Simultaneous determination of vitamin B and magnesium using capillary electrophoresis coupled with contactless conductivity detection: Method development, validation, and application to pharmaceutical and nutraceutical samples.

Vitamins and minerals are usually incorporated in pharmaceutical and nutraceutical products, but a simple, rapid, and inexpensive analytical method for their simultaneous determination is still lacking. In this study, we developed a quantification method for pyridoxine (vitamin B) and magnesium (Mg) by using purpose-made capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-CD) instrument. Main analytical conditions include: fused silica capillary (total length 55 cm, effective length 40 cm, inner diameter 50 μm); background electrolyte consisted of 10 mM L-arginine/acetic acid (pH 5) with 20% acetonitrile; separation voltage + 20 kV; hydrodynamic injection (siphoning at 20 cm in 25 s). Detection limits of vitamin B and Mg were 1 and 0.1 mg/L, respectively. Good linearity (R > 0.999) was observed for vitamin B and Mg calibration curves over concentration ranges of 3-100 and 0.3-200 mg/L, respectively. The method was applied to analyze vitamin B and Mg in several pharmaceutical and nutraceutical samples. The analytical results obtained by our method were in good agreement with reference methods (i.e., HPLC for vitamin B and ICP-OES for Mg). High-efficient and low-cost CE-CD method can accordingly serve as a promising tool for concurrent analysis of inorganic and organic species in pharmaceutical and nutraceutical analysis.