Online preconcentration of recombinant Arg-Gly-Asp-hirudin using dynamic pH junction for analysis in human urine samples by capillary electrophoresis-mass spectrometry

A sensitive and effort-saving method was established and validated for the quantitative determination of recombinant Arg-Gly-Asp-hirudin (rRGD-hirudin) in human urine samples. The assay was performed on a uncoated fused silica capillary of 70 cm × 50 μm I.D. and a positive voltage of 30 kV was applied. The sample was injected under pressure of 50 mbar for 300 s and the temperature of capillary was kept 25 °C. Sheath liquid consisting of 30% methanol and 70% of 0.1% formic acid aqueous solution flowing at 7 μL/min was supplied to the CE-electrospray interface. Utilizing the dynamic pH junction technique, a lower limit of quantitation of approximately 35 nM was achieved (concentration coefficiency was about 100-fold) without complex sample preprocessing procedure. CE-MS conditions and parameters were also optimized to obtain better performance. The method has been successfully applied in clinical research of rRGD-hirudin.