[Analysis of aldicarb and its metabolites in ginger using ultra performance liquid chromatography-tandem mass spectrometry coupled with multiplug filtration clean up with multiwalled carbon nanotubes]

A simple and rapid pretreatment procedure was developed for the simultaneous determination of aldicarb and its metabolites, aldicarb sulfone and aldicarb sulfoxide in ginger. The samples were extracted with acetonitrile, and then cleaned up with multiplug filtration using multiwalled carbon nanotubes (MWCNTS). The eluate was dried with nitrogen gas at room temperature, and redissolved in an acetonitrile-water (5:95, v/v) mixture, then quantified by ultra performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) operated in positive multiple reaction monitoring (MRM) mode. A linear relationship was achieved in the range of 0.5 -200 microg/L for the peak areas to the mass concentrations of the target compounds with the linear correlation coefficients (r2) higher than 0.99. The recoveries at three spiked levels of 2, 20 and 200 microg/kg were in the range from 71.4% to 89.8% with the relative standard deviations (RSDs, n = 6) from 0.7% to 13.2% under the selected conditions. The limits of quantification (LOQ, S/N = 10) of aldicarb, aldicarb sulfone, and aldicarb sulfoxide in ginger were 1.0, 2.0 and 1.0 microg/kg, respectively. The results demonstrate that the developed method is rapid, cost-effective, and can meet the requirements of the multiple pesticide residue analysis. The method is applicable to determine aldicarb and its metabolites in ginger.

Effects of four carbamate compounds on antioxidant parameters

The effect of four carbamates, aldicarb and its metabolites (aldicarb sulfone and aldicarb sulfoxide) and propoxur on glutathione content and the activity of the enzymes involved in the sulfur-redox cycle in the mammalian cellular model CHO-K1 cells after 24-h exposure were determined. Carbamate exposure resulted in a depletion of intracellular reduced glutathione (GSH) content, no change was observed in oxidized glutathione (GSSG) and a decrease in GSH/GSSG ratio was detected. After carbamates exposition a GSH/GSSG decreases in ranged from 12.44% to 21.35% of control was observed. Depletion of GSH levels was accompanied by the induction of glutathione reductase (GR) after 24h exposure with each of the four carbamates to CHO-K1 cells. After aldicarb sulfone, aldicarb sulfoxide, and propoxur exposure, glutathione peroxidase (GPx) activity increased in CHO-K1 cells by 198%, 32%, and 228% of control, respectively. After aldicarb sulfone and propoxur exposure, glutathione transferase (GST) activities increased by 49% and 230% of control, respectively. Due to the role played by GSH in preventing cytotoxicity via free-radical scavenging, results obtained suggest that high concentrations of aldicarb sulfone and propoxur closely resembling oxidative stress in CHO-K1 cells.

Suborganismic and organismic effects of aldicarb and its metabolite aldicarb-sulfoxide to the zebrafish embryo (Danio rerio)

The new European chemical regulation (REACH) requires a short-term fish test for chemicals where the level of production exceeds 10tons per year. For ethical reasons (3R-concept), an alternative to the acute fish test should be introduced to decrease the number of animal testing with fish. The zebrafish embryo (Danio rerio) test became a valuable tool in ecotoxicology and already replaces the acute fish test for the evaluation of wastewater in Germany. Recent efforts are targeted to use this and other fish embryo tests for the effect assessment of chemicals. The toxic effects of the carbamate insecticide aldicarb and its metabolite aldicarb-sulfoxide to zebrafish embryos were analysed using two approaches with different endpoints. Organismic tests were conducted with zebrafish embryos exposed to the pesticides for 48h. In addition, suborganismic effects were examined analysing the enzyme inhibition of cholinesterases and carboxylesterases. On the organismic level, the only sublethal effect seen was the increase of heart rate at low and decrease at higher concentration with the use of aldicarb-sulfoxide but not with aldicarb (concentration range 0.2-300microM). In contrast, analysis of enzyme inhibitions showed high to very high effects caused by the two carbamates. The enzyme inhibition analysis of whole homogenates of exposed embryos may be advantageous for toxicant screening (biomarker of exposure) and might be used to bridge the gap of sensitivity of the (48h old) zebrafish embryos to adult fish when exposed to anti-cholinesterase substances (biomarker of prospective effect).

Determination of pesticides in soy-based infant formula using liquid chromatography with electrospray ionization tandem mass spectrometry

A sensitive method using liquid chromatography with electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was developed and validated to quantify and confirm 13 pesticides, including aldicarb sulfoxide, aldicarb sulfone, oxamyl, methomyl, formetanate, 3-hydroxycarbofuran, carbendazim, thiabendazole, aldicarb, propoxur, carbofuran, carbaryl, and methiocarb, in soy-based infant formula. Data acquisition under MS/MS was achieved by applying multiple reaction monitoring of 2 fragment ion transitions to provide a high degree of sensitivity and selectivity for both quantitation and confirmation. Different approaches to constructing calibration curves were compared and discussed to address issues of the extraction efficiency or recovery, and matrix effects. Matrix-matched standard calibration curves with the use of isoprocarb as an internal standard were finally used to achieve the best accuracy of the method. Under most circumstances, recoveries of 13 pesticides, spiked at 5.0, 25.0, and 45.0 microg/kg, were close to 100%. The method detection limits (signal-to-noise ratio > or =3:1; microg/kg) of 13 pesticides were 0.2 for thiabendazole and methiocarb, 0.6 for aldicarb, and 0.1 for the others.

Assessment of leaching potential of aldicarb and its metabolites using laboratory studies

The metabolites of pesticides can contaminate groundwater and pose a risk to human health when this water is used for drinking. This paper reports the results of a laboratory study on aldicarb and its main metabolites, aldicarb sulfone and aldicarb sulfoxide. Aldicarb and its metabolites showed Koc values (6-31) which were lower than that of atrazine (55), indicating that they are very mobile in soil. They are less persistent than atrazine (DT50 = 25 days), with DT50 values from less than 1 day and up to 12 days. Aldicarb behaved as a non-leacher, whereas its metabolites clearly showed the characteristics of leachers. Aged residue leaching experiments showed that aldicarb can occur at high concentrations in the leachate, together with its two metabolites. The leachate composition depends on the incubation time of the parent compound. Aldicarb and its metabolites can form various mixtures in groundwater on the basis of the time elapsing between the application of the insecticide and the first significant rainfall. This study confirms the characteristics of contaminants of aldicarb and especially its metabolites, as reported in the literature.

Monitoring butocarboxim resistance of the woolly whitefly (Homoptera: Aleyrodidae) in citrus from Valencia, Spain

Glass vials coated internally with an insecticide were used as a resistance monitoring technique for testing field populations of the woolly whitefly, Aleurothrixus floccosus (Maskell), collected from citrus. The distribution of resistance to the insecticide butocarboxim in citrus orchards from Valencia (Spain) during 1993 and 1994 was determined by means of this technique. Adults resting on citrus shoots were captured with a portable vacuum cleaner and introduced into the vials. The technique provides control mortality of <25% when assessed 7 h after the insects are captured. In 21 populations tested, LC50s ranged from 1.8 to 42.3 mg/ml. This represents resistance ratios >20-fold among populations. Lower slopes of the concentration-mortality line were found in whitefly populations that exhibited a low level of the LC50. Resistance was widespread in the Valencia areabut spatially irregular, with nearby orchards occasionally showing wide differences in resistance levels. The levels of resistance to butocarboxim obtained with this technique closely matched the field efficacy of the insecticide. This residue bioassay provides a convenient and rapid method to monitor insecticide resistance in A. floccosus populations.

Effects of salinity on aldicarb toxicity in juvenile rainbow trout (Oncorhynchus mykiss) and striped bass (Morone saxatilis x chrysops)

Fluctuations in several environmental variables, such as salinity, can influence the interactions between organisms and pollutants in aquatic organisms, and, therefore, affect the toxicity of xenobiotics. In this study, after 2 species of fish, rainbow trout (Oncorhynchus mykiss) and hybrid striped bass (Morone saxatilis x chrysops) were acclimated to 4 salinity regimens of 1.5, 7, 14, and 21 ppt for 1 week and then exposed to 0.5 mg/l aldicarb. Mortality, brain, and muscle cholinesterase levels were measured after 96 h. Rates of (14)C-aldicarb sulfoxide formation were determined in kidney (trout only), liver, and gill microsomes from each species acclimated to the 4 salinity regimens. Salinity significantly enhanced aldicarb toxicity, cholinesterase inhibition, and (14)C-aldicarb sulfoxide formation in rainbow trout but not in striped bass. In vitro incubations with (14)C-aldicarb and the cytochrome P450 (CYP) inhibitor, N-benzylimidazole, did not significantly alter aldicarb sulfoxide formation in tissue microsomes from either species of fish, indicating CYP did not contribute to aldicarb sulfoxidation. Salinity increased flavin-containing monooxygenase (FMO) mRNA expression and catalytic activities in microsomes of liver, gill, and kidney of rainbow trout, which was consistent with the salinity-induced enhancement of aldicarb toxicity. Salinity did not alter FMO mRNA expression and catalytic activities in striped bass, which was also consistent with the lack of an effect of salinity on aldicarb toxicity in this species. These results suggest that salinity-mediated enhancement of aldicarb toxicity is species-dependent, and at least partially due to the salinity-related upregulation of FMOs, which, in turn, increases the bioactivation of aldicarb to aldicarb sulfoxide, which is a more potent inhibitor of cholinesterase than aldicarb.

Residues of aldicarb in oranges: a unit-to-unit variability study

Residues of aldicarb and its sulphoxide and sulphone oxidative metabolites in individual Navelino orange trees were determined at several time intervals after soil application of TEMIK 10G at 200 g formulated material per tree. Analysis was by HPLC with postcolumn derivatization giving average recoveries of 98% for aldicarb (RSD 6%), 34% for aldicarb sulphoxide (RSD 5%) and 77% for aldicarb sulphone (RSD 5%). Lowest calibrated levels (LCLs) were 0.02 mg/kg for aldicarb and aldicarb sulphone and 0.04 mg/kg for aldicarb sulphoxide. At the recommended preharvest interval (PHI) of 120 days no detectable residues of any compound, including the parent compound, were found in and of the samples analysed. In mature fruits (PHI of 88 days) detectable residues at the LCL for aldicarb sulphoxide and 0.03 or 0.04 mg/kg for aldicarb sulphone were found in only three of the 18 samples analYsed. In immature fruits detectable residues of aldicarb sulphoxide at concentrations ranging between 0.04 (LCL) and 0.51 mg/kg were detected in 70 out of 88 samples analysed, while residues of aldicarb sulphone at concentrations 0.02 (LCL) to 0.8 mg/kg were detected in 73 out of 88 samples. Indicative variability factors for sulphoxide and sulphone were estimated for immature fruits.

Determination of the rate of aldicarb sulphoxidation in rat liver, kidney and lung microsomes

1. The rate of sulphoxidation of aldicarb (2-methyl-2-(methylthio) propanal O-[(methylamino) carbonyl oxime], Temik) in rat hepatic, renal and pulmonary microsomes was determined by quantitating the levels of aldicarb sulphoxide and aldicarb sulphone produced during incubations. Under in vitro experimental conditions used in the present study, aldicarb sulphoxide was the only metabolite produced, and further metabolism of aldicarb sulphoxide to aldicarb sulphone was negligible. 2. The average maximal velocity (mumol/min/mg protein) for the sulphoxidation of aldicarb, based on measurements of product formation, in liver, kidney and lung microsomes was 5.41, 39.51 and 2.45 respectively. The corresponding values for the Michaelis constant (microM) were 184, 1050 and 188 respectively. 3. These results imply that under in vivo conditions (1) aldicarb sulphoxidation is not likely to be saturable even at lethal doses in the rat, and (2) aldicarb clearance in rat liver and kidney will be limited by the rate of blood flow and not metabolizing enzyme levels.

Solid-phase extraction of polar pesticides from environmental water samples on graphitized carbon and Empore-activated carbon disks and on-line coupling to octadecyl-bonded silica analytical columns

The suitability of Empore-activated carbon disks (EACD), Envi-Carb graphitized carbon black (GCB) and CPP-50 graphitized carbon for the trace enrichment of polar pesticides from water samples was studied by means of off-line and on-line solid-phase extraction (SPE). In the off-line procedure, 0.5-2 l samples spiked with a test mixture of oxamyl, methomyl and aldicarb sulfoxide were enriched on EnviCarb SPE cartridges or 47 mm diameter EACD and eluted with dichloromethane-methanol. After evaporation, a sample was injected onto a C18-bonded silica column and analysed by liquid chromatography with ultraviolet (LC-UV) detection. EACD performed better than EnviCarb cartridges in terms of breakthrough volumes (> 2 l for all test analytes), reproducibility (R.S.D. of recoveries, 4-8%, n = 3) and sampling speed (100 ml/min); detection limits in drinking water were 0.05-0.16 microgram/l. In the on-line experiments, 4.6 mm diameter pieces cut from original EACD and stacked onto each other in a 9 mm long precolumn, and EnviCarb and CPP-50 packed in 10 x 2.0 mm I.D. precolumn, were tested, and 50-200 ml spiked water samples were preconcentrated. Because of the peak broadening caused by the strong sorption of the analytes on carbon, the carbon-packed precolumns were eluted by a separate stream of 0.1 ml/min acetonitrile which was mixed with the gradient LC eluent in front of the C18 analytical column. The final on-line procedure was also applied for the less polar propoxur, carbaryl and methiocarb. EnviCarb could not be used due to its poor pressure resistance. CPP-50 provided less peak broadening than EACD: peak widths were 0.1-0.3 min and R.S.D. of peak heights 4-14% (n = 3). In terms of analyte trapping efficiency on-line SPE-LC-UV with a CPP-50 precolumn also showed better performance than when Bondesil C18/OH or polymeric PLRP-S was used, but chromatographic resolution was similar. With the CPP-50-based system, detection limits of the test compounds were 0.05-1 microgram/l in surface water.

Determination of aldicarb, aldicarb sulfoxide and aldicarb sulfone in tobacco using high-performance liquid chromatography with dual post-column reaction and fluorescence detection

A screening method for the determination of aldicarb (AS) and its sulfoxide (ASX) and sulfone (ASN) metabolites in tobacco at low ppm levels is described. Tobacco samples are extracted using methanol with the aid of sonication at ambient conditions. The extract is filtered and then injected into a high-performance liquid chromatograph equipped with a dual post-column reaction system and a fluorescence detector. Chromatographic separation is performed on a C18 column with a mixture of methanol-acetonitrile-water containing 0.1% of triethanolamine as the mobile phase. Triethanolamine is added to improve peak shape of AS residues and to reduce the undesired interaction between residual silanols and interferences, mainly amino acids and other amines. The average recoveries for AS residues spiked in tobacco are higher than 95% for AS, 91% for ASN and 85% for ASX at levels of 0.5-10 ppm (w/w). The detection limit is 0.5 ppm for each of the target compounds.

Rapid on-line precolumn high-performance liquid chromatographic method for the determination of benomyl, carbendazim and aldicarb species in drinking water

A reversed-phase high-performance liquid chromatographic (HPLC) method has been developed for the determination of trace concentrations of benomyl, carbendazim, aldicarb, aldicarb sulphoxide and aldicarb sulphone in drinking water. A 10-ml sample of water is passed through a 3-cm precolumn, packed with 5-microns C8 sorbent, at a flow-rate of 5 ml/min. The HPLC system is then switched to an acetonitrile-water gradient elution program. The preconcentrated analytes are eluted from, and separated by, the 3-cm C8 precolumn and determined by UV absorption. The total analytical time is 25 min. The lowest detectable concentrations are in the range of 2.5 x 10(-9)-11.0 x 10(-9) g/ml for the five analytes investigated with 10 ml of sample.

[Gas chromatographic analysis of aldicarb and its metabolites in urine]

A method is described for the analysis of aldicarb and its metabolites in urine by GC/FPD. The sample was concentrated with activated charcoal-Florisil column chromatography, eluted by dichloromethane-acetone (1:1v/v). The aldicarb, aldicarb sulfoxide in the eluted solution were oxidized by oxidizing reagent into aldicarb sulfone. The concentration of aldicarb sulfone was analyzed by GC/FPD. The detection limit of 0.0024 mg/L and coefficient of variation of 2.4%-7.4% were achieved. Mean recovery rates were 90.9%, 86.6%, 92.6% for aldicarb, aldicarb sulfoxide and aldicarb sulfone, respectively.

Gas chromatographic determination of aldicarb and its metabolites in urine

A method is described for the determination of aldicarb and its metabolites (the sulphoxide and sulphone) in urine by gas chromatography with flame photometric detection (GC-FPD). The sample was concentrated with a column containing activated charcoal and Florisil, and then eluted with dichloromethane-acetone (1:1, v/v). The aldicarb and aldicarb sulphoxide in the eluate solution were oxidized to aldicarb sulphone and the total sulphone concentration was determined by GC-FPD after extraction with dichloromethane and clean-up with an activated charcoal column. The detection limit was 0.0024 mg/l. The mean recoveries from spiked urine in the range 0.04-0.12 mg/l were 90.9%, 86.6%, 92.6% for aldicarb, aldicarb sulphoxide and aldicarb sulphone, respectively.

Aldicarb food poisonings in California, 1985-1988: toxicity estimates for humans

Three outbreaks of food poisoning involving watermelons or cucumbers and caused by the carbamate pesticide aldicarb occurred in California between 1985 and 1988. For each outbreak, and for an outbreak of aldicarb poisoning associated with English cucumbers previously reported in the literature, dosages of aldicarb sulfoxide that caused the illnesses were estimated. Estimated dosages ranged between 0.0023 [corrected] and 0.06 mg/kg body weight, and most were well below the 0.025 mg/kg Lowest Observed Effect Level (LOEL) for subclinical blood cholinesterase depression previously reported for humans. These findings are consistent with aldicarb sulfoxide (ASO) illnesses that have occurred in other states. Aldicarb appears to be more toxic than previously suspected. Scientific and regulatory implications are discussed.

Aldicarb residues in citrus soil, leaves and fruits

Aldicarb was applied to the soil of Late Valencia orange field plots. A comparative study between four analytical methods is reported, the NPD-gas chromatography method being the best choice. The work also reports the study of accumulation and persistence of aldicarb and its biologically active metabolites in the soil, leaves and fruits (rind and pulp, separately). Residue content, at the ppb level, was found in the order leaves much greater than rind greater than pulp. Carbamate was found to accumulate mainly in its oxidized forms. Residues had reached a maximum level in about 90 days after application.

On-line trace enrichment for determination of aldicarb species in water, using liquid chromatography with post-column derivatization

Liquid chromatography combining on-line trace enrichment together with a very selective detection technique is used for the determination of aldicarb, aldicarb sulfoxide, and aldicarb sulfone. Sensitivity is increased by loading a 10 mL volume of ground water on a concentrator column installed in the loop position of a 6-port injection valve. Switching the valves allows the concentrated material to be backflushed onto the analytical column by a methanol-water gradient mobile phase. Separation is followed by post-column hydrolysis to yield methylamine, and formation of a fluorophore with o-phthalaldehyde and 2-mercaptoethanol prior to fluorescence detection. The process requires virtually no sample cleanup and provides good precision on recoveries from different matrixes. Minimum detection limit, defined as 5 times baseline noise, is less than 70 ng/L for the 3 compounds.

Direct gas chromatographic determination of the two isomeric insecticides, aldicarb and butocarboxime and their toxic metabolites: application to residue analysis in crops and leaves

A gas-chromatographic method is described for determination of residues of butocarboxime (Drawin), its structural isomer aldicarb (Temik), and their toxic sulfoxide and sulfone metabolites. These compounds were determined intact, by gas chromatography employing a thermionic specific detector (TSD). Breakdown of these relatively thermally unstable compounds was avoided by lowering the inlet temperature to 150 degrees C, by keeping column temperature as low as possible, and by using a low-load liquid phase (2% of OV-17 on Gas-Chrom Q). These compounds were determined in enriched extracts of samples of tomatoes and apples and also in the leaves of citrus and cotton. The method is suitable for the separation, differentiation and determination of the two isomers and their metabolites at an enrichment level of 0.1 micrograms/g of fresh weight. The results were confirmed by gas chromatography--chemical-ionization mass-spectrometry.

Aldicarb sulfoxide/aldicarb sulfone mixture in drinking water of rats: effects on growth and acetylcholinesterase activity

A 1:1 mixture of aldicarb sulfoxide/aldicarb sulfone was administered to young adult Wistar rats via the drinking water at nominal concentrations of 19.2, 4.8, 1.2., 0.3, 0.075, or 0 ppm for 29 d. Blood was collected after 8, 15, and 29 d of treatment for plasma and erythrocyte cholinesterase determinations, and brain cholinesterase was determined at sacrifice. Body weight, food intake, and water consumption were measured weekly. Body weight gain and water consumption were reduced at 7, 14, 21, and 29 d in male and female rats at 19.2 ppm. Food consumption was reduced in males at 7, 14, 21, and 29 d but was reduced in females only on d 7. Both plasma and erythrocyte cholinesterase activity were reduced after 8, 15, and 29 d in male and female rats at 19.2 ppm. Males at 4.8 ppm showed reductions in plasma activity only after d 8 and in erythrocyte activity only after d 29. Female rats at 19.2 ppm also displayed depressions in brain cholinesterase activity not observed in similarly treated males. Since the only effects noted at 4.8 ppm were reductions in plasma and red blood cell cholinesterase activity in males only and at only one of three sampling periods, these two instances are not believed to be of any biological significance. The data suggest that 4.8 ppm in drinking water is a no observable ill-effect level for exposure of rats to aldicarb residues based on the parameters measured in this study.

Kinetics of aqueous base and acid hydrolysis of aldicarb, aldicarb sulfoxide and aldicarb sulfone

The kinetics of degradation of aqueous solutions of aldicarb, aldicarb sulfoxide and aldicarb sul fone by base hydrolysis were investigated. Pseudo first order rate constants of 37 micrograms/l solutions were determined at different hydroxide concentrations by acid-base titration. Second order rate constants were calculated, and it was found that aldicarb sulfone is more sensitive to hydroxide ion concentration than aldicarb sulfoxide which is more sensitive than aldicarb. Temperature effects were determined by measuring the base hydrolysis rate constant for aldicarb sulfone at 5, 15, 20, 25, 30, and 35 degrees C. An activation energy of 15.2 +/- 0.1 kcal/mole was calculated. Addition of a neutral electrolyte decreased the rate constant for base hydrolysis. Acid catalyzed hydrolysis rate constants were also measured for aldicarb sulfone, and, as expected, the reaction was much slower. The second order (reaction) rate constant for base hydrolysis of aldicarb sulfone is 40.3 (+/- 0.5) liter mole-1min-1; for acid catalyzed hydrolysis it is 7.33 (+/- 0.06) X 10(-4) liter mole-1min-1.

High pressure chromatography determination of aldicarb, aldicarb sulfoxide, and aldicarb sulfone in potatoes

An ion-suppression reverse phase high pressure liquid chromatographic method is described for the determination of aldicarb, aldicarb sulfoxide, and aldicarb sulfone in potatoes. Samples are extracted with methylene chloride and Na2SO4, evaporated to dryness, and cleaned up using Sep-Pak silica and Sep-Pak-C18 cartridges. The extract can be successfully analyzed by high pressure liquid chromatography on either a mu LiChrosorb RP-18 or mu Bondapak C18 column and quantitated using a variable wavelength ultraviolet detector set at either 220 or 247 nm. The mobile phase is acetonitrile-buffer (4 + 96) and (30 + 70), buffered to pH 7.6 and flowing at 2 mL/min. Recoveries ranged from 80 to 100%. The minimum detectable amount was 37.5 ng, which easily permitted the quantitation of 0.1 ppm aldicarb sulfone in 75 g sample. The recovery of aldicarb was low because of its rapid enzymatic oxidation to aldicarb sulfoxide and sulfone.