Determination of linezolid in human plasma by LC-MS-MS

Abstract

A rapid, sensitive and selective LC-atmospheric pressure-chemical ionization-MS-MS method for the determination of the new antimicrobial agent, linezolid, in human plasma using selected reaction monitoring (SRM) was developed. Linezolid and the internal standard were extracted from the biological samples by solid phase extraction (SPE) and analyzed on a reversed-phase Shim Pack CLC-CN, C18 column with the mobile phase of acetonitrile and 20 mM ammonium acetate solution (4 + 1 v/v). Detection was accomplished using an LCQ mass spectrometer (Finnigan), which was programmed in positive MS-MS mode to permit measurement of the fragment ions of linezolid and internal standard at m/z 296.2 and 223.2, respectively. The assay run-time was less than 3.5 min. Quantitative analysis was based on peak area ratio of linezolid to the internal standard. Calibration plots were established over the concentration range of 0.1-20 micrograms ml-1 of linezolid with the lowest detection limit of 0.05 microgram ml-1 using 10 microliters sample volume. The SPE technique quantitatively recovered linezolid and the internal standard from the plasma samples at a percentage range of 89.1-93.7%. Determination of control samples of linezolid in plasma validated the LC-MS-MS-SRM method. Intra-assay and inter-assay precision were in the range of 5.1-11.4% relative standard deviation, whereas the intra- and inter-accuracy were in the range of 97.5-114.0% of the nominal concentrations of linezolid added. The data confirmed that the plasma samples of linezolid were stable at room temperature and when stored at -20 degrees C for at least 10 d. The developed LC-MS-MS-SRM method is recommended for the determination of linezolid in human plasma.

Simple method for the assay of linezolid in Brain Heart Infusion broth by high‐performance liquid chromatography

“…There are several reports on the assay of linezolid in human plasma (Peng et al, 1999;Phillips et al, 2001), serum (Borner et al, 2001;Ehrlich et al, 2001;Tobin et al, 2001) and urine (Borner et al, 2001;Ehrlich et al, 2001). However, these methods have some limitations.…”

“…Furthermore, none of these methods employed an internal standard to prevent possible errors which may occur during sample pre-treatment and injections. The reported methods (Peng et al, 1999;Phillips et al, 2001) employing solid-phase extraction (SPE) had much longer sample pre-treatment duration due to the conditioning of SPE cartridges and evaporation of organic solvent, which make these methods time-consuming when assaying a large number of samples. In addition, the LC-MS assay (Phillips et al, 2001) did not improve the lowest limit of quantification (0.10 mg/L) obtained with the ultraviolet detection.…”

Use of liquid chromatography-tandem mass spectrometry for the analysis of pentoxifylline and lisofylline in plasma

“…As a result, analysis by mass spectrometry results in lower background noise, higher sensitivity and fewer drugmetabolite interferences compared with other analytical methods (Turpeinen and Stenman, 2003;Wallemacq et al, 2003;Ballesteros et al, 2003). Analysis by LC-MS-MS generally exhibits sensitivity in the range of 10 −6 -10 −12 g/mL plasma (Xia et al, 1999;Zhu et al, 2002;Phillips et al, 2001). The utility of LC-MS-MS has been demonstrated in the analysis of many classes of drugs including antibiotics (Ballesteros et al, 2003), antidepressants (Naidong and Eerkes, 2004), and hypoglycemics (Lin et al, 2004).…”

“Product Ion Monitoring” Assay for Prostate-Specific Antigen in Serum Using a Linear Ion-Trap

“…To our knowledge, this is the first study to use the LTQ for PIM assays and quantification on a 96-well microtiter plate. A limited number of studies have used the LCQ (an earlier version of LTQ) in SRM mode to determine the levels of certain drugs in plasma, [18][19][20][21] and some have attempted to examine the ability of a linear ion trap (LTQ) to quantitate peptides in serum in SRM mode. 11,16,17,22 PSA was chosen as the model protein since it can be obtained in a purified form, and an excellent immunoassay is available to validate the mass spectrometry data.…”