1、BRITISH STANDARD BS 5202-11: 1983 ISO 6466:1983 Methods for Chemical analysis of tobacco and tobacco products Part 11: Determination of dithiocarbamate residues ISO title: Tobacco and tobacco products Determination of dithiocarbamate pesticides residues Molecular absorption spectrometric method UDC
2、633.71+663.97:543:547.496.2BS5202-11:1983 This British Standard, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority of the BoardofBSI and comes into effect on 30November1983 BSI 10-1999 The following BSI references relate to the w
3、ork on this standard: Committee reference FAC/11 Draft for comment 82/51628 DC ISBN 0 580 13524 1 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Food and Agriculture Standards Committee (FAC/-) to Technical Committee FAC/11upon which th
4、e following bodies were represented: Department of Trade and Industry (Laboratory of the Government Chemist) Tobacco Advisory Council Amendments issued since publication Amd. No. Date of issue CommentsBS5202-11:1983 BSI 10-1999 i Contents Page Committees responsible Inside front cover National forew
5、ord ii 1 Scope and field of application 1 2 References 1 3 Definition 1 4 Principle 1 5 Reagents 1 6 Apparatus 1 7 Sampling 1 8 Procedure 1 9 Expression of results 2 10 Test report 3 Figure Distillation apparatus 4 Publications referred to Inside back coverBS5202-11:1983 ii BSI 10-1999 National fore
6、word This Part of BS5202has been prepared under the direction of the Food and Agriculture Standards Committee. It is identical with ISO6466:1983 “Tobacco and tobacco products Determination of dithiocarbamate pesticides residues Molecular absorption spectrometric method” published by the Internationa
7、l Organization for Standardization (ISO). Terminology and conventions. The text of the International Standard has been approved as suitable for publication as a British Standard without deviation. Some terminology and certain conventions are not identical with those used in British Standards; attent
8、ion is drawn especially to the following. The comma has been used throughout as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Where the words “International Standard” appear, referring to this standard, they should be read as
9、 “British Standard”. The Technical Committee has reviewed the provisions of ISO6488, to which reference is made in the text and for which there is no corresponding British Standard, and has decided that they are acceptable for use in conjunction with this standard. With reference to 9.3, the informa
10、tion in ISO1750regarding the common and systematic names and structures of the three pesticides may be found in a related standard, BS1831 “Recommended common names for pesticides”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards
11、are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard ISO 4874:1981 BS 6245Sampling tobacco and tobacco products Part 1:1982Method of sampling
12、 batches of raw material (general principles) (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. T
13、his will be indicated in the amendment table on the inside front cover.BS5202-11:1983 BSI 10-1999 1 1 Scope and field of application This International Standard specifies a molecular absorption spectrometric method for the determination of residues from pesticides of the dithiocarbamate type on toba
14、cco and tobacco products. The method is applicable to the determination, on tobacco and tobacco products, of residues from the dithiocarbamate pesticides commonly used on tobacco crops. 2 References ISO 1750, Pesticides and other agrochemicals Common names. ISO 4874, Tobacco Sampling of batches of r
15、aw material General principles. ISO 6488, Tobacco Determination of water content (Reference method). 3 Definition dithiocarbamate pesticides residues content the amount of carbon disulphide, in milligrams per kilogram of sample, determined according to the method specified NOTEIf required and if the
16、 identity of the dithiocarbamate pesticide present in the sample is known, the dithiocarbamate pesticides residues content may be expressed additionally as the dithiocarbamate by using the appropriate factor (see 9.3). 4 Principle Decomposition of the dithiocarbamates in a test portion by heating wi
17、th hydrochloric acid in the presence of tin(II) chloride. Distillation of the carbon disulphide formed and absorption in a methanolic solution of potassium hydroxide after removal of interfering substances by passing through sulphuric acid. Spectrometric determination of the potassium-O-methyl dithi
18、ocarbonate formed. 5 Reagents All reagents shall be of analytical reagent grade. Distilled water, or water of at least equivalent purity, shall be used. 5.1 Sulphuric acid, of concentration 96to 98% (m/m). 5.2 Potassium hydroxide, approximately 1mol/l solution in 95% (V/V) methanol. If there is any
19、sediment, filter the solution, using fluted filter paper, before it is used. 5.3 Tin(II) chloride (solid SnCl 2 ). 5.4 Hydrochloric acid, aqueous solution. Add 75ml of hydrochloric acid of concentration37to38% (m/m) to 150ml of distilled water. 5.5 Sodium diethyldithiocarbamate, standard solution co
20、rresponding to 10mg of carbon disulphide per litre. Dissolve29,6mg of sodium diethyldithiocarbamate trihydrate in1000ml of water. Prepare the solution on the day of use. 1ml of this standard solution is equivalent to10 4g of carbon disulphide. 6 Apparatus Ordinary laboratory apparatus and 6.1 Distil
21、lation apparatus (see the Figure), comprising 6.1.1 Round bottom flask with three necks (A), of capacity250ml. 6.1.2 Condenser (B). 6.1.3 Reservoir (C). 6.1.4 Inlet tube, through which nitrogen is introduced into the flask (D). 6.1.5 Gas wash bottles (E and F), fitted with sintered glass (pore size
22、index160to250 4m) distribution tubes for absorption of the distillation products. NOTEInstead of the gas wash bottles shown in the Figure, other absorption devices may be used, provided that they have been shown to be equally efficient. 6.2 Source of nitrogen, fitted with a three-way stopcock. 6.3 S
23、pectrometer, capable of measurement in the ultraviolet region at272, 302and332nm, equipped with10mm silica cells. 7 Sampling Carry out sampling in accordance with the procedure specified in ISO4874. 8 Procedure 8.1 Preparation of the test sample If possible, use a test sample that is in the form of
24、cut tobacco or cigarette filler, without further preparation. If a test sample in one of these forms is not available, cut the test sample into pieces of a suitable size. NOTEGrinding and drying of tobacco lead to loss of dithiocarbamates. 8.2 Test portions 8.2.1 Weigh, to the nearest10mg, duplicate
25、 test portions, each of approximately5g, from the test sample. Carry out on each test portion the procedure specified in 8.3 and 8.4.BS5202-11:1983 2 BSI 10-1999 8.2.2 Proceeding as specified in 8.2.1, take another test portion and use this to determine the water content of the test sample in accord
26、ance with ISO6488, if the result is to be calculated on the basis of water-free tobacco. 8.3 Distillation 8.3.1 Transfer one of the test portions (8.2.1) to the flask (A) of the distillation apparatus (6.1) and add2g of the tin(II) chloride (5.3), followed by50ml of water. Shake the flask until all
27、of the tobacco has been impregnated. Immediately this has been done, connect the flask to the condenser (B), which is connected to a gas wash bottle (E) containing20ml of the sulphuric acid (5.1) and then to a gas wash bottle (F) containing25ml of the potassium hydroxide solution (5.2). Put the rese
28、rvoir (C) and inlet tube (D) in position. Make sure that there are no leaks. Adjust the nitrogen supply to a flow rate of50ml/min, then connect this nitrogen flow to the apparatus via the three-way stopcock and inlet tube(D). Heat the flask to between30and40 C and allow to remain as described for at
29、 least10min to ensure that all of the tobacco is well impregnated with tin(II) chloride and that any oxygen has been purged from the apparatus. The condenser (B) shall be well cooled to prevent water passing into the sulphuric acid in the first gas wash bottle (E). Place100ml of the hydrochloric aci
30、d solution (5.4) into the reservoir (C). To prevent any suck back, turn the three-way stopcock so that the nitrogen supply is connected to the reservoir as well as passing into the flask through the inlet tube, then slowly add the hydrochloric acid solution in the reservoir to the flask. When all th
31、e hydrochloric acid solution has been added to the flask, turn the three-way stopcock so that the nitrogen flow of50ml/min passes totally through the inlet tube. Heat the contents of the flask to boiling point and boil gently for30min. 8.3.2 At the end of the30min period, stop heating, disconnect th
32、e gas wash bottles, and turn off the nitrogen supply. Transfer the contents of the second gas wash bottle (F) containing potassium hydroxide solution to a50ml one-mark volumetric flask. Wash the inside of the gas wash bottle and the distribution tube with water, adding the washings to the contents o
33、f the flask. Dilute to the mark with water, mix and allow to stand for15min. 8.4 Spectrometric measurement Fill a10mm silica cell with the test solution obtained as specified in 8.3.2. Measure the absorbance of the test solution using the spectrometer (6.3) at wavelengths of272,302and332nm, using as
34、 the reference solution a mixture of25ml of the potassium hydroxide solution (5.2) diluted to50ml with water. The measured absorbance at302nm shall not be greater than0,800, nor less than0,100. If the absorbance is greater than0,800, a further dilution or a smaller amount of tobacco shall be used. I
35、f the absorbance is less than0,100, a silica cell of longer optical path length shall be used. Calculate the corrected absorbance, A corr , of the test solution from the formula where A 272 , A 302and A 332are, respectively, the absorbances of the test solution at272,302and332nm. Repeat the determin
36、ation on the duplicate test portion. 8.5 Calibration graph Take, in turn, aliquot portions of4,6,8,10,12 and16ml of the standard sodium diethyldithiocarbamate solution (5.5), corresponding to quantities between40and160 4g of carbon disulphide, and treat as specified in 8.3, substituting the aliquot
37、portion of the standard solution for the test portion. Measure the absorbance of the standard test solutions thus prepared, as specified in 8.4. Prepare a calibration graph of corrected absorbance values against the appropriate mass of carbon disulphide. The calibration graph has been found to be ve
38、ry reproducible and a full graph need not be prepared each day. A single point check is normally sufficient. 9 Expression of results 9.1 Method of calculation and formulae 9.1.1 Read from the calibration graph the amount of carbon disulphide present in the sample test solution. 9.1.2 The content of
39、carbon disulphide, expressed in milligrams per kilogram of tobacco, is given by the formula where m is the mass, in micrograms, of carbon disulphide present in the sample test solution as read from the calibration graph; m ois the mass, in grams, of tobacco taken as the test portion. A corr A 302 A
40、272 A 332 + 2 - = CS 2 m m o - =BS5202-11:1983 BSI 10-1999 3 If the result is to be expressed on a water-free basis, use the formula where H is the water content of the sample, expressed as a percentage by mass, determined in accordance with ISO6488. A correction shall be made for any further diluti
41、on (see 8.4). Take as the result the mean of the two values, provided that the requirement for repeatability (9.2) is satisfied. 9.2 Repeatability The difference between the results of duplicate determinations, carried out at the same time or rapidly one after another, by the same analyst, shall not
42、 exceed7,5% of their mean value. 9.3 Conversion factors If required, the results expressed in terms of carbon disulphide may also be expressed in terms of any particular dithiocarbamate pesticide by multiplying by the appropriate factor. The following factors have been established: NOTEThese three c
43、ommon names are included in ISO1750, together with the systematic names and structures. 10 Test report The test report shall show the method used and the results obtained. It shall also mention any operating conditions not specified in this International Standard, or regarded as optional, as well as
44、 any circumstances that may have influenced the result. The test report shall include all details required for the complete identification of the sample. CS 2 m m o - 100 100H - = a) maneb: 1,74 b) zineb: 1,81 c) propineb: 1,90BS5202-11:1983 4 BSI 10-1999 * To assist in washing the apparatus, joints
45、 may be fitted at points X and Y, provided that they are completely leak-proof and free of grease. Figure Distillation apparatusBS5202-11:1983 BSI 10-1999 Publications referred to See national foreword.BS 5202-11: 1983 ISO6466:1983 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitut
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