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M Kinter

Publications and source records attributed to M Kinter.

29 records · Page 2Linked to original sources
PubMed1992

Determination of selenium in urine by isotope dilution gas chromatography-mass spectrometry using 4-nitro-o-phenylenediamine, 3,5-dibromo-o-phenylenediamine, and 4-trifluoromethyl-o-phenylenediamine as derivatizing reagents.

An isotope dilution gas chromatography-mass spectrometry method for selenium determination in urine using 76Se as an internal standard is described. Three different derivatizing reagents, 4-nitro-o-phenylenediamine (NPD), 3,5-dibromo-o-phenylenediamine (DBPD), and 4-trifluoromethyl-o-phenylenediamine (TFMPD) were investigated for their gas chromatographic behavior including memory and precision and accuracy of isotope ratio measurements. By these criteria, the performance of these reagents was TFMPD greater than DBPD greater than NPD. Overall precision values of 1 to 7% were observed in determining Se isotope ratios at the 10-ng level, with no significant difference in using any of the three reagents. Memory effect was observed in the order NPD greater than DBPD greater than TFMPD with TFMPD showing no measurable memory effect. Accuracy of the GC-MS method was verified by quantitation of selenium in the NIST freeze-dried urine reference material SRM 2670.

Gas Chromatography-Mass Spectrometry↗
PubMed1991

Determination of copper in urine and serum by gas chromatography-mass spectrometry.

A stable isotope dilution gas chromatography-mass spectrometry method using enriched 65Cu as an internal standard is described for the determination of Cu in urine and serum. Chelating agents N,N'-ethylenebis-(trifluoroacetylacetoneimine) [H2(enTFA2)] and lithium bis(trifluoroethyl)dithiocarbamate [Li(FDEDTC)] were used and evaluated for memory effect. H2(enTFA2) did not show any appreciable memory effect, whereas Li(FDEDTC) was found to have a strong memory effect. Overall precision of 1.6% was obtained for determining Cu isotope ratios at a 10-ng level using H2(enTFA2). Cu concentrations in the National Institute of Standards and Technology (NIST) reference materials, freeze-dried urine SRM 2670, and human serum SRM 909 determined using the H2(enTFA2) chelating agent were in good agreement with the NIST-certified values. Isotope ratios determined by gas chromatography-mass spectrometry on samples with altered isotopic composition were in good agreement with the inductively coupled plasma-mass spectrometry data.

Chelating Agents↗
PubMed1990

Determination of chromium in urine by stable isotope dilution gas chromatography/mass spectrometry using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent.

An isotope dilution gas chromatography/mass spectrometry method using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described for the determination of chromium in urine. A wet digestion procedure with HNO3-H2O2 is used for oxidizing the organic matter associated with urine samples. The isotope ratios are measured by selected ion monitoring in a general-purpose mass spectrometer using a 10-m fused silica capillary column. Memory effect, in sequential analyses of samples with different isotope ratios, was evaluated by preparing a series of synthetic mixtures and was found to be negligible. The accuracy of the method was verified by quantitation of chromium in the NIST freeze-dried urine reference material, SRM-2670, with a recommended chromium concentration of 13 micrograms/L in the normal level and certified chromium concentration of 85 +/- 6 micrograms/L in the elevated level.

Chelating Agents↗
PubMed1989

Isotope dilution gas chromatography/mass spectrometry for the determination of nickel in biological materials.

Precise and accurate methods are required to measure nickel in urine and serum samples to identify clinical states of either deficiency or toxicity. This paper presents an isotope dilution gas chromatography/mass spectrometry method for the measurement of nickel in biological samples. The method involves the preparation of a thermally stable and volatile nickel chelate using lithium bis(trifluoroethyl)dithiocarbamate as the chelating agent. Conditions were optimized for the digestion of the sample and quantitative preparation of chelate as well as the precise and accurate measurements of the isotope ratios using a capillary column gas chromatograph with a general purpose mass spectrometer. The memory effect between samples of different isotope ratios was evaluated and was found to be negligible. The quantitative accuracy of isotope dilution was validated by measuring nickel in the NIST freeze-dried urine reference material, SRM 2670, with comparison to the recommended value.

Chelating Agents↗
PubMed1988

Rat liver insulin mediator which stimulates pyruvate dehydrogenase phosphate contains galactosamine and D-chiroinositol.

It has been established that insulin treatment of cells, isolated plasma membranes, or whole animals leads to the generation of low molecular weight mediators which serve as intermediates in the signalling pathway. At least two distinct classes of mediator have been described, based on differences in apparent molecular weight, isoelectric point and biological activity (Cheng, K., and Larner, J. (1985) Ann. Rev. Physiol. 45, 407-424). Recently, Saltiel's (Saltiel, A.R., and Cuatrecasas, P. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 5793-5797) and Mato's (Mato, J.M., Kelly, K.L., Abler, A., and Jarett, L. (1987) J. Biol. Chem. 262, 2131-2137) laboratories have described an insulin "modulator" which was apparently derived from glycosylphosphoinositol linker, similar to those known to anchor proteins to the external surface of the cell membrane (Low, M.G. (1987) Bioch. J. 244, 1-13). In this paper, we report that highly purified preparations of the insulin mediator which stimulates pyruvate dehydrogenase phosphatase contain mannose, galactosamine, and D-chiroinositol. These determinations are based upon analyses using paper chromatography and gas chromatography/mass spectroscopy. Nitrous acid deamination of the mediator resulted in release of inositol phosphate, indicating that the galactosamine and D-chiroinositol are linked. Although the presence of chiroinositol in modulator from H35 hepatoma cells has been recently reported (Mato, J.M., Kelly, K.L., Abler, A., Jarett, L., Corkey, B.E., Cashel, J.A., and Zopf, D. (1987) Bioch. Biophys. Res. Comm. 146, 764-770), the optical identity of the inositol remained unknown until the present report. Likewise, the presence of galactosamine rather than glucosamine in insulin mediator is a novel finding. These findings, coupled with those of Saltiel and Mato's groups, provide clear evidence for the existence of multiple forms of insulin mediators. Additionally, the results presented here afford further confirmation for the formation of insulin mediators from glycosyl-phosphoinositol linkers.

Animals↗
PubMed1988

Measurement of cholesterol in serum by gas chromatography/mass spectrometry at moderate mass resolution, with a nonendogenous cholesterol isomer as internal standard.

We describe a gas chromatography/mass spectrometry method for the quantitative analysis of cholesterol in serum. A structural isomer of cholesterol, 7,(5 alpha)-cholesten-3 beta-ol, is used as an internal standard, its primary advantage being its lesser cost relative to that of a stable-isotope-labeled analog. Analysis of the National Bureau of Standards Certified Reference Serum (SRM 909) was used to validate the method. The results show this method to be highly accurate (bias = -0.6%) and precise (CV = 1.6% between-run, 1.2% within-run). The performance of this method is, therefore, sufficiently good to allow its use as a reference method for determinations of cholesterol in serum.

Cholesterol↗
PubMed1988

Measurement of rimantadine in plasma by capillary gas chromatography/mass spectrometry with a deuterium-labeled internal standard.

Rimantadine is a synthetic antiviral agent used in prophylaxis and in treating the early stages of uncomplicated influenza A illness. We describe a stable isotope-dilution assay involving capillary gas chromatography/mass spectrometry. We used 200 ng of d3-rimantadine, added to 1 mL of plasma, as the internal standard. The rimantadine was extracted from the plasma with a Bond-Elut CN column, the column was washed with water, and the rimantadine was eluted with methanol, dried, and treated to form the t-butyldimethylsilyl derivative. The mass spectrometer was operated in the selected ion monitoring mode. Ions at m/z 236 and m/z 239 were monitored, corresponding to the loss of C4H9 from the rimantadine derivative and d3-rimantadine, respectively. Within-run precision (CVs) ranged from 8.9% at 29 micrograms/L to 3.2% at 1666 micrograms/L. Corresponding data for between-run precision were 5.4% and 1.7%. Treated volunteers (n = 86) provided plasma samples with a concentration range of 153 to 1127 micrograms/L. This simplified method allows rapid, precise assay of rimantadine in plasma.

Adamantane↗
PubMedDate not supplied

Mercury determination in blood by gas chromatography-mass spectrometry.

A stable isotope dilution gas chromatography-mass spectrometry method using 196Hg as an internal standard is described for determining Hg in blood. In this method, the blood samples are not subjected to any digestion to avoid the loss of Hg. A solution of 0.6M HCl is used to free Hg present in blood from proteins. The pH of the solution is adjusted to 9 using borate buffer and Hg chelated using lithium bis(trifluoroethyl)dithiocarbamate. All isotope ratio measurements are made using an organic mass spectrometer. Overall precision values for the five major Hg isotopes relative to 202Hg are 1.6-2.3% when 10 ng samples of chelated Hg are analyzed. No appreciable memory or carryover effect is observed when two synthetic mixtures differing in 196Hg/202Hg ratios by a factor of 30 are sequentially analyzed. The method is validated by determining Hg in blood samples using isotope dilution GC-MS.

Calibration↗
PubMedDate not supplied

Isotope dilution gas chromatography/mass spectrometry for cadmium determination in urine.

A stable isotope dilution gas chromatographic/mass spectrometric method using 106Cd as an internal standard is described for determining Cd in urine. In this method, the urine matrix is digested with HNO3 + H2O2 and the Cd is chelated with lithium bis(trifluoroethyl)dithiocarbamate. All isotope ratio measurements are made with an organic mass spectrometer. Overall precision values for the five major isotopes relative to 114Cd are 1 to 3% when 10-ng samples of chelated Cd are analyzed. Accuracy of the method is established by measuring Cd in the NIST freeze-dried urine reference material. A small memory effect is observed when measuring isotope ratios differing by a factor of 10. This can, however, be minimized by optimum addition of the internal standard solution.

Cadmium↗