Detection of Lead in Vegetables with New Chromogenic Reagent by Spectrophotometry

A new simple, rapid selective and highly sensitive chromogenic reagent dibromo-p-methyl-carboxyazo (DBMCA) was synthesized and studied in detail for the spectrophotometric detection of lead. In 0.25 M phosphoric acid medium, which greatly increases the selectivity, Lead reacts with DBMCA to form a 1:2 blue complex having a sensitivity absorption peak at 646 nm. Under optimal conditions, Beer's Law is obeyed over the range from 0.09 to 0.8 microg mL(-1) Pb (II) and the apparent molar absorptivity is 1.03 x 10(5) mL(-1) cm(-1). The detection limit and the variation coefficient were found to be 2.12 microg mL(-1) and 1.0% respectively. It is found that, except for Ca (II) and Ba (II) all foreign ions studied do not interfere with detection. The interference caused by Ca (II) and Ba (II) can be easily eliminated by prior extraction with potassiumiodide-methylisobutylketone. The proposed method has been applied successfully for to the detection of Lead in vegetable leaves with good results.