BS 684-2 8-1977 Methods of analysis of fats and fatty oils - Other methods - Determination of total neutral oil《脂肪和油脂的分析方法 其他方法 中性油总量的测定》.pdf

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1、BRITISH STANDARD CONFIRMED APRIL 1993 BS684-2.8: 1977 Methods of analysis of Fats and fatty oils Part2: Other methods Section2.8: Determination of total neutral oil IMPORTANT NOTE. It is essential that this Section be read in conjunction with the information in the “General introduction” to BS684, w

2、hich is published separately. UDC665.1.014:543.543.851.2BS684-2.8:1977 This British Standard, having been prepared under the directionof the Oils and FatsStandardsCommittee, waspublished under the authorityof the Executive Boardon 29April1977 BSI12-1999 The following BSI references relate to the wor

3、k on this standard: Committee reference OFC/24 Draft for comment74/54405 DC ISBN 0 580 09730 7 A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does

4、not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, pages1 to5 and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the

5、amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS684-2.8:1977 BSI 12-1999 i Contents Page 0 Scope 1 1 Method1. Extraction method 1 1.1 Field of application 1 1.2 References 1 1.3 Definition 1 1.4 Principle 1 1.5 Reagents 1 1.6 Apparatus

6、1 1.7 Sampling and preparation of sampling for analysis 1 1.8 Procedure 1 1.9 Expression of result 2 1.10 Test report 2 2 Method2. Chromatographic method 2 2.1 Field of application 2 2.2 References 2 2.3 Definition 2 2.4 Principle 2 2.5 Reagents 2 2.6 Apparatus 2 2.7 Sampling and preparation of the

7、sample for analysis 3 2.8 Procedure 3 2.9 Expression of result 4 2.10 Precision data 4 2.11 Test report 5 Figure 1 Diagram of apparatus used in chromatographic method 3ii blankBS684-2.8:1977 BSI 12-1999 1 0 Scope This Section describes two methods for the determination of total neutral oil. The meth

8、od described in clause 1 is technically identical with the older method described in BS684:1958 and is generally applicable to natural fats. The procedure described in clause 2 is an alternative method that is known to have been applied satisfactorily to cottonseed, soya bean, peanut, linseed and co

9、conut oils. 1 Method1. Extraction method 1.1 Field of application The method described is applicable generally to natural fats. 1.2 References The following standards publications are referred to in this method: BS2021, Separating and dropping funnels. BS2734, Boiling flasks (narrow-necked), conical

10、, flat bottom and round bottom. BS3591, Industrial methylated spirits. 1.3 Definition For the purposes of this Section the following definition applies. total neutral oil part of a natural fat, consisting essentially of triglycerides and including the unsaponifiable matter, as determined by the meth

11、od described and expressed as a percentage (m/m) 1.4 Principle After addition of ethanol to the fat, neutralization with ethanolic potassium hydroxide, dilution with water and extraction of the total neutral oil into light petroleum, the solvent is evaporated and the total neutral oil weighed. 1.5 R

12、eagents The following reagents are required (seealsoBS684: General introduction): 1.5.1 Ethanol 1) , 95% (v/v). 1.5.2 Acetone 1.5.3 Light petroleum, boiling range between40 C and60 C, with a bromine value of less than1, free from non-volatile residue. 1.5.4 Potassium hydroxide, N reagent solution, i

13、n ethanol. 1.5.5 Potassium hydroxide, 0.5N aqueous reagent solution. 1.5.6 Phenolphthalein indicator solution, 10g/l, in95% (v/v) ethanol. 1.6 Apparatus The following items of apparatus are required (seealso BS684: General introduction): 1.6.1 Separating funnels, 250ml, complying with the requiremen

14、ts of BS2021. 1.6.2 Flask, 250ml, complying with the requirements of BS2734. 1.7 Sampling and preparation of sampling for analysis See BS684: General introduction. 1.8 Procedure 1.8.1 Test portion. Weigh, to the nearest10mg, a small vessel containing20g to30g of the fat. Pour about5g of the fat into

15、 a separating funnel(1.6.1). Weigh the vessel and remaining contents to obtain, by difference, the mass of the test portion transferred to the separating funnel. 1.8.2 Neutralization. Add to the test portion in the separating funnel50ml of the ethanol(1.5.1) and a few drops of the phenolphthalein in

16、dicator solution(1.5.6). Add the ethanolic potassium hydroxide solution(1.5.4), while shaking, until the mixture is exactly neutral to phenolphthalein. Add a further1ml of the ethanolic potassium hydroxide solution, followed by sufficient water to reduce the ethanol concentration in the separating f

17、unnel to50% (v/v). 1.8.3 Extraction. Add50ml of the light petroleum(1.5.3) and shake the separating funnel well for1min. Allow the funnel to stand and, after the contents have completely separated, run the soap layer into a second separating funnel. Repeat the extraction with two successive50ml port

18、ions of the light petroleum and combine in one separating funnel the three extracts together with a few millilitres of light petroleum used to wash through the funnels used for the extractions. 1) Ethanol may be replaced for this purpose by industrial methylated spirits(66O.P.) complying with the re

19、quirements of BS3591. It should be noted that the use of industrial methylated spirits is governed by The Methylated Spirits Regulations1952 (S.I.1952, No.2230). It is not permissible to use duty-free ethanol received under the provisions of the Customs and Excise Act1952, SectionIII, for purposes f

20、or which industrial methylated spirits is an acceptable alternative to ethanol.BS684-2.8:1977 2 BSI 12-1999 1.8.4 Washing. Wash the combined light petroleum solutions twice with20ml of water, shaking vigorously and discarding the water washings. Then wash successively with20ml portions of the aqueou

21、s potassium hydroxide solution(1.5.5), water, the aqueous potassium hydroxide solution and at least twice with water. Continue washing with20ml volumes of water until the washings no longer turn pink on addition of the phenolphthalein indicator solution. 1.8.5 Solvent removal. Transfer the washed li

22、ght petroleum solutions to the tared flask(1.6.2). Evaporate or distil off the solvent to a low volume. Add2ml to3ml of the acetone(1.5.2) and completely remove the solvent from the flask by means of a gentle air current while the flask is held obliquely and almost entirely immersed in a boiling wat

23、er bath and is rotated. Dry the flask and residue in an oven at a temperature not exceeding80 C until a further period of drying does not result in a change of mass greater than2mg. 1.9 Expression of result Calculate the percentage (m/m) of total neutral oil(N) using the following formula: where M 0

24、is the initial mass of vessel and fat M 1is the mass of vessel and fat after the test portion has been withdrawn M 2is the mass of the tared flask(1.6.2) M 3is the final mass of the flask and residue 1.10 Test report See the instructions and recommendations given in BS684: General introduction. 2 Me

25、thod2. Chromatographic method 2.1 Field of application The method described is applicable to cottonseed, soya bean, peanut, linseed and coconut oils. Although there is no reason to doubt its applicability to almost all natural animal and vegetable fats, its wider applicability has yet to be proved.

26、The method is technically identical to method Ca9f57 of The American Oil Chemists Society (AOCS). 2.2 References The following standards publications are referred to in this method: BS2021, Separating and dropping funnels. BS2734, Boiling flasks (narrow-necked), conical, flat bottom and round bottom

27、. 2.3 Definition See 1.3. 2.4 Principle After removal of free fatty acids and of miscellaneous non-fat substances by passage of a solution of the fat through a column of activated aluminium oxide, the solvent is evaporated and the residue is dried and weighed. 2.5 Reagents The following reagents are

28、 required (seealsoBS684: General introduction). 2.5.1 n-Hexane 2.5.2 Aluminium oxide, activated. The aluminium oxide shall be gradeIV, measured on the Brockmann-Schodder scale, and the loss on ignition shall be111% (m/m) when determined by the following procedure. Weigh, to the nearest1mg, about1g o

29、f the aluminium oxide into a tared covered platinum or porcelain crucible. Heat the crucible at600 C for2h, cool and weigh. The aluminium oxide shall have a particle size distribution such that100% (m/m) passes through a test sieve of mesh aperture1004m and70% to90% (m/m) is retained on a test sieve

30、 of mesh aperture2004m. 2.5.3 Mixed solvent. Mix25ml of methanol with975ml of diethyl ether. 2.6 Apparatus The following items of apparatus are required (seealso BS684: General introduction). 2.6.1 Chromatographic column, glass, as shown in Figure 1(a). 2.6.2 Flask, 20ml, with siphon arrangement, as

31、 shown in Figure 1(b). 2.6.3 Weighing base, for the flask(2.6.2), as shown in Figure 1(c). 2.6.4 Extension tube, as shown in Figure 1(d), of a length such that during use of the assembled apparatus there is a gap of5mm to15mm between the top of the aluminium oxide column and the tip of the tube. N 1

32、00 M 3 M 2 () M 0 M 1 - =BS684-2.8:1977 BSI 12-1999 3 NOTEThe appropriate length of the extension tube depends on the particular chromatographic column(2.6.1) used. Tubes100mm long should be obtained and cut to suit the columnin use. 2.6.5 Solvent reservoir, 150ml, as shown in Figure 1(e). 2.6.6 Boi

33、ling flask, 250ml, conical, complying with the requirements of BS2734. 2.6.7 Separating funnel (optional),250ml, complying with the requirements of BS2021. 2.6.8 Wash bottle, polyethylene, with fine jet. 2.7 Sampling and preparation of the sample for analysis See BS684: General introduction. 2.8 Pro

34、cedure 2.8.1 Test portion. Weigh, to the nearest even number of milligrams,5g of the prepared sample into the flask(2.6.2) fitted with the weighing base(2.6.3). Figure 1 Diagram of apparatus used in chromatographic methodBS684-2.8:1977 4 BSI 12-1999 2.8.2 Aluminium oxide column. Fill the glass chrom

35、atographic column(2.6.1) to about two-thirds of its capacity with the mixed solvent(2.5.3). Transfer201g of aluminium oxide into the column using one of the following methods. a) In a small beaker form a slurry of the aluminium oxide with mixed solvent and pour the slurry into the column. b) Transfe

36、r the aluminium oxide with the aid of a small glass or polyethylene funnel into the separating funnel(2.6.7) containing about50ml of the mixed solvent. Dispense the slurry into the chromatographic column from the tap of the separating funnel. NOTEClogging of the sintered disc in the chromatographic

37、column is minimized by adding the slurry from a separating funnel because the fine aluminium oxide dust remains suspended in the separating funnel. Maintain a high solvent level in the chromatographic column by adjusting the flow of slurry and the flow of solvent from the base of the column. Wash do

38、wn the inside of the chromatographic column, including the ground glass joint, with mixed solvent. Tap the chromatographic column to pack and level the aluminium oxide. Drain the column until the solvent level is almost down to the top of the aluminium oxide column and then add the hexane(2.5.1) unt

39、il the level rises to about1cm from the bottom of the ground glass joint. 2.8.3 Chromatography. Place the tared boiling flask(2.6.6) under the delivery tube of the chromatographic column. To prevent splashing, position a glass rod in the boiling flask to intercept the flow from the column. Remove th

40、e flask(2.6.2) containing the test portion from the weighing base and attach the extension tube(2.6.4) to the inner joint of the flask, wetting the joint with hexane and using a slight twisting pressure to seal the joint. NOTETo ensure a good seal some graphite may be rubbed from a soft lead pencil

41、on to the joint which should then be twisted to spread the graphite evenly. Place the flask(2.6.2), with extension tube fitted, on top of the chromatographic column, wetting the joint with hexane. Wash down the inside of the neck and sides of the flask(2.6.2) with mixed solvent from the polyethylene

42、 wash bottle. Direct the jet from the wash bottle carefully into the centre of the test portion to dilute and mix the fat. Continue dilution with the mixed solvent until the level in the flask(2.6.2) is just above the siphon arm. Add125ml of the mixed solvent to the reservoir(2.6.5) and place the re

43、servoir on top of the flask(2.6.2), wetting the joint with mixed solvent. Partially open the reservoir and column stopcocks and adjust the column stopcock so that the flow into the boiling flask is4ml/min to6ml/min. The level of liquid in the flask(2.6.2) should remain a little above the siphon arm.

44、 Adjust the level accordingly, raising it, if necessary, by closing the column stopcock and opening further the reservoir stopcock (tap the reservoir to start the flow, if necessary). Allow the column to drain, then wash any traces of fat from the column delivery tube into the boiling flask. 2.8.4 S

45、olvent removal. Evaporate the solvent from the boiling flask on a steam or boiling water bath with the aid of a gentle stream(25litres/min) of clean dry air or nitrogen. Deliver the air or nitrogen from a jet of suitable size at a slight angle against the inside of the neck, approximately two-thirds

46、 down the length of the neck. Discontinue the gas flow before the last trace of solvent evaporates, transfer the boiling flask to an oven with fan circulation and dry the flask for1h at105 C. NOTEIn addition to quickening the evaporation, the gas flow prevents loss of total neutral oil through creep

47、age over the top of the neck. Excessive air flow would increase the oxidation rate and give falsely high values for total neutral oil content, but the specified flow rate does not lead to detectable oxidation under the conditions described. Cool the flask in a desiccator and weigh it. 2.9 Expression

48、 of result Calculate the percentage (m/m) of total neutral oil (N) using the following formula: where M 1 is the mass of test portion M 2 is the mass of the tared boiling flask(2.6.6) M 3 is the final mass of the boiling flask and residue. 2.10 Precision data 2.10.1 Repeatability. The results of two

49、 determinations on the same prepared sample, carried out by the same analyst simultaneously or in rapid succession, should not differ by more than0.15 when expressed as described in 2.9. N 100 M 3 M 2 () M 1 - =BS684-2.8:1977 BSI 12-1999 5 2.10.2 Reproducibility. The results of two determinations carried out by different laboratories on the same prepared sample should not differ by more than0.30 when expressed as described in 2.9. 2.11 Test report See the general instructions and r