Water And Methods Of Analysis Of Pcbs In Soil Samples

Polychlorinated Biphenyls (PCBs), as one important group of Persistent Organic Pollutants (POPs) with intense toxicity, high residuary and the hardness of being metabolized, have attracted a widely concern in Environment Science. A method for detecting PCBs residue in soil and water sample was studied, including extraction method, cleanup procedure and detection technique. Method for detection PCBs residue in soil and water has been established. It was fast,accurate,low pollution,high sensitivity and content with Green Analytical Chemistry's requirement.Firstly, the microwave extraction (ME) was used for the extraction of PCBs residue in soil sample. The influence factors of microwave power, extraction temperature, time, solvent on the extraction efficiency of ME were discussed. The results indicated that the optimal analytical conditions was that microwave power, extraction time, solvent and temperature were selected as 1200w,20min, hexane-acetone(v:v=1:1,20mL)and115℃respectively. The method detection limit of PCBs was in range of 20-30ng/g .The spike standard recoveries rates were between 92.2% and 115%, relative standard deviation was 9.36%(n=7).The Soxhlet extraction (SE) and accelerated solvent extraction (ASE) were compared for the extraction of the trace PCBs in soil. The results showed that the efficiency of SE was lower while ASE was equivalent to ME. The average recoveries obtained by SE were 79.5% and ASE was105%. SE just as a classical sample preparation method for soil, it has some merits likes good reproducibility and low cost, but also has some deficiencies, such as analytical procedure is more complex, a large of solvent used is harmful for human and enviroment.ASE and ME were both rapid, high efficiency and low pollution method for PCBs extraction in soil. But ME is capable for sample's bath process, and extraction time is lower than ASE, so it is much suitable for the demand of sample batch process in laboratory.Solid phase extraction with C18 disk was developed to extract polychlorinated biphenyls (PCBs) residue in water sample. Some factors influencing the extraction efficiency of C18 disk, such as elution solution, pH of water sample, extraction pressure was studied. The results indicated that the optimal analytical conditions was that elution solution, pH of water sample, flow rate were selected as 5mL acetone,10mL hexane,pH=2, 70mL/min respectively. The spike standard recoveries rates were between 92.8%-96.8%, relative standard deviation was 2.3%-5.7% (n=7). NCI was employed to detect the PCBs in water sample, and the detection limits of this method were 0.1ng/L-70ng/L. Solid phase extraction with C18 disk has faster flow, higher absorbability ,lower counter pressure than cartridge SPE and suitable enrichment pollutants. This method has become more and more application in domestic and abroad. Secondly, the co-cleanup techniques of solid phase extraction with florisil column ,silica gel column,alunima column, Cleanert PestiCarb were used to eliminate the recoveries of PCBs.The average recoveries of the co-cleanup technique by Cleanert PestiCarb and Florisil column was the best, the recoveries of PCBs was ranged from 91.5% to 103%, relative standard deviation was 1.3%-14%.In addition, the methods for detection PCBs had been developed by gas chromatography with an electron capture detector (GC-ECD) and gas chromatography with mass spectrometric detector (GC-MS) equipped with different ionization sources, Electron Impact Ionization Source(EI),and Negative Ion Chemical Ionization(NCI).The results showed that EI was sensitive to low chloric PCBs,while NCI was sensitive to Perchlorinated Biphenyls.While detecting Hexachlorobiphenyl,Heptachlorobiphenyl,Octachlorobiphenyl,Nonachlorobiphenyl, the method had higher sensitivity compared with GC-EI-MS.In order to enhance the accuracy of the analytical method, we proposed that when detecting the trace PCBs residue in sample,EI and NCI both should be used in the method.Finally, the established pretreatment and analysis method were applied successfully to soil and water samples obtained from different regions for the determination of PCBs residue .The results showed that most of soil samples had been polluted in different levels and relative high levels of PCBs were found in dust samples from Joan's province. Whereas, the levels of PCBs in water sample were low, maybe it was related to the character of PCBs. The established pretreatment and analysis method have been proved to be credible.