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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
Methanol, analytical standard
Sigma-Aldrich
Ammonium acetate solution, BioUltra, for molecular biology, ~5 M in H2O
Sigma-Aldrich
Magnesium oxide, BioUltra, ≥97.0% (calcined substance, KT)
Sigma-Aldrich
Ammonium acetate, BioUltra, for molecular biology, ≥99.0%
Sigma-Aldrich
Formamide, BioUltra, for molecular biology, ≥99.5% (T)
Sigma-Aldrich
Magnesium hydroxide, BioUltra, ≥99.0% (KT)
Sigma-Aldrich
Sodium phosphate monobasic monohydrate, BioXtra, for molecular biology, ≥99.5% (T)
SAFC
L-Aspartic acid
Sigma-Aldrich
Magnesium carbonate, meets USP testing specifications
Sigma-Aldrich
Ammonium acetate, reagent grade, ≥98%
Sigma-Aldrich
Formamide, BioReagent, ≥99.5% (GC), for molecular biology
Sigma-Aldrich
Methanol, anhydrous, 99.8%
Sigma-Aldrich
Ammonium acetate, 99.999% trace metals basis
Sigma-Aldrich
Sodium bicarbonate, BioXtra, 99.5-100.5%
Sigma-Aldrich
L-Aspartic acid, from non-animal source, meets EP, USP testing specifications, suitable for cell culture, 98.5-101.0%
Sigma-Aldrich
L-Aspartic acid, reagent grade, ≥98% (HPLC)
Sigma-Aldrich
Phthaldialdehyde, ≥97% (HPLC), powder or crystals
Sigma-Aldrich
Sodium bicarbonate, powder, BioReagent, for molecular biology, suitable for cell culture, suitable for insect cell culture
Sigma-Aldrich
Sodium bicarbonate, tested according to Ph. Eur.
Sigma-Aldrich
Acetic acid, for luminescence, BioUltra, ≥99.5% (GC)
Sigma-Aldrich
Potassium cyanide, BioUltra, ≥98.0% (AT)
Supelco
Ammonium formate, eluent additive for LC-MS, LiChropur, ≥99.0%
Sigma-Aldrich
Magnesium oxide, tested according to Ph. Eur., heavy
Supelco
Hydrogen chloride – methanol solution, ~1.25 m HCl (T), for GC derivatization, LiChropur
Supelco
Hydrogen chloride – ethanol solution, ~1.25 M HCl, for GC derivatization, LiChropur
Supelco
Acetic acid, analytical standard
Sigma-Aldrich
Hydrochloric acid solution, ~6 M in H2O, for amino acid analysis
Sigma-Aldrich
di-Sodium hydrogen phosphate dihydrate, BioXtra, ≥98.0% (T)
Sigma-Aldrich
di-Sodium hydrogen phosphate dihydrate, BioUltra, for molecular biology, ≥99.0% (T)
Sigma-Aldrich
Potassium fluoride, BioUltra, ≥99.5% (F)