Beta-correction spectrophotometric investigation of cadmium complexation with new ligand, 2,4-dibromo-6-caboxybenzenediazoaminoazobenzene and determination of trace amounts of cadmium in wastewater

The synthesis of new ligand, 2,4-dibromo-6-caboxybenzenediazoaminoazobenzene (DBCBAA) was carried out and was used to develop sensitive, reaction with cadmium (II) in a basic solution. The surfactants, emulsifier OP and sodium dodecyl benzene sulfonate (SDBS), may both increase the sensitivity and the solubility of Cd-DBCBAA complex. Because of the strong interference of excess of ligand, the conventional spectrophotometry was limited for use. The current principle, named beta-correction theory has been applied instead of single wavelength method because it can eliminate the above interference. Such a method can give the simple determination of complex characteristic factors such as the complex ratio, real molar absorptivity (epsilon) and step or cumulative stability constant (K). Results showed that the two formed Cd-DBCBAA complexes were both expressed as Cd(DBCBAA)(4) at pH 12.5, their real not apparent absorptivities were first to be determined equal to 1.85 x 10(5) L mol(-1) cm(-1) in the presence of OP at 520 nm and 2.05 x 10(5) L mol(-1) cm(-1) in the presence of SDBS at 530 nm and the cumulative stability constants of complexes equaled 4.90 x 10(22), and 8.64 x 10(22) respectively. For analysis of wastewater samples, the detection limit of cadmium was 0.004 mg/L and the recoveries between 92.0 and 107% with the relative standard deviations of less than 4.0%.