Magnesium Citrate

Magnesium citrate in bulk trade normally means trimagnesium dicitrate, the tribasic salt (CAS 3344-18-1, C12H10Mg3O14, molecular weight 451.11), in which three magnesium ions are balanced by two citrate anions. It should not be confused with the 1:1 monomagnesium dibasic salt (CAS 7779-25-1), which carries a materially lower magnesium load. Compendial limits are expressed as magnesium content rather than as salt assay: USP requires not less than 14.5% and not more than 16.4% Mg on the dried basis, while Ph. Eur. specifies 15.0% to 16.5% Mg calculated on the dried substance. The theoretical figure for the anhydrous salt is approximately 16.2%. The practical distinction from magnesium oxide is solubility. Trimagnesium dicitrate is soluble in water and practically insoluble in ethanol (96%), and it dissolves readily in dilute hydrochloric acid, so it is the usual choice for effervescent tablets and sachets, ready-to-mix drink powders, stick packs, syrups and clear beverage fortification. It is a white or almost white fine powder and is slightly hygroscopic, which needs to be allowed for in blending and packing. Anhydrous grade carries a loss on drying of not more than 2.0%; nonahydrate grade runs at 24.0-28.0% and is specified where a controlled water of crystallisation is wanted. Granular and direct-compression grades are available where flow and compressibility matter more than dissolution rate. Magnesium is an essential mineral contributing to normal energy-yielding metabolism, normal muscle function, normal functioning of the nervous system and normal electrolyte balance. Each consignment is supplied with a certificate of analysis covering magnesium content by complexometric titration, loss on drying, heavy metals, iron, chloride and sulphate, with ICP-MS heavy-metal profiling and full microbiological testing available on request. Allergen, GMO, BSE/TSE and non-irradiation statements accompany every shipment.