Biomedical subjects

Yuzhong Deng

Publications and source records attributed to Yuzhong Deng.

5 recordsLinked to original sources

PubMed2006

Automated Tecan programming for bioanalytical sample preparation with EZTecan.

This paper reports the first successful automated Tecan (Tecan US, Research Triangle Park, NC) programming for bioanalytical sample analysis with an in-house developed software, called EZTecan. Based on the sample run list in the Watson Laboratory Information Management System (InnaPhase Corp., Philadelphia, PA), EZTecan can generate a Tecan program for bioanalytical sample preparation, including sample transfer, sample dilution, extraction, and reconstitution. Many built-in functions for EZTecan ensure the flexibility, quality, and efficiency of the liquid handling. It takes about 90 min to prepare two 96-well plates from sample transfer to reconstitution. Analytical results shown good inter- and intra-assay accuracy and precision, which meet the +/-15% Good Laboratory Performance acceptance criteria. With EZTecan, bioanalysts can prepare samples without writing a single line of Tecan program.

Automation↗

PubMed2005

Tandem mass spectrometry with online high-flow reversed-phase extraction and normal-phase chromatography on silica columns with aqueous-organic mobile phase for quantitation of polar compounds in biological fluids.

In this work, high-flow online reversed-phase extraction was coupled with normal phase on silica columns with aqueous-organic mobile phase liquid chromatography/tandem mass spectrometry (LC/MS/MS) to quantify drug candidates in biological fluids. The orthogonal separation effect obtained from this configuration considerably reduced matrix effects and increased sensitivity for highly polar compounds as detected by selected reaction monitoring. This approach also significantly improved the robustness and limit of detection of the assays. An evaluation of this system was performed using a mixture of albuterol and bamethan in rat plasma. Assay validation demonstrated acceptable accuracy (< 8% difference) and precision (< 6% CV) for these model compounds. The system has been used for the quantitation of polar ionic compounds in biological fluids in support of drug discovery programs. This assay was used to analyze samples for a BMS proprietary compound (A) in a rat pharmacokinetic study and is shown as an example to demonstrate the precision, accuracy, and sufficient sensitivity of this system.

Albuterol↗

PubMed2004

Quantitation of drug metabolites in the absence of pure metabolite standards by high-performance liquid chromatography coupled with a chemiluminescence nitrogen detector and mass spectrometer.

Quantitative information on drug metabolites with pharmacological or toxicological activities is of great interest during the drug discovery and development process. Because the analyte response with mass spectrometry can change significantly due to small variations in chemical structure, pure standards are required to construct standard curves for quantitation. However, for most programs at the discovery stage, pure metabolite standards are not available. In this work, an evaluation was conducted using a chemiluminescent nitrogen detector (CLND) as a calibrator to obtain the response factor ratio on a mass spectrometer generated from a metabolite and its parent compound in biological fluids. Using the response factor ratio obtained from the CLND, the metabolite could be quantified with the liquid chromatography/tandem mass spectrometry (LC/MS/MS) response obtained from the parent drug's standard curve. For this evaluation, oxazepam and temazepam were chosen as a 'drug/metabolite' pair. Temazepam was treated as the methylated metabolite of oxazepam. A spiked dog urine sample with a known concentration of oxazepam and unknown concentration of temazepam was injected onto the HPLC system and detected by both the CLND and MS/MS. Taking advantage of the equimolar response feature of the CLND, a response factor ratio between temazepam and oxazepam on the mass spectrometer was obtained by comparing the peak areas generated on the CLND and the mass spectrometer. From this ratio, temazepam was quantified using the oxazepam standard curve. The difference between the concentration of temazepam obtained from the reconstructed standard curve and the concentration obtained directly from a real temazepam standard curve was within 13% except the least concentrated standard (31%). This methodology has been successfully applied to measure quantities of the metabolite of a proprietary compound in a dog pharmacokinetic (PK) study.

Animals↗

PubMed2003

Fast analysis using monolithic columns coupled with high-flow on-line extraction and electrospray mass spectrometric detection for the direct and simultaneous quantitation of multiple components in plasma.

In this work, monolithic columns were used as a fast separation tool for multiple-component quantitative liquid chromatography-tandem mass spectrometry (LC-MS-MS) assays of drug candidates in biological fluids. A considerably reduced runtime was achieved while maintaining good chromatographic separations. This significantly improved separation speed demanded higher throughput on sample extraction. To this end, monolithic separations were coupled on-line with high-flow extraction, which allowed for the fast extraction and separation of samples containing multiple analytes. An evaluation of this system was performed using a mixture of fenfluramine, temazepam, oxazepam, and tamoxifen in plasma. A total cycle time of 1.2 min was achieved which included both sample extraction and subsequent monolithic column separation via column switching. A total of over 400 plasma samples were analyzed in less than 10 h. The sensitivity and responses were reproducible throughout the run. The system has been routinely used in the authors' laboratory for high-throughput quantitation of compounds in biological fluids in support of drug discovery programs. The assay for samples from a 9-in-1 dog pharmacokinetic study is shown as an example to demonstrate the capability of this system.

Animals↗

PubMed2002

High-speed gradient parallel liquid chromatography/tandem mass spectrometry with fully automated sample preparation for bioanalysis: 30 seconds per sample from plasma.

In this work, a high-throughput and high-performance bioanalytical system is described that is capable of extracting and analyzing 1152 plasma samples within 10 hours. A Zymark track robot system interfaced with a Tecan Genesis liquid handler was used for simultaneous solid-phase extraction of four 96-well plates in a fully automated fashion. The extracted plasma samples were injected onto four parallel monolithic columns for separation via a four-injector autosampler. The use of monolithic columns allowed for fast and well-resolved separations at a considerably higher flow rate without generating significant column backpressure. This resulted in a total chromatographic run cycle time of 2 min on each 4.6 x 100 mm column using gradient elution. The effluent from the four columns was directed to a triple quadrupole mass spectrometer equipped with an indexed four-probe electrospray ionization source (Micromass MUX interface). Hence, sample extraction, separation, and detection were all performed in a four-channel parallel format that resulted in an overall throughput of about 30 s per sample from plasma. The performance of this system was evaluated by extracting and by analyzing twelve 96-well plates (1152) of human plasma samples spiked with oxazepam at different concentrations. The relative standard deviation (RSD) of analyte sensitivity (slope of calibration curve) across the four channels and across the 12 plates was 5.2 and 6.8%, respectively. An average extraction recovery of 77.6% with a RSD of 7.7% and an average matrix effect of 0.95 with a RSD of 5.2% were achieved using these generic extraction and separation conditions. The good separation efficiency provided by this system allowed for rapid method development of an assay quantifying the drug candidate and its close structural analog metabolite. The method was cross-validated with a conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay.

Animals↗