EDTA and DTPA

Since the 1970s, there have been concerns about the environmental impact of poorly biodegradable cheiants such as EDTA and DTPA, as they could potentially remobilize toxic heavy metals, such as cadmium, mercury, and lead, from river sediments back into the water column [10]. More recent concern has focused on large-scale emissions from photographic laboratories, pulp and paper mills, metal treatment plants, and use of industrial detergents, as higher dosages of cheiants are more likely to cause a 

1) Human health and environmental exposure. The report concluded that at present there is no need for further information and/or testing or for risk reduction measures beyond those which are being applied. This conclusion was reached because the risk assessment showed that risk reduction measures already being applied are considered sufficient [16]. 

2) Aquatic toxicity. EDTA has low aquatic toxicity, is not persistent in the environment due mainly to photodegradation of Fe(III), Co(III), and Mn(II) EDTA complexes, does not bioaccumulate, and does not need to be classified and labeled with an environmental symbol or risk phrase. 

However, the conclusions for aquatic ecosystem health confirmed the earlier concerns that large industrial emissions exist, such as those that occur when EDTA passes through municipal water treatment plants without being degraded. It was concluded that there is a need for specific measures to limit the risks. Concern was expressed particularly about potential emissions from detergent industries, paper mills, circuit board producers, and during recovery of EDTA-containing wastes. 

European eco-labeling of paper products, and in the existing European eco-labeling for cleaners under Regulation 1980/2000/EC. In addition, the EU Commission made further recommendations on risk reduction measures for EDTA. First, it asked EU Member States to establish Environmental Quality Standards (EQS) for EDTA, and the national pollution reduction measures to achieve those EQS in 2015 should be included in the river basin management plans in line with the provisions of Directive 2000/60/EC. Second, EU Member States should specify in IPPC permits measures on EDTA to operate to BAT by October 2007, taking into account local circumstances. Further, as BAT is developed, this should be incorporated into the permits. 

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Allard A-S, L Renberg, AH Neilson (1996) Absence of evolution from -labelled EDTA and DTPA and the sediment/water partition ratio using a sediment sample. Chemosphere 33 577-583. 

One example, a candidate matrix material of organotin species in marine water, had stability determined by storage for 120 days at 4°C in the dark, at ambient temperature, and exposed to daylight (Quevauviller and Donard 1991). Frequently storage at different temperatures over at least a i-year period are reported. Examples include organochlorine pesticides (OCPs) in BCR CRM 430, where pork fat was stored at -2o°C, -i-20°C, and -r37°C (van der Paauw et al. 1992). Storage at -20°C, -i-20°C, and -i-4o°C was performed for total and methyl Hg in BCR CRMs 463 and 464, tuna fish (Quevauviller et al. 1994), and metals in BCR CRM 600, EDTA and DTPA-extractable trace metal contents in calcareous soil (Quevauviller et al. 1998m). 

Quevauviller Ph, Lachica M, Barahona E, Gomez A, Rauret G, Ure A, Muntau H (1998m) Certified reference material for the quality control of EDTA- and DTPA-extractable trace metal contents in calcareous soil (CRM 600). Fresenius J Anal Chem 360 505-511. 

There have been many studies of the complex formation of plutonium with ethylene-diaminetetraacetic acid (EDTA) and DTPA. Over the range pH 1.0 to 3.0 Pu(III) formed 1 1 complex with EDTA with a stability constant of 1.3 x 1018 (22). At pH 3.3 Pu(IV) reacted with EDTA to form two complexes with Pu EDTA ratios of 1 1 and 1 2 with stability constants of 4.5 x 1012 and 1.6 x 1024, respectively. 

It is significant that oat plants, which are known to contain the Fe3+ complexor, 2,4-dihydroxy-7-methoxy-l,4-benzoxazin-3-one (128), do not show any significant accumulation of plutonium, or the other actinides. It is possible that this complexing agent is located within plant cells which do not come into contact with the cation transporting mechanisms. Although there is evidence of the existence of microbial hy-droxamates in soil and that hydroxamates do become concentrated in plants (129), there has been no evidence presented yet that hydroxamates are the agents responsible for plutonium uptake into plants. On the other hand there is evidence that EDTA and DTPA can stimulate actinide concentration in plants (See Table 6). 

The availability of the trace metals is easily determined without any of the above risks, and the results used to assess both deficiencies and toxici-ties. The metals need to be removed from the sites where they are bound to the soil particles by use of an even stronger binding agent than the soil. This is achieved with two possible complexing reagents EDTA and DTPA. They are a class of chemicals known as complexones, which form complex molecules with metals in a cage-like structure called a chelate. 

The amount of metal extracted from the soil by both EDTA and DTPA is dependent on the pH, the metal being extracted, the soiksolution ratio, the concentration of chelating agent, the shaking time, the temperature, and the sample preparation procedure. Clearly, the methodology used should be clearly described and closely followed if repeatable work is to be possible, and comparison of results is to be meaningful. 

Figure 6. Three bifunctional metal chelates substituted cryptand, bifunctional EDTA, and DTPA.

The phosphonates DTPMP, EDTMP, and HEDP are poorly biodegradable and so are only very slowly broken down once released into the environment [22]. However, they are largely sorbed to sewage sludge (50-90%) in treatment, so that amounts entering river systems and the environment are reduced. Generally, because of the lower emissions to the environment and more diffuse use, there is less concern about the environmental impact of phosphonates as compared to EDTA and DTPA. There are... 

Clarkson et al. investigated molecular dynamics of vanadyl-EDTA and DTPA complexes in sucrose solution or attached to PAMAM dendrimers by EPR [74,75]. The motion-sensitive EPR data of the dendrimeric system have been fitted to an anisotropic model which is described by an overall spherical rotation combined with a rotation around the axis of the arm branching out of the central core. The motions around the axis of the branch connecting the chelate to the central core were found to be very rapid, whereas the overall tumbling was slow. 

Raspor, B. and Branica, M., 1975. Comparison of the polarographic reduction of Cd-NTA, -EDTA and -DTPA chelates in chloride solutions. 3. Electroanal. Chem., 60 335-339. 

Mono- and di-esters can be prepared by the action of alcohols on the bisanhydrides. The action of lithium aluminium hydride in tetrahydrofuran at - 70 °C on the tetraethyl ester of EDTA produces aldehydes in low yield116. Both EDTA and DTPA as the free acids are soluble in dimethyl sulphoxide but only the bisanhydrides are soluble in di-methylformamide116. ... 

Other lipophilic derivatives of EDTA and DTPA were synthesized by condensing the bisanhydride of the former with phosphatidylethanolamine to give PE-EDTA (16)121 whereas that of the latter was condensed with 11-aminoundecanoic acid to give Puchel, 17,122. PE-EDTA failed to mobilize plutonium from the hamster, although studies with PE-[14C]EDTA established the uptake of the radiolabel into the liver. 

Extraction methods based on solutions of chelating agents, such as EDTA and DTPA, or salts of weak acids, such as ammonium acetate (CH3COONH4) (Lakanen and Ervio, 1971 Lindsay and Norwell, 1969), can be used to assess plant-available trace element contents of soils and to evaluate more robustly human exposure to environmental risks in an urban context. A study carried out in the main cities of Campania region in southern Italy (Albanese, 2008) demonstrated how the bioavailable concentrations of some trace elements such as Zn, Pb and Cu in soils, determined using ammonium acetate-EDTA extraction, are much lower than the elemental concentrations determined by an aqua regia extraction on the same samples (Table 8.1). 

As seen in Table 2.10, the stability constants of the tartarate and citrate complexes of lead and calcium ions are much smaller than those of EDTA and DTPA complexes. The calculations show that the dominant species of cations are Pb2+ and Ca2+ at pH < 4, and so the same ion exchange can be expected as would happen without complex-forming agents. At pH > 4, the effect of citric acid is significantly higher than expected from stability constants. The structure of citrate... 

Table 4.2 Aqueous stability constants (log /3i) for lanthanide (3-I-) ions with fluoride, EDTA, and DTPA ...

Figure 3.29 The formation constants of RE(III) complexes with IDA, NTA, TEDTA, EDTA, and DTPA.

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