Determination of Benzoate Derivatives in Soy Sauce by Capillary Electrophoresis and In-Capillary Microextraction Procedure

JONG-JYH CHEN, YENU-CHUNG LEE, HUANG-CHANG LIN AND RICHIE L. C. CHEN*

Department of Bio-Industrial Mechatronics Engineering, National Taiwan University, 136 Chou-Shan Rd., Taipei City 106, Taiwan, R.O.C.

(Received: April 15, 2004; Accepted: June 14, 2004)

ABSTRACT

   Benzoate derivatives in soy sauce were analyzed by capillary zone electrophoresis (CZE) coupled with a microextraction technique. The analytes were acidified and extracted with ethyl acetate. The organic extract was directly injected (30 mbar × 1 sec) into a fused silica capillary (75 μm i.d. × 34 cm) and separated in 20 mM borax buffer (pH 9.2) with 10 kV working voltage.  Separation was completed in less than 10 min as monitored by A225. Hippuric acid was used as internal standard to improve the reproducibility for quantification (CV = 4.5%, n = 12).

Key words: p-hydroxybenzoate, ethyl acetate, capillary zone electrophoresis (CZE), hippuric acid, preservative