Study On The Simultaneous Determination Of Multiresidual Pesticides In Vegetables And Fruits By High Performance Liquid Chromatography

In this study, a high performance liquid chromatographic method for the simultaneous determination of 12 pesticides in vegetable and fruit samples was developed and evaluated. The 12 pesticides were: diazinon, omethoate, parathion-methyl , phenthoate , phoxim , pendimethalin , fenpropathion cypermethrin, deltamethrin, fenvalerate, fluvalinate, permethrin. The analytical procedure involved in ultrasonic extraction with ethyl acetate, purification using a Florisil SPE(solid phase extraction)column (6ml,1000mg) and n-hexane-dichloromethane(l:l,v/v). The elute fraction was blown to driness under the stream of nitrogen and the residue was dissolved in 0.10ml of methanol, followed by separation and quantitative analysis by reverse phase HPLC using gradient elution for the baseline separation of the 12 pesticides and programmed ultraviolet wavelength shift detection in 32min. Ethyl acetate was selected as extraction solvent. The chromatographic conditions, including column temperature,mobile phase,flow rate and ultraviolet detection wavelength were investigated. The optimized chromatographic conditions were: analytical column, phenomenex C18, 5μm, 250×4.6mm; column temperature, 25℃; mobile phase, acetonitrile-water; flow rate, 1.2ml/min; gradient elution from 0 min at 50% acetonitrile-water to 10min at 64% acetonitrile-water, from 10.00 min at 64% acetonitrile-water sharply to 10.01min at 67%, finally at 10.01min changed into 94% acetonitrile until35.00min when returned to 50% of acetonitrile-water.Wavelength shifts were adopted to achieve most sensitive ultraviolet wavelength for lower resolution paired peaks. We set the ultraviolet wavelength at 200nm at the beginning, and switched to 272nm at lO.OOmin, then 230nm at 13.00min, 289nm at 16.00min, 238nm at 22.00nm, and finally 206nm at 25.80min. The detection limit of the method was 2.65ug/kg for diazinon, 0.14ug/kg for omethoate, 0.73 ug/kg for parathion-methyl, 1.19fag/kg for phenthoate, 0.88ug/kg for phoxim,0.39ug/kg for pendimethalin, 0.29 ug/kg for fenpropathion, 0.50ug/kg for cypermethrin, O.38ug/kg for deltamethrin, 0.33ug/kg for fenvalerate, 0.23 ug/kg for fluvalinate, and 0.30 ug/kg for permethrin respectively. The relative standard deviations ranged from 0.99% to 6.85%. The average recoveries for the spiked fruit samples ranged from 65.9%-103.0%, and for the spiked vegetables from 62.8% to 111.5%. The method was applied to determining vegetables and fruit in total of 40 samples. It was concluded that this method was rapid, accurate, sensitive and repeatable for the determining trace pesticides in vegetable samples and fruit samples...