Quantitative trace analysis of L-ascorbic acid in human body fluids by on-line combination of capillary isotachophoresis and zone electrophoresis.

On-line combination of capillary isotachophoresis and zone electrophoresis performed in two coupled capillaries (ITP-CZE) is used for the trace analysis of L-ascorbic acid in human serum, urine and stomach fluid. At the ITP stage, anionic sample components are separated into individual zones and macrocomponents are detected and driven out of the migration path. In the CZE stage, only a small segment of the sample zones containing L-ascorbic acid is analyzed. High sensitivity of this hyphenated method (limit of detection, 0.09-0.15 mg/L), low sample volume consumption (2 microL), and acceptable reproducibility of the results (relative standard deviation, 8%) in the concentration range 0.1-15 mg/L demonstrate that the method is applicable for the study of the relation between the content of L-ascorbic acid in body fluids and the state of health of a person, in which lower amounts of L-ascorbic acid than the normal levels (i.e., 5.1-15.1 mg/L in human serum and 12.5-26.8 mg/L in urine) are expected. Possible interferences of other components of the body fluids are excluded by good correlation of the results obtained by the ITP-CZE method and a routine colorimetric method.