Determination of Emerging Contaminants in Cereals by Gas Chromatography-Tandem Mass Spectrometry.

Cereals are staple foods for human consumption in both developed and developing countries. In order to improve agricultural outputs, resources like reclaimed water for irrigation and biosolids and manure as fertilizers are frequently used, although they may increase the input of contaminants that can potentially be absorbed by crops and enter the food chain. Emerging contaminants (human and veterinary pharmaceuticals, personal care products, surfactants, plasticizers, and industrial additives, among others) are continuously introduced in the environment from a variety sources and these contaminants may enter the food chain through plant uptake. In this study, an analytical method, based on ultrasound-assisted extraction and dispersive solid-phase cleanup, was developed for the determination of emerging contaminants from different classes in four highly consumed cereal grains (wheat, oat, barley, and rice). These analytes were selected considering the results of our previous studies carried out in soil and vegetables and those frequently detected in real samples were chosen. The target compounds selected were bisphenol A (BPA), bisphenol F (BPF), methyl paraben, propyl paraben, linear chain nonylphenol in position 4 (4-n-NP), mixture of ring and chain isomers of NP and six pharmaceutical compounds (allopurinol, mefenamic acid, carbamazepine, paracetamol, diclofenac and ibuprofen). Recoveries ranging from 68 to 119% with relative standard deviations (RSD) <18% were obtained for all the compounds except for allopurinol, with recoveries that ranged from 30 to 66% with RSD ≤ 12% and the limits of detection achieved ranged from 0.03 to 4.9 ng/g. The method was applied to the analysis of 16 cereal samples, ten were purchased in local supermarkets and the rest were collected directly from agricultural fields, five of which were fertilized with organic amendments. Bisphenol A (BPA) was detected in all samples at levels that ranged from 1.6 to 1,742 ng/g. Bisphenol F, a substitute for BPA, was also found in six samples (up to 22 ng/g). Linear 4-n-NP was found in a reduced number of samples but the mixture of NP isomers was found in all the samples, being the mean concentrations in wheat, barley, oat and rice 49, 90, 142, and 184 ng/g, respectively.

Assessing the benefits of composting poultry manure in reducing antimicrobial residues, pathogenic bacteria, and antimicrobial resistance genes: a field-scale study.

The poultry industry in the European Union produces 13 million tons of manure annually, which represents a major health and environmental challenge. Composting is an environmental-friendly technique for the management of manure, but there are few studies about antibiotic residues and antimicrobial resistances at a field scale. The goal of this study was to determine if the composting of poultry manure at a field scale would result in the reduction of antibiotic residues, pathogenic bacteria, and antibiotic resistance genes (ARGs) in the final fertilizer product. A 10-week composting of poultry manure spiked with enrofloxacin, doxycycline, and ciprofloxacin was performed. The determination of antibiotics residues and 22 selected ARGs was carried out together with the identification of bacteria by metagenomics. In the case of ciprofloxacin and doxycycline, a 90% decrease was observed after composting for 3 weeks. Sixteen ARGs were detected at the beginning of the experiment; 12 of them decreased from week 0 to week 10 (reduction of 73.7-99.99%). The presence of potentially pathogenic bacteria, such as, Campylobacter coli or commensal bacteria such as Escherichia coli decreases along the composting process. In conclusion, 10-week composting of poultry manure promotes the reduction of antibiotic residues and most of the ARGs and pathogenic bacteria.

Rapid determination of antibiotic residues in cereals by liquid chromatography triple mass spectrometry.

Antibiotics may be present in agricultural soils through the application of organic amendments as fertilizers or by irrigation of fields with recycled water. As a result of these agricultural practices, antibiotics in soil can lead to their uptake by plants, entering in this way the food chain. Studies on the levels of antibiotics in cereal samples are scarce in the available literature. In this work, an analytical method was developed for the determination of 19 antibiotics (fluoroquinolones, sulfonamides, tetracyclines, and lincosamides) in four types of cereal grains (wheat, barley, rice, and oat). Ultrasound-assisted matrix solid-phase dispersion was selected as extraction technique with recoveries of target analytes ranging from 73 to 127% for the four cereals analyzed. Limits of quantification obtained ranged from 0.8 to 5.8 ng g-1. Compared with methods described for the analysis of antibiotics in cereals, the developed method uses a lower volume of extraction solvent and very good recoveries were obtained for all compounds. The validated method was applied to the analysis of different types of cereals samples, harvested from agricultural fields or purchased from local supermarkets. The analysis of the five cereal samples grown in fields with 3 years of consecutive organic amendments revealed that none of the nineteen antibiotics selected were found in any sample. Eleven commercial samples of cereals of different types and presentations were analyzed and enrofloxacin was detected in one rice sample; the presence of enrofloxacin in cereals or its incorporation into crops from soil or water not previously reported. Graphical abstract.

Molecularly imprinted polymer-hollow fiber microextraction of hydrophilic fluoroquinolone antibiotics in environmental waters and urine samples.

In the present work, the preparation of a new selective molecularly imprinted polymer (MIP) for the family of fluoroquinolones (FQs) in the pores of polypropylene hollow fibers (HFs) is proposed. The resulting MIP-HFs, which combine solid-phase microextraction (SPME) and molecular imprinting technologies, were used to develop a selective microextraction methodology (MIP-HFM) to determine selected FQs danofloxacin, norfloxacin, enrofloxacin and ciprofloxacin in real samples of environmental and biological interest. Measurements during the optimization of the MIP-HFM and its application to the analyses of real samples were performed by HPLC-UV and HPLC-MS/MS. In order to establish optimum rebinding conditions, the effect of key experimental parameters such as loading media, extraction time and stirring-rate were studied. The developed MIP composites exhibited recognition properties towards the selected hydrophilic antibiotics in non-polar media (toluene) and in polar protic systems such as methanol and methanol/water solutions, up to 20% water content. Recoveries by the developed method for all FQs tested in surface water, groundwater and urine spiked with the analytes of interest at two different concentration levels were within 9.4-24.5 %, with a relative standard deviation, generally <20% (n = 3). The detection limits were within 0.1-10 µg L-1, depending upon the antibiotic and the type of sample.

Persistence and availability of veterinary antibiotics in soil and soil-manure systems.

The availability and persistence of various antibiotics in soil and soil amended with composted poultry manure were investigated through laboratory incubation assays. Six veterinary antibiotics (one fluoroquinolone, two tetracyclines, two sulfonamides and one lincosamide) and one active metabolite (ciprofloxacin) were studied. The incubation assays were conducted at a controlled temperature of 25 °C with different water regimes, such as constant moisture content (80% of water holding capacity) and drying-rewetting cycles. The studied antibiotics were determined in soil and soil aqueous phase samples by LC-MS/MS using internal standards. The results indicated that the highest levels found in the soil aqueous phase were for sulfamethoxazole, followed by sulfamethazine and lincomycin, being very low the levels of chlortetracycline, doxycycline, ciprofloxacin and enrofloxacin (≤1.8%). A positive correlation was observed between the antibiotic concentrations and the content of the dissolved organic carbon in soil aqueous phase with the incubation time. An increase in the apparent sorption coefficients of these antibiotics, except chlortetracycline and lincomycin, was observed when the soil was amended with composted manure. Except for fluoroquinolones, with remaining residues around 70% after 90 days of incubation, a fast dissipation of antibiotics was observed during the assay, with half-lives ranging from 8 to 27 days. These values increased between 6% and 53% in manure amended soil; nevertheless, half-lives remained short (9 days and 27 days for lincomycin and sulfamethazine, respectively). Similar results were obtained with soil under drying-rewetting cycles showing somewhat lower values in soil aqueous phase and slightly shorter half-lives in some cases. The results obtained pointed out that the route of entry of antibiotics into the soil, through recycled water or manure, may have an important effect on their behavior, particularly regarding their availability in soil.

Analysis of macrolide antibiotics in water by magnetic solid-phase extraction and liquid chromatography-tandem mass spectrometry.

Macrolides are one of the most commonly used families of antibiotics employed in human and veterinary treatment. These compounds are considered emerging contaminants with potential ecological and human health risks that could be present in surface water. This paper describes the development and application of a simple and efficient extraction procedure for the determination of tilmicosin; erythromycin, tylosin and erythromycin-H2O from water samples. Sample extraction was carried out using magnetic solid-phase extraction using oleate functionalized magnetic nanoparticles followed by LC-MS/MS analysis. The effects of several parameters on the extraction efficiency of MLs from water were evaluated. The recovery results obtained were >84% for most of the compounds, except for erytromycin. The LOD and LOQ values ranged from 11.5 to 26ngL-1 and from 34 to 77ngL-1, respectively. The selected method was applied to monitor these contaminants in water samples from different sources. Tilmicosin and tylosin were not detected in any of the samples, but erythromycin and erythromycin-H2O were found in 50% of the surface water samples at levels from

Rapid multiresidue determination of bisphenol analogues in soil with on-line derivatization.

Bisphenol analogues are compounds extensively used which have been potentially linked to adverse health effects. Nevertheless, few studies reported the analysis of compounds, other than bisphenol A, in environmental solid samples and none in soil samples. In this study, a rapid and sensitive analytical method is presented for the simultaneous determination of 13 bisphenols in soil samples. The method combines ultrasonic-assisted extraction of samples placed in small columns and GC-MS/MS analysis. Manual and on-line derivatizations were compared and results showed that significant higher chromatographic responses were achieved with on-line derivatization. Different parameters such as the quantity of derivatization agent, the extraction solvent, or the extraction time were assayed. The detection limits for all target bisphenols ranged from 0.04 to 0.27 ng g-1, for BPC and BPA, respectively. Analysis of spiked soil samples gave satisfactory recovery results, from 70 to 111%, for all the compounds. Finally, the validated method was applied to soil samples from several Spanish areas, and 3 of the 13 target bisphenols (BPAF, BPF, and BPA) were detected, although only BPF and BPA could be quantified with levels up to 127 ng g-1. Graphical abstract Schematic diagram of the developed method for the determination of bisphenol analogues.

Determination of endocrine-disrupting compounds in water samples by magnetic nanoparticle-assisted dispersive liquid-liquid microextraction combined with gas chromatography-tandem mass spectrometry.

A rapid extraction procedure is presented for the determination of five endocrine-disrupting compounds, estrone, ethinylestradiol, bisphenol A, triclosan, and 2-ethylhexylsalicylate, in water samples. The analysis involves a two-step extraction procedure that combines dispersive liquid-liquid microextraction (DLLME) with dispersive micro-solid phase extraction (D-µ-SPE), using magnetic nanoparticles, followed by in situ derivatization in the injection port of a gas chromatograph coupled to triple quadrupole mass spectrometry. The use of uncoated or oleate-coated Fe3O4 nanoparticles as sorbent in the extraction process was evaluated and compared. The main parameters involved in the extraction process were optimized applying experimental designs. Uncoated Fe3O4 nanoparticles were selected in order to simplify and make more cost-effective the procedure. DLLME was carried out at pH 3, during 2 min, followed by the addition of the nanoparticles for D-µ-SPE employing 1 min in the extraction. Analysis of spiked water samples of different sources gave satisfactory recovery results for all the compounds with detection limits ranging from 7 to 180 ng l-1. Finally, the procedure was applied in tap, well, and river water. Graphical abstract Diagram of the extraction method using magnetic nanoparticles (MNPs).

Application of magnetic iron oxide nanoparticles for the analysis of PCBs in water and soil leachates by gas chromatography-tandem mass spectrometry.

Two magnetic solid-phase extraction methods (mSPE) were developed and compared for the extraction and preconcentration of polychlorinated biphenyls (PCBs) from water and soil leachates. Analyses were carried out by gas chromatography coupled to triple quadrupole mass spectrometry. The mSPE extraction parameters were optimised using Fe3O4 nanoparticles coated with palmitate or oleate. Differences were found between the developed mSPE methods depending on the magnetic nanoparticle coating. The extraction efficiency of both sorbents was studied by spiking soil leachates at three concentration levels (from 0.6 to 0.18 ng ml(-1) and from 0.4 to 0.04 ng ml(-1) using palmitate or oleate coated nanoparticles, respectively) and recoveries from 86 to 109 % were obtained. The developed method provided a preconcentration factor of 250. The detection limits were about 29 times lower with the oleate-coated nanoparticles. Although both mSPE procedures could be used for the extraction of PCBs from water and soil leachates, oleate-coated nanoparticles gave the best extractive conditions and lower quantifications limits. Finally, the mSPE using oleate-coated nanoparticles was applied to the analysis of PCBs in river waters and in soil leachates obtained from soil with different physico-chemical characteristics. The levels of PCBs present in the leachates depended on the soil sample. The present work demonstrates the applicability of both mSPE methods to the determination of PCBs in water and soil leachates, which is of interest for mobility and bioavailability studies of these compounds in soil.

A rapid procedure for the determination of C60 and C70 fullerenes in soil and sediments by ultrasound-assisted extraction and HPLC-UV.

In this work, a rapid and sensitive method, based on ultrasound-assisted extraction of samples with a small volume of toluene, has been developed for the quantification of C60 and C70 fullerenes in soil and sediments. Good extraction efficiencies were obtained at all of the fortification levels studied (200, 100, 20 and 2 ng/g), which ranged from 72 to 104%. An important effect of the extraction temperature was observed on C60 recoveries, and an acceptable decrease in the recovery rates was observed in aged samples. In the case of wet samples, the extraction can be done by percolating a small volume of acetonitrile before extraction. The extraction yields of the developed method for the extraction of C60 and C70 from soil were compared with those obtained by pressurized liquid extraction. Finally, analyses of fullerenes in agricultural and industrial soils and sediments were carried out, but no fullerene residues were found.

Gas chromatography-triple-quadrupole mass spectrometry for analysis of selected polyhalogenated pollutants in plants. Comparison of extraction methods.

Different extraction methods, followed by gas chromatography coupled to triple quadrupole mass spectrometry, were evaluated for simultaneous extraction of seven polychlorinated biphenyls (PCBs) and six polybrominated diphenyl ethers (PBDEs) from common weeds. Pressurized liquid extraction (PLE) with in-cell clean-up, ultrasound-assisted extraction (UAE) with in-column clean-up, and UAE with dispersive solid-phase extraction (dSPE) clean-up were evaluated and compared. In-cell clean-up with 4 g Florisil and 0.5 g graphitized carbon black (GCB) and two extraction cycles of 10 min with n-hexane-ethyl acetate 80:20 (v/v) at 60 °C were used for the PLE procedure. UAE with in-column clean-up was conducted under conditions similar to those reported for the PLE method whereas in UAE with dSPE clean-up purification of the extract was performed after extraction using primary and secondary amine sorbent (PSA) and GCB. Recovery from 82 to 104% was obtained for all the compounds by PLE whereas, in general, lower extraction efficiency was obtained by UAE with in-column clean-up (especially for BDE-17 and BDE-183, for which recovery was 70 and 41%, respectively) and by UAE with dSPE clean-up, for which the main drawback is that BDE-183 cannot be extracted. Finally, PLE was used for analysis of PCBs and PBDEs in different plants (Lolium rigidum, Lactuca serriola, Malva sylvestris, and Verbascum thapsus) collected from residential and/or rural areas of Madrid (Spain). Several of the analyzed compounds were detected at low levels in these plants, but only PCB-153 could be quantified.

Occurrence and analysis of parabens in municipal sewage sludge from wastewater treatment plants in Madrid (Spain).

A rapid method for determination of seven parabens and two chlorinated by-products in sewage sludge was developed based on matrix solid-phase dispersion and gas chromatography-tandem mass spectrometry. The analytical procedure showed good recoveries that ranged from 80 to 125%, with relative standard deviations lower than 12% and low detection limits, ranging from 0.1 to 2.0 ng g(-1) dry weight. The developed method was applied to the analysis of sewage sludge collected during 2010 in 19 wastewater treatment plants (WWTPs) located in various urban, industrial or rural zones in Madrid (Spain). Methylparaben was found in most of the WWTPs sampled (95%) at levels between 5.1 and 26.2 ng g(-1) dry weight and propylparaben was detected in 74% of the WWTPs at levels up to 44.1 ng g(-1) dry weight. In order to study the temporal variation of parabens and two chlorinated parabens during a four-year period, sludge samples were collected from 3 selected WWTPs. The levels of methylparaben encountered were rather constant throughout the sampling period whereas propylparaben levels slightly increased. In one of the WWTPs monitored, isopropylparaben was found at the beginning of the sampling period but its content decreased and was not detected in the 2010 sampling.

Determination of hexabromocyclododecane isomers in sewage sludge by LC-MS/MS.

A method has been developed to determine alpha, beta and gamma diastereoisomers of hexabromocyclododecane (HBCD), a brominated flame retardant, in sewage sludge, based on the ultrasonic-assisted extraction (UAE) of samples with dichloromethane-ACN (1:1) and the subsequent clean-up of extracts by dispersive solid phase extraction with primary-secondary amine. Levels of HBCD diastereoisomers were determined by LC coupled with ESI MS/MS. Evaluation of the matrix effect showed a high ion suppression for all the diastereoisomers studied, which was counteracted by using a mixture of labelled HBCD diastereoisomers as internal standards. This method yielded recoveries in the range of 79.6-112.5% with SDs equal or lower than 9.1 The limits of detection were 0.3 ng/g for alpha- and beta-HBCD and 0.2 ng/g for gamma-HBCD. The developed method was successfully applied to 19 sludge samples collected from the province of Madrid (Spain). In most of the samples, beta-HBCD was below the method detection limit, whereas alpha- and gamma-HBCD were quantified in all of the sludge samples, and gamma-HBCD was the predominant diastereoisomer in 63% of the analyzed samples and alpha-HBCD predominated in the rest.

A combination of ultrasonic assisted extraction with LC-MS/MS for the determination of organophosphorus pesticides in sludge.

A method has been developed for the analysis of a wide polarity range of the currently used organophosphorus pesticides (OPs) and their metabolites in sewage sludge samples. Extraction was carried out using ultrasonic assisted extraction (UAE) with different solvents. The levels of OPs in sludge were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using electrospray ionization (ESI) in positive or negative ion mode. Extraction with acetonitrile containing 1% acetic acid gave the best results with recoveries between 83.2% and 106.4% and RSD < or = 8.7%. Evaluation of matrix effect showed high ion suppression for OPs of intermediate polarity, which decreased to approximately 50% by matrix dilution to an equivalent of 0.5 g of sludge per millilitre; however, for polar OPs, the matrix effect was negligible at the same concentration. Therefore, matrix-matched standards were used for OPs quantification. The limits of quantification were in the range of 1-14 ng g(-1). This method was successfully applied to real sludge samples collected from Madrid Province and chlorpyrifos along with its metabolite TCPY were the OPs found in sludge at the highest levels, 113-344 ng g(-1) and 33-307 ng g(-1), respectively.

Molecular imprinting-based separation methods for selective analysis of fluoroquinolones in soils.

Molecularly imprinted polymers (MIPs) for fluoroquinolone antibiotics (FQs) have been synthesised in one single preparative step by precipitation polymerisation using ciprofloxacin (CIP) as template. Combinations of methacrylic acid (MAA) or 4-vinylpyridine (VP) as functional monomers, ethylene glycol dimethacrylate as crosslinker and dichloromethane, methanol, acetonitrile or toluene as porogens were tested. The experiments carried out by molecularly imprinted solid-phase extraction (MISPE) in cartridges did not allow to detect any imprint effect in the VP-based polymers whereas it was clearly observed in the MAA-based polymers. Among them, the MIP prepared in methanol using MAA as monomer showed the best performance and was chosen for further experiments. The ability of the selected MIP for the selective recognition of other widely used FQs (enoxacin, norfloxacin, danofloxacin and enrofloxacin) and quinolones (Qs) (cinoxacin, flumequine, nalidixic acid and oxolinic acid) was evaluated. The obtained results revealed the high selectivity of the obtained polymer, which was able to distinguish between FQs, that were recognised and retained onto the MIP cartridge, and Qs, which were washed out during loading and washing steps. The MIP was then packed into a stainless steel column (50mmx4.6mm i.d.) and evaluated as chromatography column for screening of FQs in soil samples. The mobile phase composition, flow rate, and the elution profile were then optimised in order to improve peak shape without sacrifying imprinting factor. Finally, under optimised conditions, soil samples spiked with CIP or with a mixture of fluoroquinolones in concentration of 0.5microgg(-1) were successfully analysed by the developed MIP-based procedures.

Selective molecularly imprinted polymer obtained from a combinatorial library for the extraction of bisphenol A.

In the present work, an analytical methodology based on molecularly imprinted solid-phase extraction (MISPE) has been developed for the determination of bisphenol A (BPA) in environmental and food samples. In order to select the optimum material, a combinatorial library of molecularly imprinted polymers in small-scale (mini-MIPs) was prepared using BPA as template. Different monomers (methacrylic acid or 4-vinylpyridine), crosslinkers (ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate) and porogens (methanol, acetonitrile or toluene) were used leading to 24 different polymerisation mixtures. After BPA removal, the ability of mini-MIPs to recognise BPA was evaluated by equilibrium rebinding-elution experiments. The copolymer of 4-vinylpyridine (4-VP) and trimethylolpropane trimethacrylate (TRIM) prepared in toluene showed the higher affinity for the template. Subsequently, a scaled-up version of the optimum polymer was prepared and used in the development of MISPE procedures for the extraction of BPA. The optimised MISPE protocols were successfully applied to the selective extraction of BPA from soils and aqueous canned peas samples.

High-performance liquid chromatography multiresidue method for the determination of N-methyl carbamates in fruit and vegetable juices.

A rapid multiresidue method has been developed for the analysis of N-methylcarbamate insecticides (oxamyl, methomyl, propoxur, carbofuran, carbaryl, and methiocarb) in fruit and vegetable juices. The method is based on the adsorption of the N-methyl carbamates in Florisil and the subsequent extraction of pesticides using a low volume of acetone. Residue levels in juice were determined by reversed-phase high-performance liquid chromatography with fluorescence detection after postcolumn derivatization. The separation of carbamates is performed on a C8 column with water-methanol as mobile phase. Recovery studies were performed at 500-, 100-, and 10-ng/ml fortification levels, and average recoveries obtained for carbamates ranged from 79 to 109%, with relative standard deviations between 1.4 and 9.9%. The method was found to be linear over the range assayed from 10 to 1,000 ng/ml, and the detection limits for carbamates varied from 0.8 to 1.9 ng/ml.

Influence of leaching medium and drying time between successive leaching periods on the emission of chromium, copper, and boron from treated wood.

Laboratory studies were conducted to determine leaching of Cu, Cr, and B from pine sapwood treated with Cr-Cu-B (CCB) preservative in different leaching media (ultrapure water [UPW], rainwater [RW], and soil water [SW]). Losses of metals from CCB-treated wood, expressed in percentage of initial content, were always highest for B (11.2-63.5%) and lowest for Cr (0.02-0.36%) in any of the leaching media assayed. Losses of B and Cr from treated wood were not affected by the leaching medium; however, losses of Cu were 1.5 to 2.5 times higher in SW than in UPW and RW. The influence of drying time between successive leaching periods on release of metals also was determined. Treated wood was submitted to wetting-drying cycles of 24 h/d, 18 h/d, and 6 h/d in contact with the leaching medium over a total contact time of 276 h. For an equivalent contact period of CCB-treated wood with either UPW or RW, leaching of B was from 1.1 to 1.9 times higher for continual wetting than under intermittent wetting conditions. Leaching of Cu was not affected by the wetting-drying periods when wood was in contact with RW, but it was 1.2 to 1.5 times higher for continual wetting with UPW. In general, leaching of Cr was not affected by the wetting-drying cycles when in contact with UPW or RW. However, when CCB-treated wood was in contact with SW under discontinuous wetting of 6 h/d, Cu and Cr emissions were approximately 1.2 and 2.5 times higher, respectively, than with continuous wetting. This study shows that the type of leaching medium and the drying time between successive wetting periods must be considered when evaluating metal losses from CCB-treated wood during service life.

Slow-stirring method for determining the n-octanol/water partition coefficient (Pow) for highly hydrophobic chemicals: performance evaluation in a ring test.

The n-octanol/water partition coefficient (Pow) is one of the most important parameters employed for estimating a chemical's environmental fate and toxicity. The currently adopted test guidelines for its determination do not allow for reliable determination of log Pow greater than 5. The slow-stirring experiment, in contrast, has been demonstrated to provide reliable log Pow data up to log Pow of 8.3. To validate this method and to obtain its approval as an official Organization for Economic Cooperation and Development (Paris, France) test guideline, a ring test was performed to evaluate the accuracy and precision of the slow-stirring experiment for determination of log Pow, particularly for highly hydrophobic compounds. Up to 15 volunteer laboratories tested 1,2,3,4-tetrachlorobenzene, hexachlorobenzene. 2,2',3,3',5,5',6,6'-octachlorobiphenyl, and decachlorobiphenyl (4.5 < log Pow < 8.2). The ring-test results for the respective chemicals were 4.62, 5.50, 7.39, and 8.18. The results deviated by less than 0.1 log Pow units from the reference log Pow. In addition, the relative standard deviations of log Pow were less than 2%. Using the protocol of the ring test, log Pow of p,p'-DDT was determined to be 6.24 +/- 0.05 (mean +/- standard deviation). In combination, these results indicate that the slow-stirring method is precise and accurate and, thus, allows for reliable determination of log Pow of highly hydrophobic chemicals.

Determination of insecticides in honey by matrix solid-phase dispersion and gas chromatography with nitrogen-phosphorus detection and mass spectrometric confirmation.

A multiresidue method was developed for the determination of 12 organophosphorus insecticides (diazinon, parathion methyl, fenitrothion, pirimiphosmethyl, malathion, fenthion, chlorpyrifos, quinalphos, methidathion, ethion, azinphosmethyl, coumaphos), one carbamate (pirimicarb), and one amidine (amitraz) in unifloral and multifloral honeys. The analytical procedure was based on the matrix solid-phase dispersion of honey on a mixture of Florisil and anhydrous sodium sulfate in small glass columns and subsequent extraction with a low volume of hexane-ethyl acetate (90 + 10, v/v), assisted by sonication. The insecticide residues were determined by capillary chromatography with nitrogen-phosphorus detection and confirmed by mass spectrometry. Average recoveries at the 0.05-0.5 microg/g levels were >80% for organophosphorus insecticides and about 60% for the other insecticides, pirimicarb and amitraz, with relative standard deviations <10%. The detection limit for the different insecticides ranged between 6 and 15 microg/kg. The main advantages of the proposed method are that extraction and cleanup are performed in a single step with a low volume of organic solvent. The method is simple, rapid, and less laborious than conventional methods. Several Spanish honeys were analyzed with the proposed method and no residues of the studied insecticides were found.