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Methods have been developed for the hydrolysis and derivatisation of protein-bound metabolites of nitrofurans and for the extraction of 2-nitrobenzaldehyde derivatives of the metabolites from chicken meat. In this work, the time needed for hydrolysis and derivatisation was reduced from the conventional 16 h to 90 min. Based on partitioned dispersed liquid-liquid microextraction, a method for extracting 2-nitrobenzaldehyde derivatives of metabolites from crude chicken meat has been developed. Under the optimised experimental conditions, enrichment factors (EFs) ranging from 92.8 to 208.9 were obtained. The method was linear over the range of 10-600 µg kg

Novel electrospun

Mondia whitei is one of the popular medicinal plants in Africa, which has been used extensively across the continent to cure various ailments. Products prepared from this plant are distributed commercially. In this study, an HPLC-DAD method was developed and validated for seven compounds to enable quality control of these products. The method was validated using the external standard-calibration and the standard-addition methods which were found not significantly different. The method was found to be linear in the ranges 1–14 mg/L and 3–14 mg/kg with correlation coefficients from 0.9942–0.9995 and 0.9907–0.9993 in the solvent and the different matrices, respectively. The limit of detection (LOD) values of the method were found to range between 0.1–1.2 mg/L in the solvent and syrup, and between 0.4–1.2 mg/kg in the teabag and root powder. The limit of quantification (LOQ) values were found to range between 0.5–3.9 mg/L in the solvent and syrup, and between 1.4–3.8 mg/kg in the teabag and root powder. The method was also found to be precise with percentage relative standard deviations below 5% and 10% in the solvent and matrices, respectively. The method was applied to Mondia whitei products for qualitative and quantitative analysis.

Pollutants mainly exist as multicomponent mixtures in the environment. Therefore, it is necessary to synthesize low-cost adsorbents that can simultaneously adsorb multiple compounds. This work presents the prospect of the adsorption of multiclass pharmaceuticals from the aqueous environment using an adsorbent derived from silk fibroin of the wild silkworm Argema mimosae. The adsorbent was prepared by dissolving degummed silk fibroin and the resultant solution was cast to obtain films that were ball-milled to powder. FTIR results revealed bands corresponding to N-H and C=O stretching vibrations. Particle size distribution data generally showed two size groups in the range of 50–90 nm and 250–625 nm. The study focused on the adsorptive removal of multiple compounds consisting of eight pharmaceuticals representing various classes including a β-blocker (pindolol), anesthetic (lidocaine), stimulant (caffeine), antiviral (nevirapine), steroid (estriol), anti-epileptic (carbamazepine), and a non-steroidal anti-inflammatory drug (naproxen). The adsorption process was best fitted to the pseudo-second-order isotherm and an overall match to the Freundlich model. Thermodynamic parameters suggested that the process was mainly exothermic and more spontaneous at lower temperatures. The performance of the adsorbent was further evaluated using environmental waters and the adsorbent demonstrated good potential for simultaneous adsorption of multicomponent pharmaceuticals.

Limited studies have been done on silk fibroins of wild silkworm species owing to their relative insolubility in many solvents. In this study, the solubility of Argema mimosae wild silk fibroin in different salts (LiBr, LiCl, Ca(NO3)2, and CaCl2) dissolved in formic acid under varying temperatures was investigated. The dissolution conditions under which the solubility was optimum were optimized using a central composite design approach. The optimum range for solvation of the fibroin were visualized using contour plots. The influence of temperature and salt concentration were found to significantly influence the solvation of the fibroin. Following the successful dissolution of the fibroin, the regenerated silk fibroin solutions were cast to obtain water insoluble films which were used in investigating optimum electrospinning conditions. Average nanofiber diameters in the 110–141 nm range were obtained under optimum electrospinning conditions. The silk forms were characterized using the FTIR, TGA, XRD, and SEM to understand their properties. The investigations revealed that formic acid—salt solvents were effective in the solvation of the wild silk fibroin. Some of the dissolution conditions induced mild effects on the silk fibroin while others were harsh. Furthermore, processing to nanofibers resulted in the degradation of the β-sheets producing nanofibers rich in α-helices. However, post-treatment using methanol and water vapor were effective in restoring β-sheet crystallinity.

The Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) from the Golinga reservoir in Northern Ghana are consumed as an alternative source of protein. In the current study, levels of selected metals (As, Cd, Fe, Co, Cr, Cu, Mn, Mo, Ni and Pb) in the two fish species and the fish condition were determined, and potential human health effects assessed. The metal concentrations in the edible fish muscles ranged from 0.16 mg kg-1 (Mn) to 101 mg kg-1 (Pb). The weight-length relationships showed that both fish were growing isometrically, and bioaccumulation of metals from the reservoir was considered insignificant with bioconcentration factors below 100 except for Mn, whose value was 161 in the gills of Oreochromis niloticus. The health risk assessment showed that Pb, Cd and As had Target Hazard Quotient values above 1 for both fish species, with that of As being as high as 19.6 for Oreochromis niloticus. The target cancer risk values for As, Cd, Cr and Pb were above the non-risk threshold of

In the current study, the removal of Cd(II), Pb(II) and Cu(II) ions from industrial effluent was investigated using powdered Moringa stenopetala seed husk. The surface functionality, morphology, crystallinity, thermal stability, the surface charge and surface area of the powdered Moringa stenopetala seed husk was studied using FTIR, SEM, XRD, TGA, zeta potential and BET, respectively. Processing parameters, namely contact time, adsorbent dosage, concentration, pH, agitation speed, temperature and particle size were investigated using the batch adsorption method. The maximum adsorption percentage for Cd(II), Pb(II) and Cu(II) ions from synthetic wastewater was found to be 99.1, 99.4 and 99.1%, compared to 95.3, 95.5 and 94.1%, respectively, for adsorption of these metal ions from real wastewater. The maximum adsorption capacity was found to be 52.63, 47.62 and 31.25 mg/g adsorbent for Cd(II), Pb(II) and Cu(II), respectively. The Freundlich isotherm provided a better fit for the adsorption equilibrium data than the Langmuir isotherm, while the kinetics were well defined by the pseudo-second-order model (R

This work demonstrates the potential of Moringa stenopetala bark powder as an adsorbent for the removal of heavy metals from wastewater. The bark powder was characterised using FTIR, XRD, zeta potential, TGA, SEM and BET techniques. Several processing parameters such as; contact time, adsorbent dose, concentration, pH, agitation speed and temperature were optimised. Using the optimum conditions the maximum removal efficiency of three heavy metals, Cd (II), Pb (II) and Cu (II) were 99.08, 99.68 and 99.60% from synthetic wastewater respectively. When applied to industrial real wastewater the removal efficiency was 94.80, 95.50 and 94.23% for Cd (II), Pb (II) and Cu (II) respectively. The adsorption equilibria observed is in accordance to the Freundlich isotherm than the Langmuir isotherm. The maximum adsorption capacity of 38.46 ± 0.21, 35.71 ± 0.86 and 34.48 ± 0.93 mg g−1 was observed for Cd (II), Pb (II) and Cu (II). The interaction of the cationic species with the bark powder was predominately via chemisorption rather than physisorption. The adsorption of the three metals ions,Cd (II), Pb (II) and Cu (II) was well defined by the pseudo-second order model (R2 = 1). The thermodynamic parameters such as ΔS, ΔH and ΔG were also determined. The calculated values of ΔH and ΔS were positive which indicated that the adsorption of metal ions on the adsorbent was an endothermic process. However, ΔG exhibited the negative values confirming that the adsorption process was spontaneous.

In this study, the removal of Cd2+, Pb2+ and Cu2+ ions from industrial effluent was investigated using Moringa stenopetala seed powder. The surface functionality, morphology, crystallinity, thermal stability and charge of the Moringa stenopetala seed powder was studied using FTIR, XRD, zeta potential, TGA, SEM and BET. Equilibrium isotherms, kinetic and thermodynamic models for three metal ions removal were also studied. The maximum percentage adsorption under optimum conditions of Cd2+, Pb2+ and Cu2+ ions from synthetic wastewater were 99.65, 99.66 and 99.42%, whereas that from industrial effluent were 94.17, 94.67 and 92.81%. The results of the adsorption equilibria fit the Freundlich isotherm (R2 ≥ 0.926) than Langmuir isotherm. The maximum adsorption capacity was found to be 23.26, 16.13 and 10.20 mg/g for Cd2+, Pb2+ and Cu2+ ions respectively. On the other hand, the adsorption of Cd2+, Pb2+ and Cu2+ ions were well defined by the pseudo-second order model (R2 = 1). Furthermore, the calculated values of ΔH were 54.59, 52.01 and 54.55 KJ mol−1, ΔS were 201.94 J/K−1 mol−1, 194.79 J/K−1 mol−1, and 199.45 J/K−1 mol−1 for Cd2+, Pb2+ and Cu2+ ions respectively. The positive value of ΔH indicated that the adsorption of metal ions on the adsorbent was an endothermic process.

The ball-milling of carbon-based materials with nanoparticles is currently emerging as a promising cost-effective alternative method of producing nanocomposites with great surface characteristics. Biochar-based nanocomposites are effective in the adsorption of heavy metals, dyes and emerging organic contaminants in water and wastewater because of the combined benefits of biochar and nanoparticles. Contaminants of emerging concern are increasingly being detected in the environment and there is, therefore, an urgent need to develop nanotechnology-based multifunctional and highly efficient processes that can remove a wide range of these chemicalsmost of which are persistent and may bioaccumulate. To date, not many reviews are available on the use of the ball-milling method for engineering biochar-based nanocomposites. Ball milling (solid-state synthesis) is a process extensively used in industry to synthesize nanomaterials. Ball milling process produces small particle size as small as 10 microns, coupled with the advantages of continuous operation. Thus, this review article aims to provide an overview of the efficiencies of the ball-milled biochar-nanoparticle composite. Ball milling approach improves the physicochemical properties of biochar and biochar–nanoparticle composite such as total and micropore surface of biochar which in turns enhance their sorption abilities. Different adsorption mechanisms of biochar and modified biochar have been reported, which include physisorption, chemisorption, ion-exchange, pore-filling, hydrophobic effects and π-π electron donor-acceptor (π-π EDA) interactions.

This contribution report is the 1st synthesis of nano-scaled Pd and PdO by a completely green process using Aspalathus linearis natural plant extract as an effective bio-reducing as well as a capping agent. Their spherical-like size was found to range within 〈O particles 〉 = 3.8–22 nm. Their morphological, structural and optical properties were investigated using various complementary surface/interface characterization techniques such as HR-TEM, DSC, XRD, EDS, XPS, and Raman spectroscopy. The results confirmed the formation of single fcc Pd and pure tetragonal PdO nanocrystals upon annealing at 100 and 600°C in standard air conditions. It was found that the dynamic of the complete oxidation of the bio-synthesized Pd nanocrystals into single phase PdO is very fast; ∼2 h instead 10–20 h classically.

The study determined the levels of selected metals (Mg, Ca, K, P, B, Na, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, As, Cd, Sb, Ba and Pb) and further performed a health risk assessment on consumption of two traditional African vegetables, jute mallow (Corchorus olitorius) and roselle (Hibiscus sabdariffa) collected from the Golinga irrigation farms in Northern Ghana. The concentration of essential elements ranged between 1.50 (Mo) and 368 (Fe) mg kg−1 for Corchorus olitorius and 1.01 (Cu) and 308 (Mn) mg kg−1 for Hibiscus sabdariffa. Most of the essential elements were within the permissible limits except for Cr (31.9 mg kg−1 in the wet season) and As (13.4–32.1 mg kg−1) which were higher than the WHO/FAO guidelines of 5 and 0.5 mg kg−1, respectively. The concentration of toxic metals (Cd and Pb) was above the permissible limits in both vegetables reaching 31.4 and 39.0 mg kg−1, respectively. Human health risk assessment using Hazard Quotients showed that only As had the potential to increase above non-acceptable levels and cause non-cancerous health risks during a life-time consumption of Hibiscus sabdariffa vegetable while Corchorus olitorius is relatively safe and can be a beneficial source of essential elements.

Silk sericin was extracted from the cocoons of three Southern African wild silk moth species, namely Gonometapostica, G. rufobrunnae (Lepidoptera: Lasiocampidae), and Argemamimosae (Lepidoptera: Saturniidae), these three sericin extracts were analysed to determine the relationship that exists between their chemical structures and their functional properties. The relationship was investigated by utilising several methods that include the determination of the amino acid composition, and characterisation of the secondary structures with Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The antibacterial properties of these three sericin extracts were evaluated by an agar well diffusion assay with three Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis) as test microorganisms, and, lastly, the antioxidant properties of the three sericin extracts were determined using several scavenging methods that include the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), 2,2&prime, azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS˙+), and the ferric reducing antioxidant power (FRAP) assay. The amino acid composition in the silk sericin extracts from G. postica, G. rufobrunnea, and Argemamimosa in terms of the polar/non-polar ratio (P/NP) was found to be 65:35, 56:44, and 59:41, respectively. The FTIR spectra of these three silk sericin extracts showed distinct major bands such as amide A (3265 cm&minus, 1), amide B (3062 cm&minus, 1), amide I (1644 cm&minus, 1), amide II (1538 cm&minus, 1), and amide III (1244 cm&minus, 1). The XRD patterns of the silk sericin extracts revealed both amorphous and &alpha, helical structures, with small crystalline regions. All three silk sericin extracts presented potent antibacterial efficacy against the three Gram-positive bacteria and were found to have excellent antioxidant activities against the tested free radicals.

In the current work, the nanofibers fabricated from Mondia whitei root extract were used for the adsorption of 13 antiretroviral (ARVs) and related drugs from wastewater (influent and effluent). The nanofibers were characterized using Fourier Transform Infrared Spectroscopy, Brunauer–Emmett–Teller method and Scanning Electron Microscopy. The adsorption capacity of the nanofibers was investigated for each optimised parameter which might affect the adsorption potential (concentration, dosage, contact time, pH and temperature). The experimental data fitted to Langmuir and Freundlich adsorption isotherms, however, equilibrium behaviour was well explained by the latter. The kinetic behaviour was well predicted by pseudo-second-order kinetics. The results from Webber-Morris model confirmed that intraparticle diffusion was involved in the adsorption process; however, diffusion was not the rate limiting step. The maximum adsorption capacity of the adsorbent for ARVs and related drugs were in the range of 75–320 mg g−1 (75.07 ± 0.9–92.85 ± 0.1.).

A novel environmentally benign method was developed for the simultaneous removal of sulphonamides and multiclass class of veterinary drugs using mesoporous nanofibers. Processing parameters which affect the removal efficiency, such as pH, initial analyte concentration, adsorbent dosage and contact time were studied. An optimised method was applied to a real wastewater samples collected from Daspoort Wastewater Treatment Plant (WWTP), South Africa. Under optimum conditions, the removal efficiency of veterinary drugs from effluent and influent ranged from 35.24–94.57 ± 0.24 and 31.71–76.91 ± 0.65 mg g−1, respectively. The surface area, cumulative volume of pores and average pore diameter of the nanofibers were determined as 2402.62 ± 13.62 m2 g−1, 2.04 cm3 g−1 and 3.39 nm, respectively. The maximum adsorption capacity was ranged from 166 to 1000 mg g−1. The adsorption kinetics obeyed the pseudo-second-order rate equation suggesting that particle diffusion was the rate-limiting mechanism for adsorption of veterinary drugs on electrospun nanofibers.

The removal of ten selected antibiotic drugs belonging to different classes (sulphonamides, fluoroquinolones, macrolides, and tetracycline) was investigated using water-soluble proteins from the seeds of Moringa stenopetala. The surface functional groups of water-soluble protein powder before and after removal of antibiotics were characterized using Fourier transform infrared (FTIR). Processing parameters that could affect the removal efficiency, such as initial analyte concentration, protein dosage, and pH were studied. An optimized method was applied to a real wastewater sample collected from Daspoort Wastewater Treatment Plant (WWTP) located in Pretoria, South Africa. Under optimal conditions, the results indicated good agreement between the efficiency of water-soluble proteins to remove antibiotics from the real wastewater sample and from the synthetic wastewater sample prepared in the laboratory using standard solutions with known concentrations. The percentage of removal under optimum conditions (protein dosage of 40 mg, initial analyte concentration of 0.1 mg L&minus, 1, and pH 7) was between 85.2 &plusmn, 0.01% and 96.3 &plusmn, 0.03% for standard mixture solution and from 72.4 &plusmn, 0.32% to 92.5 &plusmn, 0.84% and 70.4 &plusmn, 0.82% to 91.5 &plusmn, 0.71% for the real wastewater (effluent and influent) sample.

Isinuka Springs at Port St Johns in the Eastern Cape Province of South Africa is a traditional spa sacred to the AmaMpondo tribe of the Xhosa speaking people. The bathing pond is considered to have healing powers both spiritually and therapeutically. Hundreds of people flock into the spiritual pond every weekend for both recreational and its spiritual healing power. In this study, we present the metal concentrations of the bathing pond (sediments and water samples), the hole drinking water as well as sediments from a cave situated at the bottom of the hill harbouring the bathing pond. Our results show that the geophagic clays from the cave and bathing pond has elevated concentrations of earth metals (up to 134,506 mg kg−1 for calcium), trace metals (up to 36,272 mg kg−1 for iron) and toxic metals (up to 25 mg kg−1 for lead). The levels of both essential and toxic metals in the drinking water were above the recommended daily limits except for zinc and copper. Aluminium, a metal with antibacterial activity was as high as 71,792 mg kg−1 in pond sediments. Even though the results show elevated concentrations especially for toxic metals, the study observes that the spa remains limited in potential for metal toxipathy because the frequency of contact with the pond is minimal estimated at once a week by traditional healers and once a month for locals while visitors from other parts of the province rarely come back.

A valuable method for the efficient removal of sulphonamides from wastewater using protein powder extracted from the seeds of Moringa stenopetala is presented in this study. The surface morphology, crystallinity and functional groups of protein powder were characterised by SEM, XRD, FTIR and Raman spectrometry. Parameters that affect the removal of sulphonamides, such as concentration, the adsorbent dosage and pH, were optimised. The method was applied to a real wastewater sample collected from the Daspoort Wastewater Treatment Plant located in Pretoria, South Africa. The percentage removal under optimum conditions was observed to be 86.4 to 95.1% for the aqueous solution of a mixture of standards and from 83.0 to 90.5% and 75.2 to 87.7 % for the effluent and influent wastewater samples respectively. Therefore, proteins extracted from Moringa stenopetala seeds demonstrated to be effective and environmentally friendly material for possible application in water treatment in general and wastewater treatment in particular.

The focus of this study was on developing a method for the effective removal of non-steroidal anti-inflammatory drugs (ketoprofen, fenoprofen, diclofenac and ibuprofen) and carbamazepine from wastewater using nanofibres from Moringa seeds protein/PVA blend. Parameters that could affect the removal of selected pharmaceuticals such as adsorbent dosage, pH, initial concentration, temperature and contact time were optimised. The optimized method was applied to real wastewater samples collected from a wastewater treatment plant. Under optimum conditions, the percentage removal was found to range from 84.5 to 97.4% for standard mixture solution and from 70.5% to 92.5 and 77.8. to 96.1% for the real wastewater (i.e. influent and effluent respectively). The adsorption data was well fitted in the Freundlich isotherm than Langmuir isotherm for all the groups of pharmaceuticals studied. The maximum adsorption capacity obtained ranged from 31.25 to 333.33 mg g−1. The interaction between the drugs and the nanofibres predominantly occurred by chemisorption rather than by physisorption. The results obtained demonstrated that nanofibres fabricated from biomaterials could perform better than previously published materials.

Nine metals (Fe, Cu, Mn, Ni, Cd, Pb, Hg, Cr, and Zn) were determined in soil and Digitaria eriantha plants within the vicinity of three coal power plants (Matla, Lethabo, and Rooiwal), using ICP-OES and GFAAS. The total metal concentration in soil ranged from 0.05 ± 0.02 to 1836 ± 70 μg g(-1), 0.08 ± 0.05 to 1744 ± 29 μg g(-1), and 0.07 ± 0.04 to 1735 ± 91 μg g(-1) in Matla, Lethabo, and Rooiwal, respectively. Total metal concentration in the plant (D. eriantha) ranged from 0.005 ± 0.003 to 535 ± 43 μg g(-1) in Matla, 0.002 ± 0.001 to 400 ± 269 μg g(-1) in Lethabo, and 0.002 ± 0.001 to 4277 ± 201 μg g(-1) in Rooiwal. Accumulation factors (A) of less than 1 (i.e., 0.003 to 0.37) at all power plants indicate a low transfer of metal from soil to plant (excluder). Enrichment factor values obtained (2.4-5.0) indicate that the soils are moderately enriched with the exception of Pb that had significant enrichment of 20. Geo-accumulation index (I-geo) values of metals indicate that the soils are moderately polluted (0.005-0.65), except for Pb that showed moderate to strong pollution (1.74-2.53).

We report the fabrication and characterization of electrospun nanofibres from Gonometa postica and Gonometa rufobrunnae silk fibroin indigenous to Southern Africa. Nanofibres were electrospun from regenerated silk fibroin (RSF) powders obtained by freeze drying or via rotary evaporation using methanol as a desiccant. Optimal electrospinning conditions employed trifluoroacetic acid as a solvent. The solution of RSF powder prepared by rotary evaporation was electrospun at a lower concentration (27% w/v) than that of freeze dried RSF powder (40% w/v). Concentration of the fibroin solution had the most influence on electrospinnability whereas voltage and flow rate mainly affected the fibre morphology. Scanning electron microscopy (SEM) showed that nanofibres from freeze dried and rotary evaporator dried RSF powders had diameters ranging from 300–760 and 400–1,000 nm respectively. Fourier transform infrared (FTIR) analysis revealed that the RSF powders were mainly composed of β-sheets, similar to degummed silk fibroin. The nanofibres, however, exhibited predominantly random coil/α-helical structure showing degradation of the native silk structure. β-sheet structure in the nanofibres was restored upon solvent treatment resulting in improved water stability. The extent of structural transformation was dependent on the type of solvent used. This study confirms the feasibility of fabricating Gonometa fibroin into stable nanofibrous structures that could be used as scaffolds in biotechnological and biomedical applications.

Green Biosynthesis of Rhodium Nanoparticles Via Aspalathus Linearis Natural Extract This contribution report on the bio-synthesis of Rhodium metallic nanoparticles (Rh NPs) synthesized for the 1st time by a completely green process using Aspalathus linearis natural plant extract as an effective bio-oxidizing/bio-reducing agent as well as a capping compound. Their morphological, structural and optical properties were investigated using various complementary surface/interface characterization techniques such as HR-TEM, HR-SEM, EDS, XRD, XPS, UV and ATR-FTIR spectroscopy. The results confirm the formation of quais - monodisperse spherical Rh NPs in the range of 0.8-1.6 nm.

In the present study, chemical, structural and thermal properties of fibroin from Gonometa postica, a wild silkmoth species were investigated. Silk from Gonometa rufobrunnea and Bombyx mori species were included in this study for comparison. The results indicated that G. postica and G. rufobrunnea silk exhibited similar properties whereas distinct differences were observed with B. mori silk. Amino acid analysis showed that glycine, alanine and serine accounted for more than 70% of the total amino acid content in all species. The amount of polar amino acids in Gonometa fibroin was significantly higher than for B. mori fibroin suggesting increased chemical reactivity of the former. The abundance of basic amino acids in Gonometa fibroin makes it a promising biomaterial in cell and tissue culture. Structural analysis revealed a unique β-sheet structure of Gonometa fibroin which is comprised of both poly-alanine and poly-glycine–alanine sequences. The maximum decomposition temperatures for Gonometa and B. mori fibroin were 350 °C and 320 °C respectively. The influence of amino acid composition on structural and thermal properties of the silks is also discussed.

The distribution and potential sources of 15 polycyclic aromatic hydrocarbons (PAHs) in soils in the vicinity of three South African coal-fired power plants were determined by gas chromatography-mass spectrometry. PAH compound ratios such as phenanthrene/phenanthrene + anthracene (Phen/Phen + Anth) were used to provide reliable estimation of emission sources. The total PAH concentration in the soils around three power plants ranged from 9.73 to 61.24 μg g(-1), a range above the Agency for Toxic Substances and Disease Registry levels of 1.0 μg g(-1) for significantly contaminated site. Calculated values of Phen/Phen + Anth ratio were 0.48 ± 0.08, 0.44 ± 0.05, and 0.38 + 0.04 for Matla, Lethabo, and Rooiwal, respectively. Flouranthene/fluoranthene + pyrene (Flan/Flan + Pyr) were found to be 0.49 ± 0.03 for Matla, 0.44 ± 0.05 for Lethabo, and 0.53 ± 0.08 for Rooiwal. Such values indicate a pyrolytic source of PAHs. Higher molecular weight PAHs (five to six rings) were predominant, suggesting coal combustion sources. A good correlation existed between most of the PAHs implying that these compounds were emitted from similar sources. The carcinogenic potency B[a]P equivalent concentration (B[a] Peq) at the three power plants ranged from 3.61 to 25.25 indicating a high carcinogenic burden. The highest (B[a] Peq) was found in samples collected around Matla power station. It can therefore be concluded that the soils were contaminated with PAHs originating from coal-fired power stations.

Water soluble proteins extracted from Moringa stenopetala seeds were investigated as potential natural polymer for electrospinning of nanofibers after blending with poly (vinyl) alcohol (PVA). Good quality blended nanofibers were obtained using 10% (w/v) protein/PVA solution in 3% formic acid, 15 kV, 12.5 cm tip to collector distance and a flow rate of 5 μl min−1. Under these optimum conditions blended nanofibers with average diameter of 232.87 ± 59.35 nm were obtained. The functional groups, surface morphology, crystallinity, surface charge and thermal stability of the protein/PVA nanofibers were evaluated using FTIR, FT-Raman, SEM, XRD, zeta potential and TGA. The SEM images of the nanofibers showed a uniform dispersion in the polymer matrix. The morphology and diameter of the nanofibers were mainly affected by the concentration of the blend solution and weight ratio of the blend. The FTIR and FT-Raman characterization results show amine and amide functional groups as predominant groups on the protein/PVA nanofibers. Furthermore the characterization results of XRD, zeta potential and TGA confirms that protein/PVA nanofiber is amorphous with a zwitterionic surface charge and thermal stability up to the 170 °C. The stability of blended nanofibers in water showed promising results for their application in various environmental waters.

A rapid, cost effective and environmentally friendly extraction method, based on dispersive liquid-liquid microextraction (DLLME) was developed for the determination of six tetracyclines in meat destined for human consumption. Meat extracts were analysed for tetracyclines using liquid chromatography tandem mass spectrometry (LC-MS/MS), a sensitive and selective analytical technique. Various factors influencing the pre-concentration of tetracyclines such as sample pH, type and volume of both disperser solvent and extraction solvent were optimized. Validation parameters such as calibration function, limit of detection (LOD), limit of quantification (LOQ), detection capability (CCα), decision limit (CCβ), accuracy and precision were established according to Commission Decision 2002/657/EC. Linearity in the range of 25-200 µg kg(-1) was obtained with regression coefficients ranging from 0.9991 to 0.9998. Recoveries of spiked blank muscle samples at three levels (50, 100 and 150 µg kg(-1)) ranged from 80% to 105% and reproducibility was between 2% and 7%. LODs and LOQs ranged from 2.2 to 3.6 µg kg(-1) and from 7.4 to 11.5 µg kg(-1) respectively while CCα ranged from 105 to 111 µg kg(-1) and CCβ ranged from 107 to 122 µg kg(-1). The proposed method compared well with the existing accepted dispersive solid phase extraction method and was successfully applied to the pre-concentration and determination of tetracyclines in meat samples. Eleven of the thirty bovine muscle samples obtained from local abattoirs and butcheries were found to contain residues of two tetracycline antibiotics (chlortetracycline and oxytetracycline), with oxytetracycline being the most detected. Concentration levels of the tetracycline residues detected in bovine muscle samples were lower (12.4 and 68.9 µg kg(-1)) than the stipulated European Union maximum residue level (MRL) of 100 µg kg(-1), hence the meat was fit for human consumption. From this work it can be concluded that the DLLME is indeed a greener sample preparation method and could be used as an alternative to dispersive solid phase microextraction (dSPE).

An MEKC method was developed for the separation and characterization of phenyl-isothiocyanate (PITC)-labeled amino acids derived from Gonometa rufobrunnae silkworm after microdialysis sample cleanup. The influence of the buffer and SDS concentration on the resolution of the amino acids was investigated. A buffer system consisting of 25 mM phosphate, 10 mM borate buffer at pH 9.00, and 70 mM SDS showed the best results, with 13 PITC-amino acid derivatives being resolved out of 15 possible amino acids that were under study. Microdialysis sampling demonstrated its efficiency as a sample cleanup technique. Sericin protein from G. rufobrunnae was found to be characterized by at least 11 positively identified amino acids. These included His, Tyr, Ser, Ala, Phe, Lys, Gly, Arg, Cys, Glu, and Asp. Leu/Met and Val/Thr were coeluting pairs and hence could not be positively confirmed.

A column and test samples have been produced as a Certified Reference Material (CRM) for use in HPLC. A round robin certification procedure has demonstrated that the retention and relative retention properties of the column, measured as the values of shape selectivity, hydrophobicity and ion-exchange activity at pH 7.0, under closely specified separation conditions, are reproducible irrespective of the instrument and laboratory. Concurrence with the CRM values can be used to confirm that an HPLC system is compliant with these specifications, in particular the mobile phase composition and column temperature. This will enable different laboratories to determine that they are operating under equivalent separation conditions, which is a necessary requirement for the efficient interlaboratory transferability of methods.

Relative changes in the hydrophobicity and shape selectivity of standard analytes are shown to be a valuable method to monitor the reproducibility of the effective temperature experienced by the analytes in a chromatographic column in different ovens. Significant differences were observed between ovens with the same nominal temperature and could be a major cause of problems encountered in transferring methods between instruments or laboratories. By using two parameters, changes due to the column temperature can be distinguished from those caused by mobile phase composition differences. In addition marked increases in column efficiency were noted as the mobile phase temperature was reduced below the column temperature in contrast to claims that thermal equilibration is essential.

The reproducible transferability of HPLC methods between laboratories requires careful specification of the method, especially the temperature control of the column. The methods were examined in two international collaborative studies for a series of column characterisation tests for ODS-bonded phase columns. The results from 16 laboratories in the first study and 7 laboratories in the second study are analysed. Differences in the type of column oven can cause significant differences in the effective column temperature and hence in the relative retention times used to calculate hydrophobicity and shape selectivity. Water bath or water jackets gave markedly different results to air ovens at the same nominal temperature and were recommended as providing more transferable results. However, although the incoming eluent was controlled to be at the column temperature the efficiency of the separations were lower than in an air bath oven but were more repeatable.

The dual separation mechanism exhibited by capillary electrochromatography is demonstrated by the simultaneous separation of sulfonamides as charged and neutral species over a pH range of 2.5 to 6.9. The neutral sulfonamides were separated according to the difference in their hydrophobicities while charged components were separated by the differences in their electrophoretic mobilities. The limitation of capillary electrochromatography for acidic components was also examined.

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 30–500 μg kg −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 300 μg kg −1 ) ranged from 83 to 102%. LODs were between 5 and 19 μg kg −1 while LOQs ranged between 23 and 62 μg kg −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 35.3 μg kg −1 , values which are lower than the South African stipulated maximum residue limits (MRL).