The aluminum content of biological products containing aluminum adjuvants: determination by atomic absorption spectrometry.

Aluminum compounds are used as adjuvants in certain types of vaccines, toxoids and allergenic extracts for human use. The most common Al compounds used in biological products to enhance the immune response are aluminum potassium sulphate (alum), aluminum hydroxide and aluminum phosphate. This study describes an atomic absorption spectrometric method for the determination of the Al content of Al adsorbed toxoid preparations and allergenic extracts at levels of less than 0.85 mg of Al per half millilitre human dose. Aliquots of the samples which contained Al suspensions were acid digested with nitric and sulphuric acid and analysed in the nitrous oxide-acetylene flame of an atomic absorption spectrometer. The 396.2 nm Al line was used for analysis. The Al content of the National Bureau of Standards (NBS) Standard Reference Material No. 1075a aluminum 2- ethylhexanoate was determined to within 1% of the NBS certificate value by this method. Atomic absorption results for the Al content of tetanus toxoids containing aluminum potassium sulphate and aluminum phosphate were compared with polarographic and inductively coupled argon plasma (ICP) emission spectrometry results. Reproducibility and recovery data for Al are tabulated for a variety of biological products containing aluminum phosphate, aluminum potassium sulphate and aluminum hydroxide adjuvants. In addition, ICP has been used to characterize the Al and P compositions of the precipitates and supernatant solutions which resulted from centrifuging toxoid suspensions that contained the three different Al adjuvants.