Studies On Determination Of Trace Mercury In Water By Spectrophotometry After Cloud Point Extraction

Objective:Mercury is one of the most toxic metals to human body. It is well known that Minamata was caused by water including mercury. Therefore, it is necessary that an accurate, sensitive, efficient method was studied to determine content of mercury in environment.To carry out the separation and preconcentration of the analyte, traditional organic solvent extraction had been used in a variety of chemical analysis such as determination of mercury in water samples of the national standard analytical methods-by spectrophotometry at the presence of dithizone. In the method, a large amount of chloroform was used which is toxic and harmful. When the experimental waste discharged into the underground water, it will not only aggravate the environmental pollution, but also be harmful for the experimental staff.Compared with the aforesaid liquid-liquid extraction, the cloud point extraction is a newly interesting alternative. It is an easy, safe, high efficiency and economical methodology for preconcentration and separation.So, the proposed method is aimed at combination spectropotometry with cloud point extraction, which is applied to the determination of mercury in actual water samples. It will be helpful for the promotion of green chemistry, the health of experimental staff and environmental protection.Methods:Mercury was extracted as mercury-dithizone complex mediated by micelles of the non-ionic surfactant Triton X-100. After phase separation, the mercury in the surfactant phase was determined by spectrophotometry.The extraction conditions were optimized, such as [dithizone],[Triton X -100],pH,[NaCl],equilibrium temperature,equilibrium time, and so on.It was compared with national standard method-dithizone spectrophotometry and hydride generation-atomic fluorescence spectrometry for examining the accuracy of the new method.Result:1. Experimetal Results show that optimized conditions wereλmax=500nm,dithizone [1× 10-5mol/L],TritonX-100 [0.5%(V/V)],and so on.2.Under the optimum conditions, linearity was obeyed in the range of 0.002～0.100μg/mL of Hg2+. Regression equation of working curve is Y=6.5983x+0.0039, correlation coefficient r=0.9998. Recoveries are between 90% and 95%. Relative standard deviation is less than five percent (n=6).3. Compared the method with National Standard Method - dithizone spectrophotometry, by means of two-sample t-test, there was no significant difference between the results of the two methods (p>0.05).4. In order to lower detection limit, solution volume was increased to 50ml. Compared with National Standard Method– atomic fluorescence spectrometry, by means of matched t-test, there was no significant difference between the results of the two methods (p>0.05).Conclusion:Determination of mercury by spectrophotometry coupled cloud point extraction have many advantages such as simple, rapid, low detection limit, high sensitivity, saving reagents.The result was satisfied with determination of mercury in water samples.