Abstract
Propionic acid was separated by steam distillation from samples acidified with phosphoric acid and collected into alkaline solution.
An aliquot of the distillate containing from 2.5mg to 10mg of propionic acid was evaporated to dryness. The acid was then liberated through acation exchange resin, Dowex 50 X8-H type, column (1cm×3cm).
One to two microliters of the eluate containing Propionic acid and trans-crotonic acid as an internal standard was injected directly into the gas-chromatographic column (φ-4mm×3m) with Chromosorb 101. The lower determination limit was 0.002ppm.
Recovery of propionic acid added at 1250, 2500 and 5000ppm levels to bread and sponge cake were 96.3-100.6%.
