Magnetic Solid Phase Extraction Coupled With ICP-MS For Analysis Of Arsenic Species

Arsenic is widely present in nature.Excessive use of arsenic compounds leads to the accumulation of arsenic in the environment,resulting in environmental pollution.There are many different inorganic and organic arsenic species in biological and environmental samples,and their environmental,biochemical and toxicological effects are different.Therefore,analysis of arsenic species would provide more abundant information than total amount analysis.Analysis of arsenic species in environmental（e.g.,water,soil）and food（e.g.,seafood,rice）samples can reveal the degree of arsenic pollution in the environment.While arsenic speciation in biological samples（e.g.,urine,blood,hair）would reflect arsenic exposure degree and personal health.Inductively coupled plasma mass spectrometry（ICP-MS）is widely used in the determination of trace elements because of its high sensitivity,wide linear range,and simultaneous detection of multiple elements.However,when ICP-MS is directly applied to the determination of arsenic in real samples,there are some difficulties such as polyatomic ion interference of ⁴⁰Ar³⁵Cl to ⁷⁵As,matrix effect,the arsenic content lower than the detection limit of the instrument,and various arsenic species not being distinguished.Therefore,sample pre-treatment method and separation technology are needed to enrich target analyte and distinguish multiple arsenic species.Magnetic solid phase extraction（MSPE）is a new sample pretreatment method that can achieve the enrichment of target analytes in large-volume samples.Magnetic nanoparticles（MNPs）have the advantages of large specific surface area and good dispersion,and can achieve rapid phase separation under an external magnetic field.For the analysis of inorganic arsenic species（As（Ⅲ）,As（V））,sample pretreatment methods are commonly used for separation of As（Ⅲ）and As（V）by selective extraction.For the analysis of multiple arsenic species,chromatographic methods（especially high performance liquid chromatography（HPLC））are commonly combined with ICP-MS.The interface between HPLC and ICP-MS is simple and convenient.In summary,the establishment of high efficient,sensitive and fast methods for analysis of arsenic species in real samples is of great significance.The purpose of this dissertation is to synthesize new types of MSPE material for the enrichment of arsenic species,and to establish new methods of MSPE-（HPLC）-ICP-MS for speciation of arsenic in environmental and biological samples.The content is as follows:（1）Sulfhydryl（-SH）modifiedepoxy-modifiedMNPs（Fe₃O₄@Si O₂@GMA-S-SH MNPs）were prepared for selective adsorption of As（Ⅲ）.Based on it,a new method of MSPE-ICP-MS was developed for the analysis of inorganic arsenic species（As（Ⅲ）and As（V））in water samples.MNPs with-SH functional group selectively adsorbed As（Ⅲ）in the p H range of 5.0-9.0,but did not adsorb As（V）.For the determination of As（V）,As（V）was reduced to As（Ⅲ）in Na₂S₂O₃/KI prior to MSPE-ICP-MS,and the content of As（V）content was obtained by subtraction.Under the optimal conditions,the limit of detection（LOD）of the developed method was 1.5 ng L^-1,the linear range was 5-3000 ng L^-1,and the relative standard deviation（RSD）(c=10 ng L^-1,n=7)was 9.6%.This method was successfully applied to the analysis of As（Ⅲ）and As（V）in tap water and environmental water.（2）Ti（Ⅳ）modified vinyl phosphate MNPs（Fe₃O₄@Si O₂@KH570-PO₄-Ti（Ⅳ）MNPs）was prepared for simultaneous extraction of multiple arsenic species including inorganic arsenic（i As）,dimethyl arsenic acid（DMA）,monomethyl arsenic acid（MMA）,p-amino phenyl arsenic acid（p-ASA）,4-hdroxyphenylarsenic acid（4-OH）,phenyl arsenic acid（PAA）and 3-nitro-4-hydroxyphenylarsenic acid（ROX）.With Fe₃O₄@Si O₂@KH570-PO₄-Ti（Ⅳ）MNPs as the sorbent,a method of MSPE combined with HPLC-ICP-MS was developed for analysis of seven target arsenic species in chicken muscle and liver samples.It was found that seven target arsenic species were all quantitatively adsorbed on MNPs at p H 5.0,and desorbed completely with 0.1 mol/L sodium hydroxide solution as eluent.Under the optimal conditions,the developed method presented a linear range of 1-5000 ng L^-1 for seven arsenic species.The LODs were 0.39,0.60,0.23,1.85,0.54,0.48 and 0.84 ng L^-1 for DMA,MMA,p-ASA,i As,4-OH,PAA and ROX,with the RSDs(c=10 ng L^-1,n=7)of 3.6,3.9,5.5,12.4,6.1,5.8 and 5.0%,respectively.No target arsenic species were detected in tested chicken muscle and liver samples,and good recoveries（80.6-123%）were obtained for the spiked samples at low,medium and high concentration levels(0.04,0.4 and 4μg g^-1).