Capillary Ultrahigh Performance Liquid Chromatography with Elevated Temperature for Sub-One Minute Separations of Basal Serotonin in Submicroliter Brain Microdialysate Samples

Improving the time resolution in microdialysis coupled to high performance liquid chromatography (HPLC) re quires that the volume of the separation system be decreased A low-volume separation permits smaller microdialysate volumes to be injected without suffering a sensitivity loss from dilution Thus, unproved tune resolution can be achieved with offline analysis simply by decreasing the separations system volume For online (near real time) analysis, there is a further requirement. The separation speed must be at least is fast as the sampling time Here, the combined use of high column pressures and temperatures, sub 2-mu m stationary phase particles, capillary columns, and sensitive, low dead volume detection resulted in a retention time for the neurotransmitter serotonin of less than 1 mm in a 500 nL dialysate sample volume Two sensitive detectors, photoluminescence following electron transfer (PFET) and electrochemical, were used for the detection of subnano-molar concentrations of serotomn m brain,microdialysate samples The general principles developed are applicable to a wide range of separations with the additional advantages of increases in sample throughput and decreases in mobile phase usage