Anil Duhan

Quantification of flufenacet residues in soil and wheat grain

The terminal residues of flufenacet were quantified in soil and wheat grains. Flufenacet was applied at 250 and 300 g/ha on 21 and 35 days after the sowing of wheat at the Research Farm of Punjab Agricultural University, Ludhiana. Matrix solid phase dispersion (MSPD) method was used for the extraction of flufenacet from soil and grain samples. The herbicide residues were quantified using High Performance Liquid Chromatography (HPLC) equipped with UV-Vis detector and were confirmed with gas chromatographic tandem mass spectrometry (GC-MS/MS). The average recoveries of flufenacet extracted from the matrix ranged from 80.9 to 93.0% and 88.0 to 96.2% when quantified using HPLC and GC-MS/MS, respectively with relative standard deviation less than 10%. Both HPLC and GC-MS/MS offer high reproducibility, however GC-MS/MS was more sensitive having limit of detection (LOD) and limit of quantification (LOQ) as 0.001 and 0.003 μg/g, respectively. Terminal residues of flufenacet in the soil and wheat grain samples were below the detectable limit. Thus, the use of flufenacet in wheat under sub-tropical humid conditions could be considered safe.

Effect of long-term application of pretilachlor on its persistence and residues in paddy crop

ABSTRACT The effect of long-term application of pretilachlor to paddy in rice–wheat cropping system was investigated from 1997 to 2015. Additionally, in 2013, field experiment was also conducted where pretilachlor was applied to paddy field having no background of its application. The residues of pretilachlor were quantified using high-performance liquid chromatography (HPLC). The average recoveries of pretilachlor from paddy soil, paddy grain and straw samples ranged from 80.7% to 93.8% using HPLC with standard deviation less than 10%. The dissipation rate of pretilachlor in paddy soil followed first-order kinetics and half-life ranged from 9.58 to 21.19 days. In 2015, HPLC was compared with gas chromatography–tandem mass spectrometry (GC–MS/MS) for quantification of residues. Average recoveries of pretilachlor using GC–MS/MS from paddy soil, paddy grain and straw samples ranged from 81.4% to 98.3% with standard deviation less than 10%. Both HPLC and GC–MS/MS offered high reproducibility; however GC–MS/MS was more sensitive and the limit of detection was 3.0 and 1.0 ng g−1 for HPLC and GC–MS/MS, respectively. At harvest, the residues of pretilachlor in the paddy soil and crop were below the maximum residue limit and no dangerous accumulation was observed after its prolonged application.

Determination of dimethoate, lambda-cyhalothrin and malathion residues in guava fruits using GCMS-tandem mass spectrometry

Tephritidae fruit flies are considered key insect pest in guava which cause yield loss and degradation of quality. A trial was conducted in guava orchard during 2013 to study residue dissipation rate of two organophosphates, dimethoate and malathion and one synthetic pyrethroid insecticide, lambda-cyhalothrin. The insecticides were applied at recommended and double of the recommended dose on semi-ripe guava fruits. The fruits were randomly sampled at different time intervals, i.e. 0 (2 h), 3, 7 and 10 days after spray. After extraction and clean-up, the residues were estimated using GCMS tandem mass spectrometry. The half-life values at single and double dose applications were found to be 6.72 and 8.15 days for dimethoate, 4.41 and 4.71 days for lambda-cyhalothrin and 3 and 3.3 days for malathion. The residues reached below maximum residue limit (MRL) on zero day following recommended dose application of all insecticides. In double dose application, residues reached below MRL on zero day in malathion and lambda-cyhalothrin and on 3rd day in dimethoate. Washing of guava fruits removed 42.9 and 45.2% dimethoate, 33 and 36.8% lambda-cyhalothrin, 50 and 54.5% malathion residues at single and double dose applications in 0 day samples. Lambda-cyhalothrin was found most effective followed by dimethoate and malathion for controlling fruit fly in guava.

Behaviour of endosulfan in cabbage (Brassica oleracea L.)

Residue levels of endosulfan were determined in cabbage heads after being sprayed with a formulation containing the insecticide and upon storage at room temperature (15–27°C) and in a refrigerator (2–5°C). The half-life was calculated to be 4.8 and 5.5 days. Peeling removed the residues by 92%. Similarly, washing and washing followed by cooking removed 72% and 97% residue in cabbage stored at room temperature. These treatments were slightly less effective for samples stored in a refrigerator. Household processes such as peeling, washing, and washing followed by cooking should be regular practice before the vegetables are used.