Biomedical subjects

Kate Yu

Publications and source records attributed to Kate Yu.

3 recordsLinked to original sources

PubMed2006

High-throughput quantification for a drug mixture in rat plasma-a comparison of Ultra Performance liquid chromatography/tandem mass spectrometry with high-performance liquid chromatography/tandem mass spectrometry.

A quantitative Ultra Performance liquid chromatography/tandem mass spectrometry (UPL/MS/MS) protocol was developed for a five-compound mixture in rat plasma. A similar high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) quantification protocol was developed for comparison purposes. Among the five test compounds, three preferred positive electrospray ionization (ESI) and two preferred negative ESI. As a result, both UPLC/MS/MS and HPLC/MS/MS analyses were performed by having the mass spectrometer collecting ESI multiple reaction monitoring (MRM) data in both positive and negative ion modes during a single injection. Peak widths for most standards were 4.8 s for the HPLC analysis and 2.4 s for the UPLC analysis. There were 17 to 20 data points obtained for each of the LC peaks. Compared with the HPLC/MS/MS method, the UPLC/MS/MS method offered 3-fold decrease in retention time, up to 10-fold increase in detected peak height, with 2-fold decrease in peak width. Limits of quantification (LOQs) for both HPLC and UPLC methods were evaluated. For UPLC/MS/MS analysis, a linear range up to four orders of magnitude was obtained with r2 values ranging from 0.991 to 0.998. The LOQs for the five analytes ranged from 0.08 to 9.85 ng/mL. Three levels of quality control (QC) samples were analyzed. For the UPLC/MS/MS protocol, the percent relative standard deviation (RSD%) for low QC (2 ng/mL) ranged from 3.42 to 8.67% (N = 18). The carryover of the UPLC/MS/MS protocol was negligible and the robustness of the UPLC/MS/MS system was evaluated with up to 963 QC injections.

Animals↗

PubMed2005

A liquid chromatography/tandem mass spectrometry method for the simultaneous quantification of isoniazid and ethambutol in human plasma.

Isoniazid and ethambutol are commonly used in various combination treatments for tuberculosis, and for this reason a rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed and validated for simultaneous quantification of these two drugs in human plasma. After a simple protein precipitation using methanol, the analytes and the internal standard metformin were chromatographed on a C18 column and detected by MS/MS. An atmospheric pressure chemical ionization interface was chosen to reduce ion suppression from sample matrix components and provide high sensitivity. The LC retention times for isoniazid and ethambutol were 2.46 and 2.27 min, respectively. The method was linear in the concentration range of 10.0-5000 ng/mL for each analyte using 100 microL plasma. The intra- and inter-day precisions, expressed as the relative standard deviation (RSD), were less than 5.7 and 6.4%, determined from QC samples for isoniazid and ethambutol, and the accuracies were within +/-2.1% and +/-4.5% in terms of relative error, respectively. The method was successfully employed in a pharmacokinetic study after oral administration of a multicomponent formulation containing 150 mg isoniazid, 500 mg ethambutol, 150 mg rifampicin and 250 mg pyrazinamide.

Administration, Oral↗

PubMed2003

A fully automated LC/MS method development and quantification protocol targeting 52 carbamates, thiocarbamates, and phenylureas.

We have developed a fully automated LC/MS method development and quantification protocol targeting 52 carbamtes, thiocarbamates, and phenylureas. This is a simple LC/MS method with direct injection; no post-column derivatization was required. The method utilized the Waters Alliance HT Chromatography System and the Waters ZQ 2000 mass spectrometer. System control and data processing was by MassLynx 4.0 with QuanLynx Application Manager. Analyte separation was accomplished by Waters Symmetry reversed-phase C8 column. An ammonium acetate water/acetonitrile binary gradient was used for the separation. The MS multichannel ability minimized the LC method development time with less demand on chromatographic peak resolution. Quantification results were obtained for 46 analytes out of the 52 targets. The coefficients of determination ranged from 0.886 to 0.999. The automated LC/MS protocol has sufficient sensitivity to accommodate the current EPA requirements. The limits of detection (3 times the S/N) ranged from 0.091 to 19.3 ng/mL with 50-microL injection. The highly selective MS detector enabled the matrix effect to be minimized. This method was applied to local drinking water and wastewater samples. Each matrix was spiked with the 52 target analytes at 2 and 20 ng/mL. The recoveries were within the EPA acceptance range.

Journal Article↗