In an effort to reduce the time required to get a new drug on the market, bioanalytical laboratories are continually investigating new strategies for improving sample preparation, chromatography, and mass spectrometric detection. In our laboratory, we have investigated several approaches to increasing the speed and efficiency of our quantitative LC-MS/MS analyses that are in compliance with Good Laboratory Practice (GLP) to support drug development studies. We have explored a parallel analysis approach using a four-channel multiplexed electrospray ion source on a triple quadrupole mass spectrometer to increase the throughput in GLP quantitative analysis. With this interface, the effluent from four HPLC columns is introduced into the mass spectrometer simultaneously.
We have also evaluated multi-stream serial LC-MS/MS to increase bioanalytical throughput. Serial LC-MS/MS can provide high throughput capability, particularly in cases where the useful runtime is a fraction of the total analysis time. When used in conjunction with high-speed chromatographic separation, serial LC-MS/MS provides not only higher throughput but also increased sensitivity afforded by narrower chromatographic peaks.
In addition, we are utilizing a quadrupole time-of-flight mass spectrometer in quantitative bioanalysis. A quadrupole time-of-flight mass spectrometer generates high-resolution and accurate product ion spectra, which are critical for trouble-shooting matrix or metabolite interference during assay development or routine sample analysis. The enhanced full scan sensitivity of a time-of-flight mass analyzer makes it attractive in drug development where sample amount or concentration is limited. Moreover, a quadrupole time-of-flight mass spectrometer could also provide an alternative to the triple quadrupole mass spectrometer MRM approach for quantitation of small molecular weight drugs and their metabolites in biological matrices with acceptable sensitivity and superior selectivity.
In this presentation, we describe (1) a four-channel parallel (MUX) analysis, (2) multi-stream serial LC analysis, and (3) the use of a quadrupole time-of-flight mass spectrometer for drug development quantitation. These techniques were evaluated using the same assay: a 96-well plate electrospray LC-MS/MS method for the quantitative determination of loratadine, a long-acting tricyclic antihistamine, and its metabolite, descarboethoxyloratadine. The results of these experiments as well as the advantages and disadvantages of each approach will be presented.
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