Solid phase extraction in combination with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry for the detailed investigation of volatiles in South African red wines.

Comprehensive two-dimensional gas chromatography in combination with time-of-flight mass spectrometry (GC×GC-TOFMS) has been applied for the analysis of volatile compounds in three young South African red wines. In spite of the significant benefits offered by GC×GC-TOFMS for the separation and identification of volatiles in such a complex matrix, previous results utilizing headspace solid phase micro extraction (HS-SPME) demonstrated certain limitations. These were primarily associated with the choice of sample preparation technique, which failed to extract some influential semi-volatile wine constituents.

Photoelectrochemical determination of inorganic mercury in aqueous solutions.

An analytical method using an optical probe in a photoelectrochemical cell for the sensitive and selective determination of aqueous Hg(2+) is presented. A previously synthesized Hg(2+) selective chemosensor, proven to be Hg(2+) sensitive up to 2 microg L(-1), has been immobilized onto indium tin oxide (ITO) electrodes in a composite form with polyaniline. The coated ITO electrode was placed in a photoelectrochemical cell under closed circuit conditions in which the optical recognition of the chemosensor was converted to a measurable signal.

Analysis of volatiles in Pinotage wines by stir bar sorptive extraction and chemometric profiling.

A fast, simple, cost-effective, and reliable method based on stir bar sorptive extraction (SBSE) in the headspace mode was used for the analysis of 39 volatile components in Pinotage wines. The method was sensitive, with LODs ranging from 50.0 pg/L to 281 ng/L and LOQs between 180 pg/L and 938 ng/L.

Application of a headspace sorptive extraction method for the analysis of volatile components in South African wines.

A headspace sorptive extraction (HSSE) in combination with thermal desorption gas chromatography-mass spectrometry (TD-GC-MS) method for the analysis of volatile components (alcohols, esters, carbonyls, acids, phenols and lactones) in wine samples was developed. Extraction conditions such as salting-out effects, sorption time, stirring speed, phase ratio, extraction temperature, and effect of pH were thoroughly evaluated as part of method validation. The method was very sensitive with LODs and LOQs between 50 pg/L to 299 microg/L and 0.

The analysis of estrone and 17beta-estradiol by stir bar sorptive extraction-thermal desorption-gas chromatography/mass spectrometry: application to urine samples after oral administration of conjugated equine estrogens.

The development of a sensitive and solvent-free method for the measurement of estrone (E(1)) and 17beta-estradiol (17beta-E(2)) in human urine samples is described. The deconjugated estrogens were derivatized in situ with acetic acid anhydride and the derivatives were extracted directly from the aqueous samples using stir bar sorptive extraction (SBSE). The compounds containing a secondary alcohol function are further derivatized by headspace acylation prior to thermal desorption and gas chromatography/mass spectrometry (GC/MS).

Determination of copper and iron using [S,S']-ethylenediaminedisuccinic acid as a chelating agent in wood pulp by capillary electrophoresis.

A capillary electrophoresis (CE) method is described for the simultaneous determination of copper and iron after complexation with a readily biodegradable chelating agent, [S,S']-ethylenediaminedisuccinic acid (EDDS), in wood pulp. CE separation was performed in a fused-silica capillary (50 microm i.d.

Quantification of testosterone and epitestosterone in human urine samples by stir bar sorptive extraction--thermal desorption--gas chromatography/mass spectrometry: application to HIV-positive urine samples.

A simple method is described for the measurement of testosterone (T) and epitestosterone (ET) in human urine samples. The deconjugated steroids were extracted directly from the samples by stir bar sorptive extraction (SBSE) and derivatized in situ on the stir bar by headspace acylation prior to thermal desorption and GC/MS. Extraction and derivatization parameters, namely salt addition, temperature, and time, were optimized to improve the recovery of T and ET by SBSE.

Urinalysis of 4-hydroxynonenal, a marker of oxidative stress, using stir bar sorptive extraction-thermal desorption-gas chromatography/mass spectrometry.

A simple and fast method for the measurement of 4-hydroxynonenal (4HNE), a highly toxic end-product of lipid peroxidation, in urine samples is described. The method combines stir bar sorptive extraction (SBSE) with two derivatization steps, followed by thermal desorption and GC/MS. 4HNE is derivatized in situ with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine and the oxime is extracted from the aqueous phase with SBSE.

Flow counterbalanced capillary electrophoresis using packed capillary columns: resolution of enantiomers and isotopomers.

A method with the ability to increase greatly both the resolution and efficiency of a given capillary electrophoretic system is described. This method differs from traditional capillary electrophoresis (CE) in that a counterflow is induced in the direction opposite to the electrokinetic migration of the analyte. This has the effect of extending not only the time the analytes migrate in the electric field but also the effective length and the effective applied voltage of the system.

Anionic Fischer-type carbene complexes as bidentate (N,O) ligands.

New polynuclear complexes, (L1)3M2 [M2 = Cr(III) (4a,4b), Fe(III) (5), Co(III) (8)], (L1)2M2(L2)2 [M2 = Co(II) (7), Ni(II) (9)], (L1)2M2(O)L2 [M2 = V(IV) (6)] and L1M2Cp2 [M2 = Ti(III) (10)] with L1 = (CO)5M1=C[C=NC(CH3)=CHS](O-)(M1 = Cr or W) and L2 = 4-methylthiazole or THF, are described. The molecular structures of these complexes determined by X-ray diffraction show that the Fischer-type carbene complexes act as bidentate ligands towards the second metal centre, coordinating through C(carbene)-attached O-atoms and imine N-atoms of the thiazolyl groups to form five-membered chelates with the oxygen atoms in the mer configuration. Isostructural complexes have similar characteristic band patterns in their far-IR spectra.