Quantitative Determination of Piperine. II. Direct Determination with Phosphoric Acid

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Abstract
SUMMARY: Piperine in 85% phosphoric acid forms an unstable yellow color which, when heated for 8 min at l00°C, becomes a stable bluish‐green with absorption maximum at 635 mμ. This reaction was exploited for the direct determination of the piperine content of pepper samples. Pepper, ground to pass a standard U. S. 80‐mesh sieve, was treated 30 min at room temperature (29 ± 1°C) with 85% phosphoric acid. The resulting yellow color was heated 8 min at l00°C, and cooled, and the absorbance was measured against a reagent blank at 635 mμ. Results were comparable to those obtained with the chromotropic acid and H2SO4–para‐dimethylaminobenzaldehyde methods. Beers' law was obeyed between the levels of 0.04–0.28 PM of piperine per ml of 85% H3SPO4. The method requires only simple, readily available chemicals and equipment, and is rapid and reproducible with a standard deviation of ± 1.01% of the total amount of piperine as 100%.