Use of ion exchangers for the voltammetric determination of NTA and EDTA in natural waters

Abstract

The indirect trace determination of NTA and EDTA in natural waters is carried out by differential pulse anodc stripping voltammetry (DPASV), after their complexation with bismuth(II1). Chloride ions in relatively high concentrations as well as iron(1II) and copper(I1) interfere with the determination of EDTA and NTA in natural waters. These interferences can be removed by using ion exchangers in the pretreatment of the sample before the voltammetric determination. The interferences of phosphonic acids and humic acids .can also be negated. The determination was performed in sea, lake, river, rain, and waste waters.KEY WORDS : NTA, EDTA, stripping voltammetry, bismuth. INTRODUCTTONThe knowledge of the distribution of heavy metals and their species in natural waters (speciation) is of great importance, with respect to the pollution effects they introduce into the particular ecosystem. In t h i s context, a sensitive and selective method for the determination of EDTA and NTA in natural waters would be of interest, because both compounds form stable complexes with heavy metals and can be found in natural waters [1 -41.In a previous study [51 a new, reliable, sensitive, and selective indirect voltammetric determination of EDTA and NTA, based on their complex formation with bismuth, was described. In that study, however, it was mentioned that chloride ions in relatively high concentrations, iron(II1) and copper(I1) interfere with the determination of EDTA and NTA, and certain procedures to overcome these interferences were suggested. Iron(III), which forms stable complexes with both EDTA and NTA, was reduced to iron(I1) using hydroxylamine hydrochloride. Copper was removed by preelectrolysis, and the chloride interference was avoided by medium exchange. However, preelectrolysis is a quite lengthy procedure. Thus, other ways were searched out. The use of ion exchangers proved to be very promising.Additional experiments were carried out to prove the validity of the assumption that humic and phosphonic acids do not interfere with the determination of EDTA and NTA.

A Validated Reverse Phase HPLC Method for the Determination of Disodium EDTA in Meropenem Drug Substance with UV-Detection using Precolumn Derivatization Technique

“…This paper describes development and validation of derivatized method with direct UV-detection for the quantitative determination of disodium EDTA in Meropenem drug substance. This method also has advantages over some techniques as mentioned in above references, 3–12 like here EDTA response is measured by direct UV detection with enhanced sensitivity and method is simpler, highly reproducible, specific and accurate, compare to using complex techniques like titrimetry, spectrophotometric, capillary electrophoresis or GC technique. As EDTA does not contain any chromophoric group, it is very difficult to determine EDTA by direct UV detection.…”

“…Various analytical methods have been proposed for the determination of EDTA in a wide variety of sample matrices. 2 They include titrimetry, 3 spectrophotometry, 4 electrochemistry eg, polarography, 5 differential pulse polorography, 6 catalytic potential tirtrimetry, 7 differential pulse anodic stripping voltammetry, 8 amperometry, 9 capillary electrophoresis, 10 and chromatography. Among them, gas chromatography and HPLC (reverse phase ion-pair or ion exchange retention mechanism) appear to be the prevailing techniques, despite the fact that EDTA lacks volatility and exhibits low UV/visible absorptivity.…”