Shozo Endo

Adsorption and desorption characteristics of several herbicides on sediment

The objective of this study was to clarify the adsorption and desorption characteristics of several herbicides in sediment. Five herbicides, esprocarb, thiobencarb, dimethametryn, pretilachlor, and simetryn were examined in this study. The adsorption ratio on the sediment increased in the following order: pretilachlor < dimethametryn < simetryn < thiobencarb < esprocarb. On the other hand, the adsorption ratio on the sediment without organic matter increased in the following order: thiobencarb < esprocarb < pretilachlor < dimethametryn < simetryn. Furthermore, the amounts of simetryn, dimethametryn, and pretilachlor adsorbed on the sediment without organic matter increased, while those of esprocarb and thiobencarb decreased in comparison to the original sediment. These results strongly suggested that the mineral surface in the sediment was very important as the adsorption site for the herbicide, especially in the case of simetryn, dimethametryn, and pretilachlor. All the adsorption and desorption data fitted well with the Freundlich equation. The hysteresis in the adsorption-desorption phenomena in the sediment was observed for all the herbicides, and it was affected by the organic matter in sediment, especially in the case of dimethametryn and pretilachlor.

Evaluation of performance of a commercial monoclonal antibody-based fenitrothion immunoassay and application to residual analysis in fruit samples

The performance of a commercially available enzyme-linked immunosorbent assay (ELISA) kit containing highly sensitive monoclonal antibodies against fenitrothion was assessed. The experimentally estimated dynamic range (0.087 to 2 ng/g) agreed with that established by the kit manufacturer (0.075 to 1 ng/g). The linearity of the standard curve produced for the kit-assembled standard solutions (slope = -0.3829) agreed with that of the curve produced for the self-made standard solutions (slope = -0.3619). The sensitivity (I50 value) and the limit of detection for the kit were 0.23 and 0.033 ng/g, respectively. Selectivity of the ELISA indicates that the monoclonal antibody can readily distinguish the target pesticide from other structurally related analogs and some metabolites (oxon forms), with the exception of ethyl O-(p-nitrophenyl) phenyl phosphonothionate (EPN), parathion-methyl, and parathion. Methanol was the best organic solvent for the kit, with optimal sensitivity observed at a final concentration in the well of 10% (vol/vol) or less. Matrix interferences were minimized by direct dilution with water (60-fold) of the methanolic extracts fromapple and peach samples. To extract fenitrothion from these two agricultural products as simply and rapidly as possible, three extraction methods were used. The extraction method that involved shaking by hand for 3 min was the best among the three methods. High recovery percentages (116.6% for apple and 110.8% for peach) were obtained. Validation of the ELISA method was carried out using the gas chromatography-mass spectrometry method, resulting in high recovery and close correlation of results (r > 0.95). These findings strongly suggest that the ELISA kit may be routinely employed for on-site fenitrothion screening of fruit samples.

Evaluation method for susceptibility of Thrips palmi to several insecticides.

1) DMTP水和剤・BPMC乳剤を供試してミナミキイロアザミウマの薬剤感受性の検定を試みた。2) 2齢幼虫をナスの葉片と共に薬液に浸漬した後,インデン葉に移して飼育する方法は,操作による死亡が多く適当な方法ではなかったが,浸漬したナス葉片で引き続き1日問飼育し死虫率を調査する方法は操作による死亡もなく,有効であった。3) 野菜試験場久留米支場飼育系統を用い,本法により求めたDMTP水和剤,BPMC乳剤のLC 50値はそれぞ302ppm,333ppmであった。4) 水に対する溶解度の高いオキサミル粒剤を供試して,水耕したキュウリ苗を用い,浸透移行性薬剤に対する感受性検定を試みた。5) 第1本葉展開期に薬液に浸根すると,葉内のオキサミル濃度は1日後に薬液濃度とほぼ等しくなり,2日後には約2倍,5日後には約4倍になった。葉内濃度は薬液濃度と吸水量に比例した。6) 浸根1日後の葉片で2齢幼虫・1齢幼虫を1日間飼育し,死虫率を調べたところ,いずれも薬液濃度に見合った死虫率が得られ,本法は個体群間の薬剤感受性比較に有効と考えられた。7) オキサミル薬液の2齢幼虫,1齢幼虫に対するLC50値はそれぞれ117ppm,86ppmであった。