Analytical application of triethylenetetraaminehexa- acetic acid

Rubel, S.; Wojciechowski, Marek

doi:10.1016/s0003-2670(01)84003-4

Cited by 5 publications

(3 citation statements)

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“…The oxidation of mercury in the presence of chelons is well-known (15,16) and may be described by the reaction…”

Section: Resultsmentioning

confidence: 99%

“…The oxidation of mercury in the presence of chelons is well-known (15,16) and may be described by the reaction Hg + (4-)-= HgY2" + 2e" + nH+ The oxidations in which Y is EGTA or DCTA appear to be nearly reversible while that of EDTA is somewhat less so. Niki and Suzuki have studied the oxidation of mercury in the presence of EDTA in detail and have found that the overall reaction is complicated not only by reactant adsorption but also by product adsorption (19).…”

Section: Resultsmentioning

confidence: 99%

“…Because we were not interested in determining chelons bound in chelates and because we were not interested in identification of specific chelons, we adopted the direct approach of examining the electrochemical oxidation of mercury. Although the electrochemical oxidation of mercury in the presence of EDTA and other chelons its well-known (15,16) and has been used as the reaction for end point detection in amperometric titrations (17), it has not been used previously for the direct determination of chelons. The findings of Gardiner (1) suggest that EDTA is not only a convenient and chemically reasonable model compound to use in method development but also a potentially important determinant of heavy metal concentrations and the chemical form of metals in natural waters.…”

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Direct determination of chelons at trace levels by one-drop square-wave polarography

Stojek¹,

Osteryoung²

1981

Anal. Chem.

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The direct anodlc oxldaitlon of mercury In the presence of chelons can be used for determinatlon of the chelons at trace levels. One-drop square-wave polarography proved superior to dlfferential pulse polalrography for thls purpose and gave detection limits of 7, 7, 5, and 20 X IO-* M for EDTA, DCTA, EGTA, and NTA, respecttvely, with callbratlon curves linear to M. At pH 4.8 heirvy metals can be determlned In the presence of Ca2+ by using amperometrlc titratton based on this method.Chelons such as EDTA (ethylenediaminetetraacetic acid) are used in a wide range of industrial, pharmaceutical, and agricultural applicationa. It has been shown that EDTA is resistant to biodegradation ( I ) . It has also been shown that under the conditions normally obtaining in natural waters EDTA exists as negatively charged complexes with protons or metal ions and is not (absorbed on container walls, humic acid, silica, kaolin, river sediments, or humus solids (1). Gardiner infers from the existing data that complexation of trace metals in natural waters by EDTA 1s more important than complexation by humic acids ( I ) . A simple numerical example illustrates this point. With the data of Buffle and Greter (2), the overall conditional formation constants for Pb(I1) with fulvic acid (molecular weight nominally 1000) at pH 6 are given by log PI = 5.1 and log 02 := 9.7 for the complexes PbL and PbLz, where L represents fulvic acid. At the same pH the conditional iformation constant for PbY is given by log K' = 13.4, where represents EDTA. Suppose that Cy, the analytic concentration of Y, is 100 pg/L. K' is sufficiently large that the fraction of lead present as the aquated ion is negligible as long a8 the analytic concentration of lead, Cp,, is less than that of Y. Under these conditions, the fraction of lead complexed with L, is less than 0.1 for concentrations of L less than 7 g/L (7 mF). Similar conclusions are drawn for other cases. Gardiner h a carried out similar calculations which include the effects of competition of Ca(I1) for EDTA and illustrate some limitations of this generalization (1). Undoubtedly EDTA is capable of affecting natural systems to an appreciable extent by mobilizing trace metals.A variety of methods have been employed for the determination of EDTA and related compounds. Gardiner used gas-liquid chromatograplhy of the ethyl derivatives of the sample with DCTA (1,2-cyclohexanediaminetetraacetic acid) added as an internal standard for the determination of EDTA in river water, sewage, arid sewage effluent (3). Detection limits of ca. 5 X M (15 pg/L) with recoveries of ca. 99 f 13% were found with a sample size of 25 mL. Kaiser employed the absorbance of the Co(II1) complex and was able to determine EDTA in mixtures of EDTA and NTA (nitrilotriacetic acid) by selective oxidation of the NTA complex (4). Replicate analyses at the 200 pg/L level of EDTA in mixtures of EDTA and NTA gave precision of 7% (standard Present address: Uniwersiytet Warszawski, Wydzial Chemii, ul. Pasteura 1,02493 Warszawa,, Poland. deviation)....

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“…The oxidation of mercury in the presence of chelons is well-known (15,16) and may be described by the reaction…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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