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Evaluation of enantiomeric purity of magnesium-L-aspartate dihydrate.

Journal of pharmaceutical and biomedical analysis (2014-09-30)
Oliver Wahl, Ulrike Holzgrabe
ABSTRACT

Magnesium supplementation in form of organic magnesium salts is a very popular practice. We examined the enantiomeric purity of "Magnesium aspartate dihydrate" monographed in the European Pharmacopeia. A chiral capillary zone electrophoresis using (2-hydroxypropyl)-β-cyclodextrin coupled to laser induced fluorescence detection and a HPLC-fluorescence method with chiral derivatization using o-phthaldialdehyde and N-acetyl-L-cysteine as an orthogonal method were developed and validated. Two batch samples of this substance and three drug products containing the salt were analyzed by means of both methods. The concentration of the D-enantiomer of aspartic acid ranged from 0.03 to 0.12%. Simulations of the synthesis revealed that the d-aspartic acid content is elevated if the dissolution of L-aspartic acid was performed at acidic pH values.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Methanol, NMR reference standard
Sigma-Aldrich
Octylphosphonic acid, 97%
USP
Acetylcysteine, United States Pharmacopeia (USP) Reference Standard
Supelco
L-Aspartic acid, Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Hydrogen chloride solution, 3 M in cyclopentyl methyl ether (CPME)
Acetylcysteine, European Pharmacopoeia (EP) Reference Standard
Supelco
Residual Solvent - Acetonitrile(solution in DMSO), Pharmaceutical Secondary Standard; Certified Reference Material
Sigma-Aldrich
Amyloid Protein Non-Aβ Component, ≥80% (HPLC)
Supelco
Hydrogen chloride – ethanol solution, ~1.25 M HCl, for GC derivatization, LiChropur
Sigma-Aldrich
Phthaldialdehyde, for fluorescence, ≥99.0% (HPLC)
Sigma-Aldrich
di-Sodium hydrogen phosphate dihydrate, tested according to Ph. Eur.
Sigma-Aldrich
Magnesium oxide, 99.99% trace metals basis
Sigma-Aldrich
Methanol, anhydrous, 99.8%
SAFC
L-Aspartic acid
Sigma-Aldrich
Sodium bicarbonate, tested according to Ph. Eur.
Sigma-Aldrich
Ammonium acetate solution, for molecular biology, 7.5 M
Sigma-Aldrich
Phthaldialdehyde, ≥97% (HPLC), powder or crystals
Sigma-Aldrich
Ammonium acetate, reagent grade, ≥98%
Sigma-Aldrich
Ammonium acetate, for molecular biology, ≥98%
Sigma-Aldrich
Formamide, BioReagent, ≥99.5% (GC), for molecular biology
Supelco
Hydrochloric acid solution, volumetric, 0.1 M HCl (0.1N), endotoxin free
Sigma-Aldrich
Ammonium acetate, BioXtra, ≥98%
Sigma-Aldrich
Sodium bicarbonate, BioXtra, 99.5-100.5%
Sigma-Aldrich
Phthaldialdehyde, suitable for HPLC fluorimetric detection of amino acids, ≥99% (HPLC), powder or crystals
Sigma-Aldrich
Potassium fluoride, anhydrous, powder, ≥99.9% trace metals basis
Sigma-Aldrich
Magnesium oxide, ≥99.99% trace metals basis
Sigma-Aldrich
Acetic acid-12C2, 99.9 atom % 12C
Sigma-Aldrich
Potassium cyanide, BioUltra, ≥98.0% (AT)
Supelco
Ammonium formate, eluent additive for LC-MS, LiChropur, ≥99.0%
Sigma-Aldrich
Ammonium acetate, ≥99.99% trace metals basis