Difference spectrophotometric estimation of santonin

Santonin gives a characteristic alkaline vs acidic difference spectrum. This was used for its estimation in pharmaceuticals and in the crude drug. Santonin was first extracted and purified through a specific partition procedure; then the difference absorbance was measured either at the maximum, 285 nm, or the minimum, 242 nm. The percentage of santonin can be calculated either by reference to the difference absorbance of a reference santonin sample, treated similarly, or by making use of the determined absorptivity. Measurement at the maximum is advisable, especially when the crude drug is assayed, because natural contaminants may interfere with the difference absorbance at the minimum.