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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

Supelco
L-Aspartic acid, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland
Sigma-Aldrich
Methanol, suitable for NMR (reference standard)
Sigma-Aldrich
Acetic acid-12C2, 99.9 atom % 12C
Sigma-Aldrich
Magnesium oxide, tested according to Ph. Eur., heavy
Supelco
Hydrogen chloride – ethanol solution, ~1.25 M HCl, derivatization grade (GC derivatization), LiChropur
Sigma-Aldrich
Sodium bicarbonate, tested according to Ph. Eur.
Supelco
Ammonium acetate, LiChropur, eluent additive for LC-MS
Sigma-Aldrich
Octylphosphonic acid, 97%
Sigma-Aldrich
di-Sodium hydrogen phosphate dihydrate, tested according to Ph. Eur.
Sigma-Aldrich
Acetic acid, suitable for luminescence, BioUltra, ≥99.5% (GC)
Supelco
Hydrogen chloride – methanol solution, ~1.25 m HCl (T), derivatization grade (GC derivatization), LiChropur
Supelco
Ammonium formate, eluent additive for LC-MS, LiChropur, ≥99.0%
Sigma-Aldrich
di-Sodium hydrogen phosphate dihydrate, BioXtra, ≥98.0% (T)
Sigma-Aldrich
L-Aspartic acid, BioUltra, ≥99.5% (T)
Supelco
Acetic acid, analytical standard
Sigma-Aldrich
Hydrochloric acid solution, for amino acid analysis, ~6 M in H2O
Supelco
Hydrogen chloride – 2-propanol solution, ~1.25 M HCl (T), derivatization grade (GC derivatization), LiChropur
Sigma-Aldrich
Phthaldialdehyde, suitable for fluorescence, ≥99.0% (HPLC)
Sigma-Aldrich
Ammonium formate, BioUltra, ≥99.0% (calc. based on dry substance, NT)
Sigma-Aldrich
di-Sodium hydrogen phosphate dihydrate, BioUltra, Molecular Biology, ≥99.0% (T)
Sigma-Aldrich
Ammonium formate, ≥99.995% trace metals basis
Sigma-Aldrich
Ammonium acetate, 99.999% trace metals basis
Sigma-Aldrich
Isopropyl alcohol, ≥99.7%, FCC, FG
Sigma-Aldrich
Magnesium oxide, 99.99% trace metals basis
Sigma-Aldrich
Magnesium oxide, BioUltra, ≥97.0% (calcined substance, KT)
Sigma-Aldrich
Magnesium hydroxide, BioUltra, ≥99.0% (KT)
Sigma-Aldrich
Ammonium acetate solution, BioUltra, ~5 M in H2O
Sigma-Aldrich
Ammonium acetate, BioUltra, ≥99.0%
Supelco
Methanol, analytical standard
Sigma-Aldrich
Formamide, BioUltra, Molecular Biology, ≥99.5% (T)