Appendix XV B. Aluminium in Adsorbed Vaccines

Homogenise the preparation to be examined and transfer a suitable quantity, presumed to contain 5 mg to 6 mg of aluminium, to a 50 mL combustion flask. Add 1 mL of sulfuric acid R, 0.1 mL of nitric acid R and some glass beads. Heat the solution until thick, white fumes are evolved. If there is charring at this stage add a few more drops of nitric acid R and continue boiling until the colour disappears. Allow to cool for a few minutes, carefully add 10 mL of water R and boil until a clear solution is obtained. Allow to cool, add 0.05 mL of methyl orange solution R and neutralise with strong sodium hydroxide solution R (6.5 mL to 7 mL). If a precipitate forms dissolve it by adding, dropwise, sufficient dilute sulfuric acid R. Transfer the solution to a 250 mL conical flask, rinsing the combustion flask with 25 mL of water R. Add 25.0 mL of 0.02 M sodium edetate, 10 mL of acetate buffer solution pH 4.4 R and a few glass beads and boil gently for 3 min. Add 0.1 mL of pyridylazonaphthol solution R and titrate the hot solution with 0.02 M copper sulfate until the colour changes to purplish-brown. Carry out a blank titration omitting the vaccine.

1 mL of 0.02 M sodium edetate is equivalent to 0.5396 mg of Al.