Zinc gluconate is an important nutritional supplement. The following is the relevant research on its physicochemical properties and stability:
I. Physicochemical Properties
Appearance and Properties: It is usually a white crystalline or granular powder, odorless, and slightly astringent in taste.
Solubility: It is easily soluble in water, and its solubility in water increases with the rise of temperature. For example, at 20°C, its solubility is approximately 19.3 g/100 mL of water. It is insoluble in organic solvents such as ethanol, chloroform, and ether.
Melting Point: The melting point of zinc gluconate is generally between 172 - 175°C.
Molecular Formula and Molecular Weight: The molecular formula is C12H22O14Zn, and the molecular weight is 455.68 (calculated according to the common trihydrate form, the molecular weight of C12H22O14Zn is 509.73).
Chemical Properties: Zinc gluconate is a weak acid salt, which will undergo a slight hydrolysis reaction in an aqueous solution. Its zinc ions have a certain oxidizing property and can react with some reducing substances. At the same time, the gluconate radical part has some properties of carbohydrate compounds and can undergo reactions such as esterification and oxidation under certain conditions.
II. Stability Research
Thermal Stability: At room temperature, zinc gluconate has good thermal stability. However, when the temperature is too high, a decomposition reaction may occur. For example, when heated above 200°C, it will gradually lose its crystal water and may further decompose to produce zinc oxide, carbon dioxide, water, etc.
pH Stability: Zinc gluconate is relatively stable under acidic and neutral conditions, but its stability is poor under alkaline conditions. When the pH value of the solution is too high, zinc ions will combine with hydroxide ions to form zinc hydroxide precipitate, thus affecting the stability and effectiveness of zinc gluconate. Generally speaking, the zinc gluconate solution is relatively stable within the pH range of 4 - 7.
Photostability: Zinc gluconate has a certain sensitivity to light, and some photochemical reactions may occur under light conditions, leading to changes in its structure and properties. Therefore, it should usually be stored in the dark to prevent a decrease in its stability due to light exposure.
Interaction with Other Substances: When zinc gluconate coexists with some metal ions, strong oxidants, reducing agents, and other substances, chemical reactions may occur, affecting its stability. For example, when coexisting with heavy metal ions such as iron ions and copper ions, an ion exchange reaction may occur; when coexisting with reducing agents such as vitamin C, an oxidation-reduction reaction may occur. In addition, zinc gluconate may also interact with some drugs, affecting the absorption and efficacy of the drugs.
