Chelating agents edetic acid

Preservatives Antimicrobial Benzalkonium chloride Benzyl alcohol Chlorhexidine Imidazolidinyl urea Phenol Potassium sorbate 1 Benzoic acid Bronopol Chlorocresol Paraben esters Phenoxyethanol Sorbic acid Antioxidants a-Tocopherol Ascorbic acid Ascorbyl palmitate Butylated hydroxyanisole Butylated hydroxytoluene Sodium ascorbate Sodium metabisulphite Chelating agents Citric acid Edetic acid... 

Edetic acid and edetate salts are used in pharmaceutical formulations, cosmetics, and foods as chelating agents. They form stable water-soluble complexes (chelates) with alkaline earth and heavy metal ions. The chelated form has few of the properties of the free ion, and for this reason chelating agents are often described as removing ions from solution this process is also called sequestering. The stability of the metal-edetate complex depends on the metal ion involved and also on the pH. The calcium chelate is relatively weak and will preferentially chelate heavy metals, such as iron, copper, and lead, with the release of calcium ions. For this reason, edetate calcium disodium is used therapeutically in cases of lead poisoning see also Section 18. 

Comments more soluble in water than either the disodium salt or the free acid. Trisodium edetate also occurs as the monohydrate and is used in pharmaceutical formulations as a chelating agent. The EINECS number for trisodium edetate is 205-758-8. 

Oxidation reactions can be catalysed by the presence of tiny amounts of metal ions (for example, 0.05 ppm Cu2+ can initiate decomposition of fats) and so stainless steel or glass apparatus should be used wherever possible during manufacture of susceptible compounds. If the presence of metal ions cannot be avoided, then chelating agents, such as disodium edetate, are used to chelate and remove metal ions. Disodium edetate is the disodium salt of ethylenediaminetetraacetic acid, or EDTA, and is shown in Figure 8.12. 

Ethylenediaminetetraacetic acid (EDTA) is a polycarboxylic acid chelator its sodium salt (edetate disodium, Na EDTA), and a number of closely related compounds chelate many divalent and triva-lent metals. The cation used to make a water-soluble salt of EDTA has an important role in the toxicity of the chelator. Na EDTA causes hypocalcemic tetany. However, edetate calcium disodium (CaNa EDTA) can be used for treatment of poisoning by metals that have higher affinity for the chelating agent than does Ca +. 

Oxidation, in oral liquids, in practice is inhibited by removal of oxygen from water by boiling, reduction of headspace by completely filling of bottles, addition of a chelating agent (sodium edetate) for the removal of catalysing traces of metals and the addition of antioxidants, such as ascorbic acid (see Sect. 22.2.2). 

A number of natural substances, including sodium citrate and ascorbic acid, chelate Pb. Commonly used chelating agents include calcium disodium edetate (CaEDTA), dimercaprol (BAL), 2,2-dimethylcysteine (D-peniciUamine) and 2,3-dimercaptosuc-cinic acid (DMS). Chisholm and Coffin et al." have outlined the appropriate protocols for chelation therapy for children wdth Pb poisoning, whereas Friedheim et al. and the Center for Disease Control, outline the treatment of adult Pb intoxication. 

Some strains of P. aeruginosa are resistant to benzalkonium chloride and, in fact, can be grown in solutions concentrated in this agent. This has caused great concern because of the virulent nature of this organism in ocular infections, as discussed previously. Thus, it was an important finding in 1958 that the acquired resistance could be eliminated by the presence of ethylenediaminetetracetic acid (sodium edetate) in the formulation. This action of EDTA has been correlated with its ability to chelate divalent cations, and it is commonly used as a preservative aid [125]. The use of disodium EDTA, where compatible, is recommended in concentrations up to 0.1%. 

Medical treatment with chelation uses four different agents British Anti-Lewisite (2,3-dimercaptopropanol), edetate calcium disodium, D-penicillamine, and succimer or meso-2,3-dimercaptosuccinic acid (Roper et al. 1993). British Anti-Lewisite is contraindicated in children allergic to peanuts and in glucose-6-phosphate dehydrogenase deficiency D-penicillamine is contraindicated in penicillin allergy (Roper et al. 1993). 

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