Negussie Megersa

Assessment of organochlorine pesticide pollution in Upper Awash Ethiopian state farm soils using selective pressurised liquid extraction

Upper Awash Agro Industry Enterprises (UAAIE) is one of the major state farms in Ethiopia with known large-scale pesticide use. Although organochlorine pesticides (OCPs) have been applied for about three decades, no studies have been carried out on levels of residue in the region. In this work a fast selective pressurised liquid extraction (SPLE) methodology has successfully been applied for screening of 13 OCPs in 12 soil samples from different fields in UAAIE, which further strengthen this methodology. Quantitative and qualitative analyses were done using a dual column gas chromatography-electron capture detection system (GC-ECD) and a GC equipped with a mass spectrometer (MS), respectively. The main contaminants identified comprised of previously used persistent organic pollutants (POPs) and currently used insecticides. Low concentrations or non-detectable levels of certain OCPs (aldrin, dieldrin, endrin, and heptachlor) indicate a positive phasing out of these persistent organic pollutants (POPs). Similarly HCHs were found in few soils and at low concentrations. Endosulfans and DDTs were detected in substantial amounts in the soils with Sigmaendosulfans up to 56000 and SigmaDDTs up to 230 ng g(-1) dry weight, which is a threat to the surrounding and downstream ecosystems, especially considering that the investigated OCPs constituted 29000 l of the 63000 l of pesticide applied annually on the fields. Additional concerns must be raised concerning synergistic effects of all pesticides added.

Vortex-assisted ionic liquid dispersive liquid-liquid microextraction for the determination of sulfonylurea herbicides in wine samples by capillary high-performance liquid chromatography.

A new sample treatment, namely vortex-assisted ionic liquid dispersive liquid-liquid microextraction (VA-IL-DLLME), followed by capillary liquid chromatography has been developed for the determination of four sulfonylurea herbicides (SUHs): flazasulfuron (FS), prosulfuron (PS), primisulfuron-methyl (PSM) and triflusulfuron-methyl (TSM) in wine samples. The ionic liquid (IL) 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]) was used as extraction solvent and was dispersed using methanol into the sample solution, assisted by a vortex mixer. Various parameters influencing the extraction efficiency, such as type and amount of IL, type and volume of disperser solvent, sample pH, salting-out effect, vortex and centrifugation time were studied. Under the optimum conditions, the limits of detection and quantification of the proposed method were in the ranges of 3.2-6.6 and 10.8-22.0 μg kg(-1), respectively; lower than the maximum residue limits set by the EU for these matrices. The proposed method was successfully applied to different wine samples and satisfactory recoveries were obtained.

Salting-out assisted liquid–liquid extraction combined with capillary HPLC for the determination of sulfonylurea herbicides in environmental water and banana juice samples

A salting-out assisted liquid-liquid extraction (SALLE) combined with capillary high performance liquid chromatography with diode array detector (capillary HPLC-DAD) was proposed for extraction and determination of residues of nine sulfonylurea herbicides (SUHs) in environmental water and banana juice samples. Various parameters affecting the extraction process such as the type and volume of the organic solvent, sample volume, type and amount of salt, pH of the sample and vortex time were optimized. Under optimum conditions, matrix matched calibration curves were established using river water and banana juice samples. Good linear relationships as well as low limits of detection, LODs (0.4-1.3 and 3-13 µg/L) and quantification, LOQs (1.3-4.3 and 10-43 µg/L) were obtained in water and banana juice samples, respectively. The precision (intra- and inter-day) of the peak areas expressed as relative standard deviations (%, RSD), at two concentration levels were below 10 % in both matrices. Recoveries obtained from spiked environmental waters (river water and groundwater) and banana juice samples, at two concentration levels, ranged from 72 to 115%. The results of the analysis revealed that the proposed SALLE-capillary HPLC method is simple, rapid, cheap and environmentally friendly, being successfully applicable for the determination of SUH residues in waters and banana juices.

Development of a one-step microwave-assisted extraction method for simultaneous determination of organophosphorus pesticides and fungicides in soils by gas chromatography mass spectrometry

A one-step microwave-assisted extraction (MAE) procedure was developed for the simultaneous extraction of organophosphorus pesticide and fungicide residues in soil which have been greatly used in agriculture. Parameters that could influence the MAE efficiency such as irradiation power, temperature, time and solvent were investigated, and extraction efficiencies in the range of 92.6-103.7% were obtained using 400 W (100% output) at 160 °C for 10 min with only 12 mL of acetone-hexane (2:1, v/v). The analytes in extracts were analyzed directly by gas chromatography-mass spectrometry (GC-MS) without any further cleanup. At 5 and 50 ng g(-1) fortification levels for each analyte, the average recoveries obtained were ranged from 70.0% to 120.0% with relative standard deviation (RSD) between 0.2% and 14%. The method was linear over 1-250 ng g(-1) with a correlation coefficient (r(2)) between 0.9916 and 0.9966. The detection limits (S/N=3) were between 0.10 and 0.12 ng g(-1). The applicability of the method was demonstrated by analyzing field soil samples collected from six intensive horticultural sites in Ethiopia.

Low-density extraction solvent based solvent-terminated dispersive liquid–liquid microextraction for quantitative determination of ionizable pesticides in environmental waters

A rapid, efficient, and new solvent terminated dispersive liquid-liquid microextraction technique coupled with HPLC was developed for selective extraction and analysis of s-triazine herbicides from environmental water samples. Important parameters influencing the extraction process including type and volume of extraction and disperser solvent, extraction time, sample pH, ionic strength, and extraction temperature were successfully optimized. Under the optimal conditions, there are excellent linear relationships between the analytical results and concentration in the range of 10-400 mg/L for atrazine, propazine, prometryn, and terbutryn. LOD and LOQ ranged from 0.60 to 2.33 μg/L and 2.0 to 7.7 μg/L, respectively. Performance of the analytical technique was evaluated by carrying out the repeatability and reproducibility analyses that were ranged from 2.86 to 5.66% and 4.64 to 5.89% for 100 μg/L of each target analyte, respectively. The proposed method has been successfully applied to the analysis of real water samples and acceptable relative recoveries over the range of 65.93-101.46%, with RSDs ≤ 8.80%, were obtained. The overall results have been compared with the literature values. Thus, the method developed could efficiently be used for selective extraction of the target analytes from complex matrices, particularly environmental waters.

A novel equilibrium extraction technique employing hollow fibre liquid phase microextraction for trace enrichment of freely dissolved organophosphorus pesticides in environmental waters

A new design of equilibrium hollow fibre liquid phase microextraction (HF-LPME) was developed for the determination of three freely dissolved organophosphorus pesticides (OPPs), i.e. diazinon (O,O-diethyl-O-2-isopropyl-4-methyl-6-pyrimidyl thiophosphate), chlorpyrifos (O,O-diethyl-O-[3,5,6-trichloro-2-pyridyl] phosphorothioate), and fenthion (O,O-dimethyl-O-4-methylthio-m-tolyl phosphorothioate) as model compounds. In this new design a 1.2–1.4 cm length of a hollow fibre (HF), inserted to the end of 20 cm copper wire and impregnated with organic solvent, was used to extract the freely dissolved concentration of OPPs in various water samples. The limits of detection (LOD) in reagent water using gas chromatography-mass spectrometry in the selected ion monitoring (SIM) mode was in the range of 15–80 ng L−1. The relative standard deviations of the analysis (inter- and intra-day) were 8.7–30%. The method was applied to the extraction of spiked lake and ground water samples. The ground water sample was spiked at 0.1 and 0.2 µg L−1 concentrations of the analytes under study and the average extraction efficiency at the two concentrations was below 1% showing the non-depletive nature of the extraction, meaning that the freely dissolved concentrations are measured as opposed to total concentrations. Good linearity was obtained for all of the analytes in both reagent water and lake water samples with correlation coefficients, R 2, ranging from 0.991 to 0.996, in the concentration ranges of 25–400 ng L−1. The method was found to be very simple and inexpensive, with the possibility of running hundreds of samples in parallel with very minimal expenses for the determination of freely dissolved OPPs.

Carrier-mediated extraction of bipyridilium herbicides across the hydrophobic liquid membrane.

Supported liquid membrane (SLM) method for preconcentration and enrichment of the two bipyridilium herbicides, namely diquat and paraquat, from environmental water samples has been developed. The permanently charged cationic herbicides were extracted from a flowing aqueous solution to a stagnant acidic acceptor solution across a liquid membrane containing 40% (v/v) di-(2-ethylhexyl) phosphoric acid dissolved in di-n-hexyl ether. The mass transfer of analytes is driven by the counter-coupled transport of hydrogen ions from the acceptor to the donor phase. The efficiency of the extraction process depends on the donor solution pH, the amount of the mobile carrier added to the liquid membrane and the concentration of the counter ion in the acceptor solution. The applicability of the method for extraction of these quaternary ammonium herbicides from environmental waters was also investigated by spiking analyte sample solutions in river water. With 24h sample enrichment concentrations of diquat and paraquat down to ca. 10ng/L could be detected in environmental waters.

Hollow-fiber liquid-phase microextraction combined with capillary HPLC for the selective determination of six sulfonylurea herbicides in environmental waters

A three-phase hollow-fiber liquid-phase microextraction combined with a capillary LC method using diode array detection was proposed for the determination of six sulfonylurea herbicides, triasulfuron, metsulfuron-methyl, chlorsulfuron, flazasulfuron, chlorimuron-ethyl, and primisulfuron-methyl, in environmental water samples. Different factors that can affect the extraction process such as extraction solvent, acidity of the donor phase, composition and pH of the acceptor phase, salt addition, stirring speed, and extraction time were optimized. Under the optimum conditions, detection and quantitation limits between 0.1-1.7 and 0.3-5.7 μg/L, respectively, and enrichment factors ranging from 71 to 548 were obtained. The calibration curves were linear within the range of 0.3-40 μg/L. Intra- and interday RSDs were <6.3 and 8.4%, respectively. The relative recoveries of the spiked ground and river water samples were in the range of 69.4-119.2 and 77.4-111.7%, respectively. The results of the study revealed that the developed methodology involves an efficient sample pretreatment allowing the preconcentration of analytes, combined with the use of a miniaturized separation technique, suitable for the accurate determination of sulfonylurea herbicides in water.

Ion-pair assisted liquid–liquid extraction for selective separation and analysis of multiclass pesticide residues in environmental waters

A new ion-pair assisted liquid–liquid extraction (IPA-LLE) method in combination with high performance liquid chromatography-diode array detection (HPLC-DAD) has been proposed for the determination of ten multiclass (six sulfonylurea and four organophosphorus ) pesticides in environmental waters. In the IPA-LLE procedure, the ion-pairing reagent tetrabutylammonium hydrogen sulfate and the organic solvent, acetonitrile, were used for extraction of the target analytes. Various parameters influencing the extraction efficiency such as the type, composition and volume of the ion-pair, volume of acetonitrile, sample pH, type and composition of the salt and effect of sonication time were studied and optimal conditions were established. Under the optimum conditions, the limits of detection and quantification of the proposed method were in the ranges of 0.5–3.0 μg L−1 and 1.8–10.0 μg L−1, respectively, and calibration curves were linear within the range of 1.8–450 μg L−1, with coefficients of determination of 0.993 or better. Intra- and inter-day precision studies, expressed as relative standard deviations, at three concentration levels, were in the range of 0.4–9.4%. The relative recoveries of the spiked environmental water samples were in the range of 73–105%, except for nicosulfuron in lake water. The results of the study revealed that the developed method involves efficient sample preparation allowing the preconcentration of analytes, followed by the use of HPLC-DAD for quantitative analysis.

Low density solvent based dispersive liquid-liquid microextraction and preconcentration of multiresidue pesticides in environmental waters for liquid chromatographic analysis

A simple, efficient and selective sample preparation technique using low density based dispersive liquid-liquid microextraction has been developed for the analysis of nine multiresidue pesticides inculding six sulfonylurea and three organophosphorus pesticides in environmental waters by HPLC-diod array detector. Various experimental parameters affecting the extraction efficiency were investigated. Under the optimum experimental conditions, matrix-matched calibration curves were established in groundwater and good linearities were obtained with coefficient of determination (r2) of 0.990 or better. The limits of detection and quantification were in the ranges 0.8–3.3 and 2.5–11.0 µg/L, at a signal-to-noise ratio of 3 and 10, respectively. The relative standard deviations of the precision studies were varied over the range of 0.2–13%. The proposed method was successfully applied to selective extraction of the target pesticide residues in different environmental waters and acceptable recoveries, in the range 81–121%, were obtained.