Investigating the coffee flavour in South African Pinotage wine using novel offline olfactometry and comprehensive gas chromatography with time of flight mass spectrometry

Pinotage wine from several South African wine cellars has been produced with a novel coffee flavour. We have investigated this innovative coffee effect using in house developed solventless sampling and fractionating olfactometric techniques, which are unique in their ability to study synergistic aroma effects as opposed to traditional gas chromatography olfactometry (GC-O) which is designed to, ideally, evaluate single eluting compounds in a chromatographic sequence. Sections of the chromatogram, multiple or single peaks, were recaptured on multichannel open tubular silicone rubber (polydimethylsiloxane (PDMS)) traps at the end of a GC column. The recaptured fractions were released in a controlled manner for offline olfactory evaluation, and for qualitative analysis using comprehensive gas chromatography coupled to time of flight mass spectrometry (GC × GC–TOFMS) for compound separation and identification, thus permitting correlation of odour with specific compounds. A combination of furfural and 2-furanmethanol was responsible for a roast coffee bean-like odour in coffee style Pinotage wines. This coffee perception is the result of a synergistic effect in which no individual compound was responsible for the characteristic aroma.     

Two multidimensional chromatographic methods for enantiomeric analysis of o,p′-DDT and o,p′-DDD in contaminated soil and air in a malaria area of South Africa

In rural parts of South Africa the organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control where traditional dwellings are sprayed on the inside with small quantities of technical DDT. Since o,p′-DDT may show enantioselective oestrogenicity and biodegradability, it is important to analyse enantiomers of o,p′-DDT and its chiral degradation product, o,p′-DDD, for both health and environmental-forensic considerations. Generally, chiral analysis is performed using heart-cut multidimensional gas chromatography (MDGC) and, more recently, comprehensive two-dimensional gas chromatography (GC × GC). We developed an off-line gas chromatographic fraction collection (heart-cut) procedure for the selective capturing of the appropriate isomers from a first apolar column, followed by reinjection and separation on a second chiral column. Only the o,p′-isomers of DDT and DDD fractions from the first dimension complex chromatogram (achiral apolar GC column separation) were selectively collected onto a polydimethylsiloxane (PDMS) multichannel open tubular silicone rubber trap by simply placing the latter device on the flame tip of an inactivated flame ionisation detector (FID). The multichannel trap containing the o,p′-heart-cuts was then thermally desorbed into a GC with time-of-flight mass spectrometry detection (GC–TOFMS) for second dimension enantioselective separation on a chiral column (β-cyclodextrin-based). By selectively capturing only the o,p′-isomers from the complex sample chromatogram, ¹D separation of ultra-trace level enantiomers could be achieved on the second chiral column without matrix interference. Here, we present solventless concentration techniques for extraction of DDT from contaminated soil and air, and report enantiomeric fraction (EF) values of o,p′-DDT and o,p′-DDD obtained by a new multidimensional approach for heart-cut gas chromatographic fraction collection for off-line second dimension enantiomeric separation by ¹D GC–TOFMS of selected isomers. This multidimensional method is compared to the complementary technique of comprehensive GC × GC–TOFMS using the same enantioselective column, this time as the first dimension of separation.     

Optimization and validation of a low temperature microwave-assisted extraction method for analysis of polycyclic aromatic hydrocarbons in airborne particulate matter

A low temperature microwave-assisted extraction method (MAE) is reported for the analysis of polycyclic aromatic hydrocarbons (PAHs) in airborne particulate matter (PM). The main parameters affecting the extraction efficiency (choice of extractants, microwave power, and extraction time) were investigated and optimized. The optimized procedure requires a 20 ml mixture of acetone:n-hexane (1:1) for extraction of PAHs in PM at 150 W of microwave energy (20 min extraction time). Clean-up of MAE extracts was not found to be necessary. The optimized method was validated using two different SRM (1648-urban particulate matter and 1649a, urban dust). The results obtained are in good agreement with certified values. PAHs recoveries for both reference materials were between 79 and 122% with relative standard deviation ranging from 3 to 21%. Detection limits were determined based on blank determination using two kinds of quartz filter substrates (n = 10), which ranged from 0.001 (0.03) ng m⁻³ (pg/μg) for B(k)Ft to 1.119 (37.3) for Naph in ng m⁻³ (pg/μg), respectively. The repeatability and day-to-day reproducibility obtained in this study were in the range of 4-16 and 3-25% for spiked standards and SRM 1649, respectively. The optimized and validated MAE technique was applied to the extraction of PAHs from a set of real world PM samples collected in Singapore. The sum of particulate-bound PAHs in outdoor PM ranged from 1.05 to 3.45 ng m⁻³ while that in indoor PM (cooking emissions) ranged from 27.6 to 75.7 ng m⁻³, respectively.     

Pesticides in water and the performance of the liquid-phase microextraction based techniques. A review

The control of pesticides in surface, drinking and groundwater is nowadays a real necessity. In the European Community, their concentration must comply with the established parametric and environmental quality standards (EQSs). Regarding the new legislation, this article updates the information concerning the monitoring of pesticides and the technical specifications for their measurement in water samples where ultra-sensitive analytical methods are required. For some compounds, like pesticides, there is still a need to improve the performance of the existing methods. High sensitive techniques like gas chromatography tandem mass spectrometry (GC–MS/MS) and liquid chromatography coupled with mass spectrometry (LC–MS) have been developed. However, for most of the substances present at trace and ultra-trace levels the extraction and preconcentration steps are so far essential for their detection. Advances at a micro scale have been made and different types of microextractions are being developed. Liquid-phase microextraction (LPME) is an example. The study of this technique has increased in the last years and some innovations have been recently reported for pesticides water analysis. This article reviews the new developed LPME-based techniques and compares its performance with the analytical specifications established for pesticides water monitoring. The results show that LPME-based techniques can be a promising tool to improve the nowadays performance of methods used in pesticides water control.