Development and validation of a hydrophilic interaction liquid chromatography–tandem mass spectrometry method for determination of isoniazid in human plasma

An LC–MS/MS method for the determination of isoniazid in human plasma was developed and validated. Human plasma aliquots of 100 μL were used for analysis. The assay used nialamide as the internal standard. The calibration curve concentration range was 50–10,000 ng/mL. Sample preparation utilized protein precipitation, and the supernatant was directly injected onto silica column without reconstitution. The recovery was over 90% and matrix effect was negligible. The method is simple and fast, which is advantageous in respect to instability of isoniazid in human plasma and loss on reconstitution due to its low molecular weight.