| The pollutions caused by heavy metals have been serious problems which destroy ecological environment and harm human health. The migration, toxicity, and the serious harmfulness of heavy metals not only depended on the total amount, but largely on the chemical forms. Therefore, it is very important to identify and determine chemical forms of heavy metals accurately in environmental samples.New methods have been developed for determination of Cr(III) and Mn in the leaching solution of chromium residue of harmless treatment, available cobalt in soils, copper in tobaccos. These methods combined cloud point extraction technology of high enrichment ability with flame atomic absorption spectrometry(FAAS) of good selectivity and high sensitivity. The major research contents are summarized as follows:(1)Determination of Cr(Ⅲ) and Mn in chromium residue samples of harmless treatment by flame atomic absorption spectrometry after cloud point extractionA cloud point extraction (CPE) procedure has been developed for the determination of Cr(Ⅲ) and Mn in chromium residue samples of harmless treatment by flame atomic absorption spectrometry. The proposed method was based on the cloud point extraction of a complex from methyl red and Cr(Ⅲ) and Mn using emulsifier octyl polyethylene glycol phenol ether (OP) as surfactant. Cr(Ⅲ) and Mn were extracted to the surfactant phase, so as to realize the separation from other metal ions. The method was also studied several main factors which influenced the efficiency of cloud point extraction in detail. Under the optimized conditions, the calibration graphs of Cr(Ⅲ) and Mn were linear in range of0.05～2.00μg·mL-1and0.005～1.00μg·mL-1, and the correlation coefficient were0.9993and0.9999, respectively. The detection limits of Cr(Ⅲ) and Mn were0.0500μg·mL-1and0.003500μg·mL-1,respectively. The relative standard deviations (RSD) of Cr(Ⅲ) and Mn were1.3%and1.8%, respectively. The recoveries of Cr(Ⅲ) and Mn spiked in the leaching solution of chromium residue samples of harmless treatment were from 89.0%to110.0%and from90.0%to105.0%, respectively. The proposed method showed good accuracy, with the results satisfactory.(2)Determination of available cobalt in soils by flame atomic absorption spectrometry after cloud point extraction0.1mol·L-1hydrochloric acid (HC1) was selected as extracting agent. A novel method was proposed for the determination of available cobalt in soils by flame atomic absorption spectrometry after cloud point extraction.The present work used methyl red as complexing agent and TritonX-114as surfactant. And several main factors that affected the efficiency of cloud point extraction were studied. Under the optimized conditions, the calibration graph of Co was linear in range of0.10-2.0000μg·mL-1, the detection limit of the method was0.0300μg·mL-1, and the relative standard deviation was3.3%. The recoveries of Co spiked in soil samples were from94.0%to104.0%. The proposed method was successfully applied to the determination of available Co in soils, which were collected from the suburbs of Zhengzhou and Sichuan, and with the results satisfactory. It was found that the propotion of available cobalt was very different in soils of different areas after determination.(3)Determination of copper in tobaccos by flame atomic absorption spectrometry after cloud point extractionA novel method was proposed for determination of copper in tobaccos by flame atomic absorption spectrometry. Using microwave digestion for the pretreatment of tobacco samples first, and then cloud point extraction was carried out using cefazolin sodium and ammonium citrate tribasic as complexing agents, OP as surfactant. The sensitivity and selectivity of the method was improved a lot due to the formation of multiple complex. Conditions that would affect cloud point extraction were researched in detail, including the values of pH, dosages of buffer solution, concentration of the chelating agents and the surfactant, equilibration time and temperature. In addition, interference of some common cations and anions were also studied. The paper used potassium sodium tartrate as masking agent to conceal the interference of Al3+and Cd2+. Under the optimized conditions, the calibration graph of Cu was linear in range of0.03～1.0000μg·mL-1, the correlation coefficient was0.9997. The detection limit of the method was0.0100μg·mL-1, and the relative standard deviation was4.3%. The recoveries of Cu spiked in tobacco samples were from90.0%to106.7%. The method was applied to determine Cu in tobacco samples with the results satisfactory. |
PDF Full Text Request