Determination of tranexamic acid in essential cosmetics by pre-column derivatization capillary electrophoresis coupled with electrogenerated chemiluminescence detection

N-Methylation of tranexamic acid yields an unique derivative, which generates strong co-luminescence signals in the presence of an electrochemiluminescence reagent such as Ru(bpy)32+. Using this principle, we established a highly selective analytical method based on pre-column derivatization capillary electrophoresis coupled with electrogenerated chemiluminescence detection for determining the tranexamic acid content in essential cosmetics. The addition of a ternary ionic association gel, Mg2+-trehalose-SiO32-, in the components of background electrolyte greatly improved the electrophoretic separation efficiency. Under the optimized assay conditions, two electrophoretic peaks attributed to the derivatives of tranexamic acid and its internal standard (sarcosine) were completely separated in 500 s, and their electrophoretic peak intensities ratio showed a good linear relationship with the initial concentration of tranexamic acid in the range of 10-750 μmol/L (correlation coefficient r2=0.9993). The limit of detection was estimated to be 3.6 μmol/L (S/N=3). Moreover, the internal standard method was further applied to the quantitative determination of tranexamic acid content in three kinds of toothpaste and two kinds of nutrient solutions in facial masks. The results showed that the average tranexamic acid content in three toothpaste samples was 4.05, 0.24, and 6.06 mg/g, while that in two facial masks was 51.3 and 7.98 mg/mL. The recoveries for the above-mentioned samples were within the range 92.5% to 104.0%, implying satisfactory results.