前言：

　　Midazolam is a CNS depressant that is commonly used as a sedative prior to surgical or other medical procedures. It is a controlled substance which, when abused, can cause serious side effects including amnesia, respiratory depression or even death. The primary metabolite of midazolam, 1-hydroxymidazolam, is also a biologically active sedative with similar potency as the unaltered drug.1 It is known that in humans the 3A isozymes of cytochrome P450 are responsible for this oxidative biotransformation.2 In order to monitor plasma concentrations of midazolam and 1-hydroxymidazolam, either for patients treated with this sedative or for profiling cytochrome P450 drug-drug interactions, 3–6 a reliable, sensitive and selective LC-MS/MS method is required.

　　The Thermo Scientific TSQ Quantum line of triple quadrupole mass spectrometers offers the unique capability of highly-selective reaction monitoring (H-SRM). H-SRM is superior to selective reaction monitoring (SRM) given that H-SRM provides higher analyte selectivity by means of improved mass resolution of a precursor ion with Q1 while maintaining high transmission efficiency. The TSQ Quantum family achieves this increased selectivity on its mass-resolving quadrupoles by employing hyperbolicfaced rods as opposed to round rod used by all other commercially available quadrupole mass spectrometers. The practical advantage H-SRM provides is the ability to remove isobaric chemical noise thereby increasing the signal-to-noise (S/N), which translates to improved limits of quantitation (LOQs) and higher confidence in the quantitation results. Furthermore, data acquisitions using H-SRM can be executed by simply changing the Q1 peak width setting in the Instrument Setup in the Xcalibur™ data system.

　　This application report presents H-SRM data for the quantitation of midazolam and its primary metabolite in protein precipitated plasma. With the selectivity of H-SRM, sample cleanup not was required (e.g., solid phase extraction) and a short LC method was sufficient to accurately quantitate these pharmaceuticals at the level of 10 pg/mL on the Thermo Scientific TSQ Quantum Ultra.

仪器：

Thermo Scientific TSQ Quantum mass spectrometer

结论：

　　The H-SRM assay of midazolam and its primary metabolite 1-hydroxymidazolam both yielded 10 pg/mL (100 fg) LOQs from protein precipitated plasma on the TSQ Quantum Ultra. The selectivity of H-SRM yielded a 2.5-fold improvement in the LOQ for 1-hydroxymidazolam over unit-resolution SRM. Time consuming sample cleanup or long chromatographic run times were not necessary due to increased selectivity of H-SRM. Furthermore, H-SRM on the TSQ Quantum Ultra increases the confidence in the quantitation results by reducing the possibility of false positives, even for low selectivity SRM transitions (e.g., loss of H2O), without sacrificing sensitivity.