Abstract: Using a Kjeldahl distillation apparatus, a method for the simultaneous determination of sodium (or calcium) propionate and sodium diacetate in oyster sauce, soy sauce and fish sauce by high performance liquid chromatography (HPLC) was established. The sodium (or calcium) propionate and sodium diacetate in samples were converted to the corresponding acids by treatment with phosphoric acid. After that, both acids were collected by steam distillation using a Kjeldahl apparatus. The pH of the distillates was then adjusted to around 3.0 by adding phosphoric acid. Finally, the analysis was completed with HPLC. A good linear relationship was gained in the range from 0.005 to 1.000 mg/mL with a correlation coefficient of 0.999 9. Recoveries of sodium (or calcium) propionate and sodium diacetate were 88.5%–108.3%% and 86.5%–108.7% with relative standard deviations (RSDs) of 2.13%–6.42% and 2.02%–6.37% (n = 6), respectively. This method is simple, rapid, easy to operate, stable, reliable, and suitable for the determination of sodium (or calcium) propionate and sodium diacetate in oyster sauce, soy sauce, fish sauce and other liquid seasonings.

Key words: Kjeldahl distillation apparatus, sodium (or calcium) propionate, sodium diacetate, oyster sauce; high performance liquid chromatography (HPLC)