Determination of Pesticide Residues in Sewage Sludge: A Review

Pesticides are widely applied to protect plants from diseases, weeds, and insect damage, and they usually come into contact with soil where they may undergo a variety of transformations and provide a complex pattern of metabolites. Spreading sewage sludge on agricultural lands has been actively promoted by national authorities as an economic way of recycling. However, as a byproduct of wastewater treatment, sewage sludge may contain pesticides and other toxic substances that could be incorporated into agricultural products or be distributed in the environment. This article reviews the determination of pesticides in sewage sludge samples. Sample preparation including pretreatment, extraction, and cleanup, as well as the subsequent instrumental determination of pesticide residues, are discussed. Extraction techniques such as Soxhlet extraction, ultrasound-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, and matrix solid-phase dispersion and their most recent applications to the determination of pesticides in sewage sludge samples are reviewed. Determination of pesticides, generally carried out by GC and HPLC coupled with different detectors, especially MS for the identification and quantification of residues, is summarized and discussed.

Determination of Thiabendazole in Orange Juice and Rind by Liquid Chromatography with Fluorescence Detection and Confirmation by Gas Chromatography/Mass Spectrometry After Extraction by Matrix Solid-Phase Dispersion

A method was developed for the determination of thiabendazole (TBZ) in orange juice and rind based on matrix solid-phase dispersion (MSPD). TBZ was extracted with ethyl acetate and the extract was subsequently cleaned up on a solid-phase extraction column. Fungicide residues were determined by liquid chromatography with fluorescence detection. Recoveries through the method ranged from 87 to 97% with relative standard deviations ≤11%. The detection and quantitation limits were 0.15 and 0.50 μg/kg, respectively. The confirmation of TBZ residues in positive samples was performed by solid-phase microextraction followed by gas chromatography with mass spectrometric detection using selected ion monitoring. The developed method was applied to determine TBZ levels in commercial orange juices and in juice and rind of fresh oranges. The influence of storage and washing of fruits on TBZ residues was also studied.

Determination of Polycyclic Aromatic Hydrocarbons in Honey by Matrix Solid-Phase Dispersion and Gas Chromatography/Mass Spectrometry

A multiresidue method was developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in unifloral and multifloral honeys. The analytical procedure is based on the matrix solid-phase dispersion of honey on a mixture of Florisil and anhydrous sodium sulfate in small glass columns and extraction with hexane–ethyl acetate (90 + 10, v/v) with assisted sonication. The PAH residues are determined by gas chromatography with mass spectrometric detection using selected-ion monitoring. Average recoveries for all the PAHs studied were in the range of almost 80 to 101%, with relative standard deviations of 6 to 15%. The limits of detection ranged from 0.04 to 2.9 μg/kg. The simultaneous extraction and cleanup of samples makes this method simple and rapid, with low consumption of organic solvents.

Multiresidue Determination of Pesticides in Honey by Matrix Solid-Phase Dispersion and Gas Chromatography with Electron-Capture Detection

A multiresidue method was developed for the determination of 15 pesticides (organochlorines, organophosphorus compounds, pyrethroids, and other acaricides) in various commercial honeys (eucalyptus, lavender, orange, rosemary, and multifloral). The analytical procedure is based on the matrix solid-phase dispersion of honey in a mixture of Florisil and anhydrous sodium sulfate; the mixture is placed in small plastic columns and extracted with hexane–ethyl acetate (90 + 10, v/v). The pesticide residues are determined by capillary gas chromatography with electron-capture detection. Recoveries with the method at concentrations between 0.15 and 1.5 μg/g ranged from 80 to 113%, and relative standard deviations were <10% for all the pesticides studied. The pesticide detection limits were within the range 0.5–5 mg/kg for organochlorines, around 3 μg/kg for the chlorinated organophosphorus pesticides studied, near 15 μg/kg for fluvalinate, and about 3 μg/kg for the other pyrethroids.

Analysis of Multiclass Antibiotics in Lettuce by Liquid Chromatography-Tandem Mass Spectrometry to Monitor Their Plant Uptake

The main entry routes of antibiotics in the environment are the application of organic wastes to improve soil quality and the irrigation with recycled water. Once in the environment, antibiotics can be introduced in the food chain through their uptake by crops. This paper describes the development of an analytical method based on ultrasound-assisted extraction for the determination of seven antibiotics in lettuce. The developed method was applied to evaluate antibiotic uptake by lettuce grown in pots fertilized with composted poultry litter doped with a mixture of antibiotics to reach a final concentration of 2.5 µg/g in soil. Lettuce were harvested after 21, 36, and 55 days. Five of the seven studied antibiotics were found in all samples. The highest uptake was found for lincomycin (51 ng/g fresh weight) followed by sulfamethoxazole (44 ng/g fresh weight) and sulfamethazine (21 ng/g fresh weight) in lettuce harvested after 21 days. An important decrease of their levels was observed after 36 days, but these levels remained similar after 55 days. Although levels found in lettuce were low, the presence of antibiotics demonstrates the need for further assessing food safety risks related with the use of soil amendments or irrigation water contaminated with antibiotics.

Analysis of emerging organic contaminants in poultry manure by gas chromatography-tandem mass spectrometry

A multiresidue method was developed for the determination of 19 emerging organic contaminants (pharmaceutical drugs, personal care products, and bisphenol A) in poultry manure. Lyophilized samples of manure were extracted by ultrasound-assisted matrix solid-phase dispersion and the extracts were analyzed by gas chromatography with tandem mass spectrometry after derivatization. Analysis of spiked poultry manure samples, at levels ranging from 25 to 150 ng/g, gave satisfactory recovery results for all the compounds, with values from 67 to 106%. The developed procedure provided detection limits that ranged from 0.9 to 2.2 ng/g. Finally, the validated method was applied to poultry manure samples collected from 23 poultry farms in Spain. Salicylic acid was found in most of the samples analyzed at levels up to 2501 ng/g, whereas, methyl paraben, orthophenylphenol, ibuprofen, paracetamol, and carbamazepine were detected at levels up to 250 ng/g. Composting of manure showed an important decrease in the levels of the detected contaminants.

Simultaneous determination of multiclass emerging contaminants in aquatic plants by ultrasound-assisted matrix solid-phase dispersion and GC-MS

A multiresidue method was developed for the simultaneous determination of 31 emerging contaminants (pharmaceutical compounds, hormones, personal care products, biocides, and flame retardants) in aquatic plants. Analytes were extracted by ultrasound-assisted matrix solid-phase dispersion (UA-MSPD) and determined by gas chromatography-mass spectrometry after sylilation, The method was validated for different aquatic plants (Typha angustifolia, Arundo donax, and Lemna minor) and a semiaquatic cultivated plant (Oryza sativa) with good recoveries at concentrations of 100 and 25 ng g^-1 wet weight, ranging from 70 to 120 %, and low method detection limits (0.3 to 2.2 ng g^-1 wet weight). A significant difference of the chromatographic response was observed for some compounds in neat solvent versus matrix extracts, and therefore, quantification was carried out using matrix-matched standards in order to overcome this matrix effect. Aquatic plants taken from rivers located at three Spanish regions were analyzed, and the compounds detected were parabens, bisphenol A, benzophenone-3, cyfluthrin, and cypermethrin. The levels found ranged from 6 to 25 ng g^-1 wet weight except for cypermethrin that was detected at 235 ng g^-1 wet weight in O. sativa samples.

Application of matrix solid-phase dispersion followed by GC-MS/MS to the analysis of emerging contaminants in vegetables

A multiresidue method for the determination of 17 emerging contaminants in vegetables was developed based on ultrasound-assisted matrix solid-phase dispersion (MSPD). The analysis was performed using isotope dilution gas chromatography tandem mass spectrometry. In the development of the MSPD procedure, different parameters such as sonication and the type of sorbent or extraction solvent were assayed. Manual and in situ derivatization was assayed and the chromatographic response was higher when the reaction takes place in the injection port. The limits of detection obtained for the studied compounds were in the range of 0.1-0.4ngg(-1) for the different vegetables analyzed. The developed method was applied to vegetables obtained from several local markets. At least one of the organophosphates was detected in the analyzed samples at levels ranging from 0.6 to 4.6ngg(-1) and bisphenol A was detected in all the samples at concentration up to 16ngg(-1).

Screening of environmental contaminants in honey bee wax comb using gas chromatography-high-resolution time-of-flight mass spectrometry

This study reports an analytical approach intended to be used for investigation of non-targeted environmental contaminants and to characterize the organic pollution pattern of bee wax comb samples. The method comprises a generic extraction followed by detection with gas chromatography coupled to high-resolution time-of-flight mass spectrometry (GC-TOF-MS), operated in electron impact ionization (EI) mode. The screening approach for the investigation of non-targeted contaminants consisted of initial peak detection by deconvolution and matching the first-stage mass spectra EI-MS(1) with a nominal mass spectral library. To gain further confidence in the structural characterization of the contaminants under investigation, the molecular formula of representative ions (molecular ion when present in the EI spectrum) and, for at least other two fragment ions, was provided for those with an accurate mass scoring (mass error < 5 ppm). This methodology was applied for screening environmental contaminants in 50 samples of bee wax comb. This approach has allowed the tentative identification of some GC-amenable contaminants belonging to different chemical groups, among them, phthalates and polycyclic aromatic hydrocarbons (PAHs), along with residues of veterinary treatments used in apiculture.

Uptake of azoles by lamb's lettuce (Valerianella locusta L.) grown in hydroponic conditions

An uptake and translocation study of azole compounds was performed in lamb's lettuce (Valerianella locusta L.) grown in nutrient solution fortified with different azoles. Three azoles, (clotrimazole, fluconazole and propiconazole), which have different physico-chemical properties and are ubiquitous in the aquatic environment, were the compounds selected. An analytical method, based on matrix solid phase dispersion (MSPD) followed by LC-MS/MS determination, was developed to quantify these compounds in aqueous solution and in roots and leaves. The physicochemical properties of azoles are the main factors governing the uptake and plant accumulation. These azoles were detected in leaves indicating their transport within lamb's lettuce. Translocation from nutrient solution to the aerial part of lamb's lettuce was found to be highly dependent on the hydrophobicity of the azole. Clotrimazole accumulates in roots causing necrosis in roots and leaves, whereas fluconazole was the azole with the highest concentration in leaves without causing apparent phytotoxicity symptoms. The assessment of the levels of these azoles in leaves indicates that the risk for human health is negligible.

Occurrence and analysis of selected pharmaceutical compounds in soil from Spanish agricultural fields

This work describes the analysis of 15 pharmaceutical compounds, belonging to different therapeutic classes (anti-inflammatory/analgesics, lipid regulators, antiepileptics, β-blockers and antidepressants) and with diverse physical-chemical properties, in Spanish soils with different farmland uses. The studied compounds were extracted from soil by ultrasound-assisted extraction (UAE) and determined, after derivatization, by gas chromatography with mass spectrometric detection (GC-MS). The limits of detection (LODs) ranged from 0.14 ng g(-1) (naproxen) to 0.65 ng g(-1) (amitriptyline). At least two compounds where detected in all samples, being ibuprofen, salicylic acid, and paracetamol, the most frequently detected compounds. The highest levels found in soil were 47 ng g(-1) for allopurinol and 37 ng g(-1) for salicylic acid. The influence of the type of crop and the sampling area on the levels of pharmaceuticals in soil, as well as their relationship with soil physical-chemical properties, was studied. The frequent and widespread detection of some of these compounds in agricultural soils show a diffuse contamination, although the low levels found do not pose a risk to the environment or the human health.

Uptake of perfluorinated compounds by plants grown in nutrient solution

The uptake rates of three perfluorinated carboxylates and three perfluorinated sufonates by a grass (B diandrus) grown in nutrient solution at two different perfluorinated compounds (PFCs) concentrations were assessed. Grass can be ingested by grazing animals causing the PFCs to enter the food chain, which is a pathway of human exposure to these compounds. A rapid and miniaturized method was developed to determine PFCs in plants, based on a matrix solid-phase dispersion (MSPD) extraction procedure followed by quantitation by HPLC-MS/MS with an MQL in the range from 1 to 9 ng/g. An increase of PFCs levels in plant was observed along the exposure time. Differences in uptake for studied perfluorinated carboxylates were found, showing a decrease with carbon chain length (from 3027 to 1,167 ng/g at the end of assay), whereas no significant differences in absorption were obtained between perfluorinated sulfonates (about 1,700 ng/g). Initially, higher PFC transfer factors (ratio between concentration in plant and concentration in initial nutrient solution) were obtained for plants growing in the nutrient solution at the highest PFC concentration, but these factors became similar with time to plants exposed to the lowest concentration.

Influence of moisture on the availability and persistence of clotrimazole and fluconazole in sludge-amended soil

Applying sewage sludge to soil is a common practice in many parts of the world. Thus, pharmaceutical compounds, such as azoles, can be released into the environment after sludge is applied to soil. To understand the fate of clotrimazole and fluconazole (pharmaceuticals used as antifungals in humans) in soil after its amendment with sludge, a reliable and sensitive method has been developed to determine these compounds in the solid and aqueous phases of soil. Desorption of clotrimazole from soil amended with sludge was negligible, whereas a rapid desorption of fluconazole was observed. Dissipation rates of these azoles were determined in amended soil incubated at 25°C with moisture contents ranging from 4.5 to 20%. Clotrimazole was more persistent than fluconazole in dry soil, whereas the contrary occurred in wet soil. Partitioning soil:soil solution of these azoles varied with time and moisture contents. Clotrimazole was found in soil with negligible amounts in soil solution, whereas fluconazole was approximately partitioned 50:50 during the assay time (60 d) at any soil moisture content. Occasional rainfall coupled with a relatively low binding soil capacity can result in the contamination of surface and groundwaters by fluconazole, whereas clotrimazole will remain in the soil.

Analysis of salicylate and benzophenone-type UV filters in soils and sediments by simultaneous extraction cleanup and gas chromatography-mass spectrometry

An analytical method for the determination of UV filters in soil and sediment has been developed and validated considering benzophenones (BP) and salicylates as target analytes. Soil and sediment samples were extracted with ethyl acetate-methanol (90:10, v/v) assisted with sonication, performing a simultaneous clean-up step. Quantification of these compounds was carried out by gas chromatography-mass spectrometry (GC-MS) after derivatization of the extracts with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA). Recoveries from spiked soil samples ranged from 89.8% to 104.4% and they were between 88.4% and 105.3% for spiked sediment samples. The effect of the residence time and soil moisture content on the recovery of these compounds was also studied. The precision, expressed as relative standard deviation, was in all cases below 6.1% and the limits of detection (S/N=3) varied from 0.07 to 0.10 ng g(-1) and from 0.11 to 0.28 ng g(-1) for soils and sediments, respectively. The validated method was applied to the analysis of five benzophenone and two salicylate UV filters in soil and sediment samples collected in different areas of Spain.

Determination of pesticide residues in sewage sludge: a review

Pesticides are widely applied to protect plants from diseases, weeds, and insect damage, and they usually come into contact with soil where they may undergo a variety of transformations and provide a complex pattern of metabolites. Spreading sewage sludge on agricultural lands has been actively promoted by national authorities as an economic way of recycling. However, as a byproduct of wastewater treatment, sewage sludge may contain pesticides and other toxic substances that could be incorporated into agricultural products or be distributed in the environment. This article reviews the determination of pesticides in sewage sludge samples. Sample preparation including pretreatment, extraction, and cleanup, as well as the subsequent instrumental determination of pesticide residues, are discussed. Extraction techniques such as Soxhlet extraction, ultrasound-assisted extraction, pressurized liquid extraction, supercritical fluid extraction, and matrix solid-phase dispersion and their most recent applications to the determination of pesticides in sewage sludge samples are reviewed. Determination of pesticides, generally carried out by GC and HPLC coupled with different detectors, especially MS for the identification and quantification of residues, is summarized and discussed.

Evaluation of laboratory assays for the assessment of leaching of copper and chromium from ground-contact wood

Laboratory studies were conducted to assess the leaching of Cu and Cr from wood, treated with a Cu-Cr-B preservative, when placed in contact with soil. Two laboratory assays were performed: Wood in contact with soil solutions over 30 d, and wood in direct contact with soil over 30 weeks. The influence of several factors, such as soil type and fertilizer use, was studied in both assays. In addition, the effect of soil moisture content and temperature was evaluated when wood was in contact with soil. A discrepancy in the results of the laboratory assays was observed. Leaching of Cu and Cr increased when soil in contact with wood was fertilized, but only an increase of Cu leaching was observed when soil solutions from fertilized soils were used. Moreover, soil solutions from a sandy clay loam soil produced a higher Cu leaching than those from a loamy sand soil, whereas the contrary occurred when treated wood was in direct contact with these soils. In the assay of treated wood in ground contact, the highest metal losses were produced in fertilized soils maintained at constant temperature and high soil moisture content, the latter being the most important factor. These losses were in the range of 5.34 to 15.6% for Cu and 1.85 to 2.35% for Cr in the soils studied. The proposed laboratory assay, using treated wood in direct contact with soil at a moisture content near field capacity during a period of 30 weeks, produced total metal losses that were in accordance with those reported by other authors under field conditions, expressed on a per-year basis.

Determination of organochlorine pesticides in sewage sludge by matrix solid-phase dispersion and gas chromatography-mass spectrometry

A method based on matrix solid-phase dispersion (MSPD) has been developed for the determination of 16 organochlorine pesticides (OCs) in sludge from municipal sewage plants. Samples of lyophilized sludge were blended with alumina, placed in small columns and OCs extracted with dichloromethane assisted by sonication. Purification of the extracts was accomplished by solid-phase extraction on C(18) columns and OCs were eluted with acetonitrile. Analyses were performed by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM) using deuterated OCs as internal standards. The limits of detection were between 0.03 ng/g for 4,4'-DDE and 0.7 ng/g for endrin aldehyde. Levels of OCs were determined in sewage sludge collected from 19 water treatment plants located in the province of Madrid (Spain). In all of the analyzed samples, aldrin was the compound most often found with a mean concentration of 76 ng/g. Endosulfan-I, alpha-BHC, 4,4'-DDE and 4,4'-DDT were also present at high concentrations, with average values ranging from 32.3 to 74.3 ng/g. OCs were detected in all of the samples, with a total concentration ranging from 52 to 528 ng/g dry weight.

Molecularly imprinted polymeric fibers for solid-phase microextraction

Solid-phase microextraction (SPME) is widely used in analytical laboratories for the analysis of organic compounds, thanks to its simplicity and versatility. However, the current commercially available fibers are based on nonselective sorbents, making difficult in some cases the final determination of target compounds by chromatographic techniques. Molecularly imprinted polymers (MIPs) are stable polymers with selective molecular recognition abilities, provided by the template used during their synthesis. In the present work, a simple polymerization strategy allowing the obtainment of molecularly imprinted polymeric fibers to be used in SPME is proposed. Such a strategy is based on the direct synthesis of molecularly imprinted polymeric fibers (monoliths) using silica capillaries as molds, with silica being etched away after polymerization. The system propazine:methacrylic acid was used as a model for the preparation of molecularly imprinted fibers, and its ability to selectively rebind triazines was evaluated. Variables affecting polymer morphology (i.e., polymerization time, fiber thickness) and binding-elution of target analytes (i.e., solvents, time, temperature) were studied in detail. The imprinted fiber showing the best performance in terms of selectivity and affinity for triazines was successfully applied to the extraction of target analytes from environmental and food samples.

Determination of nonylphenol and nonylphenol ethoxylates in environmental solid samples by ultrasonic-assisted extraction and high performance liquid chromatography-fluorescence detection

A simple and rapid analytical method for the determination of nonylphenol (NP) and nonylphenol ethoxylates (NPEOx) in solid environmental samples has been developed. This method combines an ultrasonic-assisted extraction procedure in small columns and an enrichment step onto C(18) solid-phase extraction cartridges prior to separation using HPLC with fluorescence detection. Method optimization was carried out using soil samples fortified at different concentration levels (from 0.1 to 100 microg/g). Under optimum conditions, 2g of soil was placed in small glass columns and extraction was performed assisted by sonication (SAESC) at 45 degrees C in two consecutive steps of 15 min using a mixture of H(2)O/MeOH (30/70). The obtained extracts were collected, loaded onto 500 mg C(18) cartridges, and analytes were eluted with 3 x 1 ml of methanol and 1 ml of acetonitrile. Finally, sample extracts were evaporated under a nitrogen stream, redissolved in 500 microl H(2)O/AcN (50/50), and passed though a 0.45 microm nylon filter before final determination by HPLC-FL. The developed procedure allowed to achieve quantitative recoveries for NP and NPEOx, and was properly validated. Finally, the method was applied to the determination of these compounds in soils and other environmental solid samples such as sediments, compost and sludge.

Analysis of 27 polycyclic aromatic hydrocarbons by matrix solid-phase dispersion and isotope dilution gas chromatography-mass spectrometry in sewage sludge from the Spanish area of Madrid

A method for the determination of 27 polycyclic aromatic hydrocarbons (PAHs) in sludge from wastewater treatment plants (WWTPs) located in urban, industrial or rural zones is presented. PAHs were extracted by matrix solid-phase dispersion (MSPD) assisted by sonication. Purification of extracts was carried out by solid-phase extraction with C(18) and PAHs were eluted with acetonitrile. PAHs were determined by isotope dilution gas chromatography with electron impact mass spectrometric detection in the selected ion-monitoring mode (GC-MS-SIM), using deuterated PAHs as internal standards. The limits of detection ranged from 0.03 ng/g for acenaphthylene to 0.45 ng/g for benzo[b]naphtho[2,1-d]thyophene. After optimization, the method was validated with a certified reference sludge. The proposed analytical method was applied to determine PAH levels in sewage sludge samples collected from 19 water treatment plants located in the province of Madrid (Spain). In most of the examined samples, phenanthrene was the main compound with a mean concentration of 1062 ng/g. PAHs were detected in all of the samples, with total concentrations between 390 and 6390 ng/g dry weight for the 27 PAHs analyzed and from 310 to 5120 ng/g dry weight for the sum of the 10 PAHs considered in the draft European Union directive.

Leaching of copper, chromium, and boron from treated timber during aboveground exposure

Field studies were conducted to evaluate leaching of Cu, Cr, and B from timber treated with a Cr, Cu, and B wood preservative and exposed aboveground in Spanish weathering conditions during one year with a total rainfall of approximately 500 mm. The effect of timber orientation (horizontal for decks and vertical for fences) on metal leaching was assessed. Leaching of metals after one year was higher for decks than for fences, with total amounts of metals leached being 226.6 and 87.8 mg/m2 for Cu, 199.5 and 42.4 mg/m2 for Cr, and 110.1 and 32.6 mg/m2 for B from decks and fences, respectively. Leaching rates did not drop constantly with time, because an increase in metal leaching, except for B, was observed at the end of the year after a long dry period. The order of metal emission varied with cumulative rainfall: Leaching of B was higher than Cr initially, but the opposite occurred at the end of the assay. Total emissions of Cu and Cr obtained in a laboratory assay were lower than those for decks and fences under field conditions when expressed per unit surface area (mg/m2), but they were similar to the values obtained for fences when expressed as a percentage of the initial amount. However, the percentage of B leached from wood was higher in laboratory than in field assays for both orientations, with the amount of B leached per unit surface area under laboratory conditions being higher than that leached from fences but lower than that leached from decks. Emission rates extrapolated to one year from laboratory data underestimated metal leaching from decks and overestimated emissions from fences.

Rapid method for the determination of polycyclic aromatic hydrocarbons in agricultural soils by sonication-assisted extraction in small columns

A rapid method has been developed for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in soil based on their sonication-assisted extraction in small columns (SAESC) with a low volume of ethyl acetate and subsequent quantitation and identification by GC with electron impact mass spectrometric detection in the SIM mode (GC-MS-SIM). Spiked blank soil extracts were used as standards to counteract the matrix effect observed in the chromatographic determination. PAHs were confirmed at trace level by their retention times, their qualifier and target ions, and their qualifier/target abundance ratios. Recovery studies were performed at 0.5, 1.0, 5.0, and 10 microg/kg fortification levels for each PAH, and the recoveries obtained ranged from 91.2 to 99.8% with RSDs between 0.4 and 9.3%. The detection limits of the method ranged from 0.03 to 0.3 microg/kg for the different PAHs studied. The developed method is linear over the range assayed, 1-100 microg/L with determination coefficients higher than 0.996. PAH levels were determined using this method in soil samples taken from different agricultural areas of Spain. In general, PAH concentrations were low and the most frequently occurring PAHs were naphthalene, pyrene, phenanthrene, and fluoranthene.

Determination of pesticide residues by GC-MS using analyte protectants to counteract the matrix effect

An analytical method was developed to determine pesticides of various chemical classes in soil, juice and honey using analyte protectants to counteract the enhancement of the chromatographic response produced by the presence of matrix components (matrix effect). This effect was more pronounced for soil and honey samples than for juice samples; regarding the pesticide chemical class, organochlorine pesticides were less affected by the presence of matrix components than triazines and organophosphorus pesticides. Several analyte protectants (2,3-butanediol, L-gulonic acid gamma-lactone, corn oil and olive oil) were tested for counteracting the observed matrix effect. L-Gulonic acid gamma-lactone was an effective protecting agent for most of the pesticides studied in soil and honey samples, whereas olive oil was very effective for juice samples. The combination of these two protectants was found to be an effective analyte protectant for all compounds in soil and honey samples.

HPLC imprinted-stationary phase prepared by precipitation polymerisation for the determination of thiabendazole in fruit

A molecularly imprinted polymer (MIP) tailored for the HPLC determination of the fungicide thiabendazole (TBZ) has been synthesised in one single preparative step by precipitation polymerisation in an acetonitrile/toluene co-solvent, using TBZ as template molecule, methacrylic acid as functional monomer and divinylbenzene-80 as crosslinker. The imprinted polymer particulates obtained were characterised by scanning electron microscopy and nitrogen sorption porosimetry. These analyses showed clearly that spherical polymer particulates (polymer microspheres) with narrow size distributions (average particle diameter approximately 3.5 microm) and well-developed pore structures had been produced. The imprinted microspheres were packed into a stainless steel HPLC column (50 x 4.6 mm id) and evaluated as an imprinted stationary phase. The imprinting effect was demonstrated clearly, i.e., the column was observed to bind TBZ selectively, and the effect of different chromatographic parameters (e.g., temperature, flow-rate and elution solvents) on TBZ retention/elution studied. Under optimised conditions, the TBZ-imprinted column was used for the HPLC-fluorescence (HPLC-F) determination of TBZ directly from orange (both whole fruit and juice), lemon, grape and strawberry extracts at low concentration levels in less than 15 min, without any need for a clean-up step in the analytical protocol.

Analysis of pesticides in honey by solid-phase extraction and gas chromatography-mass spectrometry

An analytical method for the simultaneous determination of 51 pesticides in commercial honeys was developed. Honey (10 g) was dissolved in water/methanol (70:30; 10 mL) and transferred to a C(18) column (1 g) preconditioned with acetonitrile and water. Pesticides were subsequently eluted with a hexane/ethyl acetate mixture (50:50) and determined by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC-MS-SIM). Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. Pesticides were confirmed by their retention times, their qualifier and target ions, and their qualifier/target abundance ratios. Recovery studies were performed at 0.1, 0.05, and 0.025 microg/g fortification levels for each pesticide, and the recoveries obtained were >86% with relative standard deviations of <10%. Good resolution of the pesticide mixture was achieved in approximately 41 min. The detection limits of the method ranged from 0.1 to 6.1 microg/kg for the different pesticides studied. The developed method is linear over the range assayed, 25-200 microg/L, with determination coefficients of >0.996. The proposed method was applied to the analysis of pesticides in honey samples, and low levels of a few pesticides (dichlofluanid, ethalfluralin, and triallate) were detected in some samples.

Determination of herbicide residues in juice by matrix solid-phase dispersion and gas chromatography–mass spectrometry

A rapid multiresidue method was developed for the determination of 15 herbicides in carrot, grape, and multivegetable juices. The analytical procedure was based on the matrix solid-phase dispersion of juice samples on Florisil, placed in glass columns, and subsequent extraction with ethyl acetate with assisted sonication. The recoveries through the method ranged from 82 to 115% with relative standard deviations equal or lower than 10% for all the herbicides studied. The analysis of samples was accomplished using gas chromatography-mass spectrometry with selected ion monitoring. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The detection limits ranged from 0.1 to 1.6 microg/l. The developed method was applied to the analysis of herbicide residues in commercial juice samples.

Determination of thiabendazole in orange juice and rind by liquid chromatography with fluorescence detection and confirmation by gas chromatography/mass spectrometry after extraction by matrix solid-phase dispersion

A method was developed for the determination of thiabendazole (TBZ) in orange juice and rind based on matrix solid-phase dispersion (MSPD). TBZ was extracted with ethyl acetate and the extract was subsequently cleaned up on a solid-phase extraction column. Fungicide residues were determined by liquid chromatography with fluorescence detection. Recoveries through the method ranged from 87 to 97% with relative standard deviations < or = 11%. The detection and quantitation limits were 0.15 and 0.50 microg/kg, respectively. The confirmation of TBZ residues in positive samples was performed by solid-phase microextraction followed by gas chromatography with mass spectrometric detection using selected ion monitoring. The developed method was applied to determine TBZ levels in commercial orange juices and in juice and rind of fresh oranges. The influence of storage and washing of fruits on TBZ residues was also studied.

Multiresidue determination of pesticides in soil by gas chromatography-mass spectrometry detection

An analytical multiresidue method for the simultaneous determination of various classes of pesticides in soil was developed. Pesticides were extracted from soil with ethyl acetate. Soil samples were placed in small columns, and the extraction was carried out assisted by sonication. Pesticides were determined by gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. Pesticides were confirmed by their retention times, their qualifier and target ions, and their qualifier/target abundance ratios. Recovery studies were performed at 0.2, 0.1, and 0.05 microg/g fortification levels of each pesticide, and the recoveries obtained ranged from 87.0 to 106.2% with a relative standard deviation between 2.4 and 10.6%. Good resolution of the pesticide mixture was achieved in approximately 41 min. The detection limits of the method ranged from 0.02 to 1.6 microg/kg for the different pesticides studied. The developed method is linear over the range assayed, 25-1000 microg/L, with determination coefficients >0.999. The proposed method was used to determine pesticide levels in real soil samples, taken from different agricultural areas of Spain, where several herbicides and insecticides were found.

Determination of organophosphorus pesticides in fruit juices by matrix solid-phase dispersion and gas chromatography

A rapid multiresidue method was developed for the determination of nine organophosphorus pesticides in fruit juices. The analytical procedure is based on the matrix solid-phase dispersion (MSPD) of juice samples on Florisil in small glass columns and subsequent extraction with ethyl acetate assisted by sonication. Residue levels were determined by gas chromatography with nitrogen-phosphorus detection. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The NPD response for all pesticides was linear in the concentration range studied with determination coefficients >0.999. Average recoveries obtained for all of the pesticides in the different juices and fortification levels were >70% with relative standard deviations of <11%. The detection limits ranged from 0.1 to 0.6 microg/kg. The identity of the pesticides was confirmed by gas chromatography with mass spectrometric detection using selected ion monitoring. The proposed MSPD method was applied to determine pesticide residue levels in fruit juices sold in Spanish supermarkets. At least one pesticide was found in most of the samples, although the levels detected were very low, far from the maximum residue levels established for raw fruit.

Multiresidue analysis of carbamate pesticides in soil by sonication-assisted extraction in small columns and liquid chromatography

A rapid multiresidue method has been developed for the analysis of carbamate insecticides (oxamyl, methomyl, propoxur, carbofuran, carbaryl and methiocarb) in soil. The method is based on the sonication-assisted extraction of soil samples placed in small columns using a low volume of methanol. Residue levels in soil were determined by reversed-phase high-performance liquid chromatography with fluorescence detection after post-column derivatisation. The separation of carbamates is performed on a C8 column with water-methanol as mobile phase. Recovery studies were carried out at 0.5, 0.1 and 0.01 microg/g fortification levels and average recoveries obtained for carbamates ranged from 82 to 99% with relative standard deviations between 0.4 and 10%. The effect of residue residence time and soil moisture content on the insecticide recovery was also studied. The method is linear over the range assayed, from 0.1 to 1 microg/ml. The detection limit for the carbamates varied from 1.6 to 3.7 microg/kg and the quantification limit obtained was 10 microg/kg. The emission and excitation allowed the confirmation of residues at levels around 0.1 microg/g.

Determination of endosulfan isomers and endosulfan sulfate in tomato juice by matrix solid-phase dispersion and gas chromatography

A rapid method based on matrix solid-phase dispersion was developed for the determination of endosulfan isomers and endosulfan sulfate in commercial tomato juice. After the optimisation of different parameters such as the type of adsorbent, the extraction solvent, and the extraction assistance by sonication, the recoveries obtained ranged from 81 to 100% with relative standard deviations equal to or lower than 10%. The analysis of samples was accomplished using gas chromatography with electron-capture detection and the identity of endosulfan residues was confirmed by gas chromatography-mass spectrometry with selected ion monitoring. The detection limit for these compounds, calculated as three times the background noise, was 1 microg/kg. The proposed method was applied to the analysis of these compounds in commercial juice samples and levels of endosulfan between 1 and 5 microg/kg were detected in some samples.

Determination of polycyclic aromatic hydrocarbons in honey by matrix solid-phase dispersion and gas chromatography/mass spectrometry

A multiresidue method was developed for the de termination of 16 polycyclic aromatic hydrocarbons (PAHs) in unifloral and multifloral honeys. The analytical procedure is based on the matrix solid-phase dispersion of honey on a mixture of Florisil and anhydrous sodium sulfate in small glass columns and extraction with hexane-ethyl acetate (90 + 10, v/v) with assisted sonication. The PAH residues are determined by gas chromatography with mass spectrometric detection using selected-ion monitoring. Average recoveries for all the PAHs studied were in the range of almost 80 to 101%, with relative standard deviations of 6 to 15%. The limits of detection ranged from 0.04 to 2.9 microg/kg. The simultaneous extraction and cleanup of samples makes this method simple and rapid, with low consumption of organic solvents

Influence of organic fertilizer application on pendimethalin volatilization and persistence in soil

Laboratory studies were undertaken to evaluate the influence of fertilizers on pendimethalin volatilization and persistence in soil. Various organic fertilizers such as liquid humic substances and urea were used at doses of 100 L/ha or 170 kg of N/ha, respectively. Herbicide residues were determined in air, soil solution, and soil samples by GC-ECD; the recovery of pendimethalin from spiked fertilized or control samples was found to be 81-103%. Liquid humic fertilizers increased pendimethalin dissipation during the first part of the assay, although 4 months after application, herbicide levels were similar to those observed in unfertilized soil. Fertilization of soil with urea decreased, in general, pendimethalin volatilization but increased herbicide levels in soil solution and persistence in soil, with a pendimethalin half-life approximately 70% higher than that found in unfertilized soil.

Multiresidue analysis of fungicides in soil by sonication-assisted extraction in small columns and gas chromatography

A rapid multiresidue method for the simultaneous determination of 14 fungicides in soil was developed. Fungicides were exacted from soil, placed in small columns, by sonication-assisted extraction with ethyl acetate. The effect of residue residence time and soil moisture content on the fungicide recovery was studied. Residue levels in soil were determined by gas chromatography with electron-capture and nitrogen-phosphorus detection. Residue identities were confirmed by gas chromatography coupled with mass spectrometry, in the selected ion monitoring mode. Recovery studies were carried out at 0.5, 0.1 and 0.05 microg/g fortification levels for each fungicide, and average recoveries obtained for these compounds ranged from 80 to 104% with relative standard deviations between 1 and 8%. The method is linear over the range assayed, 0.5-0.05 microg/g, and the detection limit for the fungicides studied varied from 2 to 10 microg/kg.

Analysis of volatiles from Spanish honeys by solid-phase microextraction and gas chromatography-mass spectrometry

Headspace solid-phase microextraction (SPME), followed by gas chromatography (GC)-mass spectrometry (MS) determination, has been used for the analysis of honey volatiles. Two SPME fibers were employed to study the composition of volatiles from various types of Spanish honeys. The best results were obtained with the Carboxen/PDMS fiber, using a homogenization time of 1 h at 70 degrees C and a sampling period of 30 min. A total of 35 compounds were detected, most of them identified by GC-MS and quantified using external standards. Differences in the composition of honey volatiles were obtained, and these results allowed the differentiation of honeys. However, further studies are necessary to confirm the utility of this technique as an alternative tool for the characterization of the floral origin of honeys.

Analysis of endosulfan isomers and endosulfan sulfate in air and tomato leaves by gas chromatography with electron-capture detection and confirmation by gas chromatography-mass spectrometry

Rapid analytical methods for the determination of endosulfan isomers and endosulfan-sulfate in air and plant samples were developed. The insecticides were trapped from air using a column containing Florisil and extracted with a low volume of ethyl acetate, assisted by sonication. Pesticide residues were determined by gas chromatography with electron-capture detection using a nonpolar capillary column. Residue identities were confirmed by gas chromatography coupled with mass spectrometry. Recoveries of these compounds from air samples were always higher than 78% with an RSD lower than 11% and the detection limits obtained were at least 0.3 ng/l air. Leaf samples were homogenised with ethyl acetate and extracts cleaned-up on an aluminium oxide column. Pesticides were eluted with a hexane-ethyl acetate (80:20, v/v) mixture. Recoveries obtained from plant samples were higher than 78% with an RSD lower than 14% and detection limits in leaves were 0.02 microg/g for each pesticide. These methods were applied to study the volatilisation of endosulfan from tomato leaves under laboratory conditions. A volatilisation rate near 1% of the initial amount of endosulfan per hour was obtained during the first 24 h at room temperature.