Antioxidants and Complexing Agents - Module 6

Sodium Thiosulfate (Na₂S₂O₃∙5H₂O), USP

• large, transparent, colorless crystals, cooling, bitter taste 

• reagent for iodimetric/iodometric titrations 

I₂ + 2Na₂S₂O₃ → 2NaI + Na₂S₄O₆

• used for the treatment for CN^- poisoning

Sodium Nitrate (NaNO₂), USP

• white to slightly yellow granular powder 

• has a mild, saline taste & deliquescent 

• antidote to CN-

Hypophosphorous Acid (HPH₂O₂), NF

• salts are used as food preservatives

• Antioxidant: prevents formation of free I₂ in:

  • Dilute HI; and 

  • HI Syrup

• Antioxidant: prevents formation of Fe³⁺ & I₂ in:

• Ferrous Iodide Syrup

Sodium Metabisulfite (Na₂S₂O₅), NF

• white crystal or white to yellowish crystalline powder

• has odor of SO₂

• source of bisulfite:

Na₂S₂O₅ + H₂O → 2NaHSO₃

Nitrogen (N₂), NF

• inert gas

• protects chemicals, reagents, & pharmaceuticals from air oxidation 

• produces an inert atmosphere for easily oxidized products 

Sulfur Dioxide (SO₂), NF

• colorless, non-flammable gas

• suffocating odor produced by burning sulfur 

• strong reducing agent

• In neutral or alkaline solutions:

SO₂ + OH^- → HSO3^-

• produces an acidic solution in water:

SO₂ + H₂O → H₂SO₃

• an antioxidant pharmaceutical aid

• for injectable preparations in single or multiple-dose containers 

Calcium Disodium Edetate

• a.k.a. calcium disodium versenate/calcium disodium EDTA

• white crystalline granule or powder

• odorless, slightly hygroscopic, and has a faint saline taste

• used for the treatment of heavy metal poisoning, primarily by lead (plumbism)

• can also be used in copper, nickel, cadmium, zinc, chromium, and manganese poisoning, but not in mercury, arsenic, or gold

  • often happen when children are exposed to lead (which is in paint that is used for children’s toys)

Disodium Edetate

• chelates the same metals as CaNa₂EDTA

• for hypercalcemic diseases (Cardiac arrhythmias)

• has high affinity to Ca²⁺ and chelates it immediately, thus, decreasing Ca²⁺ concentration 

• hence, if low Calcium, use CaNa₂EDTA

  

Dimercaprol (British anti-Lewisite, BAL)

• anti-war gas 

• used for arsenic, mercury, and gold poisoning 

• improves the excretion of lead and copper (Wilson’s disease - accumulation of copper) 

• contraindicated in iron, cadmium, and selenium poisoning 

• metal-dimercaprol complexes tend to dissociate in acid media 

  • Dimercaprol is used as a urinary alkalinifier for Wilson’s

    

Penicillamine

• capable of forming complexes with copper, iron, mercury, lead, gold 

• primarily used for the improvement of excretion of copper 

• also used in the treatment of gold dermatitis

  

Deferoxamine

• produced naturally by Streptomyces pilosus as a ferric complex 

• Deferoxamine mesylate (methylsulfonic acid salt)

• does not have strong affinity with ferrous and other divalent metal ions