Quantitative capillary electrophoresis/ion spray tandem mass spectrometry determination of EDTA in human plasma and urine.

A quantitative method has been developed for the determination of EDTA in human plasma and urine. The samples are prepared with automated anion-exchange solid-phase extraction using 100 microL of human plasma. The extracts are analyzed by capillary electrophoresis/mass spectrometry using selected reaction monitoring in the negative ion mode. Large-volume injections (10% of the CE capillary volume) are used to improve the concentration level of detection via field-amplified sample injection. The first reported validation of a CE/MS/MS technique was carried out for this method. Using a 13C stable-label isotope for the internal standard, the lower level of detection and lower level of quantitation were determined to be 7.3 and 14.6 ng/mL EDTA in human plasma, respectively. The injection precision had a relative standard deviation (RSD) of 6.1%. The intra-assay precision was less than 15% RSD. The intra-assay accuracy was less than +/- 12% bias from the nominal concentration. The interassay precision was less than 18% RSD and the interassay accuracy was less than +/- 9% bias from the nominal concentration.