ISO 10362-2:2013 pdf free
ISO 10362-2:2013 pdf free.Cigarettes一Determination of water in smoke cond ensates
Add sufficient methanol (4.3) to the Karl Fischer titration vessel (5.1) to immerse the tips of the electrodes. Titrate any residual solution (see note) in the titration vessel to its end-point by addition of Karl Fischer reagent (KFR).
Using the 20 μl syringe (5.3), add 20 μl (Vw) of water to the titration vessel. To ensure that the syringe does not contain air bubbles, fill it to above the 20 μl mark, invert it and tap the air bubbles to the top. Then depress the plunger to the 20 μl mark and remove excess water quickly from the needle tip with a tissue.
As an alternative, fill the syringe with 20 μl of water and weigh the syringe. After dosage, weigh the syringe again and note the exact mass of water.
Transfer the volume (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 droplet 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 (V).Standardize the KFR every working 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 It is common practice with the direct-titration technique to carry out a titration“on top of” residual solution in the titration vessel, i.e. without removing the residual solution. when the volume in the vessel reaches a certain level, the liquid is run to waste, retaining just sufficient for the electrode tips to be immersed. In time, however, the methanol concentration in the 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 should be completely emptied to waste, rinsed, and recharged with methanol.ISO 10362-2 pdf download.
