The Analytical Methods Establishment And Distribution Of Hexabromocyclododecane And Its Diastereoisomer

With the rapid development of chemical industry both domestically and abroad,the environmental problems caused by chemical products has attracted a great deal of attention.For example,in order to improve fire resistance of products,the production and use of fire retardant materials has risen dramatically.Hexabromocyclododecane(HBCD)as a brominated flame retardant material with an excellent effect is gradually brought to people's attention and the risk it poses to the environment and human is becoming increasingly serious.HBCD has been detected in plenty of matrices,such as the atmosphere,water,soil,sediment and even biological matrices.Due to its strong hydrophobicity,HBCD is usually abundant in solid matrices,such as soil and sediment.However,owning to the varying operational conditions,the results obtained from analytical method for HBCD in soil vary significantly.The different sources of pollution and environmental elements make the distribution of HBCD vary massively.Given the problems with HBCD in soil,the method of supercritical fluid extraction was applied to analyze the distribution of HBCD in field soils in this paper.The major achievements are as follows:1.The uncontaminated soil with HBCD was used to make simulated soil,and the analytical methods of HBCD in soil were optimize and compared.The approaches to extracting HBCD from soil include soxhlet extraction,ultrasonic-assisted extraction and accelerated solvent extraction,which were researched previous to a new method using supercritical fluid extraction(SFE)and gas chromatography(GC)mass spectrometry(MS)/liquid chromatography(LC)mass spectrometry being established.In the experiment,the operating parameters of SFE were optimized.Further with this,the surfactant(Triton X-114)was added.The extraction efficiency of HBCD was further improved and the dynamic time was reduced using supercritical CO2 in the presence of a microemulsion containing surfactants.The experimental results showed that the extraction efficiencies of these four methods were 60.4%,68.5%,88.6%and 98.9%,respectively,with the extraction times being 12 h,50 min,30 min and 24 min,respectively.The comparison of these methods revealed that soxhlet extraction and ultrasonic-assisted extraction is disadvantageous owning to long extraction time,high solvent consumption and low selectivity to the target analyte.Accelerated solvent extraction is also required to consume some organic solvent.In contrast,supercritical fluid extraction is efficient,time-saving,and environmentally friendly.2.The established analytical method was applied to investigate the distribution trend of HBCD in a production plant and its surrounding area in Weifang,Shandong Province.The analysis results indicated that the concentration of HBCD in soil of the plant was significantly high as compared to the normal value,with the annual average concentration reaching 5405 ng/g.The soils of 1 km,2 km and 4 km away from the plant were also analyzed,which demonstrated that the concentration of HBCD in soil declined accordingly with the increase in distance away from the pollution sources.From the center to the distance of 2 km,the concentration of HBCD decreased significantly,and at 4 km the detected HBCD concentrations were found to be stable.The concentration of HBCD in soil was also influenced by seasonal prevailing wind.The distribution trend was that the soil concentration of HBCD at the downwind direction of the prevailing wind was higher than at the upwind direction.In addition,this work analyzed the distribution of HBCD in vertical section.It was found that the concentration of HBCD decreased as the soil vertical profile deepened.3.The major diastereoisomer of HBCD was also researched.Their relative percentages and distribution in the soil were analyzed.The results indicated that the percentage of y-HBCD was the highest in this area and it was the main existing form of HBCD.However,there were general proportions of a-HBCD in soil compared to those reported in commercial HBCD products.The reason was that the thermal rearrangement occurred from ?-HBCD to ?-HBCD,and the degradation rate of a-HBCD was slower than that of y-HBCD.The distribution of each diastereoisomer of HBCD was broadly the same as EHBCD.In horizontal distribution,from the center to the distance of 2 km,the concentrations of ?-,?-,?-HBCD decreased significantly,and at 4 km they were stable.In vertical distribution,the concentration of the three diastereoisomers of HBCD declined as the soil vertical profile deepened significantly,and the decline rate of ?-HBCD was faster than others.