Validation of an electrospray ionization LC-MS/MS method for quantitative analysis of raltegravir, etravirine, and 9 other antiretroviral agents in human plasma samples.

BACKGROUND: Raltegravir is the first human immunodeficiency virus-1 (HIV-1) integrase inhibitor used in treatment-experienced patients who have evidence of viral replication and HIV-1 strains resistance to multiple antiretroviral regimens. Etravirine is a novel NNRTI, active against HIV-1 strains harboring multiple NNRTI mutations. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of raltegravir, etravirine, and 9 other antiretroviral agents (amprenavir, atazanavir, darunavir, efavirenz, indinavir, lopinavir, ritonavir, saquinavir, and tipranavir) in plasma at the concentrations associated with therapy. MATERIALS AND METHODS: The ritonavir analog, methyl indinavir, and lopinavir-d8 were used as internal standards, added to 100 microL of plasma sample prior to a protein precipitation using methanol. Chromatographic separation was achieved on a C18 HPLC column (Waters Sunfire 100 x 2.1 mm, 3.5 microm) with a mobile phase gradient at a flow rate of 0.3 mL/min. Five microL of sample were injected into the LC-MS/MS system (Waters Quattro Premier XE) to determine concentrations of raltegravir, etravirine, and other antiretroviral agents. RESULTS AND DISCUSSION: This method showed an excellent linearity for all calibration curves (r2 > 0.998). The lower limit of quantification was established at 5 ng/mL for raltegravir and 40 ng/mL for etravirine, with precision and accuracy within +/-20% and 80% to 120% for all analytes. Intraassay and interassay precision and inaccuracy ranged from -9.2% to 6.9% for raltegravir and from -14.3% to 12.3% for etravirine and were less than 15% for all other compounds. No matrix effect was observed for any of the antiretrovirals studied. CONCLUSION: A rapid, specific, and sensitive LC-MS/MS method for quantification of raltegravir, etravirine, and 9 other antiretrovirals in human plasma was developed and was successfully applied for routine therapeutic drug monitoring.

Decreased levels of tobacco-specific N-nitrosamines in moist snuff on the Swedish market.

Moist snuff, or snus, on the Swedish market in 2001 and 2002 was analyzed for tobacco-specific N-nitrosamines (TSNAs) using a recently developed LC-MS/MS method. All samples of moist snuff analyzed were found to contain detectable levels of N'-nitrosonornicotine (NNN), N'-nitrosoanatabine (NAT), N'-nitrosoanabasine (NAB), and 4-(N-methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). In the survey in 2001, all samples except for one were produced by Swedish Match (n = 14), which is the dominating manufacturer on the Swedish snuff market. In the survey in 2002, samples from both Swedish Match (n = 7) and seven smaller manufacturers (n = 20) were analyzed. Total TSNA levels of between 0.15 and 3.0 microg/g wet weight were found. In the survey in 2001 and 2002, the mean level of the total TSNA content in moist snuff was 1.1 microg/g (n = 14) and 1.0 microg/g (n = 27), respectively. The result of the survey shows that the level of TSNAs in moist snuff on the Swedish market has been greatly reduced since the middle of the 1980s. Clearly, efforts have been made by the manufacturers to reduce the level of TSNAs in snuff.

Analysis of tobacco-specific N-nitrosamines in snuff by ethyl acetate extraction and liquid chromatography-tandem mass spectrometry.

A rapid, selective and sensitive method for routine analysis of the four tobacco-specific N-nitrosamines, N'-nitrosonornicotine, N'-nitrosoanatabine, N'-nitrosoanabasine and 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone in snuff has been developed. The nitrosamines were isolated by ethyl acetate extraction and analysed by LC-MS-MS. Except for evaporation and filtration, no additional clean-up steps are needed in the proposed method. The detection limits for standard in solvent are between 0.0005 and 0.001 microg/ml (0.005 and 0.01 microg/g).