Spectrophotometric determination of lead in biological samples with dibromo-p-methyl-methylsulfonazo

A new highly sensitive and selective chromogenic reagent, dibromo-p-methyl- methylsulfonazo (DBM-MSA), was studied for determination of lead. In 0.24 m ol l(-1) phosphoric acid medium, which greatly increases the selectivity, l ead reacts with DBM-MSA to form a 1:2 blue complex which has a sensitive ab sorption peak at 642 nm. Under the optimal conditions, Beer's law was obeye d over the range 0-0.6 mu g ml(-1) Pb(II). The molar absorptivity and Sande ll's sensitivity are 1.02 x 10(5) l mol(-1) cm(-1) and 0.00203 mu g cm(-2), respectively. The limit of quantification, limit of detection and relative standard deviations were found to be 7.30 and 2.21 ng ml(-1) and 1.1%, res pectively. It is found that, except for Ca(II) and Ba(II), all foreign ions studied do not interfere with the determination. The interference caused b y Ca(II) and Ba(II) can be easily eliminated by prior extraction with potas sium iodide-methylisobutylketone. The method has been applied to the determ ination of lead in some biological samples with satisfactory results. (C) 1 999 Elsevier Science B.V. All rights reserved.