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, approximately 0,1 g of the nicotine alkaloid (or the equivalent amount of nicotine salt) (m) in each of, for example, five 250 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 beaker and 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 stand overnight. Before filtering, stir the precipitate to ensure that it settles quickly and is of a crystalline form. Check for complete precipitation with a few extra drops of the tungstosilicic acid solution.
7.2 Filtration procedure
7.2.1 General Filtration can be performed by either of the procedures given in 7.2.2 or 7.2.3.
7.2.2 Glass 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 in the desiccator (6.5). Weigh, to the nearest 0,000 1 g, each glass crucible (6.6.1) (m 1 ) and filter the precipitate directly into the glass filter using the Buchner flask (6.6.2) and vacuum source (6.6.3). Ensure that the precipitate is removed from the sides of the beaker and the glass stirring rod by washing into the filter with hydrochloric 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 no opalescence 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 the desiccator and weigh to the nearest 0,000 1 g (m 2 ).
Place the filters back in the oven for 1 h, allow to cool and 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 removed from the sides of the beaker and the stirring rod by washing into the filter with hydrochloric 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 no opalescence occurs, i.e. all tungstosilicic acid has been removed. Dry each crucible (6.7.2) on the Bunsen burner (6.7.3) or in the furnace (6.7.4) at 600 °C until constant mass (±1 mg). Store in the desiccator (6.5).
Weigh, to the nearest 0,000 1 g, each crucible (6.7.2) (m 1 ). Transfer the filter paper with the precipitate to the crucible. Place the crucible on a silica triangle resting on a tripod, heat gently at first and then ignite with the Bunsen burner (6.7.3). The crucible contents have to be broken up very carefully to ensure complete removal of the carbon. The final residue should be greenish/yellow in colour. Allow to cool in the desiccator (6.5) and weigh to the nearest 0,000 1 g (m 2 ). Repeat the heating process until a constant mass (±1 mg) is obtained.
NOTE After ignition of the filter paper, it might be convenient to leave the crucible in the furnace (6.7.4) at above 600 °C overnight. This technique ensures that no further heating is required.
8 Expression of results
The nicotine purity or the nicotine salt purity, NP, expressed as a percentage by mass, is given by Formula (1):
where
m 1 is the mass, in milligrams, of the dried empty crucible;
m 2 is the mass, in milligrams, of the crucible with precipitate after drying (7.2.2) or ignition (7.2.3);
C is a factor depending on the filtration procedure:
~0,101 2 for the glass filter filtration procedure (7.2.2);
~0,114 1 for the filter paper filtration procedure (7.2.3);
m is the nicotine equivalent mass, in milligrams, of the sample.ISO 13276 pdf download.ISO 13276 pdf download
