Spectrophotometric determination of trace amounts of lead in environmental water samples in the presence of mixed microemulsion

A spectrophotometric method is described for the determination of lead(II) in mixed microemulsion. The mixed microemulsion medium composed of cetyl trimethylammonium bromide (CTMAB) and p-iso-octylphenoxy polyethoxyethanol (OP) is used to improve the sensibility of the determination. In Na2B4O7-NaOH buffer (pH 9.50), the reagent 2,6,7-trihydroxy-9-(3,5-dibromo-4-hydroxyphenyl)fluorone (DBH-PF) reacts with lead(II) to form a 3 : 1 purple complex. Under the optimal conditions. Beer's Law is obeyed up to at least 1 mug/ml Pb2+ with the molar absorptivity at 580 nm being 1.22 x 10(5) 1 mol(-1) cm(-1). Interfering ions, Al3+, Cu2+, Cr3+, Zn2+, Co2+, Ni2+ and Cd2+ can be eliminated easily by sulfhydryl dextrose gel (SDG) at pH 3.5. The important analytical parameters and their effects on the advised system are investigated. The proposed method has been applied to the environmental water samples, and the results found are satisfactory.