Capillary electrophoresis-laser induced fluorescence detection of GABA and its analogs in human serum with solid-phase extraction and fluorescein-based probes

Three fluorescein-based probes, fluorescein isothiocyanate (FITC), 5-(4,6-dichlorotriazinylamino) fluorescein (DTAF) and 6-oxy-(N-succinimidylacetate)-9-(2'-methoxycarbonyl) fluorescein (SAMF), were adopted for the analysis of gabapentin (GBP), baclofen (BAL) and gamma-aminobutyric acid (GABA) by CE-LIF. The derivatization, separation, and analytical characteristics of three methods using the above-mentioned reagents were all carefully studied and compared. The optimal derivatization yield of SAMF was achieved in borate buffer (pH 8.0) for 15 min at 20 degrees C. It was demonstrated that the derivatization with SAMF is faster and simple. For SAMF, a solid-phase extraction (SPE) procedure was further developed and a SPE-CE-LIF method was resultantly established to analyze GABA and its analogs. Under optimum conditions, the analytes were baseline separated and the LODs ranged from 2 x 10(-11) mol L-1 to 3 x 10(-11) mol L-1 in the SPE-CE-LIF method, which were about 20 times lower than those in the CE-LIF method with SAMF as the derivatizing reagent. The newly established SPE-CE-LIF method was used for the determination of GABA and its analogs spiked into human serum.