Chemiluminescent determination of EDTA and related compounds using tris(2,2'-bipyridyl)ruthenium(III) photogenerated on-line

A rapid and sensitive chemiluminescence method using flow-injection has been developed for the determination of EDTA. The method is based on the chemiluminescent reaction of EDTA with tris(2,2'-bipyridyl)ruthenium(III), which is generated on-line through the photooxidation of tris(2,2'-bipyridyl)ruthenium(II) with peroxydisulfate. After optimizing the different experimental parameters, a calibration graph was obtained over the concentration range of 7 x 10⁻⁸ M to 3 x 10⁻⁶ M, with a minimum detectability of 7.2 x 10⁻⁹ M (S/N = 3) observed. The correlation coefficient was 0.9992 (n = 8). The repeatability was 0.88 % (for a level of 4 x 10⁻⁷ M) expressed as the relative standard deviation (n = 10), and the reproducibility (studied on five consecutive days) was 1.5 %. The method was successfully applied to the determination of EDTA in ophthalmic collyrium and sauce samples. The method is also useful for determining other aminopolycarboxylic acids, such as NTA, EGTA, DTPA, DCTA and EDDS.