A modified method for the determination of aluminium-gel in vaccine

The conventional method of aluminium analysis, described in the Biological Preparation Standard for Animals, was found to give erroneous results in the case of vaccine containing aluminium-gel as an adjuvant. This is because of incomplete decomposition of the gel and unsettled reaction system for the determination. But these problems were settled definitely. Heating on a direct fire for 15 min, by which temperature of the content attained 115-120 degrees C at atmospheric pressure, allowed the gel to complete decomposition and the result came to close the theoretical value. And a constant result by the decomposition itself was obtained with 2 volumes of nitric acid against 1 volume indicated in the standard method. Quantitative reaction of the gel-decomposed solution did hold in range of about 0.75-2.0 micrograms aluminium per ml. Use of acetate buffer solution for dilution of the decomposed solution following by sampling in 2 volumes of the dilution into the reaction mixture made the variation to the least as compared with the water-dilution following by 1 volume sampling indicated in the standard method. By these modified conditions, we succeeded in reducing the relative error and the coefficient of variation to less than +/- 5% and +/- 2% respectively.