Liquid-chromatography tandem mass spectrometry (LC-MS/MS) has been shown to be an effective approach in the clinical analysis of 25-OH-vitamin D in patient serum. Test volumes vary among laboratories and different levels of throughput are required for different settings. LC-MS/MS assays with multiple LC channels can be beneficial for labs with the demand of large sample volume (e.g., 300 or more samples) to control costs and fulfill a reasonable turnaround time. We hereby present an assay that employs 4 LC channels (4-plex), which are coupled to the TSQ Endura triple-quadrupole (QqQ) MS instrument, for a high-throughput solution. Briefly, the pre- and postelution segments of the LC gradient are diverted to waste via solenoid valve controls, reserving the data acquisition for only the elution segment per injection per channel at a time. The multiplexing affords a manifold increase in throughput and the optimization of the duty cycle, without compromise in assay performance and precision.
Keywords: 25-OH-vitamin D; LC-to-LC channel precision; Multiple-reaction-monitoring (MRM); atmospheric pressure chemical ionization (APCI); duty cycle; high-throughput LC-MS/MS; multiplex HPLC.
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