Description and validation of a four-channel staggered LC-MS/MS system for high-throughput in vitro screens.
A parallel four-channel LC-MS/MS system for quantitative high-throughput in vitro screens is described. The system comprises four pumps, a four-valve autosampler equipped with a nine-port stream selector valve, and a triple quadrupole mass spectrometer. Staggered injections across the sample list are performed by four injector valves onto separate columns in such a manner that the chromatographic window of interest is always eluting from one of the columns into the mass spectrometer. To demonstrate the applicability of the system, three different compounds (verapamil, propanolol, dextromethorphan) were analyzed. The results showed that the sample throughput could be increased more than three times in comparison with a conventional single-column LC-MS/MS system. Validation results for the three compounds showed an accuracy of 85.0-108%, a precision (given as relative standard deviation) of 2.60-10.7%, and a carryover of less than 0.1%.