and, using the software for the chromatograph, the chromatograph is calibrated by setting the parameters of the calibration characteristic and the retention time of ochratoxin A.

Calculate the correlation coefficient and the deviation of the calculated values ​​of the mass concentration of ochratoxin A at each calibration point from the actual value in accordance with the procedure for preparing calibration solutions (see 7.3.3).

Graduation is considered acceptable if:

Correlation coefficient not less than 0.998:

The relative deviation of the calculated value of the mass concentration of ochratoxin A from the actual value is no more than ± 10%.

7.6 Checking the stability of the calibration characteristic

Control of the stability of the calibration characteristics is carried out daily before starting work.

8 as a control solution, use a solution of ochratoxin A in the mobile phase, prepared in the same way as 7.3.3. The mass concentration of ochratoxin A in the control solution is selected based on the expected content of ochratoxin A in the test samples: it is recommended to use a solution of ochratoxin A with a mass concentration of 20 ng/cm.

Record at least two control solution chromatograms and identify the ochratoxin A peak by retention time at a 5% identification window width. introducing, if necessary, software correction of the peak retention time, and using the calibration characteristic, the mass concentration of ochratoxin A is calculated for each input.

The repeatability of retention times and mass concentrations of ochratoxin A is checked using the formulas

l^Z^lisO.05, (3)

where h and Tr are the retention times of the ochratoxin A peak in the first and second chromatograms, respectively, min:

f is the arithmetic mean /, and t 2 , min.

i, _ "" * 0L7"

With.

where Cl and Cl2 - mass concentrations of ochratoxin A in the control solution according to the first and second chromatograms, respectively, ng/cm 3 ;

C to - the arithmetic mean of the values ​​of Cxi and C«. ng / cm 3.

The calibration dependence is recognized as stable if the condition is met where C is the actual value of the mass concentration of ochratoxin A in the control solution, ng / cm 3 -

If condition (5) is not met, then the control procedure is repeated. The results of the repeated control are considered final, and the calibration of the chromatograph according to 7.5 is carried out again.

7.7 Blank control

A blank test is carried out before testing the test samples.

15 cm * mixture of methylene chloride and acetic acid is placed in a flask for evaporation.

7.2.2 and evaporate in vacuo to dryness by placing the flask in a water bath at 40 to 45°C.

The dry residue is dissolved in 0.5 ml* of the mobile phase according to 7.2.1. stand for at least 5 minutes and carry out a chromatographic analysis of the resulting concentrate according to 8.3. If the chromatogram contains peaks that are close in retention time to the peak of ochratoxin A, then the causes of contamination of the blank sample are found and eliminated.

NOTE The most common cause of poor blank control results is insufficient purity of methylene chloride, which can be contaminated with impurities that have retention times close to those of ochratoxin A. Such methylene chloride must be replaced or subjected to thorough distillation, collecting the middle fraction with a boiling point of 39 * C to 40 * C.

8 Testing

8.1 Extraction of ochratoxin A from the sample

Pipette 5 cm 3 of the sample into a separating funnel, add 5 cm 3 of sodium chloride solution according to 7.2.3, add 5 cm 3 of a mixture of methylene chloride and acetic acid according to 7.2.2 and shake for 1 min. After phase separation, the lower organic layer is filtered through a red tape filter pre-moistened with acidified methylene chloride into an evaporating flask.

Note - When a stable emulsion is formed, it is recommended to centrifuge the mixture for 2 minutes at a speed of 5000 rpm.

Repeat the extraction of ochratoxin A from the upper layer once again with 5 cm 3 of a mixture of acetic acid and methylene chloride according to 7.2.2. The resulting extract is filtered into the same evaporation flask.

The filter is washed with acidified methylene chloride with a volume of 5 to 10 cm 3 . The extract is evaporated to dryness in vacuo by placing the flask in a water bath at a temperature of 40°C to 45°C. The dry residue is dissolved in 0.5 cm* of the mobile phase, thus obtaining a sample concentrate.

Note -On the stage mastering the method, when changing the batch of the extractant, as well as when there is doubt about the reliability of the results obtained, find the transmission coefficient of ochratoxin A in the control sample in accordance with Appendix A and check the acceptability of the obtained value.

8.2 Screening Samples

Wine sample concentrate obtained according to 8.1. hold for at least 5 minutes. and then carry out its chromatographic analysis according to 8.3.

If there is no peak on the chromatogram identified as the peak of ochratoxin A, it is concluded that there is no ochratoxin A in the sample at the level of the lower limit of the measurement range (0.001 mg / dm 3) and the sample with the addition of ochratoxin A is not prepared.

If the sample chromatogram shows a peak. identifiable software to the chromatograph as an ochratoxin A peak (see 8.3). that is, the analyzed sample is introduced

an additive in the form of a solution of ochratoxin A in the mobile phase (see 7.3.2). The recommended volume of addition of ochratoxin A solution (V 4P . cm 3) is calculated by the formula

(6) where o is a coefficient, the value of which is chosen in the range from 0.5 to 2.0:

C* is the mass concentration of ochratoxin A in the sample concentrate (see 8.3). ng / cm 3;

Us is the volume of the sample concentrate, cm 3 (0.5 cm 3);

Set - mass concentration of ochratoxin A in the solution used to add the additive. ng / cm 3.

The volume of the added additive should not exceed 5% of the sample volume (U pr. cm 3). If this requirement is not consistent with the values ​​calculated by formula (6). then, to add the additive of ochratoxin A, a solution with a different mass concentration value is used.

Analyze the spiked sample according to 8.1.

8.3 Making chromatographic measurements

Record at least two chromatograms of the test sample concentrate (see 8.1) and the sample with additive (see 8.2), under the same conditions under which the chromatograph was calibrated. Identification of ochratoxin A is carried out by matching the retention time of ochratoxin A in the sample extract with its retention time obtained by monitoring the stability of the calibration characteristic, setting the width of the identification window to 5%.

An example of a chromatogram is shown in Figure B.1 (Appendix B).

Note - If it is necessary to confirm the correct identification of the ochratoxin A peak, it is recommended to add the solution of ochratoxin A in the mobile phase to the sample concentrate. The reliability of identification can be judged by the increase in the height of the expected peak of ochratoxin A. The amount of added ochratoxin A solution is determined based on the fact that the mass concentration of ochratoxin A in the sample should increase by (50 - 150)% compared to the initial value.

If there is a peak on the chromatogram of the sample concentrate, identified as the peak of ochratoxin A. calculate the mass concentration of ochratoxin A in the sample concentrate for each registered chromatogram using the calibration characteristic established in 7.5. and check the acceptability of the obtained values ​​using condition (4). If condition (4) is met, then as a result of measuring the mass concentration of ochratoxin A in the concentrate of the test sample, the arithmetic mean of the obtained concentrations (Cx. ng / cm 3) is taken. If condition (4) is not met, then the causes of instability are found and eliminated, after which the introduction of the sample concentrate is repeated.

When analyzing the sample concentrate with the addition of ochratoxin A (see 8.2), also record two chromatograms, identify the peak of ochratoxin A and calculate the mass concentration of ochratoxin in the concentrate for each chromatogram, check the acceptability of the obtained values ​​and calculate the mass concentration of ochratoxin A in the concentrate of the sample with the addition ( C X 4 D. ng / dm 3) as the arithmetic mean of the obtained values.

If the mass concentration of ochratoxin A in the sample concentrate exceeds 100 ng/cm3, then the wine sample is diluted with water according to 6.11 and the diluted sample is reanalyzed according to 8.1. The dilution factor O is calculated by the formula

where U p is the volume of the diluted sample, cm 3;

Y 4 - the volume of an aliquot of the test sample, taken for dilution, cm 3 .

9 Processing of test results

The mass concentration of ochratoxin A in a wine sample (X. mg / dm) is calculated by the formula


V---ts--:--o-yu ’

where Cst is the mass concentration of the ochratoxin A solution used as an additive (see 8.2). ng/cm3:

Volume of addition of ochratoxin A solution to the sample (see 8.2), cm 3:

Vpp is the volume of the sample taken for testing according to 8.1. cm 3 (5cm 3);

Cx is the mass concentration of ochratoxin A in the sample concentrate (see 8.3), ng/cm3:

From x. c = mass concentration of ochratoxin A in the spiked sample concentrate (see 8.3). ng/cm3:

O is the dilution factor of the wine sample (see 8.3). If the sample was not diluted, then O g 1;

10" 3 - the coefficient of coordination of the dimensions of the units of mass and volume.

10 Metrological characteristics

The method provides measurement results with metrological characteristics not exceeding the values ​​given in Table 2.

table 2

Measuring range. mg/dm 1

Repeatability limit (the relative value of the allowable discrepancy between two measurement results obtained under repeatability conditions at P * 0.95) g 0, „. %

Critical difference (relative value of the allowable discrepancy between two measurement results obtained under reproducibility conditions at P = 0.951 C0% V. kg / dm 1

Accuracy indicator (boundaries* of relative error at confidence level Р = 0.95).

From 0.001 to 0.005 inclusive

Se. 0.005 » 0.1 »

* The established numerical values ​​of the relative error limits correspond to the numerical values ​​of the relative expanded uncertainty with a coverage factor k = 2.

Discrepancy between two measurement results (X| and X 2 , mg/dm - *). obtained in the same laboratory under repeatability conditions, must meet the condition

where X is the arithmetic mean of X, and X 2 . mg/dm:

L>p. - repeatability limit (table 2), %.

When condition (9) is met, the arithmetic mean of the obtained measurement results (X, and X 2 . mg / dm 3) is taken as the measurement result.

The discrepancy between two measurement results obtained in two laboratories (X 1gaC and Hahn, mg / dm 3) on identical samples must correspond to the condition

where Хпов is the arithmetic mean of Х 1лв0 and Х^. mg/DM 3: CO 095 - critical difference (table 2). %.


11 Quality control of measurement results

Control of quality indicators of measurement results in the laboratory provides for monitoring the stability of measurement results, taking into account the requirements of GOST ISO 5725 * 6 (section 6).

12 Presentation of test results

The test results are recorded in a test report, which is drawn up in accordance with the requirements of GOST ISO / IEC 17025, while the test report must contain a reference to this standard.

The results of measurements of the content of ochratoxin A (with laboratory-confirmed compliance of the analytical procedure with the requirements of this standard) are presented in the form

X±L or X±U. (11)

where X is the measurement result obtained in accordance with section 10. mg / dm 3:

A - the limits of the absolute error in measuring the content of ochratoxin A (P - 0.95), mg / dm 3, which are calculated by the formula

A = 0.0!bG: (12)

U is the expanded uncertainty at a coverage factor of k-2. mg / dm 3, which is calculated by formula 8

U = 0.CM (/ w x. (13)

The values ​​of S (U„J are given in Table 2.

The numerical values ​​of the boundaries of the absolute error (uncertainty) are expressed as a number containing no more than two significant figures, while the smallest digit of the numerical value of the final measurement result is taken to be the same. as well as the smallest digit of the numerical value of the boundaries of the absolute error (uncertainty).

Determination of the transmission coefficient of ochratoxin A

To determine the transmission coefficient of ochratoxin A, a control sample is used, for the preparation of which 5 ml of distilled water is placed in a separating funnel, 5 ml of sodium chloride solution according to 7.2. mobile phase (see 7.3.2).

Carry out the extraction of ochratoxin A according to 6.1. prepare the control sample concentrate according to 8.2 and carry out its chromatographic analysis according to 8.3 and. using the calibration characteristic according to 7.5. allocate the mass concentration of ochratoxin A in the control sample concentrate.

Then the transmission coefficient of ochratoxin A (p) is calculated by the formula



where V\ is the volume of the control sample concentrate, cm 9 (0.5 cm *):

Cx is the measured value of the mass concentration of ochratoxin A in the control sample concentrate, ng/cm*:

C. - the value of the mass concentration of ochratoxin A in solution according to 7.3.2. ng/cm*:

V. - volume of ochratoxin A solution according to 7.3.2. selected for the preparation of a control sample, cm* (0.5


The transmission coefficient of ochratoxin A is determined at least three times under repeatability conditions. The values ​​obtained must meet the following requirements:

Each of the obtained values ​​is not less than 0.8:

The relative value of the range of the obtained values ​​corresponds to the condition


I P||F Pchii I




where iv "t and tv". - the largest and smallest of the obtained values ​​of the transmission coefficient of ochratoxin A;

If both of these conditions are met, then the operations according to 8.1 are considered satisfactory. Otherwise, the reasons for the loss of ochratoxin A are found and the determination of the transmission coefficient is repeated.

Annex B (informative)

Chromatogram Example

semi-sweet


Figure B.1 shows an example of a chromatogram of a red wine sample concentrate (mass concentration of ochratoxin A in the sample is 0.0010 mg/dm 1).


concentration


Figure B.1 - Chromatogram example

The peak of ochratoxin A (marked as OTA in the figure) corresponds to the mass value of ochratoxin A in the concentrate of 7.7 ng/cm*.


UDC 543.544.5.068.7:663.2:006.354 MKS 67.160.10

Key words: wine, wine materials. test methods, high performance liquid chromatography, ochratoxin A. extraction of ochratoxin A. determination of the mass concentration of ochratoxin A. concentration of the extract, screening of samples, fluorimetric detection

Editor K.V. Dudko Proofreader P.M. Smirnov Computer history E.K. Kuzina

Signed for publication on February 8, 2016. Format 60x84V*.

Uel. oven l. 1.86. Circulation 45 copies. Behind*. 3872.

Prepared on the basis of the electronic version provided by the developer of the standard

Leaflet

Kits and are test systems for enzyme immunoassay. They are commercially available in accordance with ISO 9000 complete with the necessary reagents and are designed for the quantitative determination of ochratoxin in cereals, feed, grain products, beer and blood serum. Guidelines on the use of test systems RIDASCREEN® FAST Ochratoxin A And RIDASCREEN® Ochratoxin A approved by the Department of Veterinary Medicine of the Federal Agency for agriculture Ministry of Agriculture of Russia under the number MUK 5-1-14/1001. Systems are included in the "List normative documentation, approved for use in state veterinary laboratories in the diagnosis of diseases of animals, fish, bees, as well as the control of the safety of raw materials of animal and vegetable origin. "Test systems RIDASCREEN® FAST Ochratoxin A correspond GOST 34108-2017"Feed, mixed feed, mixed feed raw materials. Determination of mycotoxin content by direct solid-phase competitive enzyme immunoassay".

Determination of ochratoxin A in grain, feed, grain products, beer and blood serum

Ochratoxin is a poisonous substance formed as a result of vital activity mold fungi kind Aspergillus And Penicillium. Along with pronounced nephrotoxicity, ochratoxin has hepatotoxicity, teratogenic, carcinogenic and immunosuppressive properties. With products of plant and animal origin, ochratoxin can enter the human body. It is found not only in cereals (13% of positive samples) and animal feed, but also in pig blood (60% of positive samples) and kidneys (21% of positive samples).

Technical Regulations of the Customs Union TR CU 021/2011 "On food safety" regulate the following maximum level of ochratoxin A content: in food grains, cereals, flour - 0.005 mg / kg (5 μg / kg); in baby food, food products for preschoolers and schoolchildren, food products for pregnant and lactating women - not allowed (<0,0005 мг/кг).

Draft federal law № 349084-5 The "Technical Regulations for Wine Products" establishes requirements for the content of ochratoxin A in wine no more than 0.002 mg/l.

The draft Federal Law "On requirements for the safety of food products and processes of their production, storage, transportation, sale and disposal" also includes a requirement for mandatory control of food grains for ochratoxin A, the content of which should not exceed 0.005 mg/kg. The current legal regulations can be found on the website compact24.com.

Until recently, chromatographic methods (high performance liquid chromatography, thin layer chromatography) were predominantly used to control ochratoxin. Much more convenient method of enzyme-linked immunosorbent assay (ELISA, or ELISA), which has a very high sensitivity.

Specification: RIDASCREEN® FAST Ochratoxin A RIDASCREEN® Ochratoxin A 30/15
Format: Strip plate, 48 wells (6 strips of 8 wells) Strip plate, 96 wells (12 strips of 8 wells)
Standards: 0 / 5 / 10 / 20 / 40 µg/l 0 / 50 / 100 / 300 / 900 / 1800 ng/l
Sample preparation: Sample grinding, extraction, filtration extraction, centrifugation/filtering (grain, feed); extraction, centrifugation, filtration, shaking, over-extraction, centrifugation, evaporation (beer/serum)
Time spent:
Limit of detection: 0.005 mg/kg 0.001250 mg/kg (grain, feed)
0.000050 mg/kg (beer, blood serum)

Related products:

State Research Institute of Nutrition of the Russian Academy of Medical Sciences, Moscow

Ochratoxin A, a secondary metabolite of widespread microscopic fungi of the genera Penicillium (P. verrucosum) and Aspergillius (A. ochraceus), is among the priority mycotoxins - food contaminants, and poses a real danger to human health. Ochratoxin A has a pronounced nephrotoxic, carcinogenic, as well as teratogenic, immunotoxic, neurotoxic, genotoxic and cytotoxic effects. Ochratoxin A has been classified as possibly carcinogenic to humans by the International Agency for Research on Cancer (IARC) (Group 2B). When administered orally, LD50 varies for different animal species from 20-30 mg / kg b.w. (for rats) to 1 mg / kg b.w. (for pigs). Ochratoxin A is considered as one of the etiological factors of Balkan endemic nephropathy, a severe renal disease recorded in some Eastern European countries (in particular, Bulgaria, Romania, Serbia, Croatia, Bosnia and Herzegovina, Slovenia, Macedonia). Ochratoxin A is most commonly found in grain products, coffee, and spices. Recently there is evidence of significant contamination of dried fruits, wine and fruit juices with ochratoxin A. Thus, as a result of studies conducted in the EU countries, it was found that about 70% of batches of grain products contained ochratoxin A in the range from 0.00001 to 0.041 mg/kg, about 60% of the studied batches of wine were contaminated with ochratoxin A in an amount of 0 .000003 to 0.016 mg/l. Particularly noteworthy are the data on the frequent detection of ochratoxin A in the blood, as well as in the mother's milk of the population of many European countries, which indicates the constant intake of this mycotoxin in the human body. The main contribution to the intake of ochratoxin A with food is made by cereals (44%), wine (10%) and coffee (9%). The recommended allowable weekly intake of ochratoxin A by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) is 100 ng/kg/m. T. . The content of ochratoxin A in the EU countries is regulated at the level of 0.005 mg/kg in food raw materials and 0.003 mg/kg in food. There are no reliable data on food contamination with ochratoxin A in the Russian Federation.


The method for the determination of ochratoxin A in food products, previously developed for the needs of the USSR Sanitary and Epidemiological Service, using liquid-liquid distribution to purify the extract, has a number of disadvantages: relatively low sensitivity of the method (detection limit - 0.001-0.002 mg / kg), significant duration of analysis, as well as the need to use a large amount of chlorine-containing organic solvents.

To date, new, more efficient methods have been developed for the determination of ochratoxin A in food products, based on the use of solid phase extraction (SPE) . SPE is characterized by good extract purification, high recovery and low solvent consumption. In SPE, normal-phase adsorption chromatography on silica gel, reversed-phase distribution chromatography on silica gel chemically modified with octadecylsilane, immunoaffinity chromatography, as well as column chromatography on other sorbents (diatomite earth (celite), polyamide, polymers obtained by imprinting, etc.) are used. ) .

The weakly acidic properties (pKA = 4.4) of ochratoxin A (Fig. 1) determine the need for its extraction either in an undissociated form with mixtures of organic solvents with acidic water-salt solutions, or in the form of a salt - with slightly alkaline aqueous solutions, for example, sodium bicarbonate solution.

Reverse phase HPLC (RP HPLC) with fluorimetric detection is the most widely used method for the determination of ochratoxin A in foods.

The aim of the study was to develop a sensitive method for the detection, identification and quantification of ochratoxin A in food products by optimizing analytical approaches based on the use of SPE.

experimental part

Equipment and reagents. The chromatographic system consisted of a Jasco 880-PU high-pressure pump, a Rheodyne-7125 injector with a dosing loop volume of 20 µL, an FL Detector model LC305 fluorimetric detector (Linear Instruments) (ex=250 nm, lamis=458 nm) and a system for data collection and processing "Multichrome" (Ampersend). Chromatographic column (250 * 4.6 mm) with a stationary phase Kromasil C18 (MetaChem Technologies Inc.), with a particle size of 5 µm.

Extraction was performed using a shaker s-3.08L (ELMI) shaker; samples were centrifuged using a CLS 31M centrifuge. Solid-phase extraction was performed using a Macherey-Nagel manifold, DIAPAK Silica Gel cartridges (BioChemMac ST), OCHRAPREP immunoaffinity columns (IAC) (R-BIOFARM RHONE LTD). The pH of the solutions was measured with an MP 230 pH meter (Mettler Toledo). Samples were concentrated on a Laborota 4000 rotary evaporator (Heidolph). To dissolve standards and evaporated extracts, an ultrasonic bath UZV-12L (PKF SAPPHIRE) was used. To select the optimal excitation and emission waves, a Cary Eclipse (Varian) fluorescent spectrophotometer was used. A standard sample of ochratoxin A in a mixture of benzene-acetic acid (99:1) with a concentration of C = 9.2 ng/µl was used as a standard.


Solid phase extraction:

Purification by column chromatography (CC) on diatomaceous earth. The extraction of ochratoxin A from 25.0 g of the crushed sample was carried out with 125 ml of chloroform after adding 20 ml of 2% acetic acid. Mixed on a shaker for 30 minutes. 50 ml of the chloroform extract passed through a paper filter was applied to a column of diatomaceous earth impregnated with sodium bicarbonate. The column was washed successively with 70 ml of hexane and 30 ml of chloroform. Ochratoxin A was eluted from the column with 150 ml of a benzene–acetic acid mixture (86:12:2). The eluate was evaporated to dryness, dissolved in 3 ml of the mobile phase (acetonitrile - aqueous H3PO4 (pH=2.6) (62:38) using an ultrasonic bath.

Purification with QC on silica gel. Extraction of ochratoxin A from 20.0 g of the crushed sample was carried out with 100 ml of toluene after successive addition of 30 ml of 2M hydrochloric acid solution and 50 ml of 0.4M magnesium chloride solution. Stirred for 60 minutes, centrifuged at 3500 rpm for 5 minutes. The top toluene layer was filtered through a paper filter, taking 50 ml of the filtrate. After conditioning 10 ml of toluene, 50 ml of the filtrate was applied to the cartridge with silica gel, washed twice with 10 ml of n-hexane and 10 ml of a mixture of toluene–acetone (85:15), then with 5 ml of toluene. Ochratoxin A was eluted with 40 ml of a mixture of toluene - acetone - acetic acid (89:10:1). The eluate was evaporated to dryness, dissolved in 1 ml of the mobile phase (acetonitrile - aqueous H3PO4 (pH=2.6) (62:38) using an ultrasonic bath.

Purification by immunoaffinity CH. Extraction of ochratoxin A from 50.0 g. crushed sample was carried out with 200 ml of a mixture of acetonitrile - water (60:40). Stirred for 30 minutes. 4 ml of the extract passed through a paper filter was mixed with 44 ml of phosphate and applied to an immunoaffinity column (IAC), which was then washed with 20 ml of phosphate buffer. Residual phosphate buffer was removed by blowing IAC with air. Ochratoxin A was eluted with 3 ml of methanol-acetic acid (98:2). The eluate was evaporated to dryness, dissolved in 1 ml of the mobile phase (acetonitrile - aqueous H3PO4 (pH=2.6) (62:38) using an ultrasonic bath.

HPLC conditions. Ochratoxin A was identified and quantified by RP HPLC in isocratic elution mode with fluorescent detection (exc=250 nm, lamis=458 nm). A mixture of acetonitrile and aqueous H3PO4 (рН=2.6) (62:38) was used as the mobile phase. The elution rate was 1 ml/min. 20 μl of the test solution was introduced into the HPLC system.

Results and its discussion.

When purifying the extract by QC with diatomaceous earth impregnated with sodium bicarbonate, the AOAC 975.38 method was used as the base method, which involves the use of TLC for the identification and quantitative determination of ochratoxin A. In order to increase the sensitivity and specificity of the method, we used RP HPLC with fluorescence detection. As a result of applying the basic method, the degree of extraction of ochratoxin A from the matrix artificially contaminated with ochratoxin A at the level of 0.01 mg/kg did not exceed 40% under our conditions. In order to increase the extraction value, we made a number of changes to the extraction and purification conditions: acetic acid was added to the extracting mixture; the volume of chloroform used to wash the column is reduced to 30 ml; acetone was added to the composition of the eluting mixture; the volume of the eluting mixture was increased to 150 ml. As a result of method optimization, the extraction of ochratoxin A from wheat increased to 60% (Table 1).

The degree of extraction was significantly increased by applying the method of solid-phase extraction on cartridges with unmodified silica gel (scheme close to the ICC method No. 000). Adjustment of the basic method (toluene content in the toluene-acetone mixture used for washing the column was increased up to 85%, acetone was added to the elution mixture, the elution mixture volume was increased to 40 ml) made it possible to increase the degree of extraction to 80%.

When using immunoaffinity CH, the maximum degree of extraction of ochratoxin A from the food matrix (up to 100%) was observed, while the detection limit (0.0005 mg/kg) was higher than when purification of CH on silica gel (0.00005 mg/kg).

To detect, identify and quantify ochratoxin A using HPLC, the optimal composition of the mobile phase (MP) was selected and the wavelengths of excitation and fluorescence emission were refined, which provided the maximum signal and selectivity in the detection of ochratoxin A (Table 2). The adjusted excitation (250 nm instead of 333 nm) and fluorescence emission wavelengths for the optimized mobile phase made it possible to increase the signal-to-noise ratio with a corresponding decrease in the detection limit of the method. The change in the PF composition made it possible to improve the separation of the peaks of ochratoxin A and the components of the matrix of the food product while reducing the retention time of the peak of ochratoxin A (Fig. 2).

The possibility of using our modified method, based on the use of cartridges with silica gel, in the routine analysis of ochratoxin A was confirmed by a selective study of the frequency and level of contamination of the main types of food raw materials with this mycotoxin. For this, food grains of the 2004 harvest from various regions of the Russian Federation were studied (Table 3). Nine of the 46 grain samples examined contained ochratoxin A in the range of 0.00005 to 0.005 mg/kg, which did not exceed the regulations adopted in the EU countries.

Thus, by optimizing existing analytical approaches, two variants of the method for detecting, identifying, and quantifying ochratoxin A in food products were proposed: using QC on silica gel or immunoaffinity QC for purification of extracts and optimized HPLC conditions. The method based on the use of QC on silica gel has a low detection limit and low cost of consumables. Purification with immunoaffinity QC provides a high recovery and purity of the extract, and also has a higher detection limit (0.0005 mg/kg instead of 0.00005 mg/kg for the silica gel QC purification option). The data obtained as a result of a selective study of the content of ochratoxin A in food raw materials indicate the need for further study of food contamination with ochratoxin A in order to assess the risk of food contamination with this mycotoxin for the health of the population of the Russian Federation.

State Research Institute of Nutrition RAMS

109240, Moscow, Ustyinsky proezd, 2/14

I. V. Aksenov, K. I. Eller, V. A. Tutelyan

Optimization of analytical methods for ochratoxin A analysis in food.

Ochratoxin A is a mycotoxin produced by widely distributed Aspergillus and Penicillium species. The mycotoxin is a common contaminant of cereals, coffee, wine, dried fruits and spices. Ochratoxin A has been shown to be nephrotoxc, immunosuppressive, embryotoxic, teratogenic and carcinogenic in many mammalian species. Codex Alimentarius and EC have established maximum permissible level of 5 mg/kg for ochratoxin A in raw cereal grains and of 3 mg/kg – for ready-to-eat products derived from cereals. Two simple and reliable modifications of methods have been developed for the analysis of ochratoxin A in food which are based on immunoaffinity or silica gel column clean-up and HPLC with fluorescence detection. The detection limits were 0.5 mg/kg and 0.05 mg/kg respectively. Methods have been used successfully to analyze ochratoxin A in 46 samples of raw cereals harvested in different regions of Russia. Nine samples were found to be contaminated with ochratoxin A on levels ranged from 0.05 to 5 mg/kg.

Optimization of analytical methods for the detection, identification and quantification of ochratoxin A in food products.

Ochratoxin A is a mycotoxin produced by widespread fungi of the genera Aspergillius and Penicillium. It is a frequent contaminant of cereal products, coffee, wine, dried fruits and spices. The nephrotoxic, immunosuppressive, embryotoxic, teratogenic and carcinogenic effects of ochratoxin A have been proven for many mammalian species. The maximum allowable level of ochratoxin A in grains established by the Codex Alimentarius and the EU is 5 µg/kg, in ready-to-eat cereal products - 3 µg/kg. Two optimized methods for the detection, identification and quantification of ochratoxin A in food products have been proposed: using QC on silica gel or immunoaffinity QC for extract purification and HPLC with fluorescent detection. The limit of detection was 0.05 and 0.5 µg/kg, respectively. The developed methods were used to analyze the content of ochratoxin A in 46 grain samples collected in various regions of Russia. Nine samples were contaminated with ochratoxin A at 0.05 to 5 µg/kg.

Captions for drawings.

Figure 1. Chemical structure of ochratoxin A.

Figure 2. Chromatograms of a wheat sample contaminated with ochratoxin A at a level of 0.01 mg/kg, using various purification methods:

A) CH on diatomaceous earth B) CH on silica gel C) immunoaffinity CH.

Table 1. Comparative characteristics of various methods of extract purification.

Table 2. Comparative characteristics of HPLC parameters (for 1 ng of ochratoxin A per injection).

Composition of PF

Wavelengths of fluorimetric detection, nm

retention time Ah, min

Signal to noise ratio

acetonitrile - water - acetic acid (99:99:2)

acetonitrile - water - acetic acid (102:94:4)

Optimized Method

acetonitrile - aqueous H3PO4 (pH=2.6) (124:76)

Table 3. Sample study of the level of ochratoxin A contamination of food grains from the 2004 harvest.

Literature

Guidelines for the detection, identification and determination of the content of ochratoxin A in food products. - M., 1985. , Kravchenko (Medical and biological aspects) - M., 1985. AOAC, Determination of Ochratoxin A in Wine and Beer 2001.01 // J. AOAC Int. - 2001. - Vol. 84. - P. 1818. AOAC, Ochratoxin A in Corn and Barley 991.44 // J. AOAC Int. - 1996. - Vol. 79. - P. 1102-1105. AOAC, Ochratoxin A in Green Coffee 975.38 // J. AOAC Int. - 1975. - Vol. 58. - P. 258. Application note for analisis of ochratoxin A in cereal using sodium bicarbonate extracton in conjunction with Ochraprep. – Glasgow, 2001. Baggiani C., Giraudi G., Vanni A. // Bioseparation. - 2002. - Vol.10. – P. 389–mission Regulation (EC) No. 000/2002 // Official Journal of the European Communities. - 2002. - L 75. - P. 18-20. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 56. – Lion, 1993. Jodlbauer J., Maier N. M., Lindner W. // Journal of Chromatography A. - 2002. - Vol. 945. – P. 45–63. Jornet D., Busto O., Guasch J // Journal of Chromatography A. - 2000. - Vol. 882.–P. 29–35. Krogh P. // Endemic nephropathy, Proceedings of the second International Symposium on Endemic nephropathy 9-12 November 1972. - Sofia, 1972. - P. 266-277. Kuhn I., Valenta H., Rohr K. // Journal of Chromatography B. - 1995. - Vol. 668. – P. 333–337. Majerus P., Weber R., Wolff J. // Bundesgesundheitsblatt. - 1994. - B. 37, N. 11. - S. 454 - 458. Monaci L., Palmisano F. / / Anal. bioanal. Chem. - 2004. - Vol. 378. - P. 96-103. Monaci L., Tantillo G., Palmisano F. // Anal. bioanal. Chem. - 2004. - Vol. 378. - P. 1777-1782. Quantitative detection of Ochratoxin A.- Glasgow, 2003. Report of experts participating in Task 3.2.7 “Assessment of dietary intake of Ochratoxin A by the population of EU Member States”. – Rome, 2002. Safety evaluation of certain mycotoxins in food. // WHO Food Additives Series, No.47; FAO Food and Nutrition Paper 74. - Geneva, 2001. Schwartz G. G. // Cancer Causes Control. - 2002. - Vol.13. - P. 91-100. Scott P. M. // Adv. Exp. Med. Biol. - 2002. - Vol. 504. - P. 117-134. Skaug MA, Helland I, Solvoll K, Saugstad O. D. // Food Addit. contam. - 2001. - Vol. 18. - P. 321-327. Visconti A., Pascale M., Centonze G. // Journal of Chromatography A. - 1999. - Vol. 864.–P. 89–101. Zimmerli B., Dick R. // Journal of Chromatography B. - 1995. - Vol. 666. – P. 85 – 99.

one overlay is applied, and in the middle part - two overlays with a minimum step between them, which indicate the boundaries of the incoming and outgoing branches of the tape. The step between the overlays on the oncoming branch of the tape is determined using the dependence of an arithmetic progression, and on the descending branch - on the basis of a geometric progression. In this case, the first member of the arithmetic progression must be set and take into account that the last gap between the linings of the oncoming branch of the tape is the first member of the geometric progression, and the difference and denominator of the progressions are determined from the total gap between the linings of each branch of the tape.

In a drum-shoe brake, the leveling of specific loads is achieved by placing in a multi-section brake shoe on its incoming and outgoing parts of radially movable linings interconnected by a balancer, i.e., the principle of conventional weights is used. This technical solution is protected by a copyright certificate for an invention.

Stabilization of surface temperatures in the friction pairs of the above-mentioned brake devices is achieved due to the thermoelectric effect using thermopiles operating in the modes of a thermoelectric refrigerator and a thermoelectric generator in the linings of the incoming and outgoing branches of the tape, as well as in the incoming and outgoing sections of the friction linings of the shoe in the main and additional servo brakes, depending on the heat load their friction nodes. At the same time, it is provided

redistribution of thermal energy between the surfaces of the friction units of the brakes, which leads to its quasi-stabilization. The operation of thermopiles in the above modes is theoretically substantiated.

Rational control of operating modes of a band-shoe brake is considered provided that the level of heat loading of the surface layers of friction linings does not exceed the allowable temperature for their materials. To implement the control of braking modes, combined cooling (thermoelectric with a heat pipe) of brake friction pairs can be used.

As a result of the application of this technical solution, an increase in the efficiency of the U2-5-5 winch band-shoe brake was achieved.

Thus, the ways of controlling the dynamic and thermal loading of the friction units of the brake devices are indicated.

LITERATURE

1. Declaration Pat. 63418А (Ukraine). A method for controlling specific loads on the incoming and outgoing branches of the brake band of a band-shoe brake / A.I. Volchenko, V.V. Dyachuk, N.A. Volchenko and others - B.I. - 2004. - No. 1. - In Ukrainian. lang.

2. A.s. 1682675 A1 USSR. Drum-shoe brake / A.I. Volchenko, V.V. Moskalev, P.A. Skorokhod and others - B. I. - 1991. -

3. Pat. 2221944 C1 Russia. Cooling systems for a brake mechanism with servo action and a method for its implementation / A.I. Volchenko, A.A. Petrik, N.A. Volchenko and others - B.I. - 2004. - No. 2.

Department of Technical Mechanics

Received 22.11.04

DETERMINATION OF OCHRATOXIN A IN GRAPE WINES

E.N. RIKUNOVA, T.I. GUGUCHKINA

North Caucasian Zonal Research Institute of Horticulture and Viticulture

Among mycotoxins, ocher toxins occupy a special place. They are produced by some species of microscopic fungi of the genera Penicillium, Aspergillus, in particular A. ochraceus, P. viridicatum. These molds are ubiquitous, mostly in warm and humid conditions, causing grape rot during prolonged rains. Ochratoxins have a general toxic effect, affect the kidneys, liver, reduce productivity, have embryotoxic, mutagenic and carcinogenic effects.

The International Agency for Research on Cancer has classified ochratoxin as a potential carcinogen and classified it as a hazard class 2B. When food is contaminated with ochratoxins, a person becomes ill with Balkan endemic nephropathy.

Patu-lin was previously found in wine products, and recently information has appeared on the content of ochratoxin A. It contaminates grains, vegetables, fruits and their products, feed, malt, beer, juices and wine.

We have developed a method for determining ochratoxin in grape wine by thin layer chromatography (TLC).

Thin-layer chromatography is a type of liquid chromatography in a layer of sorbent that is flat on one side and deposited on a flat solid substrate. The main features of TLC are due to the movement of the eluent (solvent) over the sorbent layer due to capillary forces, which simplifies and facilitates the chromatographic process. The use of a universal sorbent - silica gel and an open layer provide ease of sample application, the possibility of simultaneous analysis of several samples, and ease of monitoring the elution process.

Thin layer chromatography involves the purification and concentration of mycotoxins. For this, two-dimensional or step chromatography is used.

fiu. The first stage of elution is purification, the separation of interfering substances, the second stage is the separation of mycotoxins.

Analysis of a wine sample by TLC includes the stages of preparing a sample, a plate, a chromatographic chamber and eluents, as well as a concentrating cartridge Diapak C16MT; then the actual chromatography, evaporation of the eluent from the plate, identification, quantification and documentation.

The advantage of the method is not only its simplicity, availability, the possibility of using specific developing agents, confirming that the substance belongs to the desired one, lower requirements for purification of extracts, but also the possibility of determining small amounts of ochratoxin - the detection limit is 0.1 μg / cm3.

To determine mycotoxin ochratoxin A in wine and wine materials, 10 cm3 of the sample is passed through the concentrating cartridge Diapak C16MT, concentrating the sample 10 times, and finally purified with 1 cm3 of acetonitrile. The resulting extract in the amount of 5 μl and the standard are applied to TLC plates and chromatographic separation (elution) is carried out in a prepared chromatographic chamber with appropriate eluents. The system of solvents in the form of isopropanol and ammonia turned out to be the most optimal for the separation of mycotoxin. It is quite volatile and has a low retention coefficient.

Rf on the sorbent. Mycotoxin spots were developed by irradiating with long wavelength (365 nm) ultraviolet light. When exposed to UV rays, mycotoxin spots glow blue-green.

Identification and quantitative determination of ochratoxin was carried out by scanning densometry on a Sorbfil densitometer with a specialized program for processing analysis results and calculating chromatogram parameters.

The use of a densitometer makes the TLC method quantitative, comparable in resolution to HPLC, while retaining all the advantages of TLC.

The proposed method was tested on wine samples with the preliminary introduction of certain amounts of ochratoxin. The method allows you to quickly and accurately control the content of ochratoxin in wine products.

LITERATURE

1. Kretova L. Glunev L. I. Mycotoxins. Contamination of products and analytical control. - M.: Agrprogress, 2000.

2. Proceedings of the OIM Assembly. - Paris, 2000. - S. 57-59.

3. Guide to modern thin layer chromatography / Ed. O.G. Larionova // Based on the materials of the school-seminar on thin layer chromatography. - M., 1994.

Winemaking technology laboratory

Received 08.09.04

N.T. SIYUKHOVA

Maykop State Technological University

Currently, serious attention is paid to the issues of contamination of agricultural crops with toxic substances of various nature, including pesticides. Among the crops most treated with chemical means of protection against pests and diseases, the grapevine stands out. Because of the repeated protective treatments in each growing season, vineyards have long been considered a kind of accumulator of environmentally hazardous chemicals.

These include organophosphorus compounds, which are characterized by an increased risk of accumulation in cultivated areas and are leading in terms of practical application. These drugs accumulate in plant cells. Berries are most dangerously and intensively contaminated with them, which ultimately affects the quality and environmental safety of products produced from grapes. Taking into account the high toxicity and stability of organophosphorus compounds and their metabolites, the determination of contamination of grape products by them is of great scientific and practical importance.

On the production sites of the specialized farm AF "Fanagoria" (Temryuk district) was carried out (1999-2002) toxicological control of red grape varieties. Samples were taken during harvesting, and the analysis of products for the content of residual amounts of organochlorine and phosphorus insecticides was carried out in an accredited testing toxicological laboratory of SKZNIISiV. The principle of selection of grape plots for sampling was based on the fact that the grapes harvested from them were used for factory processing and the preparation of dry red wines in the micro wine shop of the grape processing laboratory of SKZNIISiV.

When planning experiments to study the persistence of toxic substances in grapes, the possible influence of two factors was taken into account, which together determine the manifestation of the potential danger of insecticides entering cultivated grapes: the ingress of toxic residues from the soil of plantations and from the plant itself as a result of current seasonal treatments


Ochratoxins are produced by certain types of fungi. Aspergillus And Penicillium. The main producers are A.ochraceus And P. viridicatum. These mushrooms are found everywhere. Aspergillus produces ochratoxins at elevated temperature and humidity, and Penicillium already at 5°C. Ochratoxins are highly toxic compounds with a pronounced teratogenic effect.

Ochratoxins A, B, and C are a group of structurally related compounds that are isocoumarins associated with L-phenylalanine peptide bond. Depending on the nature of the radicals, various types of ochratoxins are formed (Table 2.3.).

Ochratoxin A is a colorless crystalline substance, slightly soluble in water, moderately soluble in polar organic solvents (methanol, chloroform), as well as in an aqueous solution of sodium carbonate. In a chemically pure form, it is unstable and very sensitive to light and air, but in an ethanol solution it can remain unchanged for a long time. In UV light it has green fluorescence.

Ochratoxin B is a crystalline substance, an analogue of ochratoxin A, which does not contain a chlorine atom. It is about 50 times less toxic than ochratoxin A. In UV light, it has blue fluorescence.

Ochratoxin C is an amorphous substance, ethyl ester of ochratoxin A, which is close to it in toxicity, but has not been found as a natural food and feed contaminant. In Y-light it has a pale green fluorescence.

Ochratoxins belong to toxic mycotoxins, have high toxicity to the liver, kidneys, teratogenic and immunosuppressive properties, and a pronounced hemolytic effect. Of the ochratoxins, ochratoxin A is the most toxic (LD 50 = 3.4 mg/kg, (day-old chicks, oral)). It is more toxic than aflatoxins. Other mycotoxins of this group are an order of magnitude less toxic.

Biochemical, molecular, cellular mechanisms of action of ochratoxins are not well understood. It is known that ochratoxin A inhibits protein synthesis and carbohydrate metabolism, in particular glycogenosis, by inhibiting the activity of phenylalanine, a tRNA, a specific enzyme that plays a key role in the initial stage of protein synthesis.

Ochratoxin A is found in corn, barley, wheat, oats, and barley. It is important and dangerous that ochratoxin A is found in livestock products (ham, bacon, sausages) at high contamination of feed grains and animal feed. Ochratoxin B is rare. Ochratoxins also affect all fruits of horticultural crops. Apples are especially affected: up to 50% of the crop can be contaminated with mycotoxins.

It should be noted that ochratoxins are stable compounds. So, for example, during prolonged heating of wheat contaminated with ochratoxin A, its content decreased only by 32% (at a temperature of 250–300ºС). Thus, the prevalence in food products, toxicity and persistence of ochratoxins create a real danger to human health.

Analysis Methods

Ochratoxin A is found in oxidized foods. It readily dissolves in many organic solvents, which is used for extraction. The most commonly used is extraction with chloroform and an aqueous solution of phosphoric acid, followed by purification on a column and quantitative determination using the TLC method.

An HPLC method has also been developed. Before HPLC analysis, the sample is prepared as follows. The crushed sample is treated with a mixture of 2 M hydrochloric acid and 0.4 M magnesium chloride solution. After homogenization, extract with toluene for 60 minutes. The mixture is centrifuged. The centrifuge is passed through a column of silica gel and washed with a mixture of toluene and acetone (mobile phase). Ochratoxin A is eluted with a mixture of toluene and acetic acid (9:1) and dried at 40°C. The residue is dissolved and filtered. The analysis is carried out using HPLC.

In addition, a number of bioassays on shrimp and bacteria have been developed, but the results obtained did not allow the use of these methods for the determination of ochratoxins.



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