Determination of bromoxynil and ioxynil in the presence of carbamates by supported liquid membrane-liquid chromatography in river waters

Sample pre-treatment and enrichment using the supported liquid membrane (SLM) technique for the determination of phenolic nitrile herbicides in presence of carbamates in river water samples was investigated. The uncharged herbicide molecules from the flowing aqueous solution diffuse through an immobilized water-immiscible organic solvent, supported by a porous polytetrafluoroethylene (PTFE) membrane, and trapped in a stagnant acidic acceptor phase in an ionic form. Using n-undecane as a membrane solvent, the SLM extraction methodology was successfully used for the enrichment and separation of phenolic nitrile herbicides in environmental waters with extraction efficiencies of 60% or better. A RDS (%) of 2.1 and 1.8 was obtained for the extraction of ioxynil and bromoxynil from river water, respectively. KEY WORDS: Bromoxynil, Ioxynil, Phenolic nitrile herbicides, Carbamates, Supported liquid membrane, Sample pre-treatment, Sample enrichment  Bull. Chem. Soc. Ethiop. 2003, 17(2), 119-128.

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 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

Comparative study of a vitrinite-rich and an inertinite-rich Witbank coal (South Africa) using pyrolysis-gas chromatography

Abstract This study aims to compare iso-rank vitrinite-rich and inertinite-rich coal samples to understand the impact of coal-forming processes on pyrolysis chemistry. A medium rank C bituminous coal was density-fractionated to create a vitrinite-rich and an inertinite-rich sub-sample. The vitrinite-rich sample has 83 vol% total vitrinite (mineral-matter-free basis), whereas the inertinite-rich counterpart has 66 vol% total inertinite. The vitrinite-rich sample is dominated by collotelinite and collodetrinite. Fusinite, semifusinite, and inertodetrinite are the main macerals of the inertinite-rich sample. Molecular chemistry was assessed using a pyrolysis gas chromatograph (py-GC) equipped with a thermal desorption unit coupled to a time of flight mass spectrometer (MS) (py-GC/MS) and solid-state nuclear magnetic resonance (13C CP-MAS SS NMR). The pyrolysis products of the coal samples are generally similar, comprised of low and high molecular weight alkanes, alkylbenzenes, alkylphenols, and alkyl-subtituted polycyclic aromatic hydrocarbons, although the vitrinite-rich sample is chemically more diverse. The lack of diversity exhibited by the inertinite-rich sample upon pyrolysis may be interpreted to suggest that major components were heated in their geologic history. Based on the 13C CP-MAS SS NMR analysis, the inertinite-rich sample has a greater fraction of phenolics, reflected in the py-GC/MS results as substituted and unsubstituted derivatives. The greater abundance of phenolics for the inertinite-rich sample may suggest a fire-related origin for the dominant macerals of this sample. The C2-alkylbenzene isomers (p-xylene and o-xylene) were detected in the pyrolysis products for the vitrinite-rich and inertinite-rich samples, though more abundant in the former. The presence of these in both samples likely reflects common source vegetation for the dominant vitrinite and inertinite macerals

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