Singlet and Triplet State Properties and Singlet Oxygen Yield of an Amino-Acyl-Quinoxalinone Yellow Dye.

Amino-acyl-quinoxalinone yellow dyes are cyclised analogues of the yellow azomethine dyes developed for, and still used in, silver halide colour photography. Unlike image azomethine dyes, which are rapidly deactivated in their excited states by torsion about the azomethine bond, amino-acyl-quinoxalinone dyes have an interesting photophysics because torsion is not possible due to their cyclised structure. We report results from studies on singlet and triplet state properties, and singlet oxygen yields, of the yellow dye, 7-diethylamino-3-(2,2-dimethyl-propionyl)-5-methyl-1-phenyl-1H-quinoxalin-2-one, in polar and nonpolar solvents. The dye photophysics is characterised by a weak fluorescence, with a solvent dependent emission yield (ΦF ≈ 0.002-0.004), and short singlet state lifetime (τexpt ≈ 20-50 ps), both increasing by a factor of ≈2 in going from polar acetonitrile to non-polar dioxane as solvent. DFT ZINDO calculations show a transition involving significant electron transfer from the diethyl-amino group into the carbonyl region of the molecule. In solution, in the presence of oxygen, the triplet state decays almost exclusively by oxygen quenching, and singlet oxygen is produced in high yield (Φ∆ ≈ 0.5-0.55). The triplet state absorbs across the 450-750 nm region with maxima around 480 and 650 nm, and moderate molar absorption coefficients (ca. 6000-8000 M-1 cm-1). In a glass at 77 K, triplet decay gives a red phosphorescence, with λmax ≈ 640-650 nm, and a ≈ 0.25 s lifetime. If singlet oxygen yields are a good indication of triplet yields, then internal conversion and intersystem crossing occur with roughly equal efficiency.

Distribution and Sources of n-Alkanes and Polycyclic Aromatic Hydrocarbons in Sediments Around Oil Production Facilities in the Escravos River Basin, Niger Delta, Nigeria.

This study provides data on the characteristic levels, spatial patterns, sources, and risk of n-alkanes (AHs) [octane, n-C8, to tetracontane, n-C40] and polycyclic aromatic hydrocarbons (PAHs) in surficial sediments from the Escravos River Basin (ERB), Nigeria. The n-alkane and PAH concentrations in sediments were quantified by chromatographic methods. The concentrations of AHs and PAHs in the ERB sediments varied from 95 to 3430 µg g-1 and from 0.75 to 213 µg g-1, respectively. Both the concentrations of AHs and PAHs in ERB sediments exceeded their respective guideline values. The carbon preference index and other AH markers provide evidence that the AHs in the ERB sediments originated from petroleum sources. Ecological risk assessment indicated that the ecological risk relating to an organism's contact with PAHs in the ERB sediments was high. The possible carcinogenic risk arising from human exposure with PAHs in surface sediments through accidental oral ingestion and skin contact exceeded the safe level of 10-6, indicating a considerable probable cancer risk for fishermen and other inhabitants of the ERB. PAH isomer ratios and multivariate statistics suggested that the PAHs in sediments from the ERB originated from gas flaring inputs, discharges from oil drilling platforms, diesel engines, ships, and speed boats, and combustion of wood and other biomass.

Impact of Land-Use Types on the Distribution and Exposure Risk of Polycyclic Aromatic Hydrocarbons in Dusts from Benin City, Nigeria.

The concentrations of the sixteen United States Environmental Protection Agency polycyclic aromatic hydrocarbons (PAHs) were determined in dusts from different land-use types in Benin City by means of gas chromatography-mass spectrometry. The results obtained were used to assess the ecological and human health risk and to determine the source apportionment. The Æ©16 PAH concentrations in dusts from Benin City ranged from 230 to 2300 µg kg-1 for industrial areas, 211-1330 µg kg-1 for commercial areas, 153-1170 µg kg-1 for residential areas, and from 216 to 1970 µg kg-1 for school playgrounds/parks. The ecological risk assessment suggested that the levels of PAHs in dusts from these land-use types are of low-to-moderate risk to organisms. The benzo(a)pyrene carcinogenic potency [BaPTEQ] (70.5-131 µg kg-1) and benzo(a)pyrene mutagenic potency [BaPMEQ] (62.9-122 µg kg-1) concentrations were below the Canadian soil quality guideline value of 600 µg kg-1. The incremental lifetime carcinogenic risk (ILCR) arising from exposure of adults and children to PAHs in dusts from Benin City were in the magnitude of 10-4-10-2, which exceeded the safe target levels of 10-6, implying a considerable cancer risk for residents of this city. The PAH source apportionment derived from isomeric ratios and multivariate statistics indicated that burning of biomass, wood, and charcoal, and vehicular traffic were the predominant sources of PAHs in dusts from Benin City.

Concentrations, sources, and exposure risk of polychlorinated biphenyls in soil profiles of the floodplain of the lower reaches of the River Niger, Nigeria.

The concentrations of 28 polychlorinated biphenyls (PCBs) were determined in soils collected at three depths from thirteen different sites along the floodplain of the lower reaches of the River Niger (LRRN) in Nigeria. The aim of the study was to provide data on the levels of contamination, sources of the contaminants, and risks to the ecosystem and humans. Soil samples were Soxhlet extracted with a solvent mixture of dichloromethane (DCM)/n-hexane and cleaned up on a column packed with Florisil and silica gel. The PCBs in the samples were quantified by gas chromatography-mass spectrometry. The Æ©28 PCB concentrations in the floodplain soils varied between not detected (nd) and 11,151 ng g-1 for different sampling sites and depths. The PCB concentrations and homologue distribution patterns in soil profiles of the floodplain of the LRRN showed remarkable differences with respect to sites and depths. The results obtained were used to evaluate the ecological and human health risks, which indicated that there is a potential risk to organisms and humans from exposure to PCBs in these soil profiles. The source evaluation as determined by principal component analysis suggested that PCBs in these soil profiles came from burnt circuit boards, cable wires, use of paints, discharges from transformers, long-range migration, and deposition.

Occurrence, sources and ecological and human health risks of polycyclic aromatic hydrocarbons in soils from some functional areas of the Nigerian megacity, Lagos.

The study investigated the levels of the USEPA 16 PAHs in soils collected from selected functional areas (cemetery, commercial, industrial and residential areas) of the Nigerian megacity, Lagos. The soil samples were subjected to ultrasonic-assisted extraction in a 1:1 (v/v) mixture of dichloromethane/hexane, and the PAHs in the resulting extracts were determined by gas chromatography-mass spectrometry. The Σ16 PAHs in soils of these functional areas varied between 890-4675, 485-4513, 111-15,577 and 509-2047 µg kg-1 for cemetery, industrial, commercial and residential areas, respectively. The benzo(a)pyrene carcinogenic (BaPTEQ) and mutagenic equivalency (BaPMEQ) values of PAHs in these soils spanned from 523 to 1046 and 446 to 1129 µg kg-1, respectively. The hazard index values suggested that there are adverse (non-carcinogenic) health effects for a child's exposure to PAHs in soils of commercial areas. The cancer risk values resulting from an adult's and a child's exposure to PAHs in these urban soils via dermal contact and oral ingestion surpassed the target value of 10-6 which suggested that there is a considerable cancer risk relating to human exposure to PAHs in these urban soils. An ecological risk assessment making use of soil quality guidelines and risk quotients suggested a low ecological risk to organisms in soils of these functional areas except for those from commercial areas. PAH isomeric ratios and principal component analysis indicated that PAHs in these soils arise from petrogenic inputs, such as occasional spills of liquid petroleum fuels and discharges from automobile workshops and generator houses, as well as pyrogenic processes including traffic emissions and combustion of fossil fuels and biomass.

Characterization of metals in indoor dusts from electronic workshops, cybercafés and offices in southern Nigeria: Implications for on-site human exposure.

The levels of Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn, Zn, Al and Fe were evaluated in indoor dusts from electronic workshops, cybercafés and offices in southern Nigeria. The study was aimed at providing information on the distribution patterns, and the associated risks that may arise from exposure of humans to these metals in indoor dusts from the three work environments. The dust samples were digested with aqua-regia and analyzed for the metal concentrations by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The metal concentrations (mg kg-1) in the indoor dusts from these work environments ranged from 0.2 to 20.5 Cd, 0.6-4810 Pb, 8.65-2210 Cr, 1.85-209 Ni, 6.75-2820 Cu, 0.25-19.6 Co, 22.7-597 Mn, 6.65-140 Ba, 43.3-7310 Zn, 1040-16,800 Al and 969-78,300 Fe. The metal distribution patterns in these dust samples followed the order: electronic workshops > cybercafés > offices. The concentrations of Cd, Pb and Cu in significant proportions of the dust samples from the electronic workshops and cybercafés surpassed their respective permissible limits in soils. The health risk assessment suggests considerable non-cancer risks arising from childhood contact with Pb in dust from the electronic workshops while no considerable non-cancer risk is associated with the adult and child exposure to dust from the cybercafés and offices. The results indicated that Cr and Pb are the main elements responsible for the non-carcinogenic risk arising from childhood exposure to electronic workshop dusts. The carcinogenic risk due to exposure of humans to metals in these dust samples were within the range regarded as safe by the USEPA.

Evaluation of human exposure to metals from some commonly used bathing soaps and shower gels in Nigeria.

The concentrations of nine metals (Cd, Pb, Ni, Cr, Co, Cu, Fe, Mn and Zn) were measured in selected brands of medicated, moisturizing and skin-lightening soaps and shower gels with the aim of evaluating the human health risk associated with metal exposure from the use of these products. The concentrations of metals in these products were determined by means of atomic absorption spectrophotometry after sample digestion with a mixture of acids. The concentration ranges of the metals in the bathing soaps and shower gels were found to be: <0.06-3.4 µg g-1 for Cd, <0.09-26.5 µg g-1 for Pb, <0.12-43.0 µg g-1 for Cr, <0.06-32.5 µg g-1 for Ni, <0.06-40.5 µg g-1 for Cu, <0.12-8.0 µg g-1 for Co, 61.8-4000 µg g-1 for Fe, <0.09-29.5 µg g-1 for Mn, and 25.5-1000 µg g-1 for Zn. The systemic exposure dosage values for these metals obtained from the application of these brands of bathing soaps and shower gels were below their respective provisional tolerable daily intake/or recommended daily intake values. The margin of safety values obtained for the metals were greater than 100 which indicated that there was no significant risk to the users of these brands of bathing soaps and shower gels, except in the case of Co.

Safety Evaluation of Metal Exposure From Commonly Used Hair Dyes and Tattoo Inks in Nigeria.

In the study described in this article, the concentrations of metals (cadmium, copper, chromium, aluminum, lead, nickel, zinc, cobalt, manganese, and iron) in samples of some commonly used hair dyes and tattoo inks were determined with a view to providing information on the hazards associated with the use of these products. The concentrations of metals were measured after nitric acid/perchloric acid/hydrogen peroxide digestion by atomic absorption spectrometry. Results indicated that the tattoo ink samples contained allergenic metals such as nickel, chromium, and cobalt at concentrations above the suggested limit of 1 µg/g for greater skin protection, and the toxic metals were below their respective prescribed limits, as impurities in ingredients for use for cosmetics, in the majority of the samples.

Polycyclic aromatic hydrocarbons in three commercially available fish species from the Bonny and Cross River estuaries in the Niger Delta, Nigeria.

The concentrations and compositional patterns of the USEPA 16 polycyclic aromatic hydrocarbons were investigated in three commercially available fish species, Chrysichthys nigrodigitatus, Cynoglossus senegalensis and Polydactylus quadratifilis, from the Bonny and Cross River systems in the eastern Niger Delta of Nigeria. The objective of the study was to provide useful information on the levels and sources of polycyclic aromatic hydrocarbons (PAHs) and the associated risks with their consumption. The 16 PAHs in the fish samples were extracted by ultrasonication with hexane/dichloromethane, and the concentrations of PAHs in the extracts were quantified by gas chromatography-mass spectrometry. The measured concentrations of the Æ©16 PAHs in Chrysichthys nigrodigitatus, Polydactylus quadratifilis and Cynoglossus senegalensis ranged from 106 to 491, from 43.1 to 1734 and from 96.4 to 937 µg kg(-1) in the Bonny River system and from 20.0 to 975, from 24.7 to 506 and from 24.9 to 387 µg kg(-1) in the Cross River system, respectively. The compositional patterns of the PAHs showed that the three- and four-ringed PAHs were the major contributors to the PAH burden in these fish species. The diagnostic ratios indicate that the PAHs in these fish samples originated mainly from combustion processes. The health risk assessment, as determined from the benzo[a]pyrene potency equivalent factor, margin of exposure and incremental lifetime cancer risk, indicates that PAHs in the majority of these fish species can induce potential carcinogenic effects.

Safety evaluation of metal exposure from commonly used moisturizing and skin-lightening creams in Nigeria.

The concentrations of ten metals (Cd, Pb, Ni, Cr, Cu, Co, Fe, Mn, Zn and Al) were measured in some commonly used moisturizing and skin-lightening creams in Nigeria with a view to providing information on the risk of exposure to metals from the use of these products. The metal concentrations in these products were measured by atomic absorption spectrometry after acid digestion of the samples. The measured concentrations of metals in the skin moisturizing creams ranged from <0.15 to 6.3 µg/g Cd, <0.02 to 17.5 µg/g Cu, 2.25 to 6.25 µg/g Cr, <0.25 to 124.3 µg/g Al, 0.2 to 7.3 µg/g Pb, <0.03 to 10.7 µg/g Ni, 17.3 to 372.0 µg/g Zn, <0.02 to 1.0 µg/g Co, 17.75 to 28.8 µg/g Mn, <0.1 to 89.8 µg/g Fe while the concentrations of metals in the skin-lightening products ranged from <0.15 to 16.5 µg/g Cd, <0.02 to 10.0 µg/g Cu, 4.25 to 8.0 µg/g Cr, <0.25 to 128.0 µg/g Al, 0.5 to 4.5 µg/g Pb, <0.03 to 1.65 µg/g Ni, 24.7 to 267.5 µg/g Zn, <0.02 to 2.5 µg/g for Co, 19.3 to 31.8 µg/g Mn, 9.5 to 211.63 µg/g Fe. In a significant number (>93%) of the samples investigated the concentrations of Pb, Cd, Ni and Co were below the specified limit, or the maximal limit for impurities in colour additives in cosmetics for external use. However, Cr was found at concentrations above the allergenic limit of 1 µg/g. The results also showed that skin-lightening creams contained higher concentrations of the studied metals than the moisturizing creams, except for Ni, which indicates that persons who uses skin-lightening creams in preference to moisturizing ones, are exposed to higher concentrations of metals.

Polycyclic aromatic hydrocarbons in dust from rural communities around gas flaring points in the Niger Delta of Nigeria: an exploration of spatial patterns, sources and possible risk.

Indoor and outdoor dust from three rural communities (Emu-Ebendo, EME, Otu-Jeremi, OTJ, and Ebedei, EBD) around gas flaring points, and a rural community (Ugono Abraka, UGA) without gas flare points, in the Niger Delta of Nigeria, was analysed for the concentrations and distribution of polycyclic aromatic hydrocarbons (PAHs), their sources, and possible health risk resulting from human exposure to PAHs in dust from these rural communities. The PAHs were extracted from the dust with a mixture of dichloromethane/n-hexane by ultrasonication, and purified on a silica gel/alumina packed column. Gas chromatography-mass spectrometry was employed to determine the identity and concentrations of PAHs in the cleaned extracts. The Σ16PAH concentrations in the indoor dust ranged from 558 to 167 000, 6580 to 413 000, and 2350-37 500 µg kg-1 for EME, OTJ and EBD respectively, while those of their outdoor counterparts varied from 347 to 19 700, 15 000 to 130 000, and 1780 to 46 300 µg kg-1 for EME, OTJ and EBD respectively. On the other hand, the UGA community without gas flare points had Σ16PAH concentrations in the range of 444-5260 µg kg-1 for indoor dust, and 154-7000 µg kg-1 for outdoor dust. The lifetime cancer risk values for PAHs in these matrices surpassed the acceptable limit of 10-6 suggesting a potential carcinogenic risk resulting from human exposure to PAHs in indoor and outdoor dust from these rural communities. Principal component analysis suggested that PAH contamination of dust from these communities arises principally from gas flaring, combustion of wood/biomass, and vehicular emissions.

Safety evaluation of organochlorine pesticides and polybrominated diphenyl ethers in imported canned fish in Nigeria.

Organochlorine pesticide (OCP) and polybrominated diphenyl ether (PBDE) concentrations were measured in thirty popular brands of imported canned fish (mackerel, sardines, and tuna) in Nigeria to ascertain potential threats to humans arising from their consumption. The Σ20 OCP concentrations in mackerel ranged from 0.47 to 7.36 ng g-1, while those of tuna and sardines varied from 1.06 to 2.19 and 0.11 to 12.7 ng g-1, respectively. The Σ39 PBDE concentrations in mackerel varied from 0.06 to 4.21 ng g-1, while those of tuna and sardines ranged from 0.19 to 3.18 and 0.04 to 8.26 ng g-1, respectively. The estimated daily intake (EDI) of OCPs and PBDEs from ingestion of the canned fish by adults and children were in the magnitude of 0.03 to 17.6 ng kg-1 bw day-1 and 9.9 × 10-3 to 11.5 ng kg-1 bw day-1 respectively. The hazard index (HI) and total cancer risk (TCR) values for OCPs and PBDEs from ingestion of the canned fish were less than 1 and 10-6, respectively. The dietary intakes of OCPs and PBDEs from these brands of canned fish by adults and children result in no adverse non-cancer and cancer risks.

Distribution, sources, and risk of polycyclic aromatic hydrocarbons in soils from rural communities around gas flaring points in the Niger Delta of Nigeria.

This study investigates the concentrations, sources, and ecological and human health risks resulting from exposure to polycyclic aromatic hydrocarbons (PAHs) in soils of rural communities around gas flaring points in Delta State, Nigeria. PAHs were extracted from these soil samples with hexane/dichloromethane by ultra-sonication and the extracts were cleaned on a silica gel/alumina-packed column. The PAH concentrations in the extracts were quantified by gas chromatography-mass spectrometry (GC-MS). The Σ16 PAH concentrations in soils from these communities varied from 2370-134 000, 461-389 000, and 2130-34 900 µg kg-1 for Emu-Ebendo (EME), Otu-Jeremi (OTJ) and Ebedei (EBD), respectively. The estimated lifetime carcinogenic risk values recorded in this study were above the acceptable limit of 10-6, indicating a high potential carcinogenic risk resulting from human exposure to PAHs in these soils. The isomeric ratio and principal component analysis results suggest that emissions from high-temperature combustion, potentially gas flaring, vehicular emissions, burning of wood/biomass, and fossil fuel combustion are responsible for the high concentrations of PAHs in soils of these rural communities. This study recommends implementing remediation and source control measures to minimise the impact of PAHs in the affected soils on humans and the environment.

Organochlorine pesticide contamination of soils and dust from an urban environment in the Niger Delta of Nigeria.

The concentrations, sources, and risk of twenty organochlorine pesticides (OCPs) in soils and dusts from a typical urban setting in the Niger Delta of Nigeria were examined. The Σ20 OCP concentrations (ng g-1) varied from 4.49 to 150 with an average value of 32.6 for soil, 4.67 to 21.5 with an average of 11.7 for indoor dust, and 1.6 to 96.7 with an average value of 23.5 for outdoor dust. The Σ20 OCP concentrations in these media were in the order: soil > outdoor dust > indoor dust, which was in contrast with the order of the detection frequency, i.e., indoor dust (95 to 100 %) > soil (60 to 90 %) > outdoor dust (30 to 80 %). The concentrations of the different OCP classes in these media followed the order: aldrin + dieldrin + endrin and its isomers (Drins) > chlordanes > dichlorodiphenyltrichloroethane (DDTs) > hexachlorocyclohexane (HCHs) > endosulfans for outdoor dust and soil, while that of the indoor dust followed the order: Drins > chlordanes > endosulfans > DDTs > HCHs. The cancer risk values for human exposure to OCPs in these sites exceeded 10-6 which indicates possible carcinogenic risks. The sources of OCPs in these media reflected both past use and recent inputs.

Polybrominated diphenyl ether contamination in sediments from rivers in the western Niger Delta of Nigeria.

This study investigated the concentrations of 39 polybrominated diphenyl ether (PBDE) congeners in sediments from three rivers in the western Niger Delta of Nigeria that have been affected by pollution from urbanization and industrial activities. The Σ39 PBDE concentrations in sediments from these rivers ranged from 0.29 to 95.5, 5.15 to 121, and 0.73 to 66.1 ng g-1 for the Afiesere (AR), Edor (ER), and Okpare Rivers (OR), respectively. The homologue distribution patterns indicated the prominence of tetra- and penta-BDE congeners in sediments from these rivers. The ecological risk assessment results showed that the penta-BDEs were the primary source of risk to sediment-dwelling organisms in these rivers. However, the human health risk assessment indicated negligible risks for exposure of both adults and children to PBDEs in these sediments. The source apportionment suggests that the PBDE contamination in these river sediments was derived from long-distance migration, debromination of highly brominated congeners, and commercial penta-BDEs. These results reflect the use of penta-BDE formulations in this region rather than octa- and deca-BDE formulations.

Oxyhalogen-sulfur chemistry: kinetics and mechanism of oxidation of N-acetyl homocysteine thiolactone by acidified bromate and aqueous bromine.

N-acetyl homocysteine thiolactone (NAHT), medically known as citiolone, can be used as a mucolytic agent and for the treatment of certain hepatic disorders. We have studied the kinetics and mechanisms of its oxidation by acidic bromate and aqueous bromine. In acidic bromate conditions the reaction is characterized by a very short induction period followed by a sudden and rapid formation of bromine and N-acetyl homocysteine sulfonic acid. The stoichiometry of the bromate-NAHT reaction was deduced to be: BrO3(-) + H2O + CH3CONHCHCH2CH2SCO → CH3CONHCHCH2CH2(SO3H)COOH + Br(-) (S1) while in excess bromate it was deduced to be: 6BrO3(-) + 5CH3CONHCHCH2CH2SCO + 6H(+) → 3Br2 + 5CH3CONHCHCH2CH2(SO3H)COOH + 2H2O (S2). For the reaction of NAHT with bromine, a 3:1 stoichiometric ratio of bromine to NAHT was obtained: 3Br2 + CH3CONHCHCH2CH2SCO + 4H2O → 6Br(-) + CH3CONHCHCH2CH2(SO3H)COOH + 6H(+) (S3). Oxidation occurred only on the sulfur center where it was oxidized to the sulfonic acid. No sulfate formation was observed. The mechanism involved an initial oxidation to a relatively stable sulfoxide without ring-opening. Further oxidation of the sulfoxide involved two pathways: one which involved intermediate formation of an unstable sulfone and the other involves ring-opening coupled with oxidation through to the sulfonic acid. There was oligooscillatory production of aqueous bromine. Bromide produced in S1 reacts with excess bromate to produce aqueous bromine. The special stability associated with the sulfoxide allowed it to coexist with aqueous bromine since its further oxidation to the sulfone was not as facile. The direct reaction of aqueous bromine with NAHT was fast with an estimated lower limit bimolecular rate constant of 2.94 ± 0.03 × 10(2) M(-1) s(-1).

Oxyhalogen-sulfur chemistry: kinetics and mechanism of oxidation of captopril by acidified bromate and aqueous bromine.

By nature of their nucleophilicity, all thiol-based drugs are oxidatively metabolized in the physiological environment. The key to understanding the physiological role of a hypertension drug, (2S)-1-[(2S)-2-methyl-3-sulfanylpropanoyl]pyrrolidine-2-carboxylic acid, medically known as captopril is through studying its oxidation pathway: its reactive intermediates and oxidation products. The oxidation of captopril by aqueous bromine and acidified bromate has been studied by spectrophotometric and electrospray ionization techniques. The stoichiometry for the reaction of acidic bromate with captopril is 1:1, BrO3(-) + (C4H6N)(COOH)(COCHCH3CH2)-SH → (C4H6N)(COOH)(COCHCH3CH2)-SO3H + Br(-), with reaction occurring only at the thiol center. For the direct reaction of bromine with captopril, the ratio is 3:1; 3Br2 + (C4H6N)(COOH)(COCHCH3CH2)-SH + 3H2O → (C4H6N)(COOH)(COCHCH3CH2)-SO3H + 6HBr. In excess acidic bromate conditions the reaction displays an initial induction period followed by a sharp rise in absorbance at 390 nm due to rapid formation of bromine. The direct reaction of aqueous bromine with captopril was much faster than oxidation of the thiol by acidified bromate, with a bimolecular rate constant of (1.046 (±0.08) × 10(5) M(-1) s(-1). The detection of thiyl radicals confirms the involvement of radicals as intermediates in the oxidation of Captopril by acidified BrO3(-). The involvement of thiyl radicals in oxidation of captopril competes with a nonradical pathway involving 2-electron oxidations of the sulfur center. The oxidation product of captopril under these strong oxidizing conditions is a sulfonic acid as confirmed by electrospray ionization mass spectrometry (ESI-MS), iodometric titrations, and proton nuclear magnetic resonance ((1)H NMR) results. There was no evidence from ESI-MS for the formation of the sulfenic and sulfinic acids in the oxidation pathway as the thiol group is rapidly oxidized to the sulfonic acid. A computer simulation analysis of this mechanism gave a reasonably good fit to the experimental data.

Chemical analysis and in vitro†UV-protection characteristics of clays traditionally used for sun protection in South Africa.

Clays have been used in southern Africa as photoprotectants by the indigenous people. Typically, two types of clay are used: one white in colour and the other red. In this work, the two clays were identified and characterized, and their in vitro SPF values measured. The clays afford a low SPF but offer broad-spectrum protection. No cutaneous side effects from the use of these clays are known. Further consideration should be given to the potential use of clays in sunscreen preparations.

Wastewater profiling of illicit drugs, an estimation of community consumption: A case study of eThekwini Metropolitan Municipality, South Africa.

Estimation of community-wide consumption of illicit drugs through wastewater analysis is a new concept in Africa although widely applied in developed nations as wastewater-based epidemiology (WBE). It is an important tool that can be used in understanding supply and demand patterns of illicit drug use on a local, national, and international scale. Information on illicit drug use is currently limited in Africa, because of a lack of monitoring structures by governments and financial constraints. This study hopes to bridge that gap by contributing to Africa's baseline information on illicit drug use. This study provides the first application of wastewater analysis to quantitatively evaluate daily illicit drug use in the eThekwini Metropolitan Municipality of KwaZulu-Natal Province of South Africa by quantifying the major urinary excreted metabolites, called drug target residues (DTRs), in raw wastewater from four major wastewater treatment plants (WWTPs) sampled for a week. The results showed that cocaine was the dominant illicit drug consumed in the catchment followed by amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine and 3,4-methylenedioxyamphetamine, with a per capita use of 360-3000 mg day-1 1000 inh-1, 47-800 mg day-1 1000 inh-1, 19-120 mg day -1 1000 inh-1, not detected (ND) to 4.9 mg day-1 1000 inh-1, and ND to 410 g day-1 1000 inh-1 respectively. The weekly usage patterns between the four WWTPs differed probably due to the lifestyle of the populace serving the different WWTPs. These results provide useful data on illicit drug use in eThekwini that can be utilised by public health agencies to implement suitable response strategies.

Spatial distribution of polycyclic aromatic hydrocarbons in dust and soils from informal trade sites in southern Nigeria: Implications for risk and source analysis.

Polycyclic aromatic hydrocarbons (PAHs) are a group of semi-volatile and persistent organic compounds considered priority pollutants because of their pervasive nature and high toxicity to the ecosystem and humans. Therefore, this study aimed to evaluate the PAH concentrations in dust and soils around informal trade sites (ITS) in Nigeria to determine the level of risk, sources, and significance of these activities to the PAH load of the environment. The 16 US EPA PAHs in dust and soils from ITS were determined by gas chromatography-mass spectrometry (GC-MS). The PAH concentrations in dust from these informal trade sites varied from 120 to 8790, 56 to 4780, and 102-1090 µg kg-1 for automobile mechanic workshops (AMW), car dismantling (CDS), and material recovery sites (MRS), respectively, whereas those of soils ranged from 3000 to 95,500, 554 to 14,700, and 966-25,200 µg kg-1 for AMW, CDS, and MRS respectively. The PAH profiles indicated that 3- to 5-ring PAHs were prominent in dust and soils around the ITS. The concentrations of the US EPA 16 PAHs in dust and soils from these ITS showed no correlation with organic matter, while the concentrations of PAH homologues in soils of these ITS showed no correlation with those of dust. Incremental lifetime cancer risk (ILCR) values in the magnitude of 10-4 to 101 were obtained for adult and childhood exposure to PAHs in dust and soils from these ITS. Exposure to PAHs in dust from these ITS gives rise to less risk than for soils. The results indicated that automobile mechanic workshops contribute more PAHs to the environment than car dismantling and material recovery activities. The source analysis showed that the PAH contamination of these sites arises from burning of biomass, plastic materials, and oils, and emissions from vehicles.