Determination of nickel by a new chromogenic azocalix[4]arene Original Research Article

A novel azocalix[4]arene, 5,17-bis(quinolyl-8-azo)-25,26,27,28-tetrahydroxycalix[4]arene 1, was prepared by linking 8-aminoquinoline to calix[4]arene through a diazo-coupling reaction. Based on it, a simple, sensitive and selective spectrophotometric method was developed for the determination of Ni2+. In basic media, Ni2+ formed a 1:1 complex with 1. Beer’s law was obeyed in the range 1.7×10−7–5.1×10−6 mol l−1 of Ni2+. The apparent molar absorptivity (ε) of 1-Ni2+ complex was 1.28×105 l mol−1 cm−1 at 580 nm, and the detection limit was 1.4×10−7 mol l−1 (S/N=3). The relative standard deviation for measurement of 8.5×10−7 mol l−1 Ni2+ was 2.7% (n=10). The proposed method was applied to the determination of trace amount of Ni2+ in certified samples with satisfactory results.