Electrophoretic determination of carboxylic acids in blood serum with intracapillary concentration

Electrophoretic separation and on-line concentration of short-chain fatty acids (SCFAs) in human blood serum of the patients with the inflammatory bowel disease is described in the current investigation. SCFAs are end products of carbohydrate fermentation, which are indigestible in the intestine. The highest concentrations of SCFAs are in the proximal colon, where they are absorbed by the epithelial cells of the colon (colonocytes) and then enter the tissues and blood. The changes in their serum content can indicate the metabolism disorders and inflammatory bowel diseases. The low sensitivity of capillary electrophoresis requires application of on-line concentration in order to implement this method for the detection of low concentrations of SCFAs in biological fluids. Moreover, for the salt-matrix samples, an application of common concentration techniques based on the differences in conductivity of sample matrix and background electrolyte is limited. Therefore, the development of fast, efficient and highly sensitive approaches for the determination of SCFAs in blood serum is an important task. In the current work, the improvement of the sensitivity of SFCAs has been achieved by the application of a water plug, which was proposed to be injected directly before the sample in order to form a low conductivity area for the acceleration and concentration of the analytes. The proposed preconcentration and electrophoretic separation scheme provided decreased detection limits of SCFAs (~ 50 - 70 ng/mL) due to 30 times concentration of analytes as well as fast analytes’ determination (15 min).