Functionalization Of A Gas Chromatography Micro-injector For Solid Phase Microextraction And Its Evaluation

The present paper reports a gas chromatography micro-injector functionalized with solid-phase microextraction(abbreviated as functionalized injector).A section of a micro-injector needle plug was coated with platinum-polyaniline by Electro-chemically modifying,and then the intergration of ananlyte extraction and sample injection was achieved.First,a section of the injector needle tube was cut off and a section of the stainless steel plug inside the tube was exposed.Then diamond-shaped platinum particles were uniformly electrodeposited on the exposed section of the plug by chronopotentiometry.Finally,the fibrous polyaniline(PANI)was coated on the platinum particles by cyclic voltammetry.The platinum-polyaniline on the plug was used as solid phase microextraction layer.The experinmental conditions,including the potential and acid media,for the electrodeposition of platinum and electropolymerization of aniline,were optimized and selected.The functionalized injector was evaluated in terms of longterm stability,preparation reproducibility,enrichment ability and the linear range of standard curve by gas chromatography using 100 mg/L 2,4-dichlorophen(2,4-DCP)in a 0.25 g/m L Na Cl solution(p H=2.2)as the test analyte in the way of headspace extracion.Under the extraction conditions of 900 rpm of the stirring speed,80 ℃ of the extraction temperature and 50 min of the extraction time,the obtained results were as follows.The ralative standard deviation(RSD)of peak area was 4.2%(n=21)after the injetor was used once per day for 21 days.In order to measure the stability of the extraction layer at high teperatures,the injector tip with the extraction layer was inserted into the injector room of a gas chromatograph set at 300 ℃ for 3hours.It was found the peak area droped less 10% than that of its first use.If the desorption time is less than 1 min,it is anticipated that the injector can be used repeatly more than 180 times.The above results demonstrates that the extraction layer has a good stability.The peak area RSDs were measured to be 5.6% and 8.3%(n=3)for the functionalized injectors prepared in an identical bacth and different bacthes,respectively,indicating a good preparation reproducibility.The ratio of the standard curve slope obtained with the fuctionalized injector to that with the unfunctionalized one is 5.42.The linear range is3.33-666.67 mg/L,and the correlation coefficient is 0.9988,showing a good linear relationship.After the conditions for extraction and separation were optimized,the contents of2,4-DCP and toluene in drinking water were determined.The detection limits were 1.14 and0.03 mg/L(S/N=3),and the RSDs were 6.2 and 5.2%(n=5)at the spiked concentration of 100mg/L and 66.00 mg/L,for 2,4-DCP and toluene,respectively.The recoveries range from95.0% to 107.7% and from 94.3% to 99.9% at three spiked concentration levels(10 mg/L,100 mg/L and 300 mg/L for 2,4-DCP;0.44 mg/L,22.00 mg/L and 66.00 mg/L for toluene).