Sample-multiplexing by derivatization using multiple analogous reagents for enhancing throughput in LC/ESI-MS/MS assay of steroids: Plasma 17α-hydroxyprogesterone as an example

The measurements of steroids in biological fluids are of importance for the diagnosis and treatment of many diseases. Liquid chromatography/electrospray ionization-tandem mass spectrometry (LC/ESI-MS/MS) has a high specificity and accuracy for the steroid analysis, whereas it has a lower analysis throughput, which could become a big issue in clinical practice. One of the promising solutions to this issue is the multiplexing of samples in the same injection. In this study, the utility of the sample-multiplexing by the derivatization using multiple analogous reagents was evaluated for enhancing the throughput of the LC/ESI-MS/MS assays of steroids. The plasma 17 alpha-hydroxyprogesterone (17OHP), which is a diagnostic marker for the 21-hydroxylase deficiency, was chosen as the model analyte. The four plasma samples (20 mu L each) were separately derivatized with one of four different analogous Girard-type reagents, combined, then injected together into the LC/ESI-MS/MS. By this method, four plasma samples could be analyzed within a single LC run. The developed method could significantly reduce the total LC run time (about 2/5 for 32 samples, compared with the conventional method) with a satisfactory sensitivity (lower limit of quantification 0.5 ng/mL), precision (infra- and inter-assay RSDs <= 4.0% and <= 3.5%, respectively) and accuracy (97.6-106.7%), and negligible matrix effect. The developed method had a satisfactory applicability for the quantification of 17OHP in the cord plasma samples.