Trace And Ultra Trace Dioxin-resolution Gas Chromatography / High Resolution Mass Spectrometry Analysis Technique

Dioxin is short for a series of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans(PCDFs), which are a well-known group of highly toxic and carcinogenic chemicals widely present in nearly all components of the global ecosystem, including air, soil, sediment and organism. Dioxins enter the environment via various combustion processes, chemical manufacturing/ processing, and industrial processes. They are persistent in environment and bio-accumulate. They can bring a series of toxic set effects to human, such as developmental and reproductive toxicity, incretion toxicity, immunorepressive effect and carcinogenicity. Because of the high persistence and extreme toxicity of dioxins, dioxins are present at dioxins present in environment and food at extremely low levels, i.e. part per trillion (ppt) or even part per quadrillion (ppq) , dioxin analysis is requiring low ppt or even ppq levels of detection. In addition, the endogenous constituents of environment and food samples are complex and there are many interference compounds in which. The congeners of dioxin are very many, but their toxicity is very different, so in order to truly estimate the toxicity of the sample, the each congener of 2,3,7,8-substituted PCDD/F has to be clearly separated from the many other less toxic congeners present in the samples and also from a large number of high concentrations sample constituents, and be quantificationally detected separately. Dioxin analysis is typical ultra -trace, multi-constituents, qualitative and quantitative analysis. The isotope dilution technique utilizing high-resolution gas chromatography-high-resolution mass spectrometry (ID/HRGC/HRMS) is currently the only acceptable authoritative dioxin analysis method in the world. The method can provide sufficient sensitivity and selectivity for dioxin detection. But this method need complicated and time-consuming multi-step sample pre-treatment, its requirements is very strict on laboratory, instrument and operator .There are few qualified laboratories that can perform these analyses.After the event of chicken being polluted by dioxin happening in Belgium in 1999, our country began to pay attention to the research of dioxin investigation. At that time, there wasn't any special dioxin measurement laboratory or the standard trace dioxin analysis method except one of the laboratory being established byWuhan Hydrophilic Institute corporated with Germany. In this case, a study of detecting trace and ultra-trace dioxin in incinerator fly ash by means of ID/HRGC/ HRMS carried out by CAEP and National Environmental Analysis Center in 2000. The ultimate goal was to establish universal standard trace and ultra-trace dioxin analysis method in CAEP laboratory.In the paper, we studied the technology of sample treatment on the basis of American EPA1613 method, discussed and optimized the several ways of separating and detecting conditions of HRGC/HRMS, examined the sensitivity, range of linearity, stability and reliability, evaluated synthetically the feasibility of detecting trace and super-trace dioxin analysis of HRGC/HRMS. Furthermore, we collected, prepared, analyzed and testified the dioxin sample of incinerator fly ash. The results of instrument tests have shown that the instrument of HP6890 gas chromatograph and Finnigan MAT95S mass spectrometer in our laboratory can meet the criteria of trace dioxin analysis defined by the US EPA. The detection limits for our MAT95S is 30fg 2,3,7,8-TCDD. The linearity of 2,3,7,8-TCDD/F.is very good at widely concentration range 0.1 pg to lOOOpg. The result of repeat experiments and 16-day system stability test shown the repetition and the long term stability and reliability can achieve the requirement of trace dioxin analysis. According to the analysis of real dioxin sample of incinerator fly ash, the results showed that the dioxin sample treatment we established was feasible. By the research works which have done, we established the universal standard measurement of detecting trace and super-trace dioxin by HRGC/HRMS in our laboratory successfully, the laboratory has been conferred the title of Southwest Dioxin Analysis Sub-center by National Environmental Analysis Center.