Determination of ?-aminobutyric acid in fermented soybean products by HPLC coupled with pre-column derivatization

This study reports a pre-column derivatization HPLC stragety to determine the content of GABA in fermented soybean products. 9-Fluorenylmethyloxycarbonyl chloride (Fmoc-Cl) is employed as the derivative reagent with chromophore linked to GABA, which lacks of chromophore for UV/DAD analysis in its pristine structure. After the detection wavelength was confirmed, the derivatization and analysis conditions were also optimized, including pH and amount of boric acid buffer, amount of derivative reagent, the mobile phases and their gradient. Methodological investigation showed that the derivatized GABA (Fmoc-GABA) has good linearity in the range of 1-100 mu g/mL, low limit of quantification (LOQ, at 1 mu g/mL) and limit of detection (LOD, at 0.3 mu g/mL), and good recoveries of three spiked levels (between 83.8% and 100.8% with RSDs less than 5%). Furthermore, thirty-two commercial fermented soy products in four matrices (soy sauce, soy paste, bean curd, lobster sauce) were analyzed by the proposed method for validation. As a consequence, the concentrations of GABA in these soy products were in the range of 48.4-381 mg/kg.

Automated summary

This study developed a pre-column derivatization HPLC method to quantify the content of GABA in fermented soybean products. By using 9-Fluorenylmethyloxycarbonyl chloride (Fmoc-Cl) as the derivative reagent with chromophore linked to GABA, they were able to analyze GABA using UV/DAD. The method showed good linearity, low LOD and LOQ, and good recoveries for spiked samples.