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Determination of chlorpyrifos and its metabolites in rat brain tissue using coupled‐column liquid chromatography/electrospray ionization tandem mass spectrometry
Author(s) -
Williamson Leah N.,
Terry Alvin V.,
Bartlett Michael G.
Publication year - 2006
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2647
Subject(s) - chemistry , chromatography , electrospray ionization , formic acid , selected reaction monitoring , liquid chromatography–mass spectrometry , tandem mass spectrometry , acetonitrile , detection limit , mass spectrometry , chlorpyrifos , protein precipitation , pesticide , agronomy , biology
Abstract A method has been developed to quantify chlorpyrifos ( O , O ‐diethyl‐ O ‐[3,5,6,‐trichloro‐2‐pyridyl] phosphorothionate) and its metabolites chlorpyrifos‐oxon ( O , O ‐diethyl‐ O ‐[3,5,6,trichloro‐2‐pyridinyl] phosphate) and TCP (3,5,6,‐trichloro‐2‐pyridinol) in rat brain tissue by coupled‐column liquid chromatography/electrospray ionization tandem mass spectrometry (LC/LC/ESI‐MS/MS). Rat brains were homogenized and treated by protein precipitation using ice‐cold acetonitrile. The supernatant was directly injected onto the coupled‐column system. Sample clean‐up was achieved on a Zorbax Extend‐C 18 column (2.1 × 50 mm, 5 µm) using a mobile phase of acetonitrile/water with 0.0025% formic acid (40:60, v/v). The compounds were separated isocratically on a Zorbax Eclipse XDB C 8 column (2.0 × 150 mm, 5 µm) using a mobile phase of acetonitrile/water with 0.0025% formic acid (75:25, v/v). Chlorpyrifos and chlorpyrifos‐oxon were detected in positive ion mode using multiple reaction monitoring (MRM). TCP was detected in negative ion mode using precursor‐to‐precursor transition monitoring. The method was validated and the specificity, linearity, limit of quantitation (LOQ), precision, accuracy, stability, and recoveries were determined. Calibration curves for all three analytes yielded correlation coefficients of 0.993 or greater. The LOQs were 25.3 ng/g for chlorpyrifos and 6.3 ng/g for chlorpyrifos‐oxon and TCP. All precision relative standard deviations (RSDs) were less than 16% for the LOQ and less than 11% for the other QC samples. This method was successfully applied to six rats that were injected subcutaneously with chlorpyrifos. Copyright © 2006 John Wiley & Sons, Ltd.