Chemiluminescent determination of sulfite traces based on the induced oxidation of Ni(II)/tetraglycine complex by oxygen in the presence of luminol: mechanistic considerations

The emission produced by sulfite induced autoxidation of Ni(II)/tetraglycine complex in the presence of luminol can be used to determine sulfite in the range of (0.0500–5.00)×10^-6 mol l^-1. The limit of detection is 2.8×10^-8 mol l^-1 and the relative standard deviation is 4.6% for 1×10^-7 mol l^-1 sulfite in five repeated measurements. This method has been successfully used for the determination of sulfite in wine, juices, white sugar and rainwater. The sulfite was extracted from the sample by using one gasdiffusion unit. Results for various samples of wine and juices were compared with those obtained by using a recommended procedure (correlation coefficient=0.9998,n=10), and recovery range for white sugar was between 99 and 104%. The mechanism involves a chain reaction with Ni(II) and radicals formations, which can then oxidize luminol.