0.27, respectively. The influence of some products of degradation of NTA and some chemical species expected to be present in natural and industrial waters was also investigated. Iminodiacetic acid, glycolic acid, glycine, dodecylbenzene sodium sulfonate, sodium tripolyphosphate, and calcium ion did not interfere at least in molar concentrations 100 times that of NTA. Ortho-and m-cresol, and iron(II1) ion did not interfere if present at the same molar level of NTA. Aluminum ion and sodium lauryl sulfate can be tolerated in molar concentrations 10 times that of NTA. Dissolved chlorine proved to be the only serious interference of all species considered. Figure 3 presents a working curve for NTA with a known constant amount of EDTA. This figure implies that by adding the adequate amount of Mn(I1) and selecting appropriate reference potentials, the procedure can be used for the determination of NTA in samples of aminopolycirboxylic acids (or other complexing agents) inhibiting the catalytic effect of manganese (i.e,, CDTA, DTPA, EDTA, and HEDTA).
Aminopolycarboxylic acids2 are detected and determined, individually or in mixtures, by the reaction of cyanide ion with their nickel(l1) complexes in basicsolution. The procedure is based on the large differences in the rate of formation of tetracyanonickelate ion. Simultaneous kinetic determinations of twocomponent (NTA and EDDA) and three-component (NTA, EDDA, and EGTA) mixtures are accomplished by on-line regression analysis of stopped-flow spectrophotometric data. As little as 10 ppb of NTA in natural water samples can be detected. Trace amounts of NTA in EDTA and a four-component (EGTA, HPDTA, HEEDTA, and EDTA) mixture also are determined offline.
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