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 -tetrahydro xycalix [4] arene 1, was prepared by linking 8-aminoquinoline to calix[4]ar ene 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 obe yed in the range 1.7 x 10(-7)-5.1 x 10(-6) mol l(-1) of Ni2+. The apparent molar absorptivity (epsilon) of 1-Ni2+ complex was 1.28 x 10(5) 1mol(-1) cm (-1) at 580 nm, and the detection limit was 1.4 x 10(-7) mol l(-1) (S/N = 3 ). The relative standard deviation for measurement of 8.5 x 10(-7) mol l(-1 ) Ni2+ was 2.7% (n = 10). The proposed method was applied to the determinat ion of trace amount of Ni2+ in certified samples with satisfactory results. (C) 2001 Elsevier Science B.V. All rights reserved.