T.C.
GIDA, TARIM ve HAYVANCILIK BAKANLIĞI
Gıda ve Kontrol Genel Müdürlüğü
Communiqué on the Method of Analysis for the Amount of Vinyl Chloride
Released from Materials and Articles into Foodstuffs
Authorization Law: Turkish Food Codex
The Official Gazette:22.03.2002-24703
Communication No :2002/23
Objective
Article 1. The objective of this Communiqué is to determine the method of analysis to be used for determination of the amount of vinyl chloride released from materials and articles into foodstuffs.
Scope
Article 2. This Communiqué covers the method of analysis to be used for determination of the amount of vinyl chloride released from materials and articles into foodstuffs.
Legal basis
Article 3. This Communiqué has been prepared in accordance with the Turkish Food Codex Regulation published in Official Gazette, dated 16.11.1997, reiterated No.23172.
Method of analysis
Article 4. The amount of vinyl chloride in foodstuff is determined, according to Annex 4, by gas chromatography using the headspace method.
Compliance with European Union
Article 5. This Communiqué has been prepared within the framework of compliance with European Union having regard to the Commission Directive 81/432/EEC for “Method of analysis for the official of vinyl chloride released by materials and articles into foodstuffs”. This Communiqué does not embarrass the laboratories from using the methods which are in compliance with their own legislations, experienced and having scientific validity. This Communiqué is applied compulsorily to the relations with European Union.
Provisional Article 1. Presently active laboratories using the method of analysis included in this Communiqué are obliged to obey the provisions of this Communiqué within 2 years.
Enforcement
Article 6. This Communiqué enters into force on the date of publication.
Execution
Article 7. The provisions of this Communiqué are executed by the Minister of Health and Minister of Agriculture and Rural Affairs.
ANNEX- 1
Determination of the amount of Vinyl Chloride Released from Materials and Articles into Foodstuffs
1. Scope and Field of Application
The method determines the amount of vinyl chloride in foodstuffs.
2. Principle
The amount of vinyl chloride in foodstuffs is determined by gas chromatography using the headspace method.
3. Reactives
3.1. Vinyl Chloride, VC, shall be at least 99.5%(v/v) purity in volumetric basis.
3.2. N.N-dimethyl acetamide, DMA; shall not contain any impurity having the same retention time under test conditions either with the internal standard mentioned in 3.3. or with vinyl chloride.
3.3. Diethyl ether or cis-2-butene in DMA as an internal standard; shall not contain any impurity having the same retention time with vinyl chloride under these internal test conditions.
3.4. Distilled water or demineralized water of equivalent purity.
4. Apparatus
Descriptions; “apparatus or parts of apparatus” are only used for apparatus or parts of apparatus requiring special condition.
4.1. Gas-chromotograph (GC) fitted with automatic headspace sampler or with facilities for manual sample injection.
4.2. Flame ionization detector or other detectors mentioned in Article 7,
4.3. Gas chromatographic column; shall permit the separation of the peaks of air, of vinyl chloride and of the internal standard, if used.
Furthermore, the combined system mentioned in 4.2. and 4.3. shall allow the signal obtained with a solution containing 0.005 mg vinyl chloride/L DMA or 0.005 mg vinyl chloride/kg DMA to be equal to at least five times the background noise.
4.4. Sample phials or flasks shall be fitted with silicon or butyl rubber septa.
When using manual sampling techniques, the taking of a sample from the headspace with a syringe may cause a partial vacuum to form inside the phial or flask. Hence, for manual techniques where the phial is not pressurized before the sample is taken, the use of large phials is recommended.
4.5. Micro-syringes.
4.6. as-tight syringes shall be used for manual headspace sampling.
4.7. Analytical balance accurate to 0.1 mg.
5. Procedure
Vinyl chloride is a hazardous material and a gas at ambient temperature. For this reason, the solutions should be prepared on a well-ventilated furne cupboard.
All necessary precautions shall be taken to avoid any loss of vinyl chloride or DMA.
The internal standard mentioned in 3.3. should be used for manual sampling.
When using an internal standard, the same solution must be utilized throughout the procedure.
5.1. Preparation of standard vinyl chloride solution, Solution A:
5.1.1. Concentrated standard vinyl chloride solution at approximately 2000 mg/kg
A suitable glass vessel should be accurately weigh to 0.1 mg and a certain amount, i.e. 50 mL, DMA is added. It is re-weighed. A certain amount of, i.e. 0.1 mg, vinyl chloride, either in gas or liquid form, is added by injecting slowly. Vinyl chloride may be also added by bubling it into the DMA, provided that a device is used which will prevent loss of DMA. It is re-weighed with an accuracy of 0.1 mg. Wait two hours to allow equilibrium to be attained. If internal standard is to be employed, internal standard is added until the concentration of the internal standard in the concentrated VC solution becomes the same as the concentration of internal standard solution prepared in Article 3.3. The standard solution has to be kept in the refrigerator.
5.1.2. Preparation of dilute standard vinyl chloride solution
A weighed amount of concentrated vinyl chloride standard solution is taken and diluted to a known volume or a known weight with DMA or internal standard solution. The concentration of the resultant standard solution, Solution A, is indicated as mg/L or mg/kg respectively.
5.1.3. Preparing of the response curve with Solution A
The curve must pass through seven pairs of points at least.
Repeatability must be lower than 0.002 mg vinyl chloride/L or kg of DMA.
The regression line must be calculated with the below formula using the least squares technique:
y = the height or area of peak in any definition
x = the corresponding concentration on the regression line
n = number of study (n ? 14),
The curve must be linear. The standard deviation ,s, of the differences between the measured responses and the corresponding value of responses calculated from the regression line divided by the mean value of all the measured responses shall not exceed 0.07.
This shall be calculated from:
s/ ? ? 0.07
yi= each individual measured response
zi= corresponding value of response, calculated from the regression line
n = number of study (n ? 14),
Minimum seven phials are prepared in two series. Diluted standard vinyl chloride solution and DMA or internal standard solution in DMA is added into each phial in order to obtain a final vinyl chloride concentration of the duplicate solution will be approximately equal to 0, 0.005, 0.010, 0.020, 0.030, 0.040, 0.050 mg/L or mg/kg vinyl chloride/DMA. All phials should have the same total volume of solutions. Diluted standard vinyl chloride solution must be such that the ratio between the total volume of added vinyl chloride solution in µl and quantity of DMA in g or mL or internal standard solution does not exceed five. Seal the phials and proceed as describe under points in 5.4.2., 5.4.3. and 5.4.5. A graphic is plotted while ordinate values are indicating the areas or heights of vinyl chloride peaks of the duplicate solutions or the ratio of these areas or heights to those of the relevant internal standard peaks, and the abscissa values show the vinyl chloride concentrations of the duplicate solutions.
5.2. Validition of the standard solution supplied from 5.1.
5.2.1. Preparation of a second standard vinyl chloride solution (Solution B)
The method explained in 5.1.1. and 5.1.2. is repeated in order to obtain a second standard solution having a concentration approximately 0.02 mg vinyl chloride/L or 0.02 mg vinyl chloride/kg DMA or equal to the internal standard solution.
5.2.2. Validition of Solution A
Solution A is validated if the arithmetical average of two gas-chromatographic determinations relating to the solution B, do not differ more than 5% compared with corresponding point of the response curve defined in 5.1.3. If the difference is more than 5% then the solutions defined in 5.1. and 5.2. are not accepted and the operation is repeated from the beginning.
5.3. Preperation of the “addition” curve
The curve must pass through at least seven pairs of points and must be calculated from these points using the least squares technique. The results found by dividing the standard deviation of the concentrations calculated by the differences between the measured responses, y and the corresponding concentrations calculated from the regression line over the average response value, s/?, should not exceed 0.07.
5.3.1. Preparation of sample
The sample of foodstuff to be analyzed must be representative of the foodstuff presented for analysis. The foodstuff must, therefore, be mixed or reduced to small pieces anad mixed before the sample is taken.
5.3.2. Procedure
Seven phials, at least, shall be prepared in two series. Add to each phial a quantity, not less than 5 g, of sample obtained from the foodstuff to be analyzed. Ensure that an equal quantity is added to each phial. Phial is closed immediately. Preferably, distillated water, demineralized water or ordinary water with equivalent purity or if necessary an approprate solvent is added into each phial for each gram of sample 1 ml. It is not necessary to add distillated water or demineralized water for homogenated foodstuffs. Diluted standard vinyl chloride solution including internal standard solution is added into each phial. If considered useful, such that concentrations of vinyl chloride added to the phials equal to 0.005, 0.010, 0.020, 0.030, 0.040, 0.050 mg/kg. The total volume of DMA or internal standard solution including DMA in each phial should be equal. The ratio between the amounts of diluted standard vinyl chloride solutions and additional DMA amounts, the volumes of these solutions as µl and the amount of foodstuff in the phial as g should be as small as possible and equal in all phials but not much than 5. Phials should be closed and the procedure in 5.4. is applied.
5.4. Procedures applied in gas chromatography
5.4.1. Phials are agitated in order to prepare a sample solution or suspension as homogenated as possible without letting the liquid and the septum.
5.4.2. All sealed phials are hold in a water bath at 60±1°C for two hours in order to have the equilibrium. Agitate again, if necessary.
5.4.3. A sample is taken from the headspace of the phial. Hand skill should be experienced in case of manual sampling for repeatable samplings. Syringe must be pre-warmed to the temperature of the sample. The heights and areas of the peaks of vinyl chloride and if used internal standard must be measured.
5.4.4. A graphic is plotted indicating the ordinate values to be the areas or heights of vinyl chloride peaks or the ratios of the areas or heights of the vinyl chloride and internal standard solutions while the abscissa values to be the amounts of vinyl chloride added according to the amount of food sample in each phial. The intersection of the graphic and x-axis is found. This value will give the concentration of vinyl chloride in the analyzed sample of foodstuff.
5.4.5. The excess amount of DMA in the column is removed as soon as the DMA peaks are appeared on the chromatogram.
6. Results
The amount of vinyl chloride released from materials and articles into foodstuffs
to the analyzed foodstuff is given in mg/kg as the arithmetical average of two indication in accordance with the repeatability criteria in Article 8.
7. Confirmation of the Amount of Vinyl Chloride
If the amount of vinyl chloride passing from the materials and articles into the foodstuff, calculated in Article 6, exceeds the permissible value, each of two experimental values should be verified with one of three ways given below:
a) At least, one other column with stationary phase and different polarity can be used. This procedure should continue until a chromatogram is obtained with no evidence of overlap of the vinyl chloride and/or internal standard peaks with constituents of sample foodstuff.
b) Other detectors like micro – electrolytic conductivity detector can be used.
c) Mass spectrophotometry can be used. In this case, the presence of molecular ions, with parent masses (mass/ion) of 62 and 64 are found in the ratio of 3:1, is an indicator of the presence of vinyl chloride with a high probability. In case of doubt, total mass spectrum must be checked.
8. Repeatability
The difference between the results of two determinations carried out under the same conditions, by the same analyst, simultaneously or rapidly one after the other for the same sample, according to 5.4., must not exceed 0.003 mg of vinyl chloride per kg of foodstuff.