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Analytica Chimica Acta (v.730, #)
Analytical techniques for wine analysis: An African perspective; a review by André de Villiers; Phillipus Alberts; Andreas G.J. Tredoux; Hélène H. Nieuwoudt (pp. 2-23).
Display Omitted► Analytical techniques developed for grape and wine analysis in Africa are reviewed. ► The utility of infrared spectroscopic methods is demonstrated. ► An overview of separation of wine constituents by GC, HPLC, CE is presented. ► Novel LC and GC sample preparation methods for LC and GC are presented. ► Emerging methods for grape and wine analysis in Africa are discussed.Analytical chemistry is playing an ever-increasingly important role in the global wine industry. Chemical analysis of wine is essential in ensuring product safety and conformity to regulatory laws governing the international market, as well as understanding the fundamental aspects of grape and wine production to improve manufacturing processes. Within this field, advanced instrumental analysis methods have been exploited more extensively in recent years. Important advances in instrumental analytical techniques have also found application in the wine industry. This review aims to highlight the most important developments in the field of instrumental wine and grape analysis in the African context. The focus of this overview is specifically on the application of advanced instrumental techniques, including spectroscopic and chromatographic methods. Recent developments in wine and grape analysis and their application in the African context are highlighted, and future trends are discussed in terms of their potential contribution to the industry.
Keywords: Abbreviations; AAS; atomic absorption spectroscopy; ABTS; 2,2′-azinobis(3-ethylbenzothialozinesulfonic acid); AOTF; acousto-optical tunable filter instrument; ATR; attenuated total reflection; BGE; background electrolyte; CAR; carboxen; CE; capillary electrophoresis; DAD; diode array detector; DPPH; 2,2-diphenyl-1-picrylhydrazyl radicals; DVB; divinylbenzene; ELSD; evaporative light scattering detection; ESI; electrospray ionisation; EU; European Union; FFAP; free fatty acid phase; FID; flame ionisation detector; FLD; fluorescence detector; FT-MIR; Fourier transform mid-infrared spectroscopy; FT-NIR; Fourier transform near-infrared spectroscopy; GC; gas chromatography; GC-O; gas chromatography-olfactometry; HILIC; hydrophilic interaction chromatography; HPLC; high performance liquid chromatography; HSSE; headspace sorptive extraction; HS-SPME; headspace solid phase micro-extraction; ICP-MS; inductively coupled plasma-mass spectrometry; IR; infrared; LDA; linear discriminant analysis; LLE; liquid–liquid extraction; MALDI; matrix assisted laser desorption ionisation; MIR; mid-infrared; MRM; multiple reaction monitoring; MS; mass spectrometry; NIR; near-infrared; NMR; nuclear magnetic resonance; OIV; international vine and wine office; OTTs; open tubular traps; PCA; principal component analysis; PCR; principal component regression; PDMS; polydimethylsiloxsane; PEG; polyethyleneglycol; PFPD; pulsed flame photometric detector; PLS; partial least squares regression; PSDVB; polystyrene-divinylbenzene; REA-PFGE; endonuclease analysis pulsed field gel electrophoresis; RI; refraction index; RMSEP; root mean square error of prediction; RP; reversed phase; SBSE; stir bar sorptive extraction; SEP; standard error of prediction; RPD; residual predictive deviation; SIM; selected ion monitoring; SIMCA; soft independent modelling of class analogy; SPDE; solid phase dynamic extraction; SPE; solid phase extraction; SPME; solid phase micro-extraction; TA; titratable acidity; TOF; time-of-flight; TSS; total soluble solids; UPLC; ultra-performance liquid chromatography; UV; ultraviolet; UV/Vis; ultraviolet/visibleGrapes; Wine; Spectroscopy; Chromatography; Regulatory analysis
The role of analytical chemistry in Niger Delta petroleum exploration: A review by Akinsehinwa Akinlua (pp. 24-32).
.Display Omitted► Role of analytical chemistry in petroleum exploration. ► Advancement in analytical techniques solved Niger Delta petroleum problems. ► Biomarker chemistry of oils and source rocks. ► Use of new analytical techniques discovered new compounds in oils. ► Green analytical geochemistry.Petroleum and organic matter from which the petroleum is derived are composed of organic compounds with some trace elements. These compounds give an insight into the origin, thermal maturity and paleoenvironmental history of petroleum, which are essential elements in petroleum exploration. The main tool to acquire the geochemical data is analytical techniques. Due to progress in the development of new analytical techniques, many hitherto petroleum exploration problems have been resolved. Analytical chemistry has played a significant role in the development of petroleum resources of Niger Delta. Various analytical techniques that have aided the success of petroleum exploration in the Niger Delta are discussed. The analytical techniques that have helped to understand the petroleum system of the basin are also described. Recent and emerging analytical methodologies including green analytical methods as applicable to petroleum exploration particularly Niger Delta petroleum province are discussed in this paper. Analytical chemistry is an invaluable tool in finding the Niger Delta oils.
Keywords: Analytical techniques; Geochemistry; Oil; Source rock; Niger Delta
Elemental composition and fatty acid profile of the edible fruits of Amatungula ( Carissa macrocarpa) and impact of soil quality on chemical characteristics by Roshila Moodley; Neil Koorbanally; Sreekanth B. Jonnalagadda (pp. 33-41).
Impact of soil quality parameters on elemental concentration in the Amatungula fruit.Display Omitted► Elements in fruit contribute significantly to the diet of most individuals. ► Plant accumulated Pb at toxic levels, showing influence of site on toxicity. ► Soil concentrations did not affect plant concentrations but site location did. ► Competition in soil influenced metal availability, but uptake depended primarily on plant.The Amatungula fruit, from Carissa macrocarpa, is commonly consumed by the local people of KwaZulu-Natal (KZN), South Africa. Levels of elements in the fruit were determined to assess if they conform to recommended dietary allowances (RDAs) and to assess for potential toxicities. Soils and fruit samples from nine sites in eastern KZN were investigated. Concentrations of elements in the fruit were found to be in the order of Ca>Mg>Fe>Mn≈Cu≈Pb>Se>Cr>Ni>Zn. For the elements in focus, except for Pb, all of the elements found in the fruit contribute significantly towards the RDAs. Lipid profiling was also done to determine the fruits potential as a source of essential fatty acids. The fruit was rich in monounsaturated and essential fatty acids with the linoleic acid to α-linolenic acid ratio conforming to the recommended range for cardiac health. Concentrations of elements in soil had no significant effect on plant concentrations, but competition between elements in soil influenced their availability. Total soil concentrations of most metals studied have significantly correlated Pb availability, indicating the impact of these metals on Pb availability. The Amatungula fruit showed tendency to accumulate Pb, with Pb levels in fruit at all sites being toxic to human health. Site location had a major effect on plant concentrations however uptake and distribution was primarily dependent on the plants inherent controls, as evidenced by the accumulation and exclusion of elements, to meet its physiological requirements.
Keywords: Indigenous fruit; Elemental composition; Nutrition; Soil quality; Bioaccumulation; Carissa macrocarpa
Determination of potentially toxic heavy metals in traditionally used medicinal plants for HIV/AIDS opportunistic infections in Ngamiland District in Northern Botswana by Harriet Okatch; Barbara Ngwenya; Keleabetswe M. Raletamo; Kerstin Andrae-Marobela (pp. 42-48).
Display Omitted► Determine As, Cr, Ni and Pb in traditional plants used to treat HIV/AIDS opportunistic infections. ► Metal levels and provisional tolerable weekly intake levels lower than WHO permissive maximum levels. ► Cr>Pb>As>Ni. ► Consumption of traditional medicinal plants are not health-comprising with respect to metals.The determination of four potentially toxic heavy metals, arsenic, chromium, lead and nickel in twelve plant species used for the treatment of perceived HIV and AIDS-associated opportunistic infections by traditional healers in Ngamiland District in Northern Botswana, a metal mining area, was carried out using atomic absorption spectrometry. The medicinal plants; Dichrostachys cinerea, Maerua angolensis, Mimusops zeyheri, Albizia anthelmintica, Plumbago zeylanica, Combretum imberbe, Indigofera flavicans, Clerodendrum ternatum, Solanum panduriforme, Capparis tomentosa, Terminalia sericea and Maytenus senegalensis contained heavy metals in varying quantities: arsenic 0.19–0.54μgg−1, chromium 0.15–1.27μgg−1, lead 0.12–0.23μgg−1 and nickel 0.09–0.21μgg−1 of dry weight. Chromium was found to be the most abundant followed by arsenic and lead. Nickel was undetectable in nine plant species. M. senegalensis contained the largest amounts of arsenic, chromium and lead. All metals determined were below the WHO permissive maximum levels. The possible maximum weekly intakes of the heavy metals following treatment regimes were insignificant compared to the provisional tolerable weekly intake levels recommended by WHO and the Joint FAO/WHO Expert Committee on Food Additives. This suggests that heavy metal exposure to patients originating from consumption of traditional medicinal plant preparations is within non health-compromising limits.
Keywords: Traditional medicinal plants; Arsenic; Chromium; Lead; Nickel; AASAbbreviations; AAS; atomic absorption spectrometry; AIDS; acquired immune deficiency syndrome; ARV; antiretroviral; FAO; food and agriculture organisation; HIV; human immunodeficiency virus; ICP-MS; inductively coupled plasma mass spectrometry; ICP-OES; inductively coupled plasma optical emission spectrometry; IOCG; iron oxide copper gold ore deposit; JECFA; joint FAO/WHO expert committee on food additives; PTWI; provisional tolerable weekly intake; WHO; world health organisation
Cytochrome c biosensor for determination of trace levels of cyanide and arsenic compounds by Xolile Fuku; Faiza Iftikar; Euodia Hess; Emmanuel Iwuoha; Priscilla Baker (pp. 49-59).
Display Omitted► Cytochrome c biosensor for detection of KCN, As2O3 and Fe2K (CN) was constructed. ► Detection limits in the range of 4.3–9.1μM for the analytes were obtained using CV, SWV and EIS. ► The detection limits for the biosensor were significantly lower than current EPA and WHO guidelines.An electrochemical method based on a cytochrome c biosensor was developed, for the detection of selected arsenic and cyanide compounds. Boron doped diamond (BDD) electrode was used as a transducer, onto which cytochrome c was immobilised and used for direct determination of Prussian blue, potassium cyanide and arsenic trioxide. The sensitivity as calculated from cyclic voltammetry (CV) and square wave voltammetry (SWV), for each analyte in phosphate buffer (pH=7) was found to be in the range of (1.1–4.5)×10−8AμM−1 and the detection limits ranged from 4.3 to 9.1μM. The biosensor is therefore able to measure significantly lower than current Environmental Protection Agency (EPA) and World Health Organisation (WHO) guidelines, for these types of analytes. The protein binding was monitored as a decrease in biosensor peak currents by SWV and as an increase in biosensor charge transfer resistance by electrochemical impedance spectroscopy (EIS). EIS provided evidence that the electrocatalytic advantage of BDD electrode was not lost upon immobilisation of cytochrome c. The interfacial kinetics of the biosensor was modelled as equivalent electrical circuit based on electrochemical impedance spectroscopy data. UV–vis spectroscopy was used to confirm the binding of the protein in solution by monitoring the intensity of the soret bands and the Q bands. FTIR was used to characterise the protein in the immobilised state and to confirm that the protein was not denatured upon binding to the pre-treated bare BDD electrode. SNFTIR of cyt c immobilised at platinum electrode, was used to study the effect of oxidation state on the surface bond vibrations. The spherical morphology of the immobilised protein, which is typical of native cytochrome c, was observed using scanning electron microscopy (SEM) and confirmed the immobilisation of the cytochrome c without denaturisation.
Keywords: Toxicity; Cytochrome c (cyt c); Boron doped diamond (BDD); Diffusion coefficients
Selective electronalysis of peracetic acid in the presence of a large excess of H2O2 at Au(111)-like gold electrode by M.I. Awad (pp. 60-65).
Display Omitted► Analysis of peracetic acid in the presence of a large excess of H2O2 is introduced. ► Au(111)-like gold electrode serves as an ideal for this purpose. ► The analysis is characterized by high selectivity and sensitivity.Peracetic acid (PAA) has been selectively electroanalyzed in the presence of a large excess of hydrogen peroxide (H2O2), about 500 fold that of PAA, using Au (111)-like gold electrode in acetate buffer solutions of pH 5.4. Au(111)-like gold electrode was prepared by a controlled reductive desorption of a previously assembled thiol, typically cysteine, monolayer onto the polycrystalline gold (poly-Au) electrode. Cysteine molecules were selectively removed from the Au(111) facets of the poly-Au electrode, keeping the other two facets (i.e., Au(110) and Au(100)) under the protection of the adsorbed cysteine. It has been found that Au(111)-like gold electrode positively shifts the reduction peak of PAA, while, fortunately, shifts the reduction peak of H2O2 negatively, achieving a large potential separation (around 750mV) between the two reduction peaks as compared with that (around 450mV) obtained at the poly-Au electrode. This large potential separation between the two reduction peaks enabled the analysis of PAA in the presence of a large excess of H2O2. In addition, the positive shift of the reduction peak of PAA gives the present method a high immunity against the interference of the dissolved oxygen.
Keywords: Peracetic; Hydrogen peroxide; Au(1; 1; 1)-like; Electroanalysis
Thermodynamic evaluation of the stability of the bone-seeking radiopharmaceutical [177Lu]Lu(III)–DOTP under simulated blood plasma conditions by Lebogang C. Sepini; Neil V. Jarvis; David R. Jansen; Jan Rijn Zeevaart (pp. 66-70).
Display Omitted► Thermodynamic blood plasma model supports in vivo biodistribution of [177Lu]Lu–DOTP. ► Lu3+ remains predominantly complexed (98.1%) with the DOTP under simulated physiological conditions. ► Thermodynamic and kinetic stability [177Lu]Lu–DOTP in blood plasma facilitates selectivity of the proposed radiopharmaceutical for bone.The stability and in vivo robustness of [177Lu]Lu–DOTP as a potential bone-targeting radiopharmaceutical was determined with the aid of thermodynamic blood plasma modeling simulations. Glass electrode potentiometry was employed to measure the stability constants of the complexes of Lu3+ with DOTP. Similarly, the complexes of DOTP with a selection of the important physiological metal ions: Ca2+, Mg2+, and Cu2+ were determined, representing the typical interactions that the ligand would encounter upon administration. This made possible the construction of a blood plasma model of DOTP, aiding in establishing the potential susceptibility of the radiopharmaceutical. The ligand binds predominantly to calcium in vivo, accounting for 59.6% of that initially introduced as a component of the Lu–DOTP complex. Furthermore, due to a preference of the DOTP to bind to Cu2+ it causes mobilization of the ions in blood plasma, and would therefore indicate a deficiency if the ligand is administered at a concentration of 8.5×10−5moldm−3. The lutetium-ions are preferentially bound to DOTP, with as much as 98.1% of the Lu3+ occupying the ligand under physiological conditions.
Keywords: Blood plasma modeling; [; 177; Lu]Lu–DOTP; Potentiometry; Plasma mobilization index; Bone pain palliation; Bone-seeking radiopharmaceutical
The use of multi-channel silicone rubber traps as denuders for polycyclic aromatic hydrocarbons by Patricia B.C. Forbes; Erwin W. Karg; Ralf Zimmermann; Egmont R. Rohwer (pp. 71-79).
Display Omitted► Two multi-channel silicone rubber traps with a quartz fibre filter form a miniature portable denuder. ► Gas and particle phase polycyclic aromatic hydrocarbons can be separately sampled and analysed. ► Calculated particle transmission efficiencies were 100% for particles >50nm diameter. ► Experimental transmission efficiencies were 100% for particles >200nm and <60% for those <20nm. ► Short sampling intervals are possible which provides high temporal resolution for air pollution studies.Atmospheric polycyclic aromatic hydrocarbons are ubiquitous environmental pollutants, which may be present both in the gaseous phase and adsorbed onto the surface of particles. Denuders are sampling devices which have been effectively employed in such partitioning applications. Here we describe and characterise a novel miniature denuder consisting of two multi-channel silicone rubber traps (each 178mm long, 6mm o.d. containing 22 silicone tubes), separated by a quartz fibre filter for particle phase collection. The denuder only requires a small portable personal sampling pump to provide sampling flow rates of ∼0.5Lmin−1. Theoretical considerations indicated that the air flow through the denuder was expected to be laminar, and the linear velocity arising from longitudinal diffusion was found to be negligible. The calculated particle transmission efficiency through the denuder was found to be essentially 100% for particles>50nm, whilst the experimental overall efficiency, as determined by CPC and SMPS measurements, was 92±4%. The size resolved transmission efficiency was <60% for particles below 20nm and 100% for particles larger than 200nm. Losses could have been due to diffusion and electrostatic effects. Semi-volatile gaseous analytes are pre-concentrated in the silicone of the trap and may be thermally desorbed using a commercially available desorber, allowing for total transfer and detection of the collected analytes by GC–MS. This enhances detection limits and allows for lower sampling flow rates and shorter sampling times, which are advantageous for studies requiring high temporal resolution.
Keywords: Denuder; Polycyclic aromatic hydrocarbons; Particulate; Aerosol; Silicone; Air sampling trap
Development of a dispersive liquid–liquid microextraction method for the determination of fluoroquinolones in chicken liver by high performance liquid chromatography by D. Moema; M.M. Nindi; S. Dube (pp. 80-86).
Dispersive liquid–liquid microextraction method was developed for sample cleanup of six fluoroquinolones in chicken livers. A chromatogram of well separated six fluoroquinolones in chicken livers is shown. Very important DLLME parameters which included extraction solvent, pH effect and dispersive solvent were optimized. The developed method was used for real chicken livers samples.Display Omitted► A novel DLLME technique for determination of fluoroquinolones in solids is presented. ► This greener sample preparation technique has potential for veterinary drugs residue. ► DLLME is a cheap, fast, green method of sample extraction from biological matrixes.A simple and cost effective sample pre-treatment method, dispersive liquid–liquid microextraction (DLLME), has been developed for the extraction of six fluoroquinolones (FQs) from chicken liver samples. Clean DLLME extracts were analyzed for fluoroquinolones using liquid chromatography with diode array detection (LC-DAD). Parameters such as type and volume of disperser solvent, type and volume of extraction solvent, concentration and composition of phosphoric acid in the disperser solvent and pH were optimized. Linearity in the concentration range of 30–500μgkg−1 was obtained with regression coefficients ranging from 0.9945 to 0.9974. Intra-day repeatability expressed as % RSD was between 4 and 7%. The recoveries determined in spiked blank chicken livers at three concentration levels (i.e. 50, 100 and 300μgkg−1) ranged from 83 to 102%. LODs were between 5 and 19μgkg−1 while LOQs ranged between 23 and 62μgkg−1. All of the eight chicken liver samples obtained from the local supermarkets were found to contain at least one type of fluoroquinolone with enrofloxacin being the most commonly detected. Only one sample had four fluoroquinolone antibiotics (ciprofloxacin, difloxacin, enrofloxacin, norfloxacin). Norfloxacin which is unlicensed for use in South Africa was also detected in three of the eight chicken liver samples analyzed. The concentration levels of all FQs antibiotics in eight samples ranged from 8.8 to 35.3μgkg−1, values which are lower than the South African stipulated maximum residue limits (MRL).
Keywords: Fluoroquinolones; Dispersive liquid–liquid microextraction; Biological sample; Sample pretreatment; Pre-concentration
A study of the removal of heavy metals from aqueous solutions by Moringa oleifera seeds and amine-based ligand 1,4-bis[N,N-bis(2-picoyl)amino]butane by Veronica Obuseng; Florence Nareetsile; Habauka M. Kwaambwa (pp. 87-92).
Display Omitted► Materials are effective and selective in simultaneous removal of heavy metal ions. ► Use of composite adsorbent of both materials may result in more effective material. ► Seeds biomass has various functional groups involves in metal removal. ► Attainment of sorption equilibrium is rapid for the seeds biomass. ► Seeds biomass effectiveness is not affected over wide effective pH range.Uptake for lead, copper, cadmium, nickel and manganese from aqueous solution using the Moringa oleifera seeds biomass (MOSB) and amine-based ligand (ABL) was investigated. Experiments on two synthetic multi-solute systems revealed that MOSB performed well in the biosorption and followed the decreasing orders Pb(II)>Cu(II)>Cd(II)>Ni(II)>Mn(II) and Zn(II)>Cu(II)>Ni(II). The general trend of the heavy metal ions uptake by the amine-based ligand followed decreased in the order Mn>Cd>Cu>Ni>Pb, which is the reverse trend for what was observed for MOSB. Comparing the single- and multi-metal solutions, there was no clear effect in the biosorption capacity of MOSB suggesting the presence of sufficient active binding sites for all metal ions studied. The MOSB performance is also not affected by pH in the range 3.5–8.
Keywords: Amine-based ligand; Biosorbent; Biosorption; Heavy metal; Moringa oleifera; biomass
35Cl/37Cl isotope effects in103Rh NMR of [RhCl n(H2O)6− n]3− n complex anions in hydrochloric acid solution as a unique ‘NMR finger-print’ for unambiguous speciation by Theodor E. Geswindt; Wilhelmus J. Gerber; D. Jacobus Brand; Klaus R. Koch (pp. 93-98).
35Cl/37Cl isotope effects in103Rh NMR as a unique ‘NMR-fingerprints’ leading to the unambiguous assignment of [RhCl n(H2O)6− n]3− n ( n=3–6) complexes without reliance on accurate δ(103Rh) chemical shifts.Display Omitted► Direct103Rh NMR (19.11MHz) spectroscopic method of speciation of [RhCl n(H2O)6− n]3− n in HCl. ►35Cl/37Cl isotope effects in103Rh NMR of [RhCl n(H2O)6− n]3− n anions isotopologue and isotopomer induced103Rh NMR ‘finger-print’ for unambiguous identification. ►103Rh NMR identification of stereoisomers without a need for accurate chemical shifts.A detailed analysis of the35Cl/37Cl isotope effects observed in the 19.11MHz103Rh NMR resonances of [RhCl n(H2O)6− n]3− n complexes ( n=3–6) in acidic solution at 292.1K, shows that the ‘fine structure’ of each103Rh resonance can be understood in terms of the unique isotopologue and in certain instances the isotopomer distribution in each complex. These35Cl/37Cl isotope effects in the103Rh NMR resonance of the [Rh35/37Cl6]3− species manifest only as a result of the statistically expected35Cl/37Cl isotopologues, whereas for the aquated species such as for example [Rh35/37Cl5(H2O)]2−, cis-[Rh35/37Cl4(H2O)2]− as well as the mer-[Rh35/37Cl3(H2O)3] complexes, additional fine-structure due to the various possible isotopomers within each class of isotopologues, is visible. Of interest is the possibility of the direct identification of stereoisomers cis-[RhCl4(H2O)2]−, trans-[RhCl4(H2O)2]−, fac-[RhCl3(H2O)3] and mer-[RhCl3(H2O)3] based on the103Rh NMR line shape, other than on the basis of their very similar δ(103Rh) chemical shift. The103Rh NMR resonance structure thus serves as a novel and unique ‘NMR-fingerprint’ leading to the unambiguous assignment of [RhCl n(H2O)6− n]3− n complexes ( n=3–6), without reliance on accurate δ(103Rh) chemical shifts.
Keywords: 103; Rh NMR; 35; Cl/; 37; Cl isotope effects in [RhCl; n; (H; 2; O); 6−; n; ]; 3−; n; complexes; Direct; 103; Rh NMR speciation; Isotopologues and isotopomers in NMR
Construction and performance characteristics of new ion selective electrodes based on carbon nanotubes for determination of meclofenoxate hydrochloride by Rasha M. El-Nashar; Nour T. Abdel Ghani; Sherif M. Hassan (pp. 99-111).
Display Omitted► Three different meclofenoxate electrodes were prepared. ► They showed responses over range 1.0×10−5 to 1.0×10−2M with slope of 5.15–59.74mV(concentrationdecade)−1. ► The electrodes showed good selectivity for Meclo over many inorganic cations and compounds. ► Better sensitivity was obtained on using carbon nanotubes as modifiers. ► The electrodes were used successfully for the assay of dosage forms and in biological samples.This work offers construction and comparative evaluation the performance characteristics of conventional polymer (I), carbon paste (II) and carbon nanotubes chemically modified carbon paste ion selective electrodes (III) for meclofenoxate hydrochloride are described. These electrodes depend mainly on the incorporation of the ion pair of meclofenoxate hydrochloride with phosphomolybdic acid (PMA) or phosphotungestic acid (PTA). They showed near Nernestian responses over usable concentration range 1.0×10−5 to 1.0×10−2M with slopes in the range 55.15–59.74mV(concentrationdecade)−1. These developed electrodes were fully characterized in terms of their composition, response time, working concentration range, life span, usable pH and temperature range. The electrodes showed a very good selectivity for Meclo with respect to a large number of inorganic cations, sugars and in the presence of the degradation product of the drug (p-chloro phenoxy acetic acid). The standard additions method was applied to the determination of MecloCl in pure solution, pharmaceutical preparations and biological samples. Dissolution testing was also applied using the proposed sensors.
Keywords: Meclofenoxate; Ion selective electrode; Potentiometry; Polyvinyl chloride membrane; Carbon paste electrodes; Carbon nanotube chemically modified carbon paste electrodes
Novel method for determining DDT in vapour and particulate phases within contaminated indoor air in a malaria area of South Africa by Yvette Naudé; Egmont R. Rohwer (pp. 112-119).
Display Omitted► We present a novel denuder for the determination of DDT in contaminated indoor air. ► Single step concentration of vapour phase on PDMS, particulate phase on filter. ► Solvent-free green technique, sample extraction not required. ► Ratios of airborne p, p′-DDD/ p, p′-DDT and of o, p′-DDT/ p, p′-DDT are unusual. ► Insecticidal efficacy of technical DDT may be compromised.The organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis( p-chlorophenyl)ethane) is still used for malaria vector control in certain areas of South Africa. The strict Stockholm Convention on Persistent Organic Pollutants (POPs) allows spraying on the inside of traditional dwellings with DDT. In rural villages contaminated dust presents an additional pathway for exposure to DDT. We present a new method for the determination of DDT in indoor air where separate vapour and particulate samples are collected in a single step with a denuder configuration of a multi-channel open tubular silicone rubber (polydimethylsiloxane (PDMS)) trap combined with a micro quartz fibre filter. The multi-channel PDMS trap section of the denuder concentrates vapour phase insecticide whereas particle associated insecticide is transferred downstream where it is collected on a micro-fibre filter followed by a second multi-channel PDMS trap to capture the blow-off from the filter. The multi-channel PDMS trap and filter combination are designed to fit a commercial thermal desorber for direct introduction of samples into a GC–MS. The technique is solvent-free. Analyte extraction and sample clean-up is not required. Two fractions, vapour phase and particulate phase p, p′-DDT, o, p′-DDT; p, p′-DDD, o, p′-DDD; p, p′-DDE and o, p′-DDE in 4L contaminated indoor air, were each quantitatively analysed by GC–MS using isotopically labelled ring substituted13C12 – p, p′-DDT as an internal standard. Limits of detection were 0.07–0.35ngm−3 for p, p′-DDT, o, p′-DDT, p, p′-DDD, o, p′-DDD, p, p′-DDE and o, p′-DDE. Ratios of airborne p, p′-DDD/ p, p′-DDT and of o, p′-DDT/ p, p′-DDT are unusual and do not match the ideal certified ingredient composition required of commercial DDT. Results suggest that the DDT products used for indoor residual spraying (IRS) prior to, and during 2007, may have been compromised with regards to insecticidal efficacy, demonstrating the power of this new environmental forensics tool.
Keywords: Airborne contaminants; Multi-channel open tubular trap; Polydimethylsiloxane (PDMS) sorptive extraction; Denuder; Environmental forensics; Persistent organic pollutants (POPs)
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 by Yvette Naudé; Egmont R. Rohwer (pp. 120-126).
Display Omitted► We present novel solvent free extraction of DDT from soil and air. ► A new off-line multi-dimensional GC approach involving heart-cut gas chromatographic fraction collection. ► Enantiomeric fraction determination of multiple isomers in a single chiral separation by1D GC–TOFMS. ► Chiral analysis by comprehensive GC×GC–TOFMS. ► A first report of enantiomeric fractions of o,p′-DDT, o,p′-DDD in soil/air, 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 by1D 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.
Keywords: Abbreviations; CIS; cooled injection system; EF; enantiomeric fraction; GCFC; gas chromatographic fraction collection; IRS; indoor residual spraying; MCT; multichannel open tubular silicone rubber trap; MDGC; multidimensional gas chromatography; PDMS; polydimethylsiloxane; POPs; persistent organic pollutants; TDS; thermal desorber systemPolydimethylsiloxane (PDMS) sorptive extraction; Environmental forensics; Persistent organic pollutants (POPs); Chiral chromatography; Comprehensive GC; ×; GC; Heart-cutting