Abstract: The Effects of LC/MS Interfaces on the Analysis of SteroidsChen Minxiong(The National Institute for the Control of Pharmaceutical Products,Temple of Heaven,Beijing 100050,China)D.E.Games(University College,Cardiff,UK.)Received Abstract:A mixture of eight steroids was used as model sample to evaluate the performance of moving-belt and two thermospray(TSP) LC/MS interfaces(with auxiliary filament on and off modes).The results reveals:the moving-belt LC/MS interface provides the advantage in offering the EI spectrum but column effiency reduced owing to the fluctuation of the water content in the mobile phase.Thermospay source with filament off mode offerd high sensitivity,but one of the eight constituents was not detected,also when the operation reached high solvent content,the RIC trace became very noisy owing to the crystalization of the buffer ions at the outlet of the jet.TSP source with filament on mode gave the promissing result with high sensitivity,fully sample detectability,high seperation efficiency,and less contamination to the interface and ion source,with using SIM technique trace analysis could be achieved on the TSP(filament-on).Keywords:LC/MS,interface,steroids