Commercial Pesticide Formulations Research Articles

Mid-infrared and Raman spectrometry for quality control of pesticide formulations

This article deals with recent developments in the use of vibrational spectrometry for the quantitative analysis of active components in commercial pesticide formulations. We review the techniques, such as Fourier transform infrared (FTIR) and FT-Raman spectrometries, and measurement modes, such as stopped flow or flow injection. FTIR is being used increasingly in the determination of pesticides in agrochemical products because of its relatively short analysis time. However, FT-Raman spectrometry provides direct analysis of solid and aqueous samples. It is therefore clear that these techniques enable fast, non-destructive, precise and accurate measurements, so vibrational spectrometry appears to be a promising tool for on-line process monitoring and analysis in the agrochemical industry.

FTIR Approaches for Diuron Determination in Commercial Pesticide Formulations

Two strategies have been developed for Diuron determination by FTIR spectrometry, an off-line extraction and stopped-flow determination and a fully mechanized procedure, based on the on-line extraction of Diuron and FIA-FTIR measurement of the extracts. The aforementioned procedures have been compared with a reference chromatographic method. The off-line FTIR spectra were obtained at a nominal resolution of 4 cm(-1) from 4000 to 900 cm(-1) by accumulating 25 scans. Diuron was determined using peak height measurements at 1582 cm(-1) corrected using a baseline defined between 1562 and 1614 cm(-1). The waste generation of the off-line procedure was 3.4 mL chloroform for each sample, and the method provided a LOD of 40 microg g(-1), corresponding to 0.8% (w/w) Diuron in the original sample. The fully mechanized FIA method provided a LOD of 35 microg g(-1), which corresponds to 0.7% (w/w) in the solid sample and a maximum sampling frequency of the whole procedure of 30 h(-1), with a waste generation of 9.3 mL per sample, taking into account the volume of CHCl(3) required for sample dissolution and that need as a carrier. All those methods consume less organic solvent than a HPLC method, which involves the use of 39 mL of acetonitrile per sample and a sampling frequency of 12 h(-1).

Automated Fourier Transform near Infrared Determination of Buprofezin in Pesticide Formulations

An automated procedure has been developed for Fourier transform near infrared (FT-NIR) determination of buprofezin in pesticide formulations. This methodology is based on on-line pesticide extraction with acetonitrile from solid samples and its determination by using peak area absorbance measurements between 2147 and 2132 nm, corrected with a horizontal baseline established at 2091 nm. The repeatability, as a relative standard deviation of five independent analyses of 18.9 mg g−1 of buprofezin, was 0.06% and the limit of detection 5 mg L−1. The reagent consumption was clearly reduced compared with a chromatographic reference procedure from 40.4 mL acetonitrile per sample, required by high performance liquid chromatography (HPLC), to 2 mL acetonitrile consumed for FT-NIR. The sample measurement throughput obtained by the FT-NIR methodology was 30 h−1, five times higher than that obtained by HPLC (6 h−1). It can be concluded that the proposed vibrational spectroscopic method is appropriate for the quality control of commercial pesticide formulations. The on-line sample treatment avoids contact by the operator with toxic products and this method is an environmentally friendly alternative to the measurement in the mid infrared which requires the use of CHCl3.

Continuous-flow separation and pre-concentration coupled on-line to solid-surface fluorescence spectroscopy for the simultaneous determination of o -phenylphenol and thiabendazole

A novel and single flow-injection system combined with solid-surface fluorescence detection is proposed in this work for the resolution of a mixture of two widely used pesticides (o-phenylphenol and thiabendazole). The continuous-flow methodology is based on the implementation of on-line pre-concentration and separation of both analytes on the surface of C18 silica gel beads placed just inside the flow cell, implemented with gel-phase fluorimetric multi-wavelength detection (using 305/358 and 250/345 nm as excitation/emission wavelengths for thiabendazole and o-phenylphenol, respectively). The separation of the pesticides was possible owing to the different retention/desorption kinetics of their interactions with the solid support in the zone where the stream impinges on the solid material. No previous separation of the analytes before they reach the flow cell is needed thereby simplifying substantially both the procedure and the manifold. By using a sample volume of 2,600 microL, the system was calibrated in the range 0.5-16 and 5-120 ng mL(-1) with detection limits of 0.09 and 0.60 ng mL(-1) for thiabendazole and o-phenylphenol, respectively. The RSD values (n=10) were about 1% for both analytes. The proposed methodology was applied to environmental water samples and also to various commercial pesticide formulations containing both analytes. Recovery percentages were 97-103% and 98-102% for thiabendazole and o-phenylphenol, respectively.

Effects of different plant protection programs on soil microbes

The aim of this study was to assess the effects of two pesticide regimens (conventional full insurance compared with supervised and reduced pesticide use) and two cultivation techniques (conventional tillage and fertilization compared with no tillage and lower fertilization) on soil microbes in a field study, and to evaluate the results with laboratory tests. The herbicides used were chlorsulfuron, MCPA, and bentazone; the fungicides carboxin–imazalin and propiconazole; and the insecticides dimethoate and pirimicarb. In the field studies, the effects on microbial biota were assessed by measuring biomass (ATP content) and microbial activities related to carbon and nitrogen metabolism (soil respiration, nitrification potential). Potential harmful effects of commercial formulations of the same pesticides on microbes were studied in the laboratory with two bacterial toxicity tests ( Pseudomonas putida growth inhibition and Vibrio fischeri luminescence inhibition tests) and with a soil respiration inhibition test. Bioavailability of the pesticides in the soil was assessed by a solid-phase modification of the luminescent bacteria test. In the field studies the microbial activities and biomass followed the weather conditions during the growing season, and significant effects of pesticide treatments on microbial processes were not observed. In the laboratory studies the toxicity of certain pesticides was clearly detected by bacterial toxicity tests. However, in the soil respiration inhibition assessment with soil similar to that used in the field trial, inhibition was observed only at unrealistically high concentrations. This could be due to the limited bioavailability of the pesticides in soil of high clay and organic carbon content.

CHROMATOGRAPHIC DETERMINATION OF CARBARYL AND OTHER CARBAMATES IN FORMULATIONS AND WATER USING BRIJ-35

ABSTRACT A micellar liquid chromatographic (MLC) procedure was developed for the determination of carbaryl and other carbamates (carbofuran, desmedipham, methiocarb and propoxur), using a C18 column and UV detection. Optimisation was performed using the anionic surfactant sodium dodecyl sulphate (SDS) and the non-ionic Brij-35. Both surfactants yielded similar selectivities, but Brij-35 gives shorter retention times than SDS and for this reason was preferred to speed up the analysis of the carbamates. In the selected mobile phase (0.07 M of Brij-35), the analysis time was 22 min. The procedure was applied for the determination in commercial pesticide formulations and spiked samples (distilled, tap, reservoir tank, irrigation ditch, sea and waste water). This method proved to be competitive against the EPA reference method, recommended for the determination of some N-methylcarbamates, which uses a gradient of acetonitrile. The results of the pesticide formulations obtained with both methods are in agreement with the concentrations declared by manufacturers.

FLOW INJECTION SPECTROPHOTOMETRIC DETERMINATION OF PROPOXUR WITH DIAZOTIZED 4-AMINOBENZOIC ACID

ABSTRACT A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-aminobenzoic acid as the coupling agent was developed. The determination involves on-line hydrolysis at room temperature of the propoxur with sodium hydroxide. The resulting 2-isopropoxyphenol is coupled with diazotized 4-aminobenzoic acid in order to achieve an appropriate selectivity and sensitivity to the spectrophotometric measurements. The calibration curve is linear over the range 1–10 mg L−1 of propoxur. The proposed method has provided a detection limit of 0.15 mg L−1 of propoxur and a sample frequency of 120 injections per hour. The relative standard deviation of six independent determinations of a sample containing 5 mg L−1 propoxur was 0.74%. The suitability of the proposed procedure for the determination of propoxur in commercial pesticide formulations was studied. The procedure provides results comparable to those obtained by the liquid chromatography analysis.

Determination of carbofuran in pesticide formulations by flow injection spectrophotometry

A flow injection spectrophotometric method for the determination of carbofuran in commercial pesticide formulations was developed. The determination involves on-line hydrolysis of the extracted carbofuran at room temperature with sodium hydroxide. The resulting carbofuran-phenol is coupled with diazotized 4-aminobenzoic acid in order to achieve an appropriate selectivity and sensitivity for the spectrophotometric measurements. The calibration curve is linear over the range 1–10 mg litre−1 of carbofuran. The proposed method has a detection limit of 0.15 mg litre−1 of carbofuran and a sample frequency of 120 injections per hour. The relative standard deviation of six independent determinations of a sample containing 1 mg litre−1 carbofuran was 0.6%. The suitability of the proposed procedure for the determination of carbofuran in commercial pesticide formulations was studied. The procedure provides results comparable to those obtained by liquid chromatographic analysis. © 2000 Society of Chemical Industry

Gas and liquid phase sorption studies of lindane on NaY and MCM-41 molecular sieves

Fundamental studies on the gas and liquid phase uptake of the chlorinated pesticide lindane (γ-hexachlorocyclohexane) on aluminosilicate molecular sieves NaY and MCM-41 (d-spacing=1.26 nm, Si/Al=2.6/1) were undertaken in an effort to evaluate their ability to act as barrier coatings on treated timbers. As competing water vapour from the environment could reduce the effective uptake of lindane, wet (non-activated) materials with preadsorbed water were compared with activated and silinised materials. Commercial pesticide formulations often use toluene as solvent, so this work also investigated the extent to which toluene affected lindane sorption. Liquid phase uptake measurements were analysed by FTIR spectroscopy. Both lindane and toluene were sorbed by the activated, wet and silinised forms of the NaY zeolite, with lindane able to displace approximately two-thirds and toluene approximately half of the preadsorbed water of wet NaY. Silination significantly reduced the uptake of both lindane and toluene, and this was more pronounced for the larger lindane molecule. It was found from liquid phase competitive studies that activated NaY always preferred lindane to toluene, but that selectivity for lindane on wet NaY depended on its concentration in the original solution. Gas chromatography showed that lindane was strongly retained on both NaY and MCM-41, but that even at the lowest temperatures MCM-41 was not able to retain toluene. Thermal gravimetric analysis of the gas phase uptakes of toluene and lindane were similar and independent of whether the zeolite was in its activated or wet form, with silination giving only a slight reduction in uptake. Uptake of lindane and toluene on NaY zeolite was more than twice that on MCM-41.

Side-effects of Formulations of Permethrin and Fenvalerate Insecticides on Frost Resistance and Field Performance of Picea Abies Seedlings

Side - effects of the permethrin formulations Gori 920 and Gori 920 L, the fenvalerate formulation Sumicidin 10 FW and the emulsifier of the Gori formulations were studied in seedlings of Norway spruce [Picea abies (L.) Karst.]. Whole plant treatment with the Gori formulations in early autumn resulted in a 5-10°C poorer frost tolerance (TDI) later in the autumn. Moreover, this treatment increased mortality by 30% within 2 yrs of testing in field trials. In contrast, a basal part treatment with the Gori formulations and whole plant treatment with Sumicidin 10 FW containing 10% fenvalerate had no negative effects during 2 yrs of field testing. Late autumn treatment with Gori 920 and Gori 920 L, followed by cold storage for 6 months, revealed poorer frost tolerance (3-4°C) in the spring than that in the control. These treatments also reduced leader shoot growth in the first year and increased the frequency of seedlings lacking a dominant leader after 2 yrs by 20-40%. The detrimental agent in Gori 920 L was found to be the emulsifier, ethoxylated nonylphenol, alone and in combination with the dispersal agent, linseed oil. The linseed oil had no significant additional negative effect on frost resistance and growth after the cold storage during the winter. The investigation demonstrates the necessity of testing for possible side - effects before practical use of any commercial pesticide formulation.

Induction of sister chromatid exchanges and chromosome aberrations in vivo in Etroplus suratensis (Bloch) following exposure to organophosphorus pesticides

The genotoxic potential of methyl parathion and phosphamidon, two commercial formulations of organophosphorus pesticides, was evaluated through induction of sister chromatid exchanges (SCE) and chromosome aberrations in fish gill tissues. Fishes exposed to the medium containing 0.05, 0.1 and 0.2 ppm of methyl parathion or 0.5, 1.0, and 2.0 ppm of phosphamidon for a duration of 96 h revealed significant increase in the number of SCE and chromosome aberrations against control values. This demonstrates the feasibility of the fish in vivo system in detecting genotoxic potential of pollutants.

The response of screen-printed enzyme electrodes containing cholinesterases to organo-phosphates in solution and from commercial formulations

Electrodes containing a layer of cobalt phthalocyanine, mixed with graphite ink, and a layer of acetyl- or butyryl cholinesterase were constructed by screen-printing, except for a thin layer of polyurethane applied by an airbrush. When the electrodes were made the anodes of electrochemical cells, the generation of current by the addition of enzyme substrate was inhibited by standard solutions of organo-phosphate pesticides. Cholinesterase activity was inhibited by paraoxon and dichlorvos concentrations as low as 10 −8 M. The relationship between the logarithm of concentration and the inhibition quotient (ratio between initial current and the rate of change of the inhibited current) was curvilinear. Malathion only caused an inhibition of current generated by electrodes containing acetyl cholinesterase. Inhibition by malathion required a period of pre-incubation in the pesticide before addition of enzyme substrate, and was evident down to, and including, a concentration of 10 −7 M. The addition of diluted commercial formulations of some organo-phosphate pesticides caused rapid inhibition of electrode function. Nearly linear relationships were observed between the logarithm of the degree of dilution of commercial formulations containing PO groups and the natural logarithms of the inhibition quotients. Inhibition by formulations containing malathion did not require pre-incubation of the electrodes in the mixture (only electrodes containing acetyl cholinesterase were tested). The relationship between the logarithm of the degree of dilution and the natural logarithm of the inhibition quotient was curvilinear. The responses of the screen-printed electrodes to commercial formulations of pesticides indicate that they may be a suitable platform for further development of sensors capable of detecting the presence of these pesticides in the environment.

Spectrophotometric determination of carbamate pesticides with diazotized trimethylaniline in a micellar medium of sodium dodecyl sulfate.

The spectrophotometric determination of the carbamate pesticides carbaryl, bendiocarb, carbofuran, methiocarb, promecarb and propoxur is proposed. The pesticides are hydrolyzed in alkaline medium to 1-naphthol or phenolates, which are coupled with diazotized trimethylaniline (TMA) in a sodium dodecyl sulfate micellar medium to form the azo dyes. The micellar medium increased the solubility of TMA and enhanced the sensitivity. The performance of TMA was compared with that of sulfanilic acid, which is the conventional reagent used in these determinations. Although the absorbance of the azo dyes of sulfanilic acid was also enhanced in the micellar solution, the sensitivity was still greater with TMA. Further, at the pH required for the coupling reaction (9.5), the absorbance of the blank was negligible with TMA but large with sulfanilic acid. Using TMA, the limits of detection were in the range 0.2-2 micrograms cm-3. The procedure was applied to the determination of carbaryl in spiked tap, river and pond water samples and to the evaluation of various carbamates in commercial pesticide formulations.

Pesticides and cancer.

Epidemiologic evidence on the relationship between chemical pesticides and cancer is reviewed. In animal studies, many pesticides are carcinogenic, (e.g., organochlorines, creosote, and sulfallate) while others (notably, the organochlorines DDT, chlordane, and lindane) are tumor promoters. Some contaminants in commercial pesticide formulations also may pose a carcinogenic risk. In humans, arsenic compounds and insecticides used occupationally have been classified as carcinogens by the International Agency for Research on Cancer. Human data, however, are limited by the small number of studies that evaluate individual pesticides. Epidemiologic studies, although sometimes contradictory, have linked phenoxy acid herbicides or contaminants in them with soft tissue sarcoma (STS) and malignant lymphoma; organochlorine insecticides are linked with STS, non-Hodgkin's lymphoma (NHL), leukemia, and, less consistently, with cancers of the lung and breast; organophosphorous compounds are linked with NHL and leukemia; and triazine herbicides with ovarian cancer. Few, if any, of these associations can be considered established and causal. Hence, further epidemiologic studies are needed with detailed exposure assessment for individual pesticides, taking into consideration work practices, use of protective equipment, and other measures to reduce risk.

Purification and Quantitative Analysis of Veratridine and Cevadine by HPLC

As part of a study to determine the variation in the effectiveness of commercial pesticide formulations of ester steroidal alkaloids from sabadilla (Schoenocaulon officinale Grey) seeds in the integrated pest management of citrus, a method to isolate and measure large quantities of alkaloids from natural starting materials was needed. The addition of the solvent modifier sodium dodecyl sulfate (SDS) to a previously published HPLC method greatly improved peak resolution by minimizing peak tailing. The use of the non-ester alkaloid papaverine as an internal standard permitted quantification of sabadilla alkaloids by HPLC, and this modified method was then used to monitor the breakdown of cevadine and veratridine, the two most abundant sabadilla alkaloids, in aqueous solutions as a function of time and pH.

Solar photocatalytic mineralization of pesticides in polluted waters

Results are presented on the solar, titanium-dioxide-photocatalyzed degradation of pesticides in rinse waters of agricultural sprayers and in heavily polluted well water. The half-life time of solar photomineralization in the 100 ppb to 50 ppm concentration range was less than 1 h for most of the pesticides. Comparison of the reaction in open and polyethylene-film-covered vessels showed that efficient photodegradation also occured in sealed systems. Samples of polluted waters prepared from liquid commercial pesticide formulations were also purified effectively by the titanium-dioxide-catalyzed solar photo-mineralization The photodegradation of anionic detergents within the formulations was also observed. These results demonstrate the potential of solar photocatalytic oxidation in the removal of organic pollution in water and its practical value in the purification of highly polluted agricultural rinse waters.

Simultaneous Determination of Carbaryl, Chlorpyrifos, and Its Metabolite 3,5,6-Trichloro-2-pyridinol (TCP) by Derivative Spectrophotometry. Direct Determination of the Degradation Grade of a Pesticide Formulation by Measurement of TCP

The degradation grade (DG) of a commercial pesticide formulation composed of carbaryl and chlorpyrifos has been directly determined by taking the first-derivative signal at 339 nm originated by 3,5,6-trichloro-2-pyridinol (TCP), which is the major breakdown product of chlorpyrifos. Detection and determination limits of 1.3×10 -6 and 4.4×10 -6 M, respectively, have been determined by using a commercial undegraded formulation (previously 1:50 diluted). Simultaneous determination of carbaryl, chlorpyrifos, and TCP can be performed in commercial formulations up to DG values of 25%

Reusable immobilized enzyme/polyurethane sponge for removal and detoxification of localized organophosphate pesticide spills

During the course of study on immobilization of an enzyme, parathion hydrolase, that detoxifies organophosphate pesticides, a very effective and reusable cleanup sponge was developed. This sponge was made by incorporating the enzyme through free amino-acid groups into a polymerizing isocyanate-based polyurethane foam. By controlling various reaction variables, it became possible to produce an enzyme-containing foam of high liquid-retention capacity and excellent enzyme stability. This product, which should prove valuable for easy simultaneous cleanup and detoxification of small spills, was found effective for both solutions of parathion and a typical commercial pesticide formulation

Comparative studies on acylurea insect growth regulators and neuroactive insecticides for the control of the armyworm Spodoptera exempta walk

AbstractLeaf‐dip bioassays with commercial pesticide formulations were used throughout this study. Third‐instar larvae of Spodoptera littoralis were bioassayed for comparative purposes. The end‐point mortality against the third‐instar larvae (L3) of two Spodoptera exempta populations (Bangor and Gent) and a S. littoralis population (NRI) was found to occur at 72 h and 120 h for neuroactive compounds (carbamate, organophosphate and pyrethroid insecticides) and acylureas respectively. Overall, the acylureas were found to be more toxic (up to 240‐fold at the LC50 level) than the most active of the neuroactive compounds tested, the pyrethroids. This difference was greatest against S. littoralis, which was markedly less sensitive to the latter compounds. The Gent population of S. exempta was also found to be significantly less sensitive (7‐folt at LC50) to the pyrethroid, lambda‐cyhalothrin, than the Bangor strain. Two of the most toxic neuroactive and non‐neuroactive compounds, the pyrethroid, cypermethrin and the acylurea, teflubenzuron were chosen for further studies with S. exempta (Gent) and S. littoralis. Relatively little difference in the toxicity of teflubenzuron was observed against different larval instars (L2, L3 and L4) of S. exempta when compared with cypermethrin. Choice‐chamber‐experiments on feeding behaviour showed that when L3 larvae of either species were exposed to both treated and untreated leaves. teflubenzuron had no significant effect on larval distribution, the percentage of each leaf disc consumed or larval weight gain when compared with untreated controls. In contrast, a marked dose‐dependent repellent response to cypermethrin‐treated leaves was shown by S. littralis after 6 h. together with corresponding reductions in the percentage of the treated leaf consumed and in larval weight gain. Similarly, when L3 S. exempta were exposed only to pesticidetreated leaves, cypermethrin significantly reduced premoult larval weight gain, whereas tefiubenzuron had no premoult effect. However, following exposure of L3 S. exempta and S. littoralis to teflubenzuron for 48 h prior to moulting, L4 which survived the moult showed reduced weight gain compared with controls, the reduction being more pronounced on maize than on artificial diet. This antifeedant effect increased in proportion to the concentration of teflubenzuron originally administered. The effect of exposure time to teflubenzuron was examined by placing L3 S. exempta and S. littoralis on leaves treated with the approximate LC50 or LC95 dose for 6–48 h. The exposure time required to produce appreciable mortality (relative to LC values) within the treated population was found to be 24 h.

Stigmatic Surface Degeneration and Inhibition of Pollen Germination with Selected Pesticidal Sprays during Receptivity in Pecan

Commercial pesticide formulations of triphenyltin hydroxide, benomyl plus triphenyltin hydroxide, and phosalone completely inhibited pollen germination of pecan [Carya illinoensis Wangenh C. Koch] when incorporated in in vitro germination media at one-fourth to one times the recommended rates. Scanning electron microscopic evaluations of spray effects on receptive stigmatic surfaces showed varying degrees of injury, ranging from minor surface wrinkling with triphenyltin hydroxide to severe collapse and degeneration of stigma papillae with phosalone treatments. Controlled pollinations 1 hour after pesticide sprays resulted in an inhibition of pollen germination and tube growth. Water sprays followed by pollination resulted in normal pollen adherence, hydration, and germination. Chemical names used: methyl[1-[(butylamino)carbonyl]-1H-benzimidazol-2-yl]carbamate (benomyl); S-[(6-chloro-2-oxo-3-(2H)-benzoxazolyl)methyl] 0,0-diethyl phosphorodithioate (phosalone).