Spectrophotometric Determination of Lead in Tea Leaf Sample with Dibromo-p-chloro-arsenazo

摘要

This work reports the use of dibromo-p-chloro-arsenazo (DBC-ASA) as a chromogenic agent to develop a new spectrophotometric method for the determination of lead using Pb~(2+)-(DBC-ASA) complex. In the medium of 0.10 mol L~(-1) phosphoric acid, the maximum absorption wavelength of Pb~(2+)-CDBC-ASA) violet-red complex formed is located at 614 nm. At this wavelength a good linearity is presented between the concentration range of 0.1 -3.5 ng mL"' of lead(II) and absorbance and its linear regression equation is: A = 0.130 C (C:μg/mL) + 0.007. The apparent moler absorption coefficient of the method is 3.33 x 10~4 L mol~(-1) cm~(-1) and its detection limit is 0.225 μg mL~(-1). The method was used to determine lead in som.e tea leaf samples and the obtained results are in good agreement with those of atomic absorption .spectrometry. The relative standard deviation of 13 rephcate detenninations was (0.43-0.80) %. The recovery of the standard addition of the method was (96.0-98.5) %.