# The Food Supplements (Magnesium L-threonate monohydrate) (Wales) Regulations 2026, Schedule: Purity criteria for magnesium L-threonate monohydrate


Magnesium L-threonate monohydrate
(1)The number assigned to this substance by the Chemical Abstracts Service (www.cas.org/cas-data/cas-registry).
(2)The dalton, or unified atomic mass unit, is a unit of mass defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at rest.
(3)United States Pharmacopeia.
Synonym
Magnesium L-threonate
Definition
Chemical name
Magnesium (2R,3S)-2,3,4-trihydroxybutanoate monohydrate
Chemical formula
C8H16MgO11
CAS number
500304-76-7
Molecular weight
312.51 Da
Colour (solid)
White
Assay
Magnesium: 7.2 to 8.3%
L-threonate: 82 to 91%
Description
A water-soluble white powder which is manufactured via a chemical synthetic process.
Identification
Solubility
Soluble in water at 1% concentration at 25℃ and that is clear in solution at 1% concentration.
pH (USP (1% in H2O))
5.8 to 7.0
Purity
Loss on drying
Not more than 5.0% (105℃/4 hours)
Oxalic acid/oxalate
Not more than 0.5% (as oxalic acid)
Arsenic
Not more than 1 mg/kg
Lead
Not more than 0.5 mg/kg
Cadmium
Not more than 0.2 mg/kg
Mercury
Not more than 0.1 mg/kg

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Source: https://www.legislation.gov.uk/wsi/2026/56/schedule (the official version)
Page: https://openlegislation.uk/food-supplements-magnesium-l-threonate-monohydrate-wales-regulations-2026/schedule
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.