Sample preparation using liquid membrane extraction techniques

A brief review is given of membrane extraction techniques that are seen as suitable for the extraction of various chemicals in water samples. Membrane-based extraction methods have now gained popularity as methods of choice in the extraction of both ionisable and non-ionisable molecules from different samples. The main attractive features for these techniques include the use of minimal organic solvents, high selectivity and clean-up efficiency, with high enrichment factors. In most cases the overall cost involved is low due to the simplicity of the techniques which normally involve relatively fewer steps and handling procedures as compared to many other sample-preparation techniques. The various forms and the configurations of membrane-based techniques are another attractive feature which allows the possibility of hyphenation with separation instruments such as gas/liquid chromatographs and even capillary electrophoresis.Keywords: liquid membrane extraction techniques, sample preparation, water monitoring, organic and inorganic compound

Effect of natural blue-green algal cells lysis on freshwater quality

Blue-green algae grow in freshwater bodies when they are provided with suitable factors such as nutrients and appropriate weather conditions. Their cell lysis occurs naturally when they encounter unfavourable conditions.  This study reports on the types and amounts of fatty acids added into freshwater due to the algal cell lysis. The investigation on the amount of fatty acids released into water due to algal cells lysis was performed by placing samples in two compartments, one with no light allowing the algae cells to die while the other compartment was kept in favourable conditions enough to sustain the life of algae. Fatty acids were then extracted from both dead and living cells as well as their respective water filtrates. Determination of fatty acids was performed using GCxGC-TOF-MS. Identified fatty acids were mainly; tetradecanoic acid, 7-hexadecenoic acid, hexadecanoic acid, 9,12,15-octadecatrienoic acid, 6,9,12,15-octadecatetraenoic acid, 9,12-octadecadienoic, 9-octadecenoic and octadecanoic acids. It was found that water from the dead cells had higher amounts of fatty acids than water samples from the living cells. Unsaturated fatty acids increased from 0.85 mg/L to 2.70 mg/L in filtrate water from the dead algae. The pH of water samples from the dead cells decreased from 6.8 to 6.1. Keywords: Algae, cells lysis, Fatty acids, gas chromatography time-of-flight mass spectrometry, water qualit

Voltammetric Determination of a Benzimidazole Anthelmintic Mixture at a Poly(3-methylthiophene)-modified Glassy Carbon Electrode

The voltammetric determination of benzimidazole anthelmintics at a glassy carbon rotating-disk electrode modified with poly(3-methylthiophene) is presented. The purpose of surface modification was to improve the sensitivity and limits of detection for determination of the compounds in a standard mixture. Thus, five compounds, namely thiabendazole, mebendazole, albendazole, fenbendazole and oxibendazole have been studied using square wave voltammetry. It has been possible to resolve four of the compounds, mebendazole, fenbendazole, oxibendazole and thiabendazole, in a mixture. Investigations of a number of parameters, including the mode of potential application, cathodic reduction versus anodic oxidation, the type of electrode, effect of pH and speed of electrode rotation, among others, are reported. South African Journal of Chemistry Vol.56 2003: 5-

Synthesis and characterization of molecularly imprinted polymers for the remediation of PCBs and dioxins in aqueous environments

This paper, reports on the approach devised to remediate water sources contaminated with PCBs and dioxins. The approach reported is based on the synthesis of highly selective molecularly imprinted polymers (MIPs). The paper elaborates the materials, procedures and protocols devised and followed for the synthesis of MIPs..

Measurements of distribution coefficients and lipophilicity values for oleanolic acid and betulinic acid extracted from indigenous plants by hollow fibre supported liquid membrane

Hollow fibre supported liquid membrane (HFSLM) has been applied in the measurements of distribution constants, KD and lipophilicity (log P) values for the isomeric triterpenic acids, betulinic acid (BA) and oleanolic acid (OA) isolated from indigenous plants. The results have shown that BA had an optimum pH of 3.5 while the optimum sample pH for OA was ranging from 0.5 to 2.5. The log P values obtained for BA and OA were 6.61 and 6.12, respectively. The KD value obtained for BA was 0.29 while that for OA 0.16. The method has advantages of simplicity, use of minimal organic solvents and the ability to selectively extract only one isomer (OA) in the mixture with BA by optimizing pH conditions.KEY WORDS: Betulinic acid, Oleanolic acid, Hollow fibre supported liquid membrane, Distribution coefficient, Lipophilicity Bull. Chem. Soc. Ethiop. 2011, 25(3), 321-332

Chemometric investigation of the effects of chemical properties and concentrations on the extractability of benzimidazoles with supported liquid membrane

Principle component analysis (PCA) and a two-way analysis of variance (ANOVA) were employed in the study of factors affecting extractability of benzimidazole anthelmintics using supported liquid membrane (SLM) in liver, kidney, milk and urine at four concentration levels. The SLM extraction process was monitored by liquid chromatography - mass spectrometer (LC-MS). The results showed that the extractability of benzimidazoles is dependent on both the concentration levels and the chemical properties of compounds. Based on chemical properties, extraction of the compounds from the liver matrix showed no significant difference (p = 0.05) for the following pairs; albendazole and oxibendazole, thiabendazole and mebendazole, oxibendazole and fenbendazole, and oxibendazole and mebendazole. At some of the concentration levels, mainly between 1000 and 100, 100 and 10, and 10 and 1 μg/Kg, there was no significant difference. It was also found that, there was significant difference (at p = 0.05) in the extractability in milk between oxibendazole and albendazole, and also oxibendazole and fenbendazole. For milk also, the concentration range from 10 to 100 μg/L, showed no significant difference (p = 0.05). Urine matrix on the other hand, showed significant difference in the recoveries at all concentration levels

Bioaccumulation and distribution pattern of heavy metals in aquaculture systems found in Arusha and Morogoro regions of Tanzania

This research article published by Taylor & Francis Group, 2020The assessment of the current distribution and concentrations of As, Pb, Hg, Cd, and Cr in farmed catfish and tilapia, fish feed, and pond sediment in Tanzania is important in order to establish the potential dietary exposure to heavy metals from aquaculture sources. Thirteen fish ponds were selected from each of the 10 sites (villages) studied in Arusha and Morogoro regions. Representative samples collected were analysed using polarised energy-dispersive x-ray fluorescence (PED-XRF) spectrometer. Human health risk from fish consumption was established by calculating the estimated daily intakes (EDI), target hazard quotients (THQ), total hazard indices (HI), and carcinogenic risk (CR) of the heavy metals. Arusha had the highest concentrations (dry weight) of As (2.49–4.75 mg/kg) in the fish feed. Morogoro had the highest concentrations of Hg (1.65–2.69 mg/kg), Pb (4.59–5.64 mg/kg), and Cd (1.99–3.97 mg/kg) for sediment, fish feed, and fish muscles, respectively. Cr was the most accumulated heavy metal in the fish muscles sampled in Arusha (4.61–9.50 mg/kg) and Morogoro (2.53–5.57 mg/kg). Concentrations and EDI calculated based on mean fish consumption of 22.1 g per person per day by a 60 kg Tanzanian adult found heavy metal intakes were below the recommended daily dietary allowance (RDA) while THQ values were lower than 1, indicating no health risk related to consumption of the fish. The estimated HI was greater than 1, suggesting a potential significant non-carcinogenic health risk. The CR values were below 10−4, indicating no carcinogenic health risk in humans from fish consumption. This study recommends continued surveillance given potential bioaccumulation of these heavy metals in fish

Development of a Natural Product Rich in Bioavailable Omega-3 DHA from Locally Available Ingredients for Prevention of Nutrition Related Mental Illnesses.

This research article published by Taylor & Francis Online, 2020Poor mental health remains a serious public concern worldwide. The most vulnerable individuals are children and adolescents in developing countries. Nutritional deficiency of long-chain omega-3 fatty acids, particularly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have long been recognized as a major contributing factor for mental health illnesses. Provision of ready-to-use natural product rich in preformed Omega-3 DHA and EPA could address this problem. However, most commonly used products are expensive and contain less or no preformed Omega-3 DHA and EPA, making them less suitable for prevention of mental illnesses in resource-poor countries. The main objective of this study was to develop a natural product rich in preformed Omega-3 DHA and EPA from locally available ingredients. Linear programing (LP) was used to formulate a natural product rich in preformed Omega-3 DHA and other essential nutrients using locally available ingredients other than fish and dairy products. Laboratory analysis was then performed to validate the nutritional value of the LP-formulation using standard analytical methods. The relative difference between the LP tool calculated values, and the laboratory-analyzed values were calculated. Sensory testing was also done to evaluate consumer acceptance of the final product. Optimal formulation contained about 220 mg of preformed Omega-3 DHA + EPA, enough to meet the RDI for children aged 2-10 years. The LP analysis further showed that the cost of the developed product is USD 0.15/100 g, which is 50% lower than that of Plumpy'nut. Laboratory analysis revealed similar results as that of LP at P = 0.05. These findings indicate that ready-to-use natural food rich in preformed DHA and EPA can be developed from locally available ingredients