Simultaneous Determination of Potassium Sorbate and Sodium Benzoate in Doogh Using High Performance Liquid Chromatography

In this research, high performance liquid chromatography (HPLC) as a simple and rapid technique was used for the determination of potassium sorbate and sodium benzoate in different brands of Doogh (typical Iranian drink based on fermented milk). The chromatographic separation was achieved with a C18 column (250 mm×4 I.D, 5 µm) and one buffered mobile phase, acetate buffer (0.2 mol/L, pH4.4): acetonitrile (63:37) at a flow rate of 1 mL/min. The effluent was monitored at 235nm, respectively. The main affecting factors, such as Carrez solution amount, pH and centrifuge speed were optimized. Limits of detection (LODs) were 1.823 for sorbic acid and 1.985 for benzoic acid. Relative standard deviations (RSDs) for quintuplicate analyses were 4.4 for sorbic acid and 4.087 for benzoic acid. The method also showed good linearity in a range from 4 to 1000 mg/L with correlation coefficients (R2) of 0.990 for sorbic acid and 0.995 for benzoic acid. Recoveries for the two analytes were 80 for sorbic acid and 65 for benzoic acid. Comparing to the other techniques, the proposed method was significantly less time-consuming and had more acceptable accuracy, precision and interruption elimination in samples. The developed method was successfully used for the routine monitoring of benzoate and sorbate in Doogh.