Method validation for simultaneous determination of four neonicotinoids in vegetables by liquid chromatography.

Pesticides are widely employed to boost the production of vegetable crops, but their indiscriminate application leaves residue in the crops for long, even after harvesting. Among pesticides, neonicotinoids are the most commonly applied group of insecticides which are used on vegetables to defend against a variety of sucking pests. The purpose of this study was to validate an analytical approach focused on QuEChERS extraction for the validation and simultaneous determination of residues of four neonicotinoids (imidacloprid, clothianidin, acetamiprid and thiamethoxam) in six diverse crops such as cucumber, brinjal, tomato, beans, cabbage, and cauliflower. Insecticides were quantified using high-performance liquid chromatography (HPLC) fitted with a UV-Vis detector. Specificity, linearity, precision, accuracy, limit of detection, and the limit of quantification were all considered for validation. The fortification of the vegetables was done at three different levels (0.2, 0.3 and 0.5 µg mL-1), for confirming the validity of the method adopted. The results demonstrated adequate recoveries ranging from 77.5 to 96.4% and good accuracy (RSDs between 0.3 and 8.9%). For all the insecticides, the approach had good linearity with R2 ≥ 0.99. The limit of detection (LOD) and the limit quantification (LOQ) levels of all the four analytes were 0.05 µg mL-1 and 0.2 µg mL-1, respectively. The validation characteristics of the devised method are satisfactory in terms of specificity, linearity, precision, accuracy, limit of detection and limit of quantification and thus can be successfully employed for simultaneous determination of the neonicotinoids.

Residue Behavior of Clopyralid Herbicide in Soil and Sugar Beet Crop under Subtropical Field Conditions.

ABSTRACT: Sugar beet is a major crop for the sugar industry. With growing awareness of unsystematic use of pesticides, health problem, and environmental issues, assessment of pesticide residues in soil and crops has become necessary. Studies of subtropical conditions on dissipation and residue analysis of clopyralid have not yet been reported. Therefore, dissipation kinetics and terminal residues of clopyralid for two cropping seasons in the soil and the sugar beet crop were studied under field conditions. An experiment was laid out in a randomized block design, and a herbicide was applied as a postemergent. Clopyralid was extracted from the matrix by basic water, subjected to solid phase extraction cleanup, and quantified by high-pressure liquid chromatography-UV. The method was validated, and recovery percentage of pesticide ranged from 81 to 88, 77 to 85, 78 to 86, and 89 to 94% in the soil, sugar beet roots, sugar beet leaves, and water, respectively. After application in the soil, clopyralid dissipated rapidly following monophasic first-order kinetics, with a half-life of 13.39 days. Limits of detection and quantitation were 0.007 and 0.02 µg g-1, respectively. Clopyralid does not persist long in soil, and residues were below the European Union's maximum residue levels (0.5 mg kg-1) in the roots and leaves of sugar beet. Residues were also not detected in the groundwater. It can be concluded that clopyralid could be considered a safe herbicide from the environmental aspect due to its nonpersistence and that it would not have an adverse effect on human or animal health.

Degradation of Fenoxaprop-p-Ethyl and Its Metabolite in Soil and Wheat Crops.

The dissipation kinetics of fenoxaprop-p-ethyl and its metabolite (fenoxaprop acid) at two application rates under wheat field conditions for two seasons was investigated. Herbicides were extracted by solid liquid extraction, cleaned up, and analyzed by a liquid chromatography-UV detector. Dissipation followed first-order kinetics; in soil, fenoxaprop-p-ethyl dissipated rapidly with an average half-life of 1.45 to 2.30 days, while fenoxaprop acid persisted for more than 30 days. The method was validated in terms of accuracy, linearity, specificity, and precision. Linearity was in the range of 5 to 5,000 ng, with a limit of detection (LOD) of 2 and 1 ng for fenoxaprop-p-ethyl and fenoxaprop acid, respectively. The quantitation limits in soil, grain, and straw were 5, 8, and 10 ng g-1 for fenoxaprop-p-ethyl and 5, 10, and 10 ng g-1 for fenoxaprop acid, respectively. Recovery in soil, grains, and straw ranged from 85.1 to 91.25%, 72.5 to 84.66%, and 77.64 to 82.24% for fenoxaprop-p-ethyl and 80.56 to 86.5%, 78 to 81.88%, and 75.2 to 79.68% for fenoxaprop acid, respectively. At harvest, no detectable residues of fenoxaprop-p-ethyl or acid were observed in soil, wheat grain, and straw samples. Owing to the short persistence under field conditions, fenoxaprop-p-ethyl is safe for use because parent and metabolite residues were below the European Union maximum residue limit and would not pose an adverse effect on the environment and human or animal foods.

Kinetics of diuron under aerobic condition and residue analysis in sugarcane under subtropical field conditions.

The phenylureas group includes persistent herbicides which are major pollutants to soil and water. Dissipation kinetics of diuron in different soils under sugarcane field conditions was investigated. Diuron was extracted with acetone and florisil solid phase extraction clean-up and characterized by high-performance liquid chromatography-UV. Diuron persisted for more than 100 days and dissipation followed monophasic first-order kinetics. Persistence was more in sandy loam compared to silty clay loam soil. Half-life of diuron in silty clay loam soil was 22.57 and 32.37 days and in sandy loam was 28.35 and 43.93 days at 2 and 4 kg ha-1applications, respectively. Average recovery in soil, bagasse, leaf-straw and juice ranged from 75.95% to 84.20%, 80.15% to 89.35%, 77.46% to 86.19% and 81.88% to 92.68%, respectively. The quantitation limits for soil, bagasse, leaf-straw and juice were 0.01, 0.03, 0.04 µg g-1 and 0.008 µg mL-1, respectively. Application of diuron inhibited growth of soil microbes initially but they recovered later. At harvest, diuron residues were below maximum residue limits in all samples. The study revealed that under subtropical conditions, diuron is safe for use in weed management and would not pose any residual/environmental problem and that sugarcane crop could be used safe for human/animal consumption.

Dissipation of Pendimethalin in Soybean Crop Under Field Conditions.

Persistence of pendimethalin was studied in soil, soybean pods, straw and water under field conditions. Pendimethalin was applied at 1 and 2 kg a.i. ha(-1). Residues in soil were detected up to 60 and 90 days at the recommended and double dose, respectively. Dissipation followed first order kinetics and was accounted for by a biphasic pattern. The half-life for the initial phase and later phase was 12.73 and 26.60 days, respectively, for recommended and 7.25 and 37.91 days, respectively, for double dose. The limit of quantification was 0.005 µg g(-1) of sample. Percent recovery from soil, oil, defatted cake, straw and water samples fortified with 0.01-1.0 mg kg(-1) varied from 84.5 %-89.6 %, 84.6 %-88.7 %, 79.4 %-86.0 %, 78.2 %-85.6 % and 90.2 %-93.0 %, respectively. At harvest, pendimethalin residue in soybean pods, straw, and soil were below detectable limits. No residues of pendimethalin were detected in ground water. Current application of pendimethalin in the environment is not expected to cause adverse health effects form the consumption of soybeans.

Development and Validation of GC-ECD Method for the Determination of Metamitron in Soil.

This paper aims at developing and validating a convenient, rapid, and sensitive method for estimation of metamitron from soil samples.Determination andquantification was carried out by Gas Chromatography on microcapillary column with an Electron Capture Detector source. The compound was extracted from soil using methanol and cleanup by C-18 SPE. After optimization, the method was validated by evaluating the analytical curves, linearity, limits of detection, and quantification, precision (repeatability and intermediate precision), and accuracy (recovery). Recovery values ranged from 89 to 93.5% within 0.05- 2.0 µg L(-1) with average RSD 1.80%. The precision (repeatability) ranged from 1.7034 to 1.9144% and intermediate precision from 1.5685 to 2.1323%. Retention time was 6.3 minutes, and minimum detectable and quantifiable limits were 0.02 ng mL(-1) and 0.05 ng g(-1), respectively. Good linearity (R (2) = 0.998) of the calibration curves was obtained over the range from 0.05 to 2.0 µg L(-1). Results indicated that the developed method is rapid and easy to perform, making it applicable for analysis in large pesticide monitoring programmes.

Degradation kinetics of anilofos in soil and residues in rice crop at harvest.

BACKGROUND: Pesticides used on rice, which is widely grown in India in the rainy season, must be investigated for the persistence and magnitude of their residues in the crop and soil to ensure human and environmental safety. Anilofos is widely used in rice, and its persistence and dissipation behaviour in soil and rice was investigated in field trials under subhumid and subtropical conditions. RESULTS: The persistence of anilofos in soil, husk, grain and rice straw was evaluated at two application rates (0.4 and 0.8 kg AI ha(-1) ) by RP-HPLC. In soil, residues were detected up to 45 and 75 days after application at 0.4 and 0.8 kg AI ha(-1) respectively. No residue was observed in soil, husk, grain or rice straw at the time of harvest at either application rate. Detector response was linear within the concentration range 0.1-5.0 µg mL(-1) at 2.22% standard deviation. The limit of detection was 0.003 µg mL(-1) , and the limit of quantification of the method for soil, straw, grain and husk was 0.007, 0.01, 0.008 and 0.01 µg g(-1) respectively. CONCLUSION: The dissipation of herbicide from soil appeared to occur in a single phase and conformed to pseudo-first-order kinetics. The calculated half-life values of anilofos residue in soil were 13 days for the lower rate of application (0.4 kg AI ha(-1) ) and 15.5 days for the higher rate (0.8 kg AI ha(-1) ). Anilofos residues were below the maximum residue level in soil, husk, rice grain and rice straw at harvest.

Determination and method validation of metamitron in soil by RP-HPLC.

A simple, rapid and economical method was developed and validated for the determination of metamitron using UV detector with RP-HPLC. Study of metamitron in soil was carried out. The compound was extracted from soil by methanol and clean-up was done on C-18 SPE column. Recovery ranged from 90.75 % to 94.05 % within 0.1-2.0 µg g(-1) and RSD 1.80 %. Retention time was 3.8 min and limit of detection and limit of quantification were 0.001 and 0.008 µg g(-1). The results indicated that the reported method could meet the requirement for the analysis of metamitron in trace amounts.

Dissipation studies of fentrazamide (YRC-2388) in soil under anaerobic condition.

Dissipation of fentrazamide in soil and water under flooded (anaerobic) conditions was studied. Fentrazamide was applied to soil at 100 g ha(-1). Soil was extracted with 0.1 N HCl : acetone (1 : 1 v/v) followed by partition and cleanup with silica SPE. Separation was achieved in an ODS-II column with a mobile phase of acetonitrile : water (70 : 30 v/v) and detection at 214 nm. Recovery of fentrazamide varied from 75.2-90.4% and 89.9-97.8% in soil and water, respectively. Fentrazamide dissipated rapidly and fentrazamide residues were not detected after 100 and 35 days of application in soil and water, respectively. Half life in soil and water was 9.06 and 3.66 days, respectively. Dissipation followed monophasic first order kinetics pattern. No fentrazamide was detected in soil, rice grain and rice straw at harvest of crop. Calibration curves for quantification were linear and relative standard deviation (RSD) was 1.78%. LOD for instrument was 0.002 µg mL(-1) and LOQ for methods were 0.005 µg g(-1) for soil and water.

Degradation of fentrazamide herbicide in soil under aerobic condition.

Dissipation of fentrazamide in soil under aerobic conditions was studied. Fentrazamide was extracted with 0.1 N HCl: acetone (1:1 v/v) followed by partition and cleanup. Separation was done on ODS-II column with mobile phase acetonitrile: water (70:30 v/v). Recovery varied from 74.51 % to 90.10 % percent in soil. Dissipation followed first order kinetics with monophasic pattern. Half life in soil was 9.02 days. Calibration curves were linear over the range of 0.05-1.00 µg mL(-1) and RSD was 1.82 %. LOD and LOQ were 0.002 and 0.005 µg g(-1) for soil. No residues in soil and crop were observed at harvest.

Insect growth regulatory activity of Vitex trifolia and Vitex agnus-castus essential oils against Spilosoma obliqua.

Essential oils of Vitex trifolia and Vitex agnus-castus were evaluated against Vth instar larvae of Spilosoma obliqua, when applied topically on the dorsal side of mesothoracic region, for insect growth regulatory activity. This treatment caused extended larval period and pupal period, increase in larval mortality and adult deformity and decrease in adult emergence, fecundity of female and egg fertility of test insect.