Ultrasound Assisted-Homogeneous Liquid-Liquid Phase Microextraction based on Deep Eutectic Solvents and Ethyl Acetate for Preconcentration of Selected Organochlorine Pesticides in Water Samples

Abstract: A novel and greener methodology for the simultaneous preconcentration of organochlorine pesticides in water samples based on ultrasound assisted-homogeneous liquid-liquid phase microextraction (UA-HLLME) has been developed. Gas chromatography-time of flight mass spectrometry was used for quantification of OCPS in water samples. In this method, choline-chloride-ethylene glycol deep eutectic solvent and ethyl acetate were used as the disperser solvent and extraction solvent, respectively. Univariate and multivariate approaches were used for optimization of the influential parameters that affect the extraction efficiency of the UA-HLLME method. Under the optimum conditions, enrichment factors ranging from 152 to 403 with acceptable recoveries of 85-100% were obtained. The dynamic linear ranges were obtained in the concentration range 0.015–1000 μg L−1 with correlation coefficients ranging 0.9952–0.9995. The limits of detection and quantification of the developed UA-HLLME method were in the range 1.9-8.6 ng L−1 and 5.9-26 ng L−1, respectively. The intra-day and inter-day precision expressed in terms of relative standard deviation (%RSD) ranged from 2.1-4.5% and 3.9-7.3%, respectively. The developed method was successfully applied for the preconcentration and determination of the selected OCPs from 3 different river water samples. The developed procedure displayed simplicity, environmental friendliness, relatively high extraction efficiency, short analysis time and relatively low detection limits

Strategies of sample preparation for selected trace metal speciation and determination of pesticides in environmental samples

Abstract: Soil is an environmental constituent of the earth that performs a collection of essential purposes in our humanity such as food production. With fast industrial development and growth that have happened in most areas of the world during the recent years, the soil section is getting a large amount of persistent pollutants from different sources. These include trace metals and pesticides. An immense number in the scientific literature have been documented on the concentrations of trace metals and pesticides in soil. Contamination caused by agricultural activities such as pesticides and fertilisers is the main source of low soil and groundwater quality in many countries. Ineffective administering of agricultural processes can lead to contamination of soil and groundwater by nutrients and pesticides. For this reason, there is a need for the development of simple analytical techniques for motoring of these pollutants. Therefore, the main objective of the study was to develop sample preparation methods for the fractionation of trace elements and extraction of pesticides from environmental samples collected from different areas in Bloemfontein in the Free State. An ultrasound assisted sequential extraction procedure derived from a three-step Bureau Community of Reference (BCR) method was applied for fractionation of elements in three agricultural soil samples collected in geographical areas surrounding specifically Glen Agricultural College outside Bloemfontein (Free state Province, South Africa). The results obtained demonstrated that Mn, Co, Tl and Cd (except Soil 1) were found to have the highest percentage in the easily reducible fraction compared to other elements. Cu, Zn, Mo, Pb and Cd (in Soil 1) were dominant in the oxidizable fraction. Furthermore, the highest concentration of most metals such as Fe, Ni, V, Cr, Sb, Pb and As were obtained in the residual fraction of the soil samples. The environmental risks and degree of contamination were assessed using risk assessment code (RAC), individual contamination factors (ICF) and global contamination factor (GCF). According to risk assessment code (RAC) values, the soil samples demonstrated that Mn, Co, Ni, Zn, Mo and Cd pose a medium risk to the environment while Tl and Cd showed to high risk. In addition, individual contamination factors (ICF) were computed for each element and the highest ICF values (>10) were obtained for Cd and Mo. The global contamination factor (GCF) demonstrated that Soil 2 and 3 present the highest environmental risk compared to Soil 1...M.Sc. (Chemistry

Correlation between <i>A. lumbricoides</i> and <i>P. falciparum</i> parasite densities in individuals carrying both parasites.

<p>Correlation between <i>A. lumbricoides</i> and <i>P. falciparum</i> parasite densities in individuals carrying both parasites.</p