Bismuth chelating agent

Bismuth compounds are used as an antidiarrheal. Topical applications are used in skin disorders. Overdose may cause acute bismuth intoxication but gastric lavage, purgation, use of chelating agents, 2,3-dimercapto-l-propane sulfonic acid, and hemodialysis are steps to be taken.170-172... 

Stevens PE, Moore DF, House IM, Volans GN, Rainford DJ. Significant ehmination of bismuth by haemodialysis with a new heavy-metal chelating agent. Nephrol Dial Transplant l995 l0(5) 696-8. 

There does not appear to be an antidote of choice for bismuth toxicity in humans. Gastric lavage can be used within 1 h of exposure. Replace fluids and electrolytes. Monitor renal and liver function for several days and treat failure conventionally. The newer chelating agents, meso-2,3-dimercaptosuccinic acid and D,L-2,3-dimercapto-propane-l-sufonic acid, are being investigated experimentally as antidotes for bismuth toxicity, and the latter has been shown to be effective. In mice, D-penicillamine has proven effective. 

Direct Titrations. The most convenient and simplest manner is the measured addition of a standard chelon solution to the sample solution (brought to the proper conditions of pH, buffer, etc.) until the metal ion is stoichiometrically chelated. Auxiliary complexing agents such as citrate, tartrate, or triethanolamine are added, if necessary, to prevent the precipitation of metal hydroxides or basic salts at the optimum pH for titration. Eor example, tartrate is added in the direct titration of lead. If a pH range of 9 to 10 is suitable, a buffer of ammonia and ammonium chloride is often added in relatively concentrated form, both to adjust the pH and to supply ammonia as an auxiliary complexing agent for those metal ions which form ammine complexes. A few metals, notably iron(III), bismuth, and thorium, are titrated in acid solution. 

Newer agents under investigation include tris(tropolonato) Bi(III) and nitratobis(tropolonato)Bi(in) a host of bis (mercaptoethanol)Bi(III) complexes, which are formed with 0,S-bidentate chelation, with and without deprotonation of the hydroxyl oxygen and usually having an axial fifth ligand and sialic acid derivatives of Bi(III). The interactions of Bi(III) and its compounds with metallothionein, serum albumin and transferrin have been studied by a variety of groups, as have a number of enzymes that may be related to the mechanism(s) of action of bismuth in treating ulcers. 

EDTA (ethylenediaminetetraacetic acid) forms stable metal chelates with a number of metal ions. Using this reagent as a complexing- agent, arsenic, bismuth, and selenium can be determined without any interference in the presence of nickel and cobalt. The cobalt-EDTA chelate is stable in 5 M HCl solution, whereas the corresponding bismuth complex is not. The influence of copper on the determination of arsenic can also be eliminated with EDTA, but not in the determination of selenium. Thiourea has been used to eliminate the influence of copper in the determination of antimony and sodium oxalate to eliminate the influence of copper and nickel in the determination of tin. An addition of thiosemicarbazide and 1,10-phenanthro-line reduces the interference of copper, nickel, platinum, and palladium in the determination of arsenic. 

---