Method for determination of total cysteamine in human plasma by high performance capillary electrophoresis with acetonitrile stacking.

An analytical procedure enabling routine analysis of human plasma for total cysteamine (CASH) has been developed and validated. The method includes reduction of CASH disulfides to thiol with tri-n-butylphosphine, derivatization of the thiol with 2-chloro-1-methylquinolinium tetrafluoroborate, separation of CASH 2-S-quinolinium derivate from those of plasma endo- and exogenous thiol derivatives by capillary zone electrophoresis based on acetonitrile stacking and quantitation with the use of ultraviolet detection. A large volume of sample is injected to achieve analyte concentration directly on the capillary, according to the transient pseudo-isotachophoresis principle, before the separation step takes place. Method performance characteristics, for example recovery, calibration, precision, limit of detection and limit of quantitation are presented. The procedure was applied to analysis of plasma samples donated by apparently healthy volunteers spiked with known amounts of cystamine standard solution.