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

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. Beerʹs law was obeyed in the range 1.7×10-7-5.1×10-6moll-1 of Ni2+. The apparent molar absorptivity (epsilon) of 1-Ni2+ complex was 1.28×105lmol-1cm-1 at 580nm, and the detection limit was 1.4×10-7moll-1 (S/N=3). The relative standard deviation for measurement of 8.5×10-7moll-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.