On-line electroextraction in capillary electrophoresis: Application on the determination of glutamic acid in soy sauces.

We present an on-line, single step coupling between liquid-liquid extraction and capillary electrophoresis with capacitively coupled contactless conductivity detection, which allows an efficient analysis of complex food matrices with high sodium content. The sodium depletion was demonstrated using an aqueous two-phase system. The aqueous two-phase system enables the electrically driven extraction of the target compounds. The sample was prepared in Dextran-rich phase (8% w/v 500 kDa Dextran, DEX). The background electrolyte (acetic acid 5.0 mol/L) contained 6% w/v of 6 kDa PEG. As proof of applicability, we employed the developed method for glutamic acid quantification on soy sauces. The peak area of glutamic acid presents no significant difference (α = 0.05), while the peak area of the sodium presented a reduction of 11.7 ± 0.2 and 19 ± 3% for premium and low-cost soy sauce samples analyzed. The glutamic acid concentration for premium soy sauce sample was 2.7 ± 0.8 and 4.8 ± 0.4 g/L, and for low-cost soy sauce sample, the concentration was 9.9 ± 0.9 g/L, which agreed with those obtained by other analytical techniques.