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Study on Residual Determination and Degradation of Abamectin in Cabbage and Soil

Author: DengLiGang
Tutor: GengYue
School: Shandong Normal University
Course: Cell Biology
Keywords: abamectin cabbage soil residue LC-MS-MS
CLC: S481.8
Type: Master's thesis
Year: 2009
Downloads: 148
Quote: 1
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Abstract

Abamectin is macrolides antibiotics isolated from a fermentation broth of the soil actinomycete,Streptomyces avermitilis.Avermectin B1a is its main active component. Abamectin comprises at least 80% avermectin B1a and not more than 20% avermectin B1b,and for this reason the avermectin B1a component is considered as the target analyte in this study. Abamectin is potent insecticide,acaricide and antiparasitics used on a variety of agricultural crops as well as livestocks. Because its dosage is small and low-residual. Ultraviolet detector coupled with HPLC couldn’t fit for the low-level residue measurement,and yet Liquid chromatography-fluorescence detector requires derivatization during sample preparation and is restricted by stringent derivatization conditions.As a result,its repeatability and reproducibility are not good enough.So a new method for the determination of abamectin in cabbage and soil by ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS-MS),and degradation dynamics and final residue of abamectin in cabbage and soil was studied, which could provide scientific basis for evaluating the safety of abamectin in environment and establishing secure,reasonable using guideline of abamectin in cabbage.The analytical method was developed. The samples were extracted with acetonitrile, then concentrated and cleaned up by solid phase extraction (SPE) with a NH2 cartridge, separated by LC with gradient elution,and detected by tandem mass spectrometry with electrospray ionization in positive mode(ESI+).Experimental results indicated that the calibration curve of abamectin was well linear and its correlation coefficient was 0.9998 from 1μg?L-1 to 200μg?L-1.Cabbages and soils were spiked with abamectin at 1,10 and 100μg?kg-1 levels.The recoveries of abamectin in cabbage ranged from 75.4% to 90.0%, and the relative standard deviation(RSD) was 3.8%~ 5.2%.The recoveries in soil ranged from 77.4% to 109.7% ,and the RSD was 4.3%~5.7%.The quantification limit was found to be 1μg?kg-1. The method was sensitive,accurate and selective without interference and suitable for the determination and confirmation of abamectin residue in vegetables as well as fruits.Using UPLC-MS-MS method determined the abamectin residues in cabbage and its soil samples which came from field trial.The results showed that the degradation rate of abamectin in cabbage and soil samples followed the first-order kinetics equation C=C0?e-kt .The degradation rate of abamectin in cabbage is quicker than that in soil.The half-lives of abamectin were 1.52~1.89 days in cabbage,and 2.01~2.23 days in soil.Abametin is easily degradable pesticide.The results of final residual trial revealed that when the cabbage was sprayed at 1~2 times successively at the recommended dosages(10.8g ai·hm-2) and the higher dosages(16.2g ai·hm-2), The residues in cabbage were lower than 0.01mg?kg-1 after 7 days treatments and hadn’t been detected after 14 and 21days respectively, and the residues in soil were between 1.72μg?kg-1 and 5.94μg?kg-1 after 7 days, and hadn’t been detected after 14 and 21days.Based on the results of the field results and maximum residue limit(MRL) which is according to China current standard or refers to other international countries or organizations, the conclusion was that the cabbage was edible safely after 7 interval days if the cabbage was sprayed 1 time at the recommended dosage(10.8g ai·hm-2) during the growth season of cabbage.

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