Study On Extraction, Separation And Detection Of Trichlorfon Residue And Capillary Electrophoresis Separation And Detection Of Heavy Metal

Residue of pesticides found in food,drinking water and environmental bad substance has raised much concern from the general public in recent years.In order to protect persons' healthy,the maximum levels(MRL) of bad substance in food were constituted by WHO/FAO-CAC.It is important to exploit simply,fast,efficient pre-treatment technologies for samples and high sensitive,high selective detections technologies accord with regulation.The thesis includes two parts:In chapterâ… :Three different detection methods were used to analyse residues of trichlorfon in vegetable sample.1.Trichlorfon has the capacity to catalyze the oxidation of benzidine(4, 4'-diamino-biphenyl) to 4-amino-4'-nitro biphenyl in the presence of sodium perborate.The product of the catalyzed reaction was validated by LC-MS method.Reversed-phase high performance liquid chromatography with 365 nm UV detection was used for separation and quantification of 4-amino-4'-nitro biphenyl.It can be proven there is a linear relationship between the peak areas of 4-amino-4'-nitro biphenyl and trichlorfon in the concentration range of 0.02-0.5 mg/L(r=0.9988).Limit of detection was 2.0μg/L.A method for the indirect determination of trichlorfon using HPLC was developed based on catalytic effect of trichlorfon.Method validation was performed on samples spiked at three levels(0.5,1.0, 1.5 mg/kg),the recoveries ranged from 67.5 to 82.1%,with relative standard deviations between 4.5 and 7.3%.0.01 mol/L sodium dodecyl sulphate(SDS) solution Was used to extract trichlorfon from samples and solid-phase extraction was used to isolate and concentrate trichlorfon in SDS solution.The recoveries of trichlorfon obtained with percolating the extraction through a SPE system were essentially in agreement with those obtained by liquid-liquid extraction.This new isolation technique decreases the use of toxic solvents and satisfies the requirements of Green Analytical Chemistry.2.On basis of the former method,we have improved on pre-treatment technologies.The sample is extracted with a cloud point extraction method and then detected using a high performance liquid chromatography with ultraviolet detection(HPLC-UV).Under the optimum experimental conditions,there was a linear relationship between trichlorfon in the concentration range of 0.01-0.2 mg/L and the peak areas of 4-amino-4'-nitrobiphenyl(r= 0.996).Limit of detection was 2.0μg/L,recoveries of spiked water and cabbage samples ranged between 95.4-103%and 85.2-91.2%,respectively.Compared with the former method,recoveries were improved 10-20%.It was proved that the cloud point extraction (CPE) method was simple,cheap,and environment friendly than extraction with organic solvents and had more effective extraction yield.3.According to the fact that trichlorfon had strong catalytic effect on the decolour reaction between sodium perborate oxidation benzidine,we found that there was a linear relationship between the joining concentration of trichlorfon and the decreasing concentration of benzidine after reaction.Separation and direct detection of benzidine in 4.38 cm separation channel made of glass with end-column amperometric detection at a carbon electrode was developed.Under the optimum experimental conditions,there was a linear relationship between trichlorfon in the concentration range of 0.01-0.5 mmol/Land the peak areas of benzidine(r=0.9934).Limit of detection was 5μmol/L.Variances influencing the separation efficiency and amperometric response,including concentration and pH of buffer solution,injection time,separation voltage or detection potential are assessed and optimized.In chapterâ…¡:Heavy metals were detected with glass capillary electrophoresis.Separation and direct detection of Cd²⁺,Zn²⁺,Cr³⁺and Hg²⁺in 4.38 cm separation channel made of glass with end-column amperometric detection at a carbon electrode was developed.The migration time is less 200 s and the reproducibility of migration of Zn²⁺ is satisfactory with relatime standard deviation(RSD) of 1.121%in 15 successive injections. The limits of detection of Cd²⁺,Zn²⁺,Cr³⁺and Hg²⁺ are estimated to be 2.5,5.8,3.5 and 1.5μmolL^-1 at S/N=3,respectively.Variances influencing the separation efficiency and amperometric response,including concentration and pH of buffer solution,injection time, separation voltage or detection potential are assessed and optimized.The method has been applied to the determination of Cd²⁺ in soil with satisfactory result.