| Dynamic microwave-assisted sample pretreatment can be divided into the dynamic microwave-assisted extraction(DMAE)and the dynamic microwave-assisted leaching(DMAL).For DMAE,the extraction solvent can be transferred out quickly and samples are always extracted by fresh extraction solvent,so the mass transfer efficiency can be improved.In addition,the DMAE can be coupled with other sample pretreatment techniques easily and has high sample throughput,which is helpful to improve the efficiency of pretreatment.So far,DMAE has been widely applied for the analysis of pesticides residue.For DMAL,the release of metal elements relies on the use of diluted acid instead of concentrated acid.Application of DMAL to the analysis of heavy metal has many advantages such as the fast,simple and mild operation of sample pretreatment and the high sample throughput.In this paper,based on the DMAE device developed by our laboratory,we firstly coupled the DMAE method with other sample pretreatment techniques for the extraction,cleanup and enrichment of pesticides in soil and rice samples,and subsequently we employed the device to leach five heavy metal elements in purified cotton textile.The main contents are as follows:1.A multi-throughput DMAE coupled with salting-out-assisted liquid-liquid extraction method was developed to analysis of chlorpyrifos in soils.First,the chlorpyrifos was extracted with acetonitrile aqueous.With the assistance of salting-out reagent,the obtained extract was separated into an acetonitrile phase and an aqueous phase,and the acetonitrile phase was concentrated for the determination by LC-MS/MS.The experimental parameters were optimized and the optimum conditions were as followed: extraction solvent,acetonitrile aqueous(50%,v/v);volume of receiving extract,12 m L;extraction solvent flow-rate,2.0 m L min-1;salting-out reagent,ammonium acetate;ammonium acetate amounts,1.5 g.The limits of detection(0.17 ng g-1)and quantification(0.5 ng g-1)for chlorpyrifos were obtained.The recoveries of chlorpyrifos for the spiked soil samples were ranged from 90.0% to 100.5%,with relative standard deviations in the range of 1.3% to 5.7%.The proposed method was used for the analysis of chlorpyrifos in different soil samples and satisfactory results were obtained.Compared with reported method,the proposed method can reduce solvent consumption and simplify the operation procedure.2.A multi-throughput DMAE coupled with matrix solid phase dispersion method was developed to the anaysis of abamectin and chlorfenapyr in rice.In the proposed method,microwave energy was introduced into the elution process of MSPD and therefore improved the extraction efficiency.The obtained extract was concentrated for the determination by LC-MS/MS.Different parameters affecting the extraction efficiency were studied and optimized and the optimum conditions were:dispersing sorbent,basic alumina;ratio of dispersing sorbent to sample,2:1;extraction solvent,acetonitrile;volumes of extraction solvent,7 m L;flow rate of extraction solvent,2 m L min-1;microwave power,600 W.Under optimal conditions,the interference in rice extract were removed effectively,moreover,the extraction and clean-up were combined in a single step and 15 samples were treated simultaneously within 4 min.Low limits of detection(0.76 ng g-1)for chlorfenapyr and abamectin were obtained.The RSDs of intra-and inter-day were in the range of 2.6 to 8.1 %.The recoveries of chlorfenapyr and abamectin from rice samples at spiking levels of 5,50 and 100 ng g-1 were 92.1-96.5 % and 88.6-91.0 %,respectively.Finally,the proposed method was successfully applied to analyze chlorfenapyr and abamectin in six rice samples,and satisfactory results were obtained.3.A multi-throughput dynamic microwave-assisted leaching coupled with inductively coupled plasma optical emission spectrometry(ICP-OES)method was developed to the leaching and determination of Cr,Cd,Cu,Pb and Ni in purified cotton textile.The dilute nitric acid was used as the leaching reagent and therefore the obtained leachate can be directly used for ICP-OES detection after simple dilution.The experimental parameters were optimized and the optimum conditions were as followed: microwave power,375 W;leaching reagent,dilute nitric acid(20%,v/v);volumes of receiving leaching reagent,20 m L;flow rate of leaching reagent,1 m L min-1.Under optimal conditions,the proposed method was applied for the detection of the five element in six purified cotton textiles and obtained similar results with the standard method,with the leaching efficiency of the five elements in the range of 82.0-98.7%.The proposed method avoided the tedious acid evaporation and transfer steps since no concentrated acid was used,moreover,six samples can be treated simultaneously with the proposed method. |
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