Determination Of Chelating Agents Research Articles

Evaluation of Commercial Fe(III)‐Chelates Using Different Methods

A collaborative assay among three laboratories was made in order to compare both the ion (CEN. EN 13368‐2:2001 E. Determination of chelating agents in fertilizers by ion chromatography. Part 2: EDDHA and EDDHMA, 2001a) and the ion‐pair (Lucena, J.J.; Barak, P.; Hernandez‐Apaolaza, L. Isocratic ion‐pair high‐performance liquid chromatographic method for the determination of various iron(III) chelates. J. Chromatogr. A 1996, 727, 253–264) high performance liquid chromatography (HPLC) methods as well as the soluble and complexed Fe (CEN. EN 13366:2001 E. Treatment with a cation exchange resin for the determination of the chelated micronutrient content and of the chelated fraction of micronutrients, 2001b) methods. Fifteen and ten samples of commercial fertilizers of Fe‐EDDHA, Fe‐EDDHMA, respectively were analysed by three laboratories using these methods. No significant differences were observed between the results obtained for the Fe‐EDDHA content using the Lucena et al. or CEN method. The first method makes it possible to distinguish between the meso and DL‐racemic diasteroisomers of Fe‐o, o‐EDDHA. For the Fe‐EDDHMA formulations, the CEN method gives higher values than the ion‐pair method, since in the first one Fe‐EDDH4,6MA coelutes with FeEDDHMA. Also the CEN method does not makes it possible to distinguish between Fe‐EDDHMA and Fe‐EDDH5MA products. The variability among laboratories was larger for the CEN method than for the Lucena et al. method.

EDTA Determination by Urease-Based Inhibition Biosensor

Urease immobilized into poly(vinylpyridine-co-styrene) film on the surface of ion sensitive field effect transistor (ISFET) has been used for determination of chelating agents (sequestrants). These species, particularly EDTA, restored catalytic activity of the enzyme if it was inhibited with cupric ions. Enzyme immobilization into a positively charged polymer seems to cause an increase of the EDTA restoration effect because of anion accumulation in the polymeric matrix. The resulting biosensor can measure EDTA concentration in the range of 5–500 ppm. The influence of other sequestrants (citrate and phosphate) were also examined.

Determination of chelating agents in Hanford tank waste simulant by capillary zone electrophoresis

AbstractA capillary electrophoretic method has been developed which achieves rapid quantitative separation and determination of ethylenediaminetetraacetic acid, N‐(2‐hydroxyethyl)ethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, ethylenediaminediacetic acid, and nitrilotriacetic acid in Hanford tank waste simulant (TWS). Direct UV detection of Cu2+/chelator complexes is used to achieve enhanced sensitivity. The qualitative and quantitative reliability of the method and the quality of separations, as given by efficiency and resolution, is presented. In addition, the limits of detection and linearity of detector response with concentration are given for each chelator. The selection of Cu as the UV‐absorbing species over other transition metals present in the waste is discussed.

Determination of chelating agents and metal chelates by capillary zone electrophoresis

Aminopolycarboxylic acids such as diethylenetriaminepentaacetic acid (DTPA) are commonly used as chelating agents in many pulp and paper industries, particularly as scavengers of metal ions which catalyze the decomposition of hydrogen peroxide used as a bleaching agent. Concern for the effect of waste DTPA in the aquatic environment has led to a need for the development of methods to determine its levels in waste water. This paper describes the determination of free DTPA and several metal-DTPA complexes in water and waste water by capillary zone electrophoresis. The optimization of separation conditions included the selection of an appropriate carrier electrolyte composition (pH, organic solvents, ion-pairing reagents) and the systematic investigations of selective complexation of free DTPA as well as metal exchange reactions for metal-DTPA complexes in order to achieve selective and sensitive direct UV detection. The determination of DTPA in waste water from a paper mill was possible in the low ppm range.

Determination of chelating agents in fertilizers by ion chromatography

In agronomy, chelating agents are used to complex trace elements (Fe, Mn, Zn, Cu, Co) for fertilization. An EEC directive allows the use of six chelating agents (EDTA, HEEDTA, DTPA, EDDHA, EDDHMA and EDDCHA), and requires an effective stability of at least 80%. An ion chromatographic method was developed to identify and determine the total amount of chelating agents in fertilizers. Precolumn derivatization of the metal chelates to the corresponding FE(III) chelates is followed by elution with HNO 3-NaOAc mixture, postcolumn reaction with HClO 4, and UV-Vis detection at 330 nm. The method offers a specific, sensitive technique for determining EDTA, HEEDTA and DTPA in fertilizers.