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1、INTERNAT.IONAL STANDARD IS0 10362-2 First edition 1994-02-01 ANSII Internat Dot se Cigarettes - Determination of water in smoke condensates - Part 2: Karl Fischer method Cigarettes - Dosage de I eau dans /es condensats de fumbe - Partie 2: M this value decreases on storage; 1 Copyright International
2、 Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 03:28:27 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10362-2:1994(E) Q IS0 b) as two separate reagents (Karl Fischer so
3、lution A: methanol, pyridine, sulfur dioxide; Karl Fischer solution B: methanol, iodine) which, when mixed in equal volumes, give a reagent with a water equivalent of approximately 3 mg/ml. The latter reagent is strongly recommended since in the unmixed form it is quite stable, especially if stored
4、in a refrigerator. Its water equivalent is also more ap- propriate to this analysis. There is a limit, however, to the time the mixed reagent can be stored, even in a refrigerator, and regular replacements are necessary. 6 Procedure Care shall be taken during all operations to avoid contamination fr
5、om atmospheric moisture. All glassware used in the preparation of the test por- tion and in the water determination shall be heated at (105 k 5) “C for at least 1 h after visible water has evaporated, and cooled and stored in a desiccator over silica gel until used. 6.1 Test portion Reagents which d
6、o not contain pyridine are preferred if these are available. If these are not available, take special care during handling. See also CAUTION con- cerning waste disposal in 6.3.1. 4.3 Methanol, CH,OH, with a water content of less than 0,05 g per 100 g. The following procedure shall be used when ciga-
7、 rettes are smoked in accordance with IS0 4387. When non-standard smoking or collection of smoke condensate has been used, the procedure described below shall be modified accordingly to give a suitable smoke condensate solution. In this event, a note of the alternative procedure shall be included wi
8、th the test results. 4.4 Silica gel, freshly activated. Collect the cigarette smoke condensate in accordance with IS0 4387 on a routine analytical cigarette- 5 Apparatus smoking machine complying with the requirements of IS0 3308. Normal laboratory apparatus and in particular the fol- lowing items:
9、5.1 Karl Fischer apparatus, preferably of the auto- matic or semi-automatic type set up according to the manufacturer s instructions for direct titration. Wearing gloves, remove the sealing devices from the smoke trap, open it and remove the filter disc with forceps. Place the folded disc in a dry c
10、onical flask (maximum 150 ml for 44 mm discs; maximum 250 ml for 92 mm discs). two separate quarters of an unused conditioned filter disc and add these to the flask. Wipe the inner surface of the filter-holder front with 5.2 Solvent dispenser. A suitable container type is a 5 litre aspirator bottle
11、with a silica gel moisture trap in the neck and the bottom outlet connected to a 25 ml double-action automatic pipette or an electronically operated pipette. The silica gel has a drying effect on the sur- face of the solvent causing the water content to vary during use. To avoid this, stir the solve
12、nt continuously during use by mounting the dispenser on an auto- matic stirrer. 5.3 Syringe, of capacity 20 1. Run an appropriate quantity of extraction solvent (4.1) into the flask. The folded disc shall be covered with solvent. In the case of a 44 mm glass fibre filter trap, 25 ml is necessary. In
13、 the case of a 92 mm glass fibre filter trap, 50 ml is necessary. Stopper the flask immediately and shake gently on an electric flask shaker (5.6) for at least 20 min, ensuring that the disc does not disintegrate. This provides the smoke condensate solution. 6.2 Blank test 5.4 Syringe, of capacity 1
14、0 ml, fitted with a wide- bore needle, or pipette of capacity 10 ml. 5.5 Hot-air oven, capable of maintaining a tem- perature of (105 f 5) “C. 5.6 Flask shaker, horizontal-action type. Due to the absorption of water by smoke traps and solvent, determine a value for the sample blank. Pre- pare sample
15、 blanks by treating additional smoke traps iat least 2 per 100 cigarettes smoked) in the same manner as that used for smoke collection. Place them near the smoking machine during smoking, and ex- tract and analyse them together with the smoke samples. 2 Copyright International Organization for Stand
16、ardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 03:28:27 MDTNo reproduction or networking permitted without license from IHS -,-,- 0 IS0 IS0 10362-2:1994(E) 6.3 Standardization of Karl Fischer reagent 6.3.1 Standardization p
17、rocedure stoppered until such time as safe disposal can be arranged, preferably through a waste-disposal agency, or in compliance with other national regulations. Add sufficient methanol (4.3) to the Karl Fischer titration vessel (5.1) to immerse the tips of the elec- trodes. Titrate any residual so
18、lution (see note 31 in the titration vessel to its end-point by addition of Karl Fischer reagent (KFR). Using the 20 1 syringe (5.31, add 20 j.l (VW) of water to the titration vessel. To ensure that the syringe does not contain air bubbles, fill it to above the 20 PI mark, invert it and tap the air
19、bubbles to the top. Then de- press the plunger to the 20 1 mark and remove ex- cess water quickly from the needle tip with a tissue. As an alternative, fill the syringe with 20 pi of water and weigh the syringe. After dosage, weigh the syringe again and note the exact mass of water. Transfer the vol
20、ume (VW) of water to the titration vessel taking care to inject the water directly into the solution, not allowing any to fall on to the neck or walls of the vessel. Where the vessel can be fitted with a rubber membrane cap, this shall be used and the needle inserted through the cap. If a water drop
21、let remains on the needle tip, remove it by touching the surface of the solution in the vessel. Titrate with KFR (4.2) and record the titration value. Repeat the process and again record the titration value. Repeat a third time. Calculate the mean titration volume (VJ. Standardize the KFR every work
22、ing day. For best results with the Karl Fischer technique, it is important to ensure that all stages of the analysis are carried out in a uniform manner, extract-to-extract, sample-to-sample, day-to-day. NOTE 3 It is common practice with the direct-titration technique to carry out a titration “on to
23、p of” residual sol- ution in the titration vessel, i.e. without removing the re- sidual solution, When the volume in the vessel reaches a certain level, the liquid is run to waste, retaining just suf- ficient for the electrode tips to be immersed. In time, how- ever, the methanol concentration in th
24、e vessel falls to a level such that the reaction cannot proceed satisfactorily. A precipitate may form and false titration values be obtained. Only experience will tell when titrating “on top of” residual solution has reached this point and then the titration vessel must be completely emptied to was
25、te, rinsed, and re- charged with methanol. CAUTION - Waste from the titration vessel should be run into a container which is kept w _ cvS - vB)E vk 4-v, 6.3.2 Calculation of water equivalent The water equivalent, E, of the Karl Fischer reagent, expressed in milligrams of water per millilitre, is giv
26、en by the equation E=$ t where m is the mass, in milligrams, of the volume of water (VW) used for the standardization of the Karl Fischer reagent; V, is the mean volume, in millilitres, of the Karl Fischer reagent used for the titration of the water. 6.4 Determination Add to the titration vessel 10
27、ml of the propan-2-01 extract from the blank, preferably using a syringe with a wide-bore needle (5.4) to enable rapid transfer. Titrate with KFR and record the titration volume. Repeat and again record the titration volume. Deter- mine the mean titration volume for the blank, V,. Re- peat the dupli
28、cate determination for all sample blanks. Add 10 ml of the smoke condensate solution to the titration vessel. Use a minimum volume of solution to wash the syringe or pipette since the residue of the extract may be required for the determination of nicotine. Titrate with KFR and record the titration
29、vol- ume of the sample, Vs. Dependent on the use to be made of the remaining condensate solution, it may be possible to repeat this determination. However, when this method is used to determine the water content, the remaining sol- ution is frequently used to determine nicotine by steam distillation
30、. This does not allow sufficient sol- ution to duolicate the water determination. 7 Expression of results The water content, W, of the smoke condensate for each trap, expressed in milligrams per cigarette, is given by the equation 3 Copyright International Organization for Standardization Provided b
31、y IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 03:28:27 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10362-2:1994(E) Q IS is the mean volume, in millilitres, of the Karl Fischer reagent used for the blank titrat
32、ion; is the water equivalent, in milligrams of wa- ter per millilitre, of the Karl Fischer reagent; is the number of cigarettes smoked into the smoke trap; is the volume, in millilitres, of solvent used for dissolving-the smoke condensate; is the volume, in millilitres, of the smoke condensate.solut
33、ion for the titration. Express the test results as follows: a) water content, expressed in milligrams per ciga- rette smoked, to the nearest 0,Ol mg for each individual smoking run; b) mean water content, expressed in milligrams per cigarette smoked, to the nearest 0,l mg for the whole test sample.
34、8 Test report The test report shall give the water content from each cigarette smoked and the method used, and shall in- clude all conditions which may affect the result (e.g. atmospheric pressure during smoking). It shall also give all details necessary for the identification of the cigarettes smok
35、ed. Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 03:28:27 MDTNo reproduction or networking permitted without license from IHS -,-,- IS0 10362-2:1994(E) KS 65.160.00 Descriptor
36、s: tobacco, cigarettes, smoke, tests, physicochemical tests, determination of content, water, Karl Fischer method. Price based on 4 pages Copyright International Organization for Standardization Provided by IHS under license with ISO Licensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/27/2007 03:28:27 MDTNo reproduction or networking permitted without license from IHS -,-,-