Dissipation pattern of flubendiamide in/on brinjal (Solanum melongena L.).

Residues of flubendiamide and desiodo flubendiamide were studied following three applications of flubendiamide 480 SC at 7 days interval at 90 and 180 g a.i. ha(-1) in/on brinjal fruits. An average initial deposit of 0.33 and 0.61 mg kg(-1) of flubendiamide was observed respectively after application at single and double dosages. The residues of flubendiamide dissipated quickly at both the dosages, and after 3 days, the extent of dissipation was found to be about 76% and 79% at the single and double dosages, respectively. Brinjal fruit samples analysed at different time intervals did not show the presence of desiodo flubendiamide. The half-life of flubendiamide was observed to be 0.62 and 0.54 days at single and double dosages, respectively. The limit of determination of flubendiamide and desiodo flubendiamide was observed to be 0.05 mg kg(-1). Soil samples analysed after 15 days of the last application did not reveal the presence of flubendiamide and desiodo flubendiamide at their determination limit of 0.05 mg kg(-1). An assessment of the total intake of flubendiamide resulting through the consumption of brinjal fruits and its comparison with acceptable daily intake seems to be quite safe from consumer point of view.

Direct estimation of carbaryl by gas liquid chromatography with nitrogen phosphorus detection.

A simple and efficient analytical method was standardized for the estimation of residues of carbaryl in various substrates comprising grape berries, kinnow pulps, kinnow rind and soil. The samples were refluxed using mixture of methanol: 0.5 N HCl (1:1 v/v); diluted with brine solution, partitioned into chloroform and dried over anhydrous sodium sulfate. Further the samples were treated with anhydrous magnesium sulfate and primary secondary amine. Final clear extracts were concentrated under vacuum and reconstituted the volume into acetone. The residues were estimated directly on gas liquid chromatograph equipped with nitrogen phosphorus detection system equipped with a capillary column packed with 5 % diphenyl 95 % dimethyl polysiloxane non-polar phase. A consistent recovery from 82 % to 97 % for carbaryl was observed when samples were spiked at levels ranging from 0.05 to 1.00 mg kg(-1). The limit of quantification of the method was worked out to be 0.05 mg kg(-1) for grape berries, kinnow pulp, kinnow rind and soil.

Persistence of trifloxystrobin and tebuconazole on grape leaves, grape berries and soil.

Following four foliar applications of Nativo 75 WG (trifloxystrobin 25% + tebuconazole 50%) on grapes @ 175 and 350 g/ha, resulting in active applications of trifloxystrobin @ 43.75 and 87.5 g a.i./ha and that of tebuconazole @ 87.5 and 175 g a.i./ha, the average initial deposits of trifloxystrobin were observed to be 7.76 and 15.53 mg/kg, respectively, at single and double the application rates. These residue levels dissipated to >85% after 10 days of its application at both the dosages. Similarly, the average initial deposits of tebuconazole were observed to be 13.84 and 26.55 mg/kg at single and double the application rate, respectively. These residue levels dissipated to >90% after 10 days of application at both the dosages. The half-life (t(1/2)) periods of trifloxystrobin on grape leaves were observed to be 2.92 and 3.48 days at single and double application rates, respectively, whereas these values were 2.68 and 3.96 days for tebuconazole. Ripe grape berries and soil samples collected at harvest which happened to be 34 days after the last application, did not show the presence of residues of trifloxystrobin and tebuconazole at their determination limit of 0.01 and 0.02 mg/kg, respectively.

Persistence of imidacloprid on grape leaves, grape berries and soil.

Residues of imidacloprid were estimated in grape leaves, grape berries and soil following four applications of Confidor 200SL at 400 and 800 mL ha(-1) using 1,000 L water. The average initial deposits of imidacloprid on grape leaves were found to be 10.01 and 16.97 mg kg(-1) at single and double dosages, respectively. These residues of imidacloprid dissipated to be the extract of 98.8% and 97.0%, respectively, at single and double dosages in 15 days, with half-life period of 2.35 and 2.97 days. Residues of imidacloprid in grape berries at harvest time were observed to below determination limit of 0.05 mg kg(-1) at single dose and 0.06 mg kg(-1) at double dose. However, acceptable daily intake (ADI) of imidacloprid is 0.06 mg kg(-1) body weight day(-1), which means an adult of 60 kg and a child of 10 kg can safely tolerate intake of 3,600 and 600 microg imidacloprid, respectively, without any appreciable risk to their life. Assuming consumption of 200 g grape berries contaminated at 0.06 mg kg(-1), it will lead to an intake of only 12 microg of imidacloprid, which is quite safe for a child as well as for an adult. Hence, the use of imidacloprid on grape crop seems to be toxicologically acceptable.

Simple and efficient method for the estimation of residues of flubendiamide and its metabolite desiodo flubendiamide.

An analytical method was standardized for the estimation of residues of flubendiamide and its metabolite desiodo flubendiamide in various substrates comprising cabbage, tomato, pigeonpea grain, pigeonpea straw, pigeonpea shell, chilli, and soil. The samples were extracted with acetonitrile, diluted with brine solution, and partitioned into chloroform, dried over anhydrous sodium sulfate, and treated with 500 mg of activated charcoal powder. Final clear extracts were concentrated under vacuum and reconstituted into HPLC grade acetonitrile, and residues were estimated using HPLC equipped with a UV detector at 230 lambda and a C18 column. Acetonitrile/water (60:40 v/v) at 1 mL/min was used as mobile phase. Both flubendiamide and desiodo flubendiamide presented distinct peaks at retention times of 11.07 and 7.99 min, respectively. Consistent recoveries ranging from 85 to 99% for both compounds were observed when samples were spiked at 0.10 and 0.20 mg/kg levels. The limit of quantification of the method was worked out to be 0.01 mg/kg.