Liquid phase microextraction of hallucinogenic compounds from human urine samples based on single hollow fibre followed by chromatographic determination

A dissertation submitted to the Faculty of Science, University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science. University of the Witwatersrand, Johannesburg, March 2016A liquid phase microextraction based on single hollow fibre followed by liquid chromatographic determination was developed for the extraction and quantification of the hallucinogenic muscimol and its two precursors, tryptophan and tryptamine from urine samples. A multivariate design of experiment was used in which a half fractional factorial approach was applied to screen six potential factors (donor phase pH, acceptor phase concentration, supported liquid membrane composition, stirring rate, extraction time and salt content) for their extent of vitality on the extraction of muscimol, tryptophan and tryptamine using the developed method. Four factors were identified as essential for an enhanced enrichment of each of the three research analytes from diluted urine samples. The paired vital factors were then optimized using central composite designs where empirical quadratic response models were used to visualize the response surface through contour plots, surface plots and optimization plots of response output. When the muscimol-based optimum factor levels were applied for the simultaneous extraction of the three research analytes, a composite desirability of 0.687 was obtained implying that the set conditions were ideal for a combined extraction of the analytes from the donor phase into the acceptor phase across a supported liquid membrane impregnated with a carrier molecule. This was an acceptable result considering that only the optimized muscimol factor levels were set as universal factor values. Muscimol was the analyte of interest in this research. The composite desirability value was predicted by setting the extraction conditions to 20% (w/w) di-(2-ethylhexyl) phosphoric acid (DEHPA) in dihexyl ether (DHE) supported on the walls of a hollow fibre into a 200 mM HCl acceptor phase inside the hollow fibre from a 20% (v/v) diluted urine donor phase spiked in the 0.1 – 10 μg mL-1 analyte concentration range maintained at pH 4 and stirred at 800 rpm for 60 mins. Experimentally, average enrichments of 4.1, 19.7 and 24.1 were obtained for muscimol, tryptophan and tryptamine, respectively. iv The complexity of urine and the anionic nature of the carrier molecule embedded on the supported liquid membrane resulted in interfering peaks that could not be completely resolved from the analyte peaks. Thus matrix-based calibration curves were used to address matrix effects. Various statistical approaches were used to validate suitability of the developed method for its potential use in quantifying muscimol and its precursors from urine samples. These validation measures were used as a way of determining the method’s ability to maintain the extraction process at equilibrium over a specific range of analyte concentrations over a period of analyte existence in a urine sample. The r² values of the matrix-based linear regression prediction models ranged from 0.9933 to 0.9986. The linearity of the regression line of the matrixbased calibration for each analyte was directly linked to the analyte enrichment repeatability. Simultaneous analyte enrichment repeatability over a 0.1 – 10 μg mL-1 analyte spiking concentration ranged from an RSD value of 8.3% to 13.1%. Limits of detection were 0.021 μg mLˉ¹, 0.061 μg mL-1 and 0.005 μg mL-1 for muscimol, tryptophan and tryptamine, respectively. Other validation parameters that were considered included specificity (and selectivity), accuracy, robustness, extraction range and system suitability. The accuracy of the developed method was reported as the reproducibility of enrichment factor values over six spiking concentrations used in constructing matrix-based calibration curves. System suitability was limited to an HPLC-UV approach. Method suitability was addressed through a comparative summary in which the LOD, LOQ and r² values for the developed method were compared to other methods that have been used to extract muscimol from urine samples. The relevance or acceptability of the enrichment factor values obtained for the extraction of the three analytes was achieved by comparison with enrichment factor values of several compounds with similar polarity that have been extracted from urine samples using carrier-mediated hollow fibre liquid phase microextraction.GR201

Bioaccumulation and Human Risk Assessment of Heavy Metals in Oreochromis niloticus and Clarias gariepinus Fish Species from the Golinga Reservoir, Ghana

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 ≤10−6, indicating the risk of  cancer developing over the years due to fish consumption. The metal concentration in the fish in the reservoir should therefore be constantly monitored  and potential health risks associated with frequent consumption of the fish assessed

Pharmaceuticals and their metabolites in the marine environment: Sources, analytical methods and occurrence

This is an accepted manuscript version. Embargo until October 4 2021.The occurrence of pharmaceuticals in the environmental waters is a global concern. There is little research conducted on the monitoring of pharmaceuticals in the marine environment. In this article, the occurrence of pharmaceuticals and their metabolites in the coastal waters as well as associated risks related to their uptake by marine organisms are critically reviewed. The literature showed antibiotics as the most plentiful pharmaceuticals in the marine environment. Other therapeutic classes of pharmaceuticals appeared prominently in the marine environment are non-steroidal anti-inflammatory drugs and β-blockers, while gemfibrozil and carbamazepine were singled-out as the most studied lipid regulator and antiepileptic, respectively. Some pharmaceuticals have been found present in the marine organisms that are regarded as important food sources for humans. We reviewed the negative effects associated with the presence of pharmaceuticals in the marine environment. This article is concluded by deliberating on the possible future studies in this research niche area.acceptedVersio

Application of Hollow Fibre-Liquid Phase Microextraction Technique for Isolation and Pre-Concentration of Pharmaceuticals in Water

In this article, a comprehensive review of applications of the hollow fibre-liquid phase microextraction (HF-LPME) for the isolation and pre-concentration of pharmaceuticals in water samples is presented. HF-LPME is simple, affordable, selective, and sensitive with high enrichment factors of up to 27,000-fold reported for pharmaceutical analysis. Both configurations (two- and three-phase extraction systems) of HF-LPME have been applied in the extraction of pharmaceuticals from water, with the three-phase system being more prominent. When compared to most common sample preparation techniques such as solid phase extraction, HF-LPME is a greener analytical chemistry process due to reduced solvent consumption, miniaturization, and the ability to automate. However, the automation comes at an added cost related to instrumental set-up, but a reduced cost is associated with lower reagent consumption as well as shortened overall workload and time. Currently, many researchers are investigating ionic liquids and deep eutectic solvents as environmentally friendly chemicals that could lead to full classification of HF-LPME as a green analytical procedure

Evaluation of organochlorine pesticide residues in Beta vulgaris, Brassica oleracea, and Solanum tuberosum in Bloemfontein markets, South Africa

Abstract This study evaluated the level of selected pesticide residues in the staple vegetables; Brassica oleracea var. capitata (cabbage), Beta vulgaris var. cicla (Swiss chard), and Solanum tuberosum (potato) from fresh produce markets in the city of Bloemfontein, South Africa. A QuEChERS extraction method was used followed by quantitation using GC‐HRT/MS. The pesticide residues were detected in levels lower than the recommended Maximum Residue Levels ranging from not detected to 121.6 ng/kg recorded for heptachlor in cabbage samples. Cabbage was generally susceptible to pesticide residue accumulation with the average total concentration for different markets at 222 mg/kg. The pesticide residues were predicted to be from recent applications but their existence within guideline limits indicated that their use in vegetable farming was within the FAO/WHO recommended good agricultural practices. While the current situation points that consumption of the vegetables in the province poses limited health concerns due to organochlorine pesticides, the unmonitored use of products containing these compounds may result in elevated levels. Continued monitoring and a call for the South African legislature to revise its regulations of the Fertilizers Act to reflect the current international laws on pesticides management is recommended

A Comparative Study on the Dissolution of <i>Argema mimosae</i> Silk Fibroin and Fabrication of Films and Nanofibers

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

Trace Detection and Quantitation of Antibiotics in a South African Stream Receiving Wastewater Effluents and Municipal Dumpsite Leachates

One of the major concerns in the consumption of antibiotics is the discovery of antibacterial resistant genes due to prolonged exposure which makes their presence in environmental samples a priority. In this study, we screened 52 antibiotics along a South African stream polluted with wastewater effluents and municipal dumpsite leachates. Of these antibiotics, 15 were detected in the stream while 3 sulfonamides (sulfamethizole, sulfamethazine, sulfamethoxazole), a fluoroquinolone (flumequine) and a diaminopyrimidine (trimethoprim) were further quantified. The concentrations of sulfamethizole, sulfamethazine, sulfamethoxazole ranged from not detected to 0.133 µg L−1, flumequine ranged from 0.222 to 0.686 µg L−1, while trimethoprim was up to 0.0618 µg L−1. The highest concentrations were recorded at the point source discharge with most antibiotics not detected further downstream. The current study has further confirmed wastewater effluents and dumpsite leachates as pathways of antibiotics into the environment. Only the persistent unsanctioned antibiotic, flumequine had its risk quotient above 0.1 making it an antibiotic of environmental concern. Multiresidue studies are still limited in Africa and the current study offers a platform for a research paradigm shift with more studies expected to emerge providing an improved overview of the release of antibiotics and other pharmaceuticals into Africa’s vulnerable surface water systems

Health Risk Assessment of Metals in African Aphrodisiacs: A Case Study of Aqueous Concoctions from Johannesburg and Durban Herbal Markets, South Africa

Consumption of aphrodisiacs is a common practice in South Africa. Hence, determining the levels of trace metals as potential pollutants is necessary to protect consumers’ health. The current study reports a health risk assessment due to metals in aphrodisiacs collected from herbal markets in Johannesburg and Durban, South Africa. Samples were digested using microwave-assisted digestion followed by inductively coupled plasma-optical emission spectrometry analysis. The results showed that the concentrations of common metals (Na, K, Mg, and Ca) were within the guideline limits for human consumption, while the trace metals (Ni, Cr, Co, As, Cd, and Pb) were above the limits, recording values of 0.132–0.268, 0.209–0.308, 0.224–0.405, 0.0884–0.230, 0.0402–1.11, and 0.146–0.207 mg L−1, respectively. The source of the trace metals was traced to the tap water probably collected from dilapidated buildings where the water systems are ailing. A strong correlation for metals with similar sources was observed, notably for Pb and Cd that leach from water pipes. The aphrodisiacs had low consumption rates, and the health risk assessment gave a hazard quotient of 0.225 as a total for all studied metals. The group of aphrodisiacs investigated in the current study therefore poses minimal health risks and can be consumed without fear of metal contamination. More inclusive studies are, however, needed to have a better understanding of aphrodisiacs with the aim of potentially commercializing them like the other commercialized herbal concoctions currently distributed in South African markets and pharmacies