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-caboxybenzenediazoaminoazobenzen e (DBCBAA) was carried out and was used to develop sensitive, reaction with cadmium (II) in a basic solution. The surfactants, emulsifier OP and sodiu m dodecyl benzene sulfonate (SDBS), may both increase the sensitivity and t he solubility of Cd-DBCBAA complex. Because of the strong interference of e xcess of ligand, the conventional spectrophotometry was limited for use. Th e 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 s tep or cumulative stability constant (K). Results showed that the two forme d Cd-DBCBAA complexes were both expressed as Cd(DBCBAA)(4) at pH 12.5, thei r real not apparent absorptivities were first to be determined equal to 1.8 5 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 stab ility constants of complexes equaled 4.90 x 10(22), and 8.64 x 10(22) respe ctively. 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%.