This article introduces capillary electrophoresis using capacitively coupled contactless conduction detector (CE-C4D) and several applications that were developed for food analysis in Vietnam. The target analyte groups include: oxalate, sweeteners (acesulfam potassium, aspartame, cyclamate, saccharine) and food preservation (citric, benzoic and sorbic acids). This study aims to develop simple, easy to operate analytical procedures that are suitable for quick analysis or screening in food analysis in field or at local laboratories. The obtained results were compared with those measured by conventional standards method (HPLC) and proved the high reliability of CE-C4D method.

A simple, rapid and specific method using high performance liquid chromatography with fluorescence detector (HPLC-FLD) was developed for quantification of glucosamine in supplements after derivatization with 9-fluorenylmethyl chloroformate (FMOC-Cl). The chromatographic separation was achieved on a C18 column (150 mm × 4.6 mm × 5 µm) using a gradient mobile phase containing acetonitrile and water at a flow rate of 1.0 mL/min. The FLD detector was operated at excitation and emission wavelengths of 265 and 315 nm, respectively. The analytical method was validated for specificity, linearity, accuracy, and precision. The detector response for glucosamine was linear over the selected concentration range from 6.7 to 135 ppm with a correlation coefficient of 0.9988. The repeatability (RSD, n = 6) and reproducibility (RSD, n = 4) were from 2.54 to 3.23 % and from 2.24 to 3.07 %, respectively. The recovery was between 98.0 and 101.5 %. In addition, we also joined the interlaboratory proficiency testing program (code: H21.11) organized by the National Institute of Food Control with good result (z-score value was - 0.89 < 2). The method was successfully applied for the analysis of glucosamine in 15 supplement samples.

The quantification of glucosamine in dietary supplements was investigated by using capillary with capacitively coupled contactless conductivity detection (CE-C4D). Optimal conditions included electrophoresis buffer solution 10 mM Tris/Ace; pH = 5,0; sample injection height 25 cm; sample injection time 30 s; separation voltage 20 kV. The limit of detection (LOD) and the limit of quantification (LOQ) of glucosamine were 8.00 ppm and 26.67 ppm, respectively. Calibration curve was constructed over the range from 20 to 1000 ppm giving a good linear correlation coefficient (R2 = 0.9993). The relative standard deviation (RSD) ranged from 1.28% to 2.33% (n = 3) and the recovery efficiency ranged from 95.2 to 102.3% which indicated good precision and trueness of our method. The method was applied to determine glucosamine in 4 dietary supplement samples randomly collected at the local markets. The CE-C4D results were compared with those obtained by reference HPLC-FLD method, showing good agreement between the two methods (relative error < 15%).