Dissolve 0.2 g completely, without heating, in 15 ml of a 70 per cent m/m solution of sulphuric acid R. Pour the solution with stirring into 100 ml of iced water R and dilute to 250 ml with iced water R. In a test-tube, mix thoroughly while cooling in iced water 1 ml of the solution with 8 ml of sulphuric acid R, added dropwise. Heat in a water-bath for exactly 3 min and immediately cool in iced water. While the mixture is cold, carefully add 0.6 ml of ninhydrin solution R2 and mix well. Allow to stand at 25 �C. A pink colour is produced immediately and becomes violet within 100 min.
Toelichting.
Alle hydroxy propylcelluloses gaan (na hydrolyse) een condensatiereactie aan met het ninhydrine. Propyleenglycol, polycondensatieproducten van propyleenglycol (met zichzelf, of andere stoffen) evenals polymeren van propylenoxide zullen deze reactie storen.
2 juli 1999