Solid-phase extraction for multi-residue analysis of pesticides in honey

A fast and simple multi-residue method for the analysis of 15 organophosphorus (OP), 17 organochlorine (OC), 8 pyrethroids (PYR), 12 N-methyl-carbamate (NMC) pesticide residues and bromopropylate in honey is presented. Ready–to–use EXtrelut®NT 20 column, eluted with dichloromethane, was used to extract the pesticide residues from the aqueous-acetone honey sample, obtaining a clean extract directly analyzable. Determination was carried out by gas chromatography (GC) coupled with flame photometric detector (FPD) for OP compounds and by GC coupled with mass spectrometry detector (MSD) for OC and PYR pesticides and bromopropylate. The NMC pesticides were analysed by liquid chromatography-double derivatization coupled with spectrofluorimetric detector (LC/DD/Fl). This method allows the determination of the 53 pesticide residues at low concentrations (0.0005–0.074 mg/kg) and can be used to assess the compliance with the Maximum Residues Levels (MRLs) set by the European Union. The performance of the method was evaluated and specificity, linearity, recovery, repeatability, reproducibility, limit of quantification (LOQ) and limit of detection (LOD) were determined. A good linearity (r²? 0.99) was found in the range 0.0005–0.074 mg/kg for the majority of the compounds studied. Most of the pesticides had recoveries in the range 70–103 % and values of relative standard deviation (RSD) < 20 for repeatability and reproducibility, showing good accuracy and precision of the method. Aldicarb partially degraded in aldicarb sulphoxide during the analytical procedure, giving anomalous values. The LOQ for all pesticides investigated was from 0.0005 to 0.025 mg/kg while the LOD ranged from 0.0002 to 0.008 mg/kg.     

Solid phase extraction with silicon dioxide microsphere adsorbents in combination with gas chromatography-electron capture detection for the determination of DDT and its metabolites in water samples

The goal of the present study was to investigate the feasibility of silicon dioxide (SiO₂) microspheres without special modification to enrich dichlorodiphenyltrichloroethane (DDT) and its main metabolites, p,p′-dichlorodiphenyl-2,2-dichloroethylene (p,p′-DDD) and p,p′-dichlorodiphenyldichloroethylene (DDE) in combination with gas chromatography-electron-capture detection. The experimental results indicated that an excellent linear relationship between the recoveries and the concentrations of DDT and its main metabolites was obtained in the range of 0.2–30 ng mL^?1 and the correlation coefficients were in the range of 99.96–99.99%. The detection limits based on the ratio of signal to the baseline noise (S/N = 3) were 2.2, 2.9, 3.8 and 4.1 ng L^?1 for p,p′-DDD, p,p′-DDT, o,p′-DDT, and p,p′-DDE, respectively. The precisions of the proposed method were all below 10% (n = 6). Four real water samples were utilized for validation of the proposed method, and satisfactory spiked recoveries in the range of 72.4–112.9% were achieved. These results demonstrated that the developed method was a simple, sensitive, and robust analytical method for the monitoring of pollutants in the environment.     

Validation of QuEChERS method for the determination of 36 pesticide residues in fruits and vegetables from Ghana,using gas chromatography with electron capture and pulsed flame photometric detectors

In this study, “Quick, Easy, Cheap, Effective, Rugged and Safe” ‘QuEChERS’ method was modified for the determination of 36 pesticides fortified at (0.01–1.0) mg kg^?1 in three vegetables and a fruit (lettuce, carrot, tomatoes and pineapples respectively) from Ghana. The method involved extraction with acetonitrile, phase separation with primary secondary amine and magnesium sulfate; the final injection solution was reconstituted in ethyl acetate. Organochlorine and synthetic pyrethroids residues were detected with electron capture detector whereas organophosphorus, pulsed flame photometric detector was used. The recoveries at different concentration levels (0.01, 0.1 and 1.0 mg kg^?1) were in the range of 83% and 93% with relative standard deviation ranging from 2% to 10% (n = 5) and the coefficient of determination (R²) was greater than 0.99 for all the 36 pesticides. The method was successfully tested on 120 real samples from Accra markets and this proved to be useful for monitoring purposes particularly in laboratories that have no gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.     

Persistence of seven pesticides as influenced by soil moisture1

Abstract

Pesticides are often applied in combination, but less‐often is soil persistence measured this way. The present field and laboratory study determined relative persistence of five herbicides and two insecticides, co‐applied, as a function of three soil water contents. Losses were modeled adequately by first‐order dissipation, with no significant improvement by using a two‐compartment model. The order of persistence in a silt loam, at 25% moisture, was carbofuran < cyanazine < metribuzin = alachlor < atrazine < ethoprop < metolachlor (t_½ ranged from 7–91 days). Carbofuran degradation increased greatly from 12–25% soil moisture; atrazine was unaffected by 12–35%, whereas the remaining compounds showed limited increasing loss in wetter soil. Field‐based persistence was more variable, but generally similar to lab rankings.     

Comparative acute toxicities of selected pesticides to Anguilla anguilla

Abstract

The acute toxicities (24, 48, 72 and 96 hr) of eight pesticides to Anguilla anguilla were determined. The organochlorine pesticide, endosulfan was the most toxic, with LC50 values in the range of 0.042 to 0.041 mg/L Endosulfan was followed in order of decreasing toxicity by diazinon, fenitrothion, chlorpyrifos, lmdane, methidathion, trichlorfon and methylparathion. When fishes were exposed to the pesticides tested they exhibited signs of restlessness, erratic swimming, convulsions and difficulty in respiration. This response was more persistent in fishes exposed to organophosphorus pesticides.     

Estimating Contributions of Nitrate and Herbicides From Groundwater to Headwater Streams,Northern Atlantic Coastal Plain,United States1

Abstract: Groundwater transport often complicates understanding of surface‐water contamination. We estimated the regional flux of nitrate and selected herbicides from groundwater to nontidal headwater streams of the Atlantic Coastal Plain (New Jersey through North Carolina) based on late‐winter or spring base‐flow samples from 174 streams. Sampled streams were selected randomly, and flux estimates are based on resulting population estimates rather than on empirical models, which have been used previously for similar estimates. Base‐flow flux in the estimated 8,834 headwater streams of the study area are an estimated 21,200 kg/day of nitrate (as N) and 5.83, 0.565, and 20.7 kg/day of alachlor, atrazine, and metolachlor (and selected degradates), respectively. Base‐flow flux of alachlor and metolachlor is <3% of the total base‐flow flux of those compounds plus degradates. Base‐flow flux of nitrate and herbicides as a percentage of applications is typically highest in well‐drained areas and lowest in areas with abundant poor drainage and anoxic conditions. In Coastal Plain watersheds of Albemarle and Pamlico Sounds, <2% of applied nitrogen reaches headwater streams as base flow. On the Delmarva Peninsula part of the Chesapeake Bay watershed, however, more than 10% of such applications are transported through groundwater to streams, and base‐flow nitrate flux represents 70% of total nitrogen flux in headwater streams.     

Potential Impacts of Stormwater Runoff on Water Quality in Urban Sand Pits and Adjacent Groundwater1

Whittemore, Donald O., 2012. Potential Impacts of Stormwater Runoff on Water Quality in Urban Sand Pits and Adjacent Groundwater. Journal of the American Water Resources Association (JAWRA) 48(3): 584-602. DOI: 10.1111/j.1752-1688.2011.00637.x Abstract: Entrance of stormwater runoff into water-filled pits and adjacent aquifers is a contamination concern. The water and sediment quality in several sand pits and surrounding groundwater in Wichita, Kansas, were studied to comprehensively address stormwater runoff impact. The pits are used for residential development after sand and gravel mining. Water samples were analyzed for inorganic constituents, bacteria, and 252 organic compounds, and pit sediments for inorganic components and 32 organic chemicals. Although many pesticide and degradate compounds were found in the pit and well waters, none of these chemicals exceeded existing health levels. Other organic contaminants were detected in the waters, with those exceeding health levels at one site attributed to an undiscovered groundwater contamination plume and not to stormwater runoff. Persistent insecticides and polychlorinated biphenyls detected in sediment of two pits are related to the age of residential development. The concentration distributions of pesticides and other organics at most of the sites, as well as iron, manganese, and ammonia patterns in downgradient well waters relative to upgradient well and pit waters, indicate that groundwater quality at the sites is affected by contaminants entering the pit surface waters. Thus, although current stormwater runoff does not appear to have contaminated sand-pit water and adjacent groundwater above health levels, the data show that the potential exists if stormwater became polluted.     

Heterogeneous reactions of suspended parathion, malathion, and fenthion particles with NO(3) radicals

Organophosphorus pesticides (OPPs) emit into the atmosphere in both gas and particulate phases via spray drift from treatments and post-application emission, but most of their degradations in the atmosphere are not well known. In this study, the heterogeneous reactions of nitrate (NO₃) radicals with three typical OPPs (parathion, malathion, and fenthion) absorbed on azelaic acid particles are investigated using an online vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The reaction products observed with the VUV-ATOFMS are identified on the basis of GC/MS analysis of the products in the reaction between NO₃ radicals and the coating of the pesticide. Paraoxon is identified as the only product of parathion; malaoxon and bis(1,2-bis-ethoxycarbonylethyl)disulfide as the products of malathion; fenoxon, fenoxon sulfoxide, fenthion sulfoxide, fenoxon sulfone, and fenthion sulfone as the products of fenthion. The degradation rates of parathion, malathion, and fenthion under the experimental conditions are 5.5 × 10⁻³, 5.6 × 10⁻², and 3.3 × 10⁻² s⁻¹, respectively. The pathways of the heterogeneous reactions between the three OPPs and NO₃ radicals are proposed. The experimental results reveal the possible transformations of these OPPs through the oxidation of NO₃ radicals in the atmosphere.     

Polychlorobiphenyls and organochlorine pesticides in conventional and organic brands of milk: occurrence and dietary intake in the population of the Canary Islands (Spain)

The population of the Spanish archipelago of the Canary Islands has been studied in depth regarding its levels of contamination by organochlorine pesticides (OCs) and polychlorinated biphenyls (PCBs). Foodstuffs of animal origin, such as milk, are prominent contributors to the body burden of these contaminants. As this population presents one of the highest milk-intake in Spain and Europe, we evaluated the level of OCs and PCBs in 26 commercially available brands of milk (16 conventional and 10 organic brands) present in the market of these Islands, in order to estimate the relevance of milk as a source of these chemicals for the Canary population. Our findings showed that hexachlorobenzene, trans-chlordane, and PCB153 were present in almost all the samples with independence of the type of milk. For both types of milks, the concentration of OCs was very low, showing organic milks lower levels than conventional ones. As a consequence, the estimated daily intake for OCs was lower than the tolerable daily intake (TDI) established by International Agencies. The levels of PCBs in milk were also found to be very low, but, in this case, the situation was the opposite: there were higher levels of PCBs in organic than in conventional brands of milk. Unexpectedly, levels of dioxin-like PCBs (DL-PCBs) reached values higher than 25 pg WHO-TEQ g⁻¹ fat in percentile 75 for both types of milk indicating the existence of a number of brands of milk highly contaminated by these toxicants. Consequently, the population who consume the most contaminated milk brands could have estimated daily intakes well above the recommended TDI (2 pg WHO-TEQ kg⁻¹ b.w. d⁻¹) established by European Union Authorities. These results are of concern if we consider the well known adverse health effects exerted by dioxin-like compounds.     

Partitioning of persistent organic pollutants (POPs) between human serum and breast milk: A literature review

The literature was reviewed to assess the relationship between the lipid adjusted concentration in human serum and breast milk (expressed as the serum/milk ratio) of a broad range of POPs in paired samples. Thirteen studies were identified, including seven studies that reported serum/milk ratios for polychlorinated dibenzo-dioxins and -furans (PCDD/Fs), ten for polychlorinated biphenyls (PCBs), five for polybrominated diphenyl ethers (PBDEs), and five for organochlorine pesticides (OCPs). Mean serum/milk ratios ranged between 0.7 and 25 depending on the compound and congener. For PCDD/Fs, PCBs and PBDEs, a clear trend of increasing mean serum/milk ratio by increasing molar volume, hydrophobicity and number of halogen substitutes was observed. The mean serum/milk ratios reported by the 13 studies summarized here will aid comparison between human POPs exposure studies using either serum or milk samples. More studies are needed to allow a valid comparison between data obtained from analysis of breast milk and serum samples for a broader range of POPs. Furthermore such studies may shed light on compound specific factors as well as other determinants that may affect the partitioning and partition kinetics of POPs between serum and breast milk.