Liquid chromatography: Is it essential for the determination of arginine and methylated arginines by tandem mass spectrometry?

A liquid chromatography–tandem mass spectrometry assay for simultaneous determination of the plasma concentration of 11 antiretroviral agents (nevirapine, indinavir, atazanavir, amprenavir, saquinavir, ritonavir, lopinavir, efavirenz, tipranavir, darunavir and maraviroc) has been developed. Sample pre-treatment is limited to protein precipitation with a mixture of methanol and zinc sulfate. After centrifugation the supernatant is injected in the chromatographic system, which consists of on-line solid phase extraction followed by separation on a phenyl–hexyl column. This method, with its simple sample preparation provides sensitive, accurate and precise quantification of the plasma concentration of antiretroviral drugs and can be used for therapeutic drug monitoring in patients infected with HIV.