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PubMed2001

Refinement of risk assessment of dermally and intermittently exposed pesticide workers: a critique.

The regulatory requirements for the registration of pesticides are mainly evolved from concern about dietary exposure and risk, i.e. chronic oral exposure. Pesticide workers, however, are predominantly exposed dermally and intermittently. The present critique provides suggestions for improvement of toxicity studies to refine the risk assessment of pesticide workers. In this respect it is considered of utmost importance that toxicity studies (either toxicokinetic or toxicodynamic) should be tuned towards the anticipated exposure scenario. Apart from suggestions for improvement of dermal toxicokinetic and dynamic studies, recommendations for further research and guidance are given, amongst which the request for information on the robustness of in vitro dermal absorption studies and guidance on how to use these data. With respect to the intermittent exposure of pesticide workers it is recognised that both information on the anticipated exposure scenario as well as knowledge on the effect of intermittent exposure on the toxicity are needed. From a toxicological point of view, the setting of more than one Acceptable Operator Exposure Level (AOEL), covering effects that may arise after different periods of exposure, as well as the development of more robust acute and short term studies are strongly recommended.

Administration, Cutaneous↗
PubMed1991

Reproductive performance in population exposed to pesticides in cotton fields in India.

Data on reproductive histories were collected from 1016 couples in which the males were directly exposed to pesticides. For comparison data were collected from 1020 couples who were not exposed to pesticides and belong to the same socioeconomic group and age range. Statistical analysis revealed a significant decrease in fertile males and a significant increase in abortions among the wives of these exposed males when compared to the control group. The frequency of live births decreased significantly and still births, neonatal deaths, and congenital defects showed a significant increase in the offspring of exposed males when compared to the offspring of control group. Smokers exposed to pesticides showed a higher effect than nonsmokers exposed to pesticides. Eighty percent males in the exposed group showed ill health effects such as severe giddiness, nervous, skin, and eye disorders.

Abortion, Spontaneous↗
PubMed2000

Recent and future developments of liquid chromatography in pesticide trace analysis.

Until recently, the application of liquid chromatography (LC) in pesticide analysis was usually focused on groups of compounds or single compounds for which no suitable conditions were available for analysis with gas chromatography (GC). However, recent developments in both detection and column material technology show that LC significantly enlarged its scope in this field of analysis. Obviously, the most striking example is the rather abrupt transition of LC coupled to mass spectrometric detection (MS) from an experimental and scientifically fashionable technique to a robust, sensitive and selective detection mode rendering LC-MS being increasingly used in pesticide trace analysis. Other recent major developments originate from the innovation of new LC column packing materials, viz. immuno-affinity sorbents, restricted access medium materials and molecular imprinted polymers improving considerably the screening of polar pesticides by means of reversed-phase LC with UV detection. In this review the merits and perspectives of these important LC developments and their impact to current and future applications in pesticide trace analysis are presented and discussed.

Chromatography, Liquid↗
PubMed2000

Multi-residue methodology for pesticide screening in wines.

A multi-residue solid-phase microextraction/gas chromatography/electron-capture detection method for pesticide screening (nine organochlorine, eleven organophosphorous and a tiadiazine insecticides, a benzoylurea acaricide and a halogenated sulfamide fungicide) in wine was developed. Fiber coating, extraction time and temperature, exposure of the fiber to the headspace or to the liquid phase and the ethanol effect on pesticides extraction were the parameters studied. The best results were obtained for a 100 microm poly(dimethylsiloxane) fiber, with 30 min immersion, in a 3 ml sample, at 45 degrees C. Pesticides extraction yield from aqueous spiked solutions was studied, for different ethanol concentrations (9%, 12.5% and 20%, v/v), which are representative of the main types of Portuguese wines. Calibration curves for extracted standards gave linear responses for all the pesticides, except dichlorvos, mevinphos, disulfoton and methidathion. Average detection limits were lower than 5 ppb and no significant interference from the matrix was found in the conditions studied, except for buprofezin.

Chromatography, Gas↗
PubMed2001

Optimization and evaluation of low-pressure gas chromatography-mass spectrometry for the fast analysis of multiple pesticide residues in a food commodity.

A fast method of analysis for 20 representative pesticides was developed using low-pressure gas chromatography-mass spectrometry (LP-GC-MS). No special techniques for injection or detection with a common quadrupole GC-MS instrument were required to use this approach. The LP-GC-MS approach used an analytical column of 10 m x 0.53 mm I.D., 1 microm film thickness coupled with a 3 m x 0.15 mm I.D. restriction capillary at the inlet end. Thus, the conditions at the injector were similar to conventional GC methods, but sub-atmospheric pressure conditions occurred throughout the analytical column (MS provided the vacuum source). Optimal LP-GC-MS conditions were determined which achieved the fastest separation with the highest signal/noise ratio in MS detection (selected ion monitoring mode). Due to faster flow-rate, thicker film, and low pressure in the analytical column, this distinctive approach provided several benefits in the analysis of the representative pesticides versus a conventional GC-MS method, which included: (i) threefold gain in the speed of chromatographic analysis; (ii) substantially increased injection volume capacity in toluene; (iii) heightened peaks with 2 s peak widths for normal MS operation; (iv) reduced thermal degradation of thermally labile analytes, such as carbamates; and (v) due to larger sample loadability lower detection limits for compounds not limited by matrix interferences. The optimized LP-GC-MS conditions were evaluated in ruggedness testing experiments involving repetitive analyses of the 20 diverse pesticides fortified in a representative food extract (carrot), and the results were compared with the conventional GC-MS approach. The matrix interferences for the quantitation ions were worse for a few pesticides (acephate, methiocarb, dimethoate, and thiabendazole) in LP-GC-MS, but similar or better results were achieved for the 16 other analytes, and sample throughput was more than doubled with the approach.

Food Contamination↗
PubMed2001

Determination of octanol-water partition coefficients of pesticides by microemulsion electrokinetic chromatography.

Microemulsion electrokinetic chromatography (MEEKC) was evaluated as a screening tool for the indirect measurement of octanol-water partition coefficients (log Po/w) of pesticide compounds. Over 80 pesticide compounds representing a variety of structural characteristics were studied, and good correlation of log Po/w with the logarithm of the retention factor was found. The microemulsion system studied allowed the separation of compounds in the log Po/w range of -1 to 7. In addition, a smaller set of simple organic molecules that vary in structural features was evaluated and compared to the pesticide log Po/w calibration. The pesticide and simple organic molecule log Po/w calibration lines were statistically similar. This suggests that a universal set of standard compounds may be employed for the log Po/w calibration to provide measurements for a variety of compounds with good accuracy.

Calibration↗
PubMed2002

Trace level determination of organochlorine, organophosphorus and pyrethroid pesticides in lanolin using gel permeation chromatography followed by dual gas chromatography and gas chromatography-negative chemical ionization mass spectrometric confirmation.

A methodology for multi-class pesticide determination at trace level in lanolin is presented. Gel permeation chromatography on a Bio-Beads SX-3 column followed by a dual GC chromatographic determination has been developed. The effluent of the analytical column (50% diphenyl-methyl- or 14% cyanopropyl-phenylpolysiloxane) was split into an electron-capture and a nitrogen-phosphorus detection system. The chromatographic system was optimised for 28 pesticides commonly used to control sheep pests and corresponding to organochlorine, organophosphorus and pyretroid classes. Identification has been carried out by gas chromatography coupled to negative chemical ionization mass spectrometry. Recoveries ranged from 72 to 94% and the detection limits from 20 to 97 ng/g depending on the pesticide class, the RSDs were below 10%. Finally, the developed analytical methodology has been successfully applied to the determination of pesticides in several lanolin samples.

Chromatography, Gas↗
PubMed2002

Alternative calibration approaches to compensate the effect of co-extracted matrix components in liquid chromatography-electrospray ionisation tandem mass spectrometry analysis of pesticide residues in plant materials.

The aim of this study was to evaluate the applicability of different calibration approaches in a multi- and single-residue analysis of modern pesticides in plant matrices using liquid chromatography-electrospray mass spectrometry (HPLC-ESI-MS). In the first set of experiments the determination of eight pesticides representing different groups of polar/unstable pesticides (carbamates, benzimidazoles, azoles, benzoylphenylurea) in apple samples was performed. The trueness and precision of data obtained by using: (i) external solvent standard calibration, (ii) external matrix-matched standard calibration and (iii) echo-peak internal standard calibration was compared. The last mentioned method is a novel technique providing the possibility to inject internal standard of the same identity as a target analyte, so that its retention time is close to the analyte from the sample. According to expectation, when using external standard solvent calibration the results were under- or overestimated due to suppression or enhancement of analyte's signal by matrix components. On the other hand with the use of matrix-matched calibration accurate data were obtained. With echo-peak technique accurate results comparable to those obtained by matrix calibration were obtained for six out of eight pesticides. In the second set of experiment we used the echo-peak technique to overcome the problem with the response instability in the analysis of chlormequat in pear concentrate samples. As an internal standard method the echo-peak technique provided the possibility of monitoring of signal decrease during the analytical sequence and to compensate this decrease by relating sample peak area relatively to this internal standard.

Calibration↗
PubMed2003

Rapid analytical method for the determination of pesticide residues in sunflower seeds based on focused microwave-assisted Soxhlet extraction prior to gas chromatography-tandem mass spectrometry.

A rapid analytical method for determination of organochlorine pesticide residues in sunflower seeds based on focused microwave-assisted Soxhlet extraction has been developed. The main factors affecting the extraction efficiency--namely microwave power, irradiation time, volume of extractant and number of cycles--were optimized by a two-level factorial fractional design. After extraction, a liquid-liquid extraction and a clean-up step including the use of Florisil macrocolumns were required prior to injection of the extracts into the chromatograph in order to isolate the pesticide residues from the lipid fraction of the original extract. The MS-MS ion preparation mode was selected due to the high sensitivity and selectivity it provides. Seed samples were used collected near a crop subjected to aerial pesticide application. Residues of hexachlorocyclohexane isomers and endosulfan were found in the seeds although they were not subjected to pesticide application, thus showing the spray-drift contamination. The validation of the proposed approach was carried out by comparison with the ISO 659-1988 reference extraction method obtaining similar, or even better efficiencies by the proposed approach.

Gas Chromatography-Mass Spectrometry↗
PubMed1996

Screening and analysis of polar pesticides in environmental monitoring programmes by coupled-column liquid chromatography and gas chromatography-mass spectrometry.

Screening and analysis of polar pesticides based on coupled-column reversed-phase liquid chromatography (LC-LC) and GC- or LC-MS is a powerful tool in the execution of environmental monitoring programmes. This paper presents a unified approach utilising LC-LC screening followed by GC-MS confirmation. As polar pesticides are not generally amenable to GC a widely applicable derivation technique is used. The results demonstrate that the proposed LC and MS techniques are capable of analysing a wide range of polar pesticides down to levels of 0.1 microgram/l (EU limit for drinking water). LC switching techniques for group analysis or individual compounds rely on the reversed-phase retention and the UV detectability of the pesticides in combination with the choice of the LC columns. Fast miniaturised derivatization prior to GC-MS forms an integral part in the proposed strategy. In order to avoid extraction losses, derivation in the aqueous sample, preferably with electrophoric reagents with enhanced sensitivity in GC-NICI-MS are employed where possible. In this communication, method development and validation fitting in the strategy are evaluated and the results of the combined approach are discussed.

Chromatography, Liquid↗
PubMed1996

Selective, solid-matrix dispersion extraction of organophosphate pesticide residues from milk.

A rapid procedure has been developed that allows a single-step, selective extraction and cleanup of organophosphate (OP) pesticide residues from milk dispersed on solid-matrix diatomaceous material filled into disposable cartridges by means of light petroleum saturated with acetonitrile and ethanol. Recovery experiments were carried out on homogenized commercial milk (3.6% fat content) spiked with ethanolic solutions of 24 OP pesticides, viz., ethoprophos, diazinon, dimethoate, chlorpyrifos-methyl, parathion-methyl, chlorpyrifos-ethyl, malathion, isofenphos, quinalphos, ethion, pyrazophos, azinphosethyl, heptenophos, omethoate, fonofos, pirimiphos-methyl, fenitrothion, parathion, chlorfenvinphos, phenthoate, methidathion, triazophos, phosalone, azinphos-methyl, at levels ranging for the different OP pesticides from 0.02 mg/kg to 1.11 mg/kg. Average recoveries of four replicates were in the range 72-109% for the different OP pesticides, with relative standard deviations (R.S.D.) from ca. 1 to 19%, while dimethoate and omethoate were not recovered. Coextracted fatty material amounted to an average of about 4.0 mg/ml of milk. The extraction procedure requires about 30 min. The main advantages are that extraction and cleanup are carried out in a single step, emulsions do not occur, several samples can be run in parallel by a single operator, reusable glassware is not needed and simple operations are required.

Animals↗
PubMed1997

Supercritical fluid extraction of pesticides in foods.

This article summarizes research findings involving the supercritical fluid extraction (SFE) of pesticides in food and other tissue matrices. Emphasis is placed on multiresidue analysis of pesticides in nonfatty foods, including some previously unpublished aspects of SFE in this application. Brief overviews of pesticides and traditional multiresidue methods are given, followed by discussion of results for SFE applications in the pesticide residue analysis of foods.

Chromatography, Gas↗
PubMed1998

Multiresidue determination of pesticides in plants by high-performance liquid chromatography following gel permeation chromatographic clean-up.

Gel permeation chromatography was applied as a clean-up step in a HPLC multiresidue method for the determination of several pesticides in plants, not amenable to analysis by GC. The pesticides investigated were diflubenzuron, triflumuron, clofentezine, hexythiazox and flufenoxuron. The clean-up technique resulted in a good separation of analytes from co-extractive matrix compounds. Complete HPLC separation of all pesticides was achieved under the conditions selected. The analytical procedure was characterized with high accuracy and precision and acceptable sensitivity to meet requirements for monitoring these pesticides in crops.

Benzamides↗
PubMed1999

Trace analysis of pesticides by gas chromatography.

The analysis of pesticides is relevant to both food quality and the environment. Many laboratories are occupied with the analysis of pesticides in food, water or soil. Capillary gas chromatography is the technique most widely used in pesticide analysis. In present laboratory practice it serves as a screening method for over 300 pesticides. In this review we describe the role of gas chromatography as an analytical tool in combination with currently used or recently developed sample preparation techniques.

Chromatography, Gas↗
PubMed1999

Semiautomatic method for the screening and determination of 23 organochlorine pesticides in horticultural samples by gas chromatography with electron-capture detection.

A rapid, simple, efficient device for the extraction-preconcentration of 23 organochlorine pesticides currently applied to vegetables is proposed. Pesticide residues are extracted from chopped samples by using a mixture of distilled water and light petroleum (1:1, v/v). After phase separation, an aliquot of the organic layer is continuously evaporated to dryness under a N2 stream as it is dropped into a glass tube containing distilled water. The aqueous phase, containing the analytes, is then passed through a miniaturized RP-C18 column for preconcentration, clean-up and subsequent elution with 150 microliters of ethyl acetate. A volume of 1 microliter of the extract containing pesticides is injected into the gas chromatograph, fitted with an electron-capture detector, for their selective determination. Limits of detection vary between 0.04 and 10 ng/ml, with linear ranges from 0.2 to 500 ng/ml; the average relative standard deviation at the low nanogram-per-millilitre level is 5.3%. The potential of the proposed method was realized by applying it to the screening/determination of organochlorine pesticides in horticultural commodities.

Automation↗
PubMed1999

Atmospheric pressure ionisation multiple mass spectrometric analysis of pesticides.

Liquid chromatography-multiple mass spectrometry (LC-MS") has been investigated for analysis of polar pesticides in water using an ion-trap instrument and atmospheric pressure ionisation. Carbamate, triazine and phenylurea pesticides were best ionised as positive ions with atmospheric pressure chemical ionisation, while phenoxy acid herbicides, nitrophenols and bentazone yielded stronger signals as negative ions with pneumatically assisted electrospray. The ion fragmentation processes and pathways were studied in detail by MS, MS2, MS3 and MS4. All compounds were observed as their protonised or deprotonised molecular ions by MS and in the successive fragmentation by MS" the structures of typical (diagnostic) product ions were tentatively identified for each class of pesticide. Phenylureas yield an ion at m/z 72 by MS2, corresponding to O=C=N+(CH3)2. Carbamates produce [M+H-CONCH3]+ fragments by MS2 from neutral loss of methylisocyanate. Characteristic fragmentation pathways for triazine pesticides are [M+H]+-->m/z 174-->m/z 146-->m/z 110 and [M+H]+-->m/z 174-->m/z 132-->m/z 104 by MS-MS2-MS3-MS4 from cleavage of lateral chains in the triazine ring followed by ring opening. Phenoxy acid herbicides produce peculiar fragments by MS2 from loss of the acidic group possibly as the corresponding lactone. Nitrophenols are subject to loss of both *OH radical and NO groups thereby forming the correspondent phenols and quinones. The performance of the method with respect to quantitation compares favourably with traditional methods. With the ion-trap run in a time scheduled single ion monitoring mode, typical limits of detection (LODs) are in the low pg range and the repeatability standard deviations are between 3 and 15%. Assuming extraction of 1-l water samples and 1 ml final volumes the injection of 50-microl aliquots corresponds to LODs well below the requirement for the European Union water directive (EC/80/778).

Atmospheric Pressure↗
PubMed2000

Determination of pesticides in waters by automatic on-line solid-phase extraction-capillary electrophoresis.

The separation of seven pesticides by micellar electrokinetic capillary chromatography in spiked water samples is described, allowing the analysis of pesticides mixtures down to a concentration of 50 microg l(-1) in less than 13 min. Calibration, pre-concentration, elution and injection into the sample vial was carried out automatically by a continuous flow system (CFS) coupled to a capillary electrophoresis system via a programmable arm. The whole system was electronically coupled by a micro-processor and completely controlled by a computer. A C18 solid-phase mini-column was used for the pre-concentration, allowing a 12-fold enrichment (as an average value) of the pesticides from fortified water samples. Under the optimal extraction conditions, recoveries between 90 and 114% for most of the pesticides were obtained.

Automation↗
PubMed2000

Does further clean-up reduce the matrix enhancement effect in gas chromatographic analysis of pesticide residues in food?

Sample extracts of apples, peas, green beans, oranges, raspberries, clementines, carrots, and wheat obtained using the Food and Drug Administration (acetone extraction) and Canadian Pest Management Regulatory Agency (acetonitrile extraction) multiresidue methods for pesticides were subjected to clean-up using different solid-phase extraction (SPE) cartridges in an attempt to reduce or eliminate the matrix enhancement effect. The matrix enhancement effect is related to the blocking of active sites on the injector liner by matrix components, thereby increasing signal in the presence of matrix versus standards in solvent in which the pesticides themselves interact with the active sites. Graphitized carbon black (GCB) was often used in combination with various anion-exchange SPE cartridges. The extracts were then spiked with organophosphorus insecticides. These process standards were then compared to standards in acetone of the same concentration using gas chromatography with flame photometric detection or ion trap mass spectrometric detection. Sample matrix enhancement varied from little to no effect for some pesticides (e.g. chlorpyrifos, malathion) to >200% in the case of certain susceptible pesticides. The GCB removed color components but showed little effect in reducing matrix enhancement by itself. The anion-exchange cartridges in combination with GCB or not, substantially reduced the matrix enhancement effect but did not eliminate it.

Acetone↗