BS ISO 13276:2020 pdf download – Tobacco and tobacco products — Determination of nicotine purity — Gravimetric method using tungstosilicic acid 7 Procedure 7.1 Precipitation procedure A suitable amount of replicates should be measured. Weigh, to the nearest 0,000 1 g, approximately0,1 g of the nicotine alkaloid (or the equivalent amount of nicotine salt) (m) in each of,for example, five250 ml beakers (6.2) equipped with glass stirring rods (6.4). Add 100 ml of water to each beaker.Add 2 ml of 20 % hydrochloric acid solution (5.2) to each beakerand stir. Do not remove the stirring rod. Add slowly 15 ml of the tungstosilicic acid solution (5.1) while stirring constantly during the addition.Cover each beaker with a watch glass (6.3), leaving the stirring rod in place, and allow to standovernight.Before filtering, stir the precipitate to ensure that it settles quickly and is of a crystallineform.Check for complete precipitation with a few extra drops of the tungstosilicic acid solution. 7.2Filtration procedure 7.2.1 General Filtration can be performed by either of the procedures given in 7.2.2 or 7.2.3. 7.2.2Glass filter filtration procedure Dry each glass filter crucible(6.6.1) in the oven (6.6.4) at(120±5)°C to constant mass (±1 mg).Store inthe desiccator (6.5). Weigh, to the nearest 0,000 1 g, each glass crucible (6.6.1)(m ) and filter the precipitate directly intothe glass filter using the Buchner flask(6.6.2) and vacuum source (6.6.3).Ensure that the precipitateis removed from the sides of the beaker and the glass stirring rod by washing into the filter withhydrochloric acid solution (5.3) approximately three times using 15 ml each. Discard the washings. Rinse with a further aliquot portion of hydrochloric acid solution(5.3)(up to 400 ml may be required)which should be collected and tested with a few drops of nicotine solution (5.4) to ensure that noopalescence occurs, i.e.all tungstosilicic acid has been removed. Dry each glass crucible and precipitate in the oven (6.6.4) for 3 h at (120± 5) °C.Allow to cool in thedesiccator and weigh to the nearest 0,000 1g(mz).Place the filters back in the oven for 1 h,allow to cooland reweigh. Repeat, if necessary, until a constant mass (±1 mg) is obtained. 7.2.3 Filter paper filtration procedure Filter the precipitate directly onto an ashless filter paper (6.7.1).Ensure that the precipitate is removedfrom the sides of the beaker and the stirring rod by washing into the filter with hydrochloric acidsolution (5.3) approximately three times using 15 ml each. Discard the washings. Rinse with...
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