Spectrophotometric determination of nickel(II) using 5-Br-PADAP and N-hydroxy-N,N′-diphenylbenzamidine

A sensitive and simple spectrophotometric method for determination of Ni-II with 2-[(5-bromo-2-pyridylazo)]-5-diethylaminophenol (5-Br-PADAP) and N-hydroxy-N,N'-diphenylbenzamidine (HDPBA) is described. The Ni-II-2-[(5-bromo-2-pyridylazo)]-5-diethylaminophenol (5-Br-PADAP) complex is extracted with N-hydroxy-N,N'-diphenylbenzamidine (HDPBA) in chloroform at pH range 4.0-6.0 to give red colour complex. Extracted complex shows lambda(max) at 530 nm. Procedure is checked by finding relative standard deviation (RSD, n = 10) value for solutions each containing 2.0 mug ml(-1) Ni-II, and the RSD value of the procedure is found to be 1.6%. The system obeyed Beer's law up to 0.5 mug ml(-1) of nickel and the identification limit of the method is 7.4 x 10(-10) g ml(-1) on a three times the standard deviation of the blank absorbance basis. The Sandell's sensitivity and molar absorptivity of the complex are 0.00056 mug ml(-1) and 1.04 x 10(5) dm(3) mol(-1) cm(-1) respectively. The effect of foreign ions and other experimental variables are studied.