Biomedical subjects

T D Parker

Publications and source records attributed to T D Parker.

10 recordsLinked to original sources

PubMed1998

Automated sample preparation for drugs in plasma using a solid-phase extraction workstation.

An automated solid-phase extraction workstation was used to develop, characterize and validate two separate HPLC methods for quantifying drugs in plasma. Method development was facilitated by workstation functions which allowed wash solvents of varying organic composition to be mixed and tested automatically. The precision estimates for the two methods were within 6.0 and 2.0% RSD across their respective calibration ranges. Accuracies for replicate determinations of quality controls were between -1.2 and +4.8 RE over ng ml-1 calibration ranges, respectively. Optimized recoveries were quantitative and were generally greater than 90% for the four analytes tested, and depended to a great extent, as expected, on the composition of the wash solvent. Sample throughput benchmarks for the two methods ranged from 3 to 10 min per sample, depending on the extent of air drying used. Because of parallel sample processing, 60 samples could be extracted in as little as 17 min.

Blood Chemical Analysis↗

PubMed1997

Tandem-in-time mass spectrometry as a quantitative bioanalytical tool.

Tandem-in-time mass spectrometry, as implemented on an ion-trap detector (ITD), is the process whereby precursor ions are created, stored in a radio frequency (rf) trapping field, and then sequentially fragmented to form product ions by application of additional rf waveforms. As with any form of tandem mass spectrometry (MS/MS), tandem-in-time MS is highly selective, by virtue of both mass discrimination and specific gas-phase chemistry. Beyond this, however, tandem-in-time MS offers ion throughput efficiency and cost advantages over either quadrupole or sector instruments. This paper will describe the use of capillary gas chromatography combined with tandem-in-time mass spectrometry to quantify a novel therapeutic agent extracted from human plasma. For an example compound, a quantitation limit of 25 pg/mL (S/N approximately 10, 15 fmol on-column) was attained out of plasma. The interday imprecision was < or = 12.2% over a dynamic range extending to 10 ng/mL. Due to favorable ionization conditions for the test analytes, electron ionization resulted in formation of M+ ions, with very little fragmentation, allowing for maximum assay sensitivity. Although method characterization and validation demonstrated adequate instrumental performance, some lack of ruggedness was encountered during routine application.

Cholinesterase Inhibitors↗

PubMed1996

Design and evaluation of an automated solid-phase extraction method development system for use with biological fluids.

An automated solid-phase extraction method development system, utilizing a Zymate XP robot and a custom-designed solid-phase extraction manifold, has been developed and validated. This system spikes blank liquid matrix, such as plasma, with solutions containing drug, internal standard, and up to three metabolites. Samples are then buffered or diluted with an appropriate reagent. After these samples and corresponding blanks have been prepared, solid-phase cartridges containing selected sorbents are automatically conditioned. Samples are robotically vortexed and transferred to the conditioned cartridges, and analytes are extracted. Validation of this robotic system demonstrated acceptable precision and accuracy for three types of liquid transfer, including metering pump ( < 6% RSD and RE for > or = 2.0 mL dispensation), syringe-based laboratory station ( < or = 2.9% RSD and 0.5% RE for volumes between 0.25 and 1.00 mL), and syringe hands ( < 3.5% RSD and RE for volumes between 0.10 and 1.00 mL). For two example compounds, the system provided data which effectively distinguished good solid-phase sorbents from marginal ones through precision, recovery, and chromatographic selectivity. Solid-phase extraction of these compounds from human plasma gave precision (2-10% RSD) and extraction efficiency (96 +/- 6%) comparable to results obtained from manual extractions (92 +/- 11%).

Body Fluids↗

PubMed1986