Multivariate optimization of a combined static and dynamic supercritical fluid extraction method for trace analysis of pesticides pollutants in organic honey.

The intensive application of pesticides to increase crop production has resulted in contamination of the agricultural products. Due to their occurrence at trace levels and the complexity of food samples, analysis of pesticide residues requires selective and efficient sample preparation methods. For this purpose, an extraction method based on supercritical carbon dioxide and acetonitrile as entrainer solvent was developed for trace analysis of atrazine, diazinon, chlorothalonil, and deltamethrin pesticides in honey samples. A Box-Behnken experimental design was applied to optimize extraction variables including static extraction time (5-15 min), pressure (200-700 bar), and temperature (45-70°C). The optimum extraction conditions were found to be 11.5 min static extraction time, 252 bar, and 70°C. The proposed analytical method showed a good linearity (≥0.998), low limit of detection (0.005-0.009 mg/kg), and good extraction recovery (74-111%). The precision study of the proposed method at two concentration levels of each pesticides, 0.25 and 1.0 mg/kg was found to be in the ranges of 2.3-4.21% for intraday (n = 3) and 3.93-8.02% for interday precisions (n = 3). The developed method is promising for use in trace analysis of pesticides in complex food samples including honey.

High Density Supercritical Carbon Dioxide for the Extraction of Pesticide Residues in Onion with Multivariate Response Surface Methodology.

The excessive use of pesticides is a serious health problem due to their toxicity and bioaccumulation through the food chain. Due to the complexity of foods, the analysis of pesticides is challenging often giving large matrix effects and co-extracted compounds. To overcome this problem, a selective and "green" supercritical fluid extraction method was developed, using neat carbon dioxide as a solvent at pressures of up to 800 bars. A Box-Behnken response surface experimental design was used, with the independent variables of density (0.70-1.0 g mL-1), temperature (40-70 C), and volume (10-40 mL) of solvent, and the dependent variable of extracted amount of pesticides. The optimum extraction condition was found at the use of 29 mL of supercritical CO2 at 0.90 g mL-1 and 53C (corresponding to 372 bars of pressure). It was observed that increasing the density of CO2 significantly increased the extraction recovery of endrin and 2,4'-dichlorodiphenyldichloroethane. Matrix-matched calibration curves showed satisfactory linearity (R2 ≥ 0.994), and LODs ranged from 0.2 to 2.0 ng g-1. Precision was lower than 11% and recoveries between 80%-103%. Thus, the developed method could efficiently be used for trace analysis of pesticides in complex food matrices without the use of organic solvents.

Ionic-liquid-based dispersive liquid-liquid microextraction combined with high-performance liquid chromatography for the determination of multiclass pesticide residues in water samples.

Ionic-liquid-based dispersive liquid-liquid microextraction in combination with high-performance liquid chromatography and diode array detection has been proposed for the simultaneous analysis of four multiclass pesticide residues including carbaryl, methidathion, chlorothalonil, and ametryn from water samples. The major experimental parameters including the type and volume of ionic liquid, sample pH, type, and volume of disperser solvent and cooling time were investigated and optimum conditions were established. Under the optimum experimental conditions, limits of detection and quantification of the method were in the range of 0.1-1.8 and 0.4-5.9 µg/L, respectively, with satisfactory enrichment factors ranging from 10-20. The matrix-matched calibration curves, which were constructed for lake water, as a representative matrix were linear over wide range with coefficients of determination of 0.996 or better. Intra- and interday precisions, expressed as relative standard deviations, were in the range of 1.1-9.7 and 3.1-7.8%, respectively. The relative recoveries of the spiked environmental water samples at one concentration level were in the range of 77-102%. The results of the present study revealed that the proposed method is simple, fast, and uses environmentally friendly extraction solvent for the analysis of the target pesticide residues in environmental water samples.

Development and validation of one-step ultrasound-assisted extraction for simultaneous determination of multiclass fungicides in soils.

A rapid, efficient, and simple one-step ultrasound-assisted extraction (UAE) method was developed for the analysis of seven fungicides (cymoxanil, metalaxyl, mandipropamid, folpet, chlorothalonil, kresoxim-methyl, and famoxadone) in horticultural soils. Analytes in the samples were determined by HPLC with variable wavelength detection. Key parameters that influence the UAE procedure were optimized, such as the nature and volume of extraction solvent, number of sonication steps, and sonication time. The highest extraction efficiencies in the range of 61.1-87.8% were obtained by using only 7.5 mL of ethyl acetate-hexane (1+1, v/v) and sonicating for 10 min. At 0.5 and 2.0 µg/g fortification levels, satisfactory recoveries (>60%) with RSD<13% were obtained for each analyte, except for folpet (>52%). The method was linear over the range of 0.005 to 10 µg/g and the correlation coefficients (r2) obtained ranged from 0.9955 to 0.9992. The LODs (S/N=3) varied from 0.0015 to 0.006 µg/g. The proposed UAE procedure was compared to classical extractions (shake-flask and Soxhlet extraction) and showed satisfactory extraction efficiencies using shorter time and smaller amounts of organic solvents, thereby minimizing the costs of the analysis and the disposal of waste solvent.

Trace level enrichment of lead from environmental water samples utilizing dispersive liquid-liquid microextraction and quantitative determination by graphite furnace atomic absorption spectrometry.

Dispersive liquid-liquid microextraction (DLLME) was developed and successfully applied, as a sample preconcentration and extraction method, for the determination of trace quantities of lead (Pb) in environmental water samples utilizing graphite furnace atomic absorption spectrometer (GFAAS). Experimental parameters optimized include; extraction and disperser solvent types and their volumes, pH, extraction period, effect of the co-existing ions and the amount of chelating agent, ammonium pyrrolidine dithiocarbamate (APDC). Under the optimized conditions, enrichment factor of 195 at 5 µg L(-1) level and detection limit of 0.16 µg L(-1) were obtained. Linearity from 25-75 µg L(-1) with R(2) of 0.995 was achieved. The procedure was validated utilizing four environmental water samples at the spiking levels of 10 and 20 µg L(-1) and the corresponding recoveries ranged from 89.6 to 95.1% and 91.6 to 97.1%, respectively, indicating the reliability and applicability of the method for selective extraction of trace level lead.

The non-edible and disposable parts of oyster mushroom, as novel adsorbent for quantitative removal of atrazine and its degradation products from synthetic wastewater.

In this study, the non-edible part of oyster mushroom was utilized for quantitative removal of the most commonly used s-triazine herbicide; atrazine and its breakdown products including deethylatrazine (DEA), hydroxyatrazine (ATOH) and deisopropylatrazine (DIA) from aqueous samples. The functional groups available on the oyster mushroom were studied applying FTIR before and after adsorption. Experimental parameters influencing the uptake process including acidity, sorbent mass, sorption time, initial analyte quantities, and agitation speed were analysed and the maximum removal was found at 4, 0.3 g, 120 min, 0.5 mg L-1, and 150 rpm, respectively. Accordingly, the adsorption capacities of 0.994, 1.113, 0.991 and 1.016 mg g-1 were obtained for DIA, DEA, ATOH and atrazine, respectively. The adsorption characteristics were discussed utilizing Langmuir and Freundlich isotherm models. The fundamental characteristic of the Langmuir isotherm, which can be elaborated using separation factor or equilibrium parameter, RL, and coefficient of variation, R2, were (0.761, 0.996), (0.884, 0.975), (0.908, 0.983) and (0.799, 0.984) for DIA, DEA, ATOH and Atrazine, respectively. These findings showed that all analytes' adsorption processes were fitted well to the Langmuir adsorption isotherm, indicating that the adsorbent surface was covered in a monolayer. The kinetics was also evaluated using the pseudo-first and pseudo-second order models. The coefficient of determination, r2, were found to be 0.09703, 0.9989, 0.9967 and 0.9998 for DIA DEA, ATOH and atrazine, respectively, for pseudo-second order, signifying that, all analytes were found to follow the pseudo-second order rate model showing that the rate limiting step is chemisorption in the sorption process. Based on these findings, the non-edible and disposable part of the oyster mushrooms can be utilized as a preferred alternative biosorbent for the uptake of the target compounds analysed and other pollutants possessing comparable physicochemical characteristics occurring in various water bodies.

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.

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.

A Highly Selective Analytical Method Based on Salt-Assisted Liquid-Liquid Extraction for Trace-Level Enrichment of Multiclass Pesticide Residues in Cow Milk for Quantitative Liquid Chromatographic Analysis.

In this study, a simple, inexpensive, selective, and fast salting-out assisted liquid-liquid extraction (SALLE) technique coupled with high-pressure liquid chromatography-diode array detection (HPLC-DAD) was developed for the extraction, preconcentration, and analysis of trace level seven multiclass pesticide residues in pasteurized and raw cow milk samples. The significant factors that affect the extent to which the target analytes are extracted, such as the type of extraction solvent and its volume, the type and concentration of salting-out salts, the pH of the solution, and the extraction time, have been investigated. Under optimum conditions, the correlation coefficient (r2) was obtained within a range of 0.9982-0.9997 for a broad linear range concentration of 2-1500 ng·mL-1. Reliable sensitivity was achieved with limits of detection (LODs) and limits of quantification (LOQs) ranging from 0.58-2.56 ng·mL-1 and 1.95-8.51 ng·mL-1, respectively. While precision with interday and intraday in terms of relative standard deviations (RSDs) was observed in the range of 1.97 - 7.88% and 4.52 - 8.04%, respectively. The results of the precision studies reveal that good repeatability and reproducibility (RSDs <9) were achieved, thus showing a low variability extraction of the developed method. Finally, the proposed and validated approach was effectively used to extract and determine pesticide residues in real milk matrices; however, the target analytes were not detected in all samples.

Validation of modified QuECHERS extraction method for quantitative enrichment of seven multiclass antibiotic residues from vegetables followed by RP-LC-UV analysis.

A modified rapid, simple quick, cheap, effective, robust and safe (QuEChERS) extraction method was developed for the simultaneous extraction and purification of seven antibiotic residues in lettuce, carrot and tomato using liquid chromatography UV detector. The method was validated for linearity, sensitivity, accuracy, repeatability, and reproducibility at six concentration levels for all matrices, according to the guidelines of UNODC. A matrix-matched calibration method was used for the quantitative analysis. Linear range of 0.01-250 µg kg-1 for target compounds with correlation coefficient (R2) 0.9978-0.9995 was obtained. The limits of detections (LODs) and quantifications (LOQs) were 0.02-2.48 µg kg-1 were 0.06-7.52 µg kg-1, respectively. The average recoveries of the seven antibiotics ranged from 74.5 to 105.9%, with relative standard deviation RSD (%) < 11, for all matrices and matrix effects were less than 20% for most of compounds. This comprehensive simple QuEChERS extraction method can be used for the investigation of multi-residue drugs belonging to different chemical families in vegetables.

Biological management of coffee wilt disease (Fusarium xylarioides) using antagonistic Trichoderma isolates.

Coffee wilt disease (CWD) is a serious threat to the food security of small-scale farmers in Ethiopia, causing significant reductions in coffee yield. Currently, there are no effective control measures available against the causative agent of CWD, Fusarium xylarioides. The main objective of this study was therefore to develop, formulate, and evaluate a range of biofungicides against F. xylarioides, derived from Trichoderma species and tested under in vitro, greenhouse, and field conditions. In total, 175 Trichoderma isolates were screened as microbial biocontrol agents against F. xylarioides. The efficacy of two biofungicide formulations, wettable powder and water dispensable granules, were tested on the susceptible Geisha coffee variety in three different agro-ecological zones in southwestern Ethiopia over three years. The greenhouse experiments were set up using a complete block design, while in the field a randomized complete block design was used, with twice yearly applications of biofungicide. The test pathogen spore suspension was applied to the coffee seedlings by soil drenching, and the subsequent incidence and severity of CWD evaluated annually. The mycelial growth inhibition profiles of the Trichoderma isolates against F. xylarioides ranged from 44.5% to 84.8%. In vitro experiments revealed that T. asperelloides AU71, T. asperellum AU131 and T. longibrachiatum AU158 reduced the mycelial growth of F. xylarioides by over 80%. The greenhouse study indicated that wettable powder (WP) of T. asperellum AU131 had the highest biocontrol efficacy (84.3%), followed by T. longibrachiatum AU158 (77.9%) and T. asperelloides AU71 (71.2%); they also had a significant positive impact on plant growth. The pathogen-treated control plants had a disease severity index of 100% across all the field experiments, and of 76.7% in the greenhouse experiments. In comparison to untreated controls, the annual and cumulative disease incidence over the three years of the study period varied from 46.2 to 90%, 51.6 to 84.5%, and 58.2 to 91%, at the Teppi, Gera and Jimma field experimental locations. Overall, the greenhouse and field experiments and in vitro assays support the biocontrol potential of Trichoderma isolates, and T. asperellum AU131 and T. longibrachiatum AU158 in particular are recommended for the management of CWD under field conditions.

Depletion of Amoxicillin Residue in Edible Tissue of Broiler Chicken by Different Cooking Methods.

A new simple isocratic, RP-HPLC method, was developed and validated to estimate amoxicillin (Amox) residue depletion caused by different cooking methods in broiler chicken tissue. The limit of detection (LOD) and the limit of quantitation (LOQ) were 1.32 and 4.00 µg mL-1, respectively. The calibration plot was linear over the concentration range of 0.05-250 µg mL-1, and the relative standard deviation (RSD) values were less than 8%. The effects of various cooking methods (boiling, pan-frying, and microwaving) on residues of Amox were conducted under different combinations of temperature and time. Moreover, the heat stability of Amox standard solutions under boiling water and cooking oil at 100°C was investigated. Amox remained stable for 5-15 min in boiling water, the concentration was significantly reduced in the range of 70-87%, and additional new peaks of the degraded compounds appeared at 30-45 min. In pan-frying, the residue remained stable for 15 min at 100°C and then depleted to 81-92% after 30-45 min. Due to dehydration, the residue concentration showed an increment from 101 to 112% at 150°C. The total decomposition of Amox was observed at 200°C, 30-45 min due to high temperature and long-time effects. In microwave cooking using 500 W, 0.5-2 min, the depletion was insignificant. This study shows that sufficient cooking temperature and time can have a significant effect on the depletion of Amox residues.

Antifungal compounds, GC-MS analysis and toxicity assessment of methanolic extracts of Trichoderma species in an animal model.

Fungi of the genus Trichoderma have been marketed for the management of diseases of crops. However, some Trichoderma species may produce toxic secondary metabolites and it should receive due attention to ensure human safety. In this study, we investigated the in vitro antagonistic potential of T. asperellum AU131 and T. longibrachiatum AU158 as microbial biocontrol agents (MBCAs) against Fusarium xylarioides and the associated antagonistic mechanism with bioactive substances. Swiss albino mice were used to evaluate the in vivo toxicity and pathogenicity of T. asperellum AU131 and T. longibrachiatum AU158 methanolic extracts and spore suspensions, respectively, in a preliminary safety assessment for use as biofungicides. Gas Chromatography-Mass Spectrometry (GC-MS) was used to profile volatile organic metabolites (VOCs) present in the methanolic extracts. The agar diffusion assay of the methanolic extracts from both T. asperellum AU131 and T. longibrachiatum AU158 were effective at a concentration of 200 µg/mL (1×107 spores/mL), causing 62.5%, and 74.3% inhibition, respectively. A GC-MS analysis of methanolic extracts from both bioagents identified 23 VOCs which classified as alcohols, acids, sesquiterpenes, ketones and aromatic compounds. The oral administration of methanolic extracts and spore suspensions of each Trichoderma species to female Swiss albino mice over 14 days did not show any significant signs of toxicity, mortality or changes to body weight. It can be concluded that the tested spore suspensions and methanolic extracts were not pathogenic or toxic, respectively, when administered to Swiss albino mice at various doses.

Development and validation of liquid chromatography method for simultaneous determination of multiclass seven antibiotic residues in chicken tissues.

BACKGROUND: Antibiotics are routinely used on poultry for therapy and prevention of diseases and to enhance animal growth. The objective of this study was to develop and validate a sensitive and reliable liquid chromatography with UV detection (LC-UV) method for the simultaneous determination of seven multiclass antibiotic residues (amoxicillin, ampicillin, penicillin, sulfamethoxazole, gentamicin, ciprofloxacin, and erythromycin) in chicken tissues. METHODS: The liquid chromatography method with UV detection was optimized for complete separation of the seven selected antibiotic compounds with reversed phase and isocratic elution using Hypersil BDS-C18 (3 µm, 100 mm × 4 mm) column. The mobile phase consisted a ratio of 0.05 M Na2HPO4, acetonitrile and methanol (70:10:20), at UV absorption wavelength of 230 nm. The column thermostat was set at 40 °C, the mobile phase flow rate was 1 mL min-1, and the injection volume was 20 µL. RESULTS: All the seven standard compounds were eluted within 14 min. The results for: linearity, precision, sensitivity, accuracy, specificity, decision limit (CCα), detection capability (CCß), suitability and method robustness were validated according to the criteria of Commission Decision 2002/657/EC guidelines. Calibration plot correlation coefficients ranged from 0.9983 to 0.9998 and the percent relative standard deviations for repeated analysis were below 5% indicating acceptable method precision. The limits of detection (LODs) and quantification (LOQs) ranged from 0.098-0.255 µg kg-1 to 0.297-0.574 µg kg-1, respectively. The accuracy study yielded recoveries in the ranges 98.1-107% for the pure compounds and 94.0-102% for the spiked drug free chicken tissue samples. CONCLUSIONS: The method was found to be appropriate for simultaneous determination of five different classes of seven antibiotic residues in chicken tissues. Furthermore, this is the first instance for the simultaneous determination of seven multiclass, multi-residues analysis using LC-UV from chicken tissue samples. This is a cost-effective and alternative method with simple instrumentation approach for laboratories that lack highly specialized state-of-the-art instrumentation.

Optimization of Culture Conditions and Production of Bio-Fungicides from Trichoderma Species under Solid-State Fermentation Using Mathematical Modeling.

Agro-industrial wastes suitable for economical and high mass production of novel Trichoderma species under solid-state fermentation were identified by optimizing the culture conditions using a mathematical model and evaluating the viability of the formulated bio-product. Fourteen inexpensive, locally available, organic substrates and cereals were examined using a one-factor-at-a-time experiment. The fungus colonized nearly all substrates after 21 days of incubation, although the degree of colonization and conidiation varied among the substrates. A mixture of wheat bran and white rice (2:1 w/w) was found to support maximum growth of T. asperellum AU131 (3.2 × 107 spores/g dry substrate) and T. longibrachiatum AU158 (3.5 × 107 spores/g dry substrate). Using a fractional factorial design, the most significant growth factors influencing biomass production were found to be temperature, moisture content, inoculum concentration, and incubation period (p ≤ 0.05). Analysis of variance of a Box-Behnken design showed that the regression model was highly significant (p ≤ 0.05) with F-values of 10.38 (P = 0.0027, T. asperellum AU131) and 12.01 (p < 0.0017, T. longibrachiatum AU158). Under optimal conditions, maximum conidia yield of log10 (8.6) (T. asperellum AU131) and log10(9.18) (T. longibrachiatum) were obtained. For wettable powder Trichoderma species formulations, it was possible to maintain conidial viability at room temperature (25 °C) for eight months at concentrations above 106 CFU/g.

Phytochemical Composition and Antioxidant Property of Mandillo, Crassocephalum macropappum (Sch.Bip. ex. A.Rich.) S.Moore.

The object of this study was to analyze the major bioactive components and to evaluate biological activity of Mandillo [Crassocephalum macropappum (Sch.Bip. ex. A.Rich.) S. Moore], an Ethiopian endemic herbaceous plant. The stem, leaf, and aerial parts of this plant were separately extracted using different solvents before which various biological assays were performed. The ethanolic extract of aerial part showed the highest total phenolic and flavonoid contents (101.48 mg gallic acid equivalents/g and 293.25 mg quercetin equivalent/g, respectively). Interestingly, a phytochemical screening assay revealed the presence of saponins, tannins, anthraquinones, steroids, terpenoids, and flavonoids in the aerial part. The aerial part was also shown to have a strong 2,2-diphenyl-1-picryl hydrazyl scavenging potential (IC50≤100 µg/mL) and a promising protective activity against oxidative DNA damage. Thus, the results of the present study reveal Mandillo contains highly bioactive components, and these properties may be as an antioxidant and to prevent oxidative DNA damage.

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.

Selective pressurized liquid extraction for multi-residue analysis of organochlorine pesticides in soil.

A selective pressurized liquid extraction (SPLE) procedure capable of performing simultaneous extraction and clean-up has been demonstrated for multi-residue analysis of organochlorine pesticides (OCPs) in soil. The final method was performed at 100 degrees C for 3 x 10 min using acetone/n-heptane (1:1, v/v). Florisil was placed inside the extraction cell downstream the sample to remove interfering compounds. Extraction of two soil samples by SPLE gave a recovery which was over 80% for beta-endosulfan, endosulfan sulfate, p,p'-DDT and p,p'-DDE compared to PLE with off-line clean-up. The same trend was observed when applying the SPLE method to a certified reference soil sample (CRM 811-050) containing 13 OCPs, where the SPLE method gave 80-90% recovery vis-à-vis the PLE method with off-line clean-up. Feasibility of the SPLE method was further demonstrated by applying it to five real soil samples collected in Ethiopia.

Determination of trace levels of dinitrophenolic compounds in environmental water samples using hollow fiber supported liquid membrane extraction and high performance liquid chromatography.

A hollow fiber supported liquid membrane extraction method for the liquid chromatographic determination of dinitrophenolic compounds at ppt levels has been developed. Different variables affecting the extraction process, such as extraction time, shaking speed, acceptor pH, acceptor buffer concentration, salt content and humic acids have been studied. Enrichment factors up to 7000 times were obtained. Validation of the method included calibration experiments and studies of the linearity of the responses in different matrices. Good linearity was obtained in the environmental matrices evaluated. Detection limits range from 6.0 to 8.0 ng/L, and the relative standard deviations do not exceed 7% in terms of repeatability.

Development of a pressurized liquid extraction and clean-up procedure for the determination of alpha-endosulfan, beta-endosulfan and endosulfan sulfate in aged contaminated Ethiopian soils.

Pressurized liquid extraction (PLE) was investigated for the extraction of two endosulfan isomers and their metabolite from two real contaminated soil samples. PLE for 3x10min at 100 degrees C was proven to be more exhaustive than Soxhlet extraction (SOX) in one soil sample. On the other soil sample investigated the method was found to be equally exhaustive as SOX. The use of hazardous organic solvents such as n-hexane, toluene, and diethyl ether has been avoided in PLE and clean-up. Instead less toxic solvents have been used both at the extraction step (acetone/n-heptane) and clean-up step (ethyl acetate/n-heptane). A column Florisil clean-up procedure that consumes relatively low solvent volumes has been optimized and applied to purify soil extracts. The developed analytical procedure was validated by applying it to a certified reference soil material (CRM811-050). A recovery of 103% total endosulfan residue was obtained versus certified values.