Micellar mediated trace level mercury quantification through the rhodamine B hydrazide spirolactam ring opening process

Abstract

The micellar mediated trace level estimation of mercury in industrial effluent sample by the rhodamine B hydrazide spirolactam ring opening process is described. The catalytic reaction of mercuric ion with colorless rhodamine B hydrazide to form pink colored rhodamine B through amide bond cleavage at pH 5 forms the basis of this reaction. The dye obtained was extracted from the aqueous phase into non-ionic surfactant using Triton X-114 through cloud point formation and its absorbance was measured at 556 nm. The reaction conditions such as concentrations of rhodamine B hydrazide and Triton X-114, effect of NaCl concentration on cloud point temperature and the efficiency of extraction were optimized. The selectivity of the method towards mercury in the presence of various ions was studied. The validity of the method was examined by spiking real samples with known amounts of mercury and carrying out recovery studies. The results obtained by the proposed method were compared with the standard dithiazone method. The preconcentration and enrichment factors were found to be 5 and 12 respectively. The limit of detection and the linear range were found to be 1.4 ng ml⁻¹ and 10–100 ng ml⁻¹ respectively. The relative standard deviation was found to be 0.35% at 20 ng ml⁻¹.