BS 6392-2-1983 Testing of ethanol for industrial use - Method for determination of carbonyl compounds content present in small amounts (photometric method)《工业用乙醇试验 第2部分 少量的羰基化合物含量的.pdf

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1、BRITISH STANDARD BS6392-2: 1983 Incorporating Amendment No.1 Testing of ethanol for industrial use Part 2: Method for determination of carbonyl compounds content present in small amounts (photometric method) NOTEIt is recommended that this Part be read in conjunction with the information given in th

2、e“General introduction” published separately as BS6392-0. UDC 661.722:543.42.062:543.854.6BS6392-2:1983 This British Standard, having been prepared under the directionof the Chemicals Standards Committee, was published under the authority ofthe Board of BSI and comes into effect on 31August1983 BSI

3、10-1999 The Committees responsible for this British Standard are shown inPart 0 The following BSI references relate to the work on this standard: Committee reference CIC/4 Draft for comment80/51209 DC ISBN 0 580 13368 0 Foreword This Part of BS6392 is technically equivalent to ISO1388 “Ethanol for i

4、ndustrial use Methods of test Part3: Estimation of content of carbonyl compounds present in small amounts Photometric method”, published in1981 by the International Organization for Standardization (ISO). For ease of production, the text of ISO1388-3:1981, with the omission of theAnnex, has been use

5、d for this British Standard. Some terminology and certain conventions 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 a

6、s the decimal marker. This standard describes a method only and should not be used as a specification defining limits of purity. Reference to the standard should indicate that the method of test used is in accordance withBS6392-2. A British Standard does not purport to include all the necessary prov

7、isions 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, pagesi andii, pages1 and2, an i

8、nside 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. Amendments issued since publication Amd. No. Date of issue Comments 4938 March 1986 Indicated by a

9、 sideline in the marginBS6392-2:1983 BSI 10-1999 i Contents Page Foreword Inside front cover 1 Scope and field of application 1 2 Principle 1 3 Reagents 1 4 Apparatus 1 5 Procedure 1 6 Expression of results 2 Publication referred to Inside back coverii blankBS6392-2:1983 BSI 10-1999 1 1 Scope and fi

10、eld of application This Part of BS6392 describes a photometric method for estimation of the content of carbonyl compounds present in small amounts in ethanol for industrial use. The method is applicable to products having carbonyl compounds contents, expressed as acetaldehyde, between0,00025 and0,01

11、% (m/m). NOTE 1This method, which is used commercially, allows determination of only those carbonyl compounds which react under the specified conditions. NOTE 2The title of the publication referred to in this standard is given on inside back cover. 2 Principle Reaction in acid medium of the carbonyl

12、 compoundsin a test portion with2,4-dinitrophenylhydrazine. Formation of the corresponding2,4-dinitrophenylhydrazones, which, after making the solution alkaline, take on a red coloration. Photometric measurement of this red coloration at a wavelength of about445nm. 3 Reagents During the analysis, us

13、e only reagents of recognized analytical grade, and distilled water or water of equivalent purity. 3.1 Ethanol, free from carbonyl compounds, purified as follows. Boil under reflux500ml of ethanol with5g of2,4-dinitrophenylhydrazine and5drops of the hydrochloric acid solution(3.3), for2 to3h. Distil

14、 the ethanol slowly using a Widmer distillation column, about300mm long and about25mm in diameter, or any other suitable column. Reject the first50ml of distillate and collect the next400ml, rejecting the remainder. If the distillate is coloured, redistil it. NOTEIndustrial methylated spirits95% (V/

15、V) is not suitable for use in place of the ethanol used in the preparation of this reagent. 3.2 2,4-Dinitrophenylhydrazine, saturated solution in the ethanol(3.1) at ambient temperature. WARNING 2,4-Dinitrophenylhydrazine is harmful by inhalation, in contact with the skin or if swallowed, and carrie

16、s the risk of explosion by shock, friction, heat or other sources of ignition, particularly when dry. Avoid inhalation of dust. Avoid contact with skin and eyes. Take care in using the material, particularly if it is dry. 3.3 Hydrochloric acid, approximately1,18/ml, about36% (m/m) solution. 3.4 Pota

17、ssium hydroxide, 100g/l solution in a70% (V/V) solution of the ethanol(3.1). 3.5 Carbonyl compounds, standard solution corresponding to0,440g of carbonyl compounds, expressed as acetaldehyde, per litre. Weigh, to the nearest0,0001g,1,200g of acetophenone, and dissolve it in a little of the ethanol(3

18、.1). Transfer quantitatively to a100ml one-mark volumetric flask, dilute to the mark with ethanol of the same quality and mix. Take10,0ml of this solution, transfer it to a100ml one-mark volumetric flask, dilute to the mark with the ethanol(3.1) and mix. 1ml of this standard solution contains4404g o

19、f carbonyl compounds, expressed as acetaldehyde. 4 Apparatus Ordinary laboratory apparatus, and 4.1 Water bath, capable of being controlled at50 2 C. 4.2 Test tubes, fitted with ground glass stoppers. 4.3 Spectrophotometer, or 4.4 Photoelectric absorptiometer, fitted with filters giving maximum tran

20、smission at a wavelength of about445nm. 5 Procedure 5.1 Test portion Take1,0ml of the laboratory sample and place it in one of the test tubes(4.2). 5.2 Blank test Carry out a blank test at the same time as the determination, following the same procedure and using the same quantities of all the reage

21、nts used for the determination, but replacing the test portion by1,0ml of the ethanol(3.1).BS6392-2:1983 2 BSI 10-1999 5.3 Preparation of the calibration graph 5.3.1 Preparation of dilute standard solutions, with a view to preparation of standard colorimetric solutions Into a series of seven25ml one

22、-mark volumetric flasks, introduce the volumes of the standard carbonyl compounds solution(3.5) indicated in the following table and dilute to the mark with the ethanol(3.1). 5.3.2 Preparation of standard colorimetric solutions, for photometric measurements carried out in cells of optical path lengt

23、h1cm Into a series of seven of the test tubes(4.2), place1,0ml of each of the dilute standard solutions(5.3.1). 5.3.3 Colour development Add1,0ml of the2,4-dinitrophenylhydrazine solution(3.2) and one drop of the hydrochloric acid solution(3.3). Stopper the tubes and heat for30min on the water bath(

24、4.1), controlled at50 2 C. Allow to cool, add5,0ml of the potassium hydroxide solution(3.4), mix, and allow to stand for5min. 5.3.4 Photometric measurements Immediately carry out the photometric measurements on each of the standard colorimetric solutions, using either the spectrophotometer(4.3), set

25、 at a wavelength of about445nm, or the photoelectric absorptiometer(4.4) fitted with appropriate filters, after having first adjusted the instrument to zero absorbance against the ethanol(3.1). 5.3.5 Plotting the graph Deduct the absorbance of the compensation solution from those of the standard col

26、orimetric solutions(5.3.2). Plot a graph having, for example, the masses, in micrograms, of carbonyl compounds in1ml of each dilute standard solution(5.3.1) as abscissae, and the corresponding corrected values of absorbance as ordinates. 5.4 Determination 5.4.1 Colour development Treat the test port

27、ion(5.1) in the test tube, following the procedure specified in5.3.3. 5.4.2 Photometric measurements Immediately carry out the photometric measurements on the test solution and the blank test solution following the procedures specified in5.3.4, after having adjusted the instrument to zero absorbance

28、 against the ethanol(3.1). NOTEIf the absorbance exceeds the maximum of the calibration graph, repeat the determination (5.4) using as the test portion1,0ml of a test solution prepared by diluting1,0ml of the laboratory sample with an appropriate volume (not more than4,0ml) of the ethanol (3.1). 6 E

29、xpression of results By means of the calibration graph(5.3.5), determine the masses of carbonyl compounds corresponding to the values of the photometric measurements. The carbonyl compounds content, expressed as acetaldehyde (CH 3 CHO) as a percentage by mass, is given by the formula where m 0 is th

30、e mass, in micrograms, of carbonyl compounds found in the blank test solution; m 1 is the mass, in micrograms, of carbonyl compounds found in the test solution; is the density, in grams per millilitre, of the sample at20 C (seeBS4522); r D is the ratio of the volume of the diluted test solution (see

31、the note to5.4.2) to the volume of the aliquot portion taken for the determination (if the test portion was not diluted, r Dis equal to1); 1,0is the volume, in millilitres, of the test portion(5.1). Standard carbonyl compounds solution(3.5) Corresponding mass of carbonyl compounds, expressed as CH 3

32、 CHO Mass of carbonyl compounds in1ml of dilute standard solution ml 4g 4g 0 a 0,15 0,25 0,50 0,75 1,00 1,25 0 66,0 110,0 220,0 330,0 440,0 550,0 0 2,6 4,4 8,8 13,2 17,6 22,0 a Compensation solution.BS6392-2:1983 BSI 10-1999 Publication referred to BS4522, Method for the determination of density of

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