A New Composite Of O-aminobenzene Sulfonic Acid Self-doped Polyaniline And Multi-walled Carbon Nanotubes As A Fiber Coating For Solid-phase Microextraction

A new composite of o-aminobenzene sulfonic acid self-doped aniline and multiwalled carbon nanotubes(MWCNTs-SPAN)was reported as a fiber coating for solid-phase microextraction(SPME).The fiber coating was combined with a self-made SPME assembly for the extraction of target analytes.Firstly,the SPME assembly was fabricated by using stainless steel wires and tubes,and then MWCNTs-SPAN fiber coating was prepared on the pretreated stainless steel wire by cyclic voltammetry.The fiber coating was used to extract target analytes from water samples.In the experiment,the dosage of reagents and the parameters of cyclic voltammetry were optimized,the morphology of the coating was observed,and the preparation conditions were determined.2,4-dichlorophenol(2,4-DCP)was selected as the test analyte,and gas chromatography(GC)combined with headspace SPME was used to evaluate the performance of MWCNT-SPAN fiber coating in terms of thermal stability,lifetimes,extraction efficiency and reproducibility.A water sample containing 500 ?g/L 2,4-DCP,Na Cl concentration of0.35 g/m L and p H=2 was used,under the condition of extraction temperature of 80? and extraction time of 50 min,the measured results were as follows.Thermogravimetric analysis showed that the MWCNT-SPAN coating was stable at 350?.The MWCNTs-SPAN fiber coating was directly inserted into the injection port of the GC at 320?,the chromatogram was stable,and no chromatographic peak was observed,indicating that the composite was not decomposed by heat.The MWCNTs-SPAN fiber coating was used to simulate the adsorption-desorption process of 2,4-DCP standard solution 300 times at 280?,and the relative extraction efficiency of the coating assembly decreased by about 20%,indicating that the MWCNT-SPAN fiber coating has a long lifetimes.The relative standard deviations of peak areas were 4.3%,6.3% and 7.1%(n=5)for identical fiber coating,fiber coatings prepared in identical batch and fiber coatings in different batches,respectively,exhibiting good repeatability and reproducibility.The ratio of the slopes of the two standard curves obtained by MWCNTs-SPAN fiber coating headspace SPME and direct liquid injection with liquid-free microinjector was 192.67.the fiber coating has good enrichment ability.The extraction conditions of o-nitrophenol(O-NP)and 1,2,4-trichlorobenzene(1,2,4-TCB)were optimized.The linear ranges of standard curves of 2,4-DCP,O-NP and1,2,4-TCB were from 50 to 10000 ng/L,from 50 to 5000 ng/L and from 50 to 5000 ng/L,respectively,and the detection limits were 1.30,5.20 and 10.00 ng/L(S/N=3),respectively.2,4-DCP,O-NP and 1,2,4-TCB were analyzed by SPME-GC.At three different additive concentration levels,2,4-DCP,O-NP and 1,2,4-TCB were measured in three water samples.The spiked recoveries were in the ranges from 91.5% to 113.0%,from 86.2% to 98.1% and from 81.5% to 94.3%,respectively.