Quattro micro lc triple quadrupole mass spectrometry

Plasma samples of 200 μL were added with the internal standard solution (mexiletine, 5 μg/mL), 25 μL of 1 M sodium hydroxide aqueous solution and 2 mL methyl tert-butyl ether. TAM, NDTAM, 4-HTAM and END were resolved on an RP-Select B LiChroCART® C18 column using as a mobile phase a mixture of 10 mM ammonium formate and acetonitrile (1:1, v:v) added with 0.1% formic acid. TAM and its metabolites were quantified by Quattro Micro LC triple-quadrupole mass spectrometry (Waters, Milford, EUA) in the positive ion electrospray ionization mode as described previously with some modifications [22 (link)]. The method had no matrix effect and showed linearities for TAM and END in the range of 1–1250 ng/mL, for 4-HTAM of 0.4–500 ng/mL and for NDTAM of 2–2500 ng/mL of plasma. The coefficients of variation and the relative standard errors of the accuracy and precision studies were less than 15%.

Aliquots of 1 mL plasma supplemented with clobazam (2.5 ng) as an internal standard were extracted with toluene-isoamyl alcohol (100:0.1, v/v). The compounds were separated on a Purospher RP 18e column (MerckKGaA, Darmstadt, Germany) using acetonitrile:10 mmol/L ammonium acetate aqueous solution (1:1, v/v) as the mobile phase and quantified by Quattro Micro LC triple-quadrupole mass spectrometry (Waters, Milford, USA) in the positive ion electrospray ionization mode [25 (link)]. Calibration curves were constructed from 0.1 to 50 ng/mL plasma. The method showed coefficients of variation and relative standard errors less than 15%, respectively, in the studies of precision and accuracy.