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G Zurek

Publications and source records attributed to G Zurek.

7 recordsLinked to original sources
PubMed2000

2,4-Dinitro-3,5,6-trideuterophenylhydrazones for the quantitation of aldehydes and ketones in air samples by liquid chromatography-mass spectrometry.

The quantification of carbonyl compounds in air samples using an internal calibration approach with stable isotope-labelled standards and HPLC-atmospheric pressure chemical ionization MS analysis is presented. 2,4-Dinitro-3,5,6-trideuterophenylhydrazine and various of its hydrazones have been synthesized and characterized for the first time. The respective stable isotope-labelled hydrazones of a series of aldehydes and ketones are applied as internal standards for the determination of the carbonyls in car exhaust samples. Various aldehydes are identified and quantified by MS detection. The results exhibit good agreement to quantification data obtained with UV detection.

Air↗
PubMed2000

Determination of acetaldehyde in tobacco smoke using N-methyl-4-hydrazino-7-nitrobenzofurazan and liquid chromatography/mass spectrometry.

A liquid chromatography/mass spectrometry (LC/MS) method for the determination of carbonyl compounds based on derivatization with N-methyl-4-hydrazino-7-nitrobenzofurazan (MNBDH) has been developed. Atmospheric pressure chemical ionization (APCI) in the positive mode proved the most versatile ionization technique for MNBD-hydrazones. APCI/MS spectra were recorded and the detection limits were determined for [M+H]+, 13C2 acetaldehyde MNBD-hydrazone has been synthesized and characterized. It is applied as internal standard for the quantification of acetaldehyde. Tobacco smoke has been investigated concerning its carbonyl content. Acetaldehyde was identified as main product and quantified by LC/MS using internal standardization. The result is in good agreement to quantification data obtained with UV/vis detection.

Acetaldehyde↗
PubMed1999

Liquid chromatography-mass spectrometry method for the determination of aldehydes derivatized by the Hantzsch reaction.

A liquid chromatography-mass spectrometry method for the determination of aliphatic aldehydes after derivatization with acetylacetone or dimedone by means of the Hantzsch reaction is presented. Two molecules of a beta-diketone, one molecule of ammonia and an aliphatic aldehyde cyclisate under formation of colored and fluorescent reaction products. Atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) in the positive mode are suitable to ionize the formed dihydropyridine and decahydroacridine derivatives under protonation of their basic secondary amine functionality. The method has been used to identify the oxidation product of the formaldehyde derivatives as side product. The acetaldehyde derivative, presumably formed in the reaction of residual acetaldehyde in the acetic acid or acetate reagents, is mainly responsible for the increasing fluorescence background of the reagent solutions.

Aldehydes↗
PubMed1999

Determination of carbonyls using liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization.

A liquid chromatographic method for the determination of aldehydes and ketones based on mass spectrometric detection is described. Recently developed modular derivatizing agents are employed for analysis. These hydrazine reagents, e.g. 4-dimethylamino-6-(4-methoxy-1-naphthyl)-1,3,5-triazine-2-hydrazine (DMNTH), react with the carbonyl compounds with the formation of the respective hydrazones, which are separated by HPLC-MS with atmospheric pressure chemical ionization in the positive mode. Electrospray ionization may also be used for analysis. Particular focus is directed on various calibration approaches, including external calibration with standard solutions and internal calibration with a hydrazone standard of cyclobutanone, an aldehyde not likely to occur in real samples. A second approach for internal calibration is based on the 13C2-labelled acetaldehyde hydrazone standard. Different calibration approaches may then be used for the analysis of real samples. Limits of detection range from 2 x 10(-8) to 5 x 10(-8) mol L-1 for a series of hydrazones, including hydrazones of saturated aldehydes with alkyl chain lengths from 1 to 7 carbon atoms, and hydrazones of selected unsaturated and aromatic aldehydes as well as ketone hydrazones.

Air Pollution, Indoor↗
PubMed1986

Effects of oral calcium carbonate on blood pressure in subjects with mildly elevated arterial pressure.

Recent investigations suggest that calcium supplementation may cause a lower arterial pressure in hypertensive individuals. We studied 32 patients with mildly elevated arterial pressure (diastolic pressure 88-95 mmHg) and inadequate dietary calcium intake (less than 750 mm/day), who were randomly assigned to placebo or 1500 mg/day elemental calcium for 4 weeks. Baseline and post-treatment urinary calcium concentrations and 3 biweekly supine blood pressures were recorded. Supine systolic blood pressure in the calcium group rose during the first 2 weeks of treatment (delta systolic blood pressure +5.9 mmHg; P less than 0.025) compared with no change in supine blood pressure for the placebo group. Within the calcium group, seven out of 15 patients had decreased or unchanged supine blood pressure during treatment. A lower urinary calcium concentration and a lower dietary sodium intake were found in this subgroup compared with those whose supine blood pressure increased with calcium administration.

Blood Pressure↗