Biomedical subjects

M P Barbalas

Publications and source records attributed to M P Barbalas.

3 recordsLinked to original sources

PubMed1991

A computer program for the deconvolution of mass spectral peak abundance data from experiments using stable isotopes.

A computer program is described for deconvoluting the overlap which is often found in mass spectral peak abundance data from stable isotope experiments. Peak intensity data from calibration standards are corrected using parameters calculated from the analysis of separate external standard solutions of analytes and internal standard. If the calibration data are satisfactory, the same parameters and the slope and intercept values from the least squares analysis of the calibration data are used to correct and quantitate the mass spectral peak intensity data from the quality assurance and experimental samples. Reports and graphs appropriate to the process are produced. Applications are given for the analysis of plasma samples from stable isotope experiments with carprofen, cifenline, and midazolam.

Carbazoles↗

PubMed1988

Quantitative selected ion monitoring processing system: software and hardware for the automated collection and analysis of selected ion monitoring data acquired for use in pharmacokinetic studies.

The Quantitative Selected Ion Monitoring Processing System (QSIMPS) is a collection of software and hardware which was designed with the capacity to analyze 30,600 samples per year in support of pharmacokinetic studies. On a per sample basis, QSIMPS was designed to inject a sample into the GC, control the GC divert valve, collect selected ion monitoring data, identify the peaks for the drug and one metabolite and each compound's reference standard, fit the peaks to a relevant chromatographic model, calculate chromatographic features of merit, calculate the peak heights and ratio of the drug and its reference standard and the metabolite and its reference standard, and, using calibration data, convert the ratio to an amount of drug. On a per tray (batch) basis, QSIMPS was designed to fit all the peak height ratios from the calibration standards to either a linear equation, or a generalized nonlinear isotope dilution equation, report a statistical analysis of the fit, and, using aliquot factors, convert the measured amount of drug into concentrations. On a per project basis, QSIMPS prints reports summarizing statistical data on the calibration standards and the quality assurance samples, and prints reports presenting the concentration data as a function of, for examples, subject, drug treatment, time postdose, etc., along with other ancillary data such as subject sex, weight, species, etc. In addition, QSIMPS can fit the concentration data to a number of common pharmacokinetic model-derived equations, and report the resulting pharmacokinetic parameters along with a statistical comparison of the parameters.

Chromatography, Gas↗

PubMedDate not supplied

Applications to analytic chemistry: an evaluation of stable isotopes in mass spectral drug assays.

We evaluated stable isotope analogues (SIAs) as internal standards in mass spectral drug assays on the analytic parameters of accuracy, precision, specificity, and limit of quantitation. Only one literature report suggests that the use of an SIA made an assay more accurate, although theoretic considerations strongly support their use. There is substantial evidence, however, that their use made assays more precise. Potentially, the chromatographic peak shape and retention time of the SIA can be compared with those of the analyte to support assay specificity, and this type of comparison has been implemented as a new computer program (QSIMPS). There is some evidence that SIAs can serve in "carrier" substances to increase recoveries and thus lower the limit of quantitation of an assay. However, the use of large amounts of an SIA (relative to the analyte) leads to analytic imprecision, because of memory effects, large blank values, and unacceptable confidence limits.

Animals↗