Abstract:Complex formation between curcumin and Hg(II) ion MeOH/H 2 O (1: 1 v/v) was investigated and monitored by the spectrophotometric method. The absorption peak of unreacted curcumin which was close and overlapped with that of the complex, was removed by calculation using Microsoft Excel, thereby, allowing determination of the stoichiometry of the complex by the mole-ratio and the Job's continuous variation methods. Both methods indicated that a 1:1 complex of curcumin and Hg(II) was formed in solution. The formation constant of the 1:1 Hg(II) complex was obtained from two methods, the equilibrium concentration calculation and the linear plot of Benesi-Hildebrand equation, as log K = 4.44 ± 0.16 and 4.83 ± 0.02, respectively. The structure is proposed as a tetrahedral complex of Hg(II) with one curcumin and two chloride ions as ligands.© Versita Warsaw and Springer-Verlag Berlin Heidelberg.
A sensitive and rapid method to analyse Pb(II) in canned fish samples was developed using square-wave adsorptive cathodic stripping voltammetry based on the adsorptive accumulation of 8-hydroxyquinoline complexes of Pb(II) onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan with square wave pulse modulation. The optimum conditions were found to be 0.1 M CH 3 COONH 4 as a supporting electrolyte, pH 7.5, 8-hydroxyquinoline concentration of 15 µM, accumulation potential −0.70 V (versus Ag/AgCl), accumulation time 120 s, scan rate 0.3 V/s, and pulse amplitude 20 mV. Under the optimum conditions a linear calibration graph was obtained in the concentration range of 0.5-90.0 µg/l with correlation coefficient 0.9973, a limit of detection of 0.108 µg/l, and a limit of quantification of 0.360 µg/l. The recovery values were obtained in the range 93.7-95.1%. The relative standard deviations (n = 10) at lead concentration 5.0 µg/l was 2%. The method was successfully applied to the determination of lead content in canned fish samples. The concentration of Pb(II) in canned fish samples (wet weight) was found to be in the range of 0.121-0.285 µg/g, which is lower than the limit (1.00 µg/g) issued by the Ministry of Public Health of Thailand.
The concentrations and the distribution of organic matter in SLB (e.g. the outer part of Thale Sap Songkhla area) were examined during the period of September 1988 to September 1989. Organic matter in water samples were analyzed by gravimetry. Total organic matter and dissolved organic matter concentrations ranged from 74 to 7908 mg/L and from 23 to 7813 mg/L, respectively. Except for a set of observations which showed low concentrations during the flood season in November 1988, organic matter was regularly distributed throughout SLB. Domestic effluent and aquaculture are hypothesized as major sources of organic matter contamination. The levels of organic matter concentrations in SLB are significantly higher than would be expected for an area considered to be uncontaminated. The data also indicated a linear relationship between concentrations of suspended organic matter and suspended solids. This may be due to the organic matter associated with suspended solids.
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