1、BRITISH STANDARD CONFIRMED NOVEMBER 1992 BS 684-2.36: 1983 ISO 6463:1982 Methods of analysis of Fats and fatty oils Part 2: Other methods Section 2.36 Determination of butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT) ISO title: Animal and vegetable fats and oils Determination of butylhydroxya
2、nisole (BHA) and butylhydroxytoluene (BHT) Gas-liquid chromatographic method IMPORTANT NOTE. It is essential that this Section be read in conjunction with the information in BS 684-0 “General Introduction” which is published separately. UDC 665.1.014:543.544.45:547.56BS684-2.36:1983 This British Sta
3、ndard, having been prepared under the directionof the Food and Agriculture Standards Committee,was published underthe authority of the BoardofBSI and comes into effect on 31 May 1983 BSI 09-1999 The following BSI references relate to the work on this standard: Committee reference FAC/18 Draft for co
4、mment 81/51283 DC ISBN 0 580 11943 2 National foreword This Section of BS 684 was prepared under the direction of the Food and Agriculture Standards Committee and is identical with ISO 6463:1982 “Animal and vegetable fats and oilsDetermination of butylhydroxyanisole (BHA) and butylhydroxytoluene (BH
5、T)Gas-liquid chromatographic method” published by the International 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 conventi
6、ons are not identical with those used in British Standards; attention is drawn especially to the following. The comma has been used as a decimal marker. In British Standards it is current practice to use a full point on the baseline as the decimal marker. Wherever the words “International Standard”
7、appear, referring to this standard, they should be read as “British Standard”. Additional information. With reference to the note to clause 1, the method is not now considered suitable for the determination of TBHQ. There is a proposal to amend the text of the International Standard. With regard to7
8、.2.2.2 it is sometimes useful to use an additional solution containing 20 4g of antioxidant per millilitre. With regard to 7.2.3 it is recommended that a graph is always plotted. If the graph is a straight line, the mean value of K can be calculated. A British Standard does not purport to include al
9、l the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and
10、 ii, pages 1 and 2, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Cross-reference International Standard Corresponding British Standard ISO 5
11、558:1982 BS 684 Methods of analysis of fats and fatty oils Section2.33:1983 Detection and identification of antioxidants (Identical) Amendments issued since publication Amd. No. Date of issue CommentsBS684-2.36:1983 BSI 09-1999 i Contents Page National foreword Inside front cover 1 Scope and field o
12、f application 1 2 Reference 1 3 Principle 1 4 Reagents 1 5 Apparatus 1 6 Detection 1 7 Procedure 1 8 Expression of results 2 9 Test report 2 Publication referred to Inside back coverii blankBS684-2.36:1983 BSI 09-1999 1 1 Scope and field of application This International Standard specifies a gas-liq
13、uid chromatographic method for the determination of butylhydroxyanisole (tert-butyl-4-methoxyphenol) (BHA) and butylhydroxytoluene (2,6-di-tert-butyl-4-methylphenol) (BHT), used as antioxidants, in animal and vegetable fats and oils. NOTEThe method also permits quantitative determination of tertiobu
14、tylhydroquinone (TBHQ). 2 Reference ISO 5558, Animal and vegetable fats and oils Detection and identification of antioxidants Thin-layer chromatographic method. 3 Principle Dissolution of the fat or oil in a suitable solvent, direct injection into a gas chromatograph, and use of the internal standar
15、d method of calibration. 4 Reagents 4.1 Carrier gas: an inert gas (such as nitrogen, helium or argon), carefully dried and containing less than 10 mg of oxygen per kilogram. 4.2 Auxiliary gases: hydrogen, minimum purity 99,9 %, free from organic compounds; air or oxygen, free from organic compounds.
16、 4.3 Dichloromethane or, failing this, carbon disulphide, containing no impurities which could interfere with the determination of BHA or BHT by gas chromatography. WARNING Dichloromethane and carbon disulphide are toxic. In addition, carbon disulphide is very volatile and explosive and particular c
17、are must be exercised in using it. 4.4 Methyl undecanoate, minimum purity 99 %. 4.5 Butylhydroxyanisole, minimum purity 98 %. 4.6 Butylhydroxytoluene, minimum purity 98 %. 5 Apparatus Usual laboratory equipment, and in particular: 5.1 Gas chromatograph, with a flame ionization detector and recorder,
18、 comprising: 5.1.1 Injection device, together with one of the following systems to retain the non-volatile fats and oils: a) a pre-column packed with siliconized glass wool or glass beads; b) a sleeve lined with siliconized glass wool placed in the injector (only in the case of a horizontal injector
19、). 5.1.2 Column, made of stainless steel or glass, permitting good separation of BHA and BHT, of length about 2 m and 2 to 4 mm in internal diameter, packed, for example, with 10 % methylpolysiloxanes 1) on acid-washed, silylated brick dust. 2) 5.2 Volumetric flasks, of capacities 10, 20 and 100 ml.
20、 5.3 Graduated pipettes, of capacities 1 and 2 ml. 5.4 Analytical balance 6 Detection See ISO 5558. 7 Procedure 7.1 Setting up the apparatus 7.1.1 Injection device Temperature: 250 C The sleeve or pre-column (5.1.1) shall be removed after each day of analysis and conditioned overnight at the test te
21、mperature. NOTEVerify the proper condition of the sleeve or pre-column by passing, from time to time, a fat or oil of known composition through the chromatograph. 7.1.2 Oven and column Temperature under isothermal conditions: 160 C Flow rate of carrier gas: optimum value to be established by the ope
22、rator. Before first use, condition the filled columns for 24 h at 220 C with the carrier gas flowing. 7.1.3 Detector Temperature: 250 C Flow rate of auxiliary gases: hydrogen: approximately 20 ml/min air or oxygen: according to the manufacturers instructions. 1) DC 200 of kinematic viscosity 1,25 m
23、2 /s (12 500 cSt) is suitable. 2) Gas/Chrom Q, of particle size 150 to 180 4m (80 to 100 mesh) is suitable.BS684-2.36:1983 2 BSI 09-1999 7.2 Calibration 7.2.1 Method Use the internal calibration method, in which a known quantity of a known compound, the peak corresponding to which does not interfere
24、 with other peaks, is added to the sample and the measurements of the peaks of the various constituents, corrected using their respective calibration coefficients, are compared with the measurement of the peak of the known compound. 7.2.2 Standard mixtures 7.2.2.1 Internal standard Use as the intern
25、al standard a 30 4g/ml methyl undecanoate solution, prepared as follows. Weigh, to the nearest 0,1 mg, 30 mg of the methyl undecanoate (4.4) into a 100 ml volumetric flask(5.2). Dilute to the mark with the solvent (4.3). Transfer 2 ml of this solution, by means of a pipette(5.3), to a 20 ml volumetr
26、ic flask (5.2) and dilute to the mark with the solvent. 7.2.2.2 Standard antioxidant solutions Weigh, to the nearest 0,1 mg, exactly 100 mg of antioxidant (BHA or BHT) (4.5 or 4.6) into a 100 ml volumetric flask (5.2). Dilute to the mark with the solvent (4.3). Transfer 1ml of this solution, by mean
27、s of a pipette (5.3), to a 10 ml volumetric flask(5.2) and dilute to the mark with the solvent. Into a series of five 10 ml volumetric flasks (5.2), introduce, by means of a pipette (5.3), 0,2 0,5 0,81 and 1,2 ml of the antioxidant solution. Add, by means of a pipette, to each flask, 2 ml of the int
28、ernal standard (7.2.2.1) and dilute to the mark with the solvent. These five solutions contain, respectively, 2, 5, 8, 10 and 12 4g of antioxidant per millilitre. NOTEVerify, by means of a blank test, that there is no interference with the methyl undecanoate. If there is, use methyl myristate as the
29、 internal standard. 7.2.3 Determination of the calibration coefficient and plotting the calibration graph Inject each solution (7.2.2.2) into the chromatograph and calculate the proportionality coefficient K from the formula If required, plot a graph having the ratios of the area of the peaks corres
30、ponding to the antioxidant to the area of the peak corresponding to the internal standard as ordinates and the concentrations of antioxidant in the solutions injected as abscissae. 7.3 Determination Weigh, to the nearest 1 mg, 1 g of the fat or oil and transfer it to a 10 ml volumetric flask (5.2).
31、Add 2 ml of the internal standard (7.2.2.1) and dilute to the mark with the solvent (4.3). Ensure that the volumetric flask is stoppered each time. Inject 1 to 74l of the mixture into the chromatograph. 8 Expression of results The BHA or BHT content, expressed in milligrams per kilogram (ppm) of pro
32、duct, is equal to 9 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 any circumstances that may have influenced the results. The test report
33、 shall include all the information necessary for the complete identification of the sample. where A ais the area of the peak corresponding to the antioxidant; A sis the area of the peak corresponding to the internal standard; m ais the mass, in grams, of antioxidant in the standard solution; K A a A
34、 s - = m s m a - m sis the mass, in grams, of internal standard added. where m is the mass, in grams, of the test portion (7.3); m sis the mass, in micrograms, of internal standard added (approximately 60 4g); A a is the area of the peak corresponding to the antioxidant; A sis the area of the peak c
35、orresponding to the internal standard; K is the proportionality coefficient for the antioxidant with respect tothe internal standard. m s A a mA s K -BS684-2.36:1983 BSI 09-1999 Publication referred to See national foreword.BS684-2.36: 1983 ISO6463:1982 BSI 389 Chiswick High Road London W4 4AL BSIBr
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