Spectrophotometric determination of beryllium with Chromazurol S in the presence of Zephiramine.

Abstract

In the presence of Zephiramine, beryllium(II) reacted with Chromazurol S (CAS, H4L) in the pH range 7.5 to 10.6 to form two kinds of 1 : 2 complexes with an absorption maximum at 525 nm and near 600 nm, respectively. In the spectrophotometric determination of beryllium by measuring the absorbance at 525 nm and pH 10, the calibration curve obeyed Beer's law for less than 1.3 × 10-5 mol dm-3 of beryllium. Therefore, more than 1.4 × 10-5 mol dm-3 of beryllium was not successfully determined. However, the wide concentration range of beryllium could be determined precisely by measuring the absorbance at the isosbestic point 561 nm. The optimum conditions for the determination of beryllium were as follows : pH =10, [CAS] =1.8 × 10-4 mol dm-3, [Zephiramine] =2.2 × 10-3 mol dm-3, [EDTA] = (14) × 10-3 mol dm-3, and the standing time>2 min. Beer's law was obeyed at 561 nm for (0.044.4) x 10-5 mol dm-3 beryllium. The apparent molar absorptivity at 561 nm was 3.51 × 104 dm3 mol-1 cm-1. The relative standard deviation for the determination of 0.04 ppm and 0.32 ppm beryllium was 0.5 % and 0.4 %, respectively. It was considered that the two kinds of 1 : 2 complexes with the individual absorption maximum at 525 nm and 600 nm were the mononuclear and the binuclear complexes, respectively.