Strontium Citrate

Strontium citrate is the strontium salt of citric acid, correctly named strontium hydrogen citrate and traded in the 1:1 stoichiometry, CAS 813-97-8, FDA UNII ZZG3847S6Y, molecular formula C6H6O7Sr, molecular weight 277.73. It delivers 30.4 to 32.4% elemental strontium on the dried basis against a theoretical 31.6%, which is the figure formulators work from when converting a label dose of elemental strontium into a fill weight. A tribasic form, tristrontium dicitrate Sr3(C6H5O7)2, also exists and carries a higher strontium fraction, so buyers should confirm which stoichiometry a quoted assay refers to before comparing prices. The material is a white to off-white odourless granular or crystalline powder, practically to sparingly soluble in water with solubility rising in dilute acid. Manufacture starts from celestine, the natural strontium sulfate mineral, which is converted to strontium carbonate and then reacted with citric acid, so the product is entirely mineral in origin. That makes it vegan and vegetarian, with no bovine, porcine, marine, fish, crustacean, milk, egg, soy, gluten or nut input anywhere in the process, and no allergen carry-over to declare. There is no USP, EP, BP or other pharmacopoeial monograph for strontium citrate, so it is supplied against a Thovek in-house specification modelled on general food-chemical purity criteria for mineral salts: loss on drying NMT 5.0% at 105 C for four hours, chloride and sulfate NMT 0.1% each, heavy metals NMT 10 ppm as lead, and arsenic NMT 3 ppm. Every batch ships with a full certificate of analysis. Market access is the constraint that decides whether this ingredient is usable at all, and it varies more than for almost any other mineral salt in the catalogue. Strontium does not appear in Annex I of EU Directive 2002/46/EC, the closed list of minerals permitted in food supplements, so strontium citrate cannot be used in EU food supplements under the harmonised rules. It is used as a dietary supplement ingredient in the United States. Health Canada has published a summary safety review on strontium-containing products. Strontium is not classified as an essential nutrient and no RDA or nutrient reference value exists for it, although it occurs naturally in drinking water, in the ordinary diet and in bone mineral. One technical point buyers routinely need on their artwork: because strontium has a higher atomic number than calcium, its presence raises DXA densitometry readings, an analytical artefact rather than a measured change. Thovek supplies the chemical and its documentation and makes no therapeutic or disease claim of any kind for it; buyers are responsible for confirming permitted status, dose limits and warnings in each destination market before formulating.