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

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

Ammonium acetate, 99.999% trace metals basis

Sigma-Aldrich

Isopropyl alcohol, ≥99.7%, FCC, FG

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Ammonium formate, ≥99.995% trace metals basis

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di-Sodium hydrogen phosphate dihydrate, tested according to Ph. Eur.

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Potassium fluoride, BioUltra, ≥99.5% (F)

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Potassium cyanide, BioUltra, ≥98.0% (AT)

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Acetic acid, for luminescence, BioUltra, ≥99.5% (GC)

Supelco

Ammonium formate, eluent additive for LC-MS, LiChropur^™, ≥99.0%

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Formamide, BioUltra, for molecular biology, ≥99.5% (T)

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Ammonium acetate, BioUltra, for molecular biology, ≥99.0%

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Magnesium hydroxide, BioUltra, ≥99.0% (KT)

Supelco

Methanol, analytical standard

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Ammonium acetate solution, BioUltra, for molecular biology, ~5 M in H₂O

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Sodium phosphate monobasic monohydrate, BioXtra, for molecular biology, ≥99.5% (T)

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Hydrochloric acid solution, ~6 M in H₂O, for amino acid analysis

Supelco

Hydrogen chloride – 2-propanol solution, ~1.25 M HCl (T), for GC derivatization, LiChropur^™

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Magnesium oxide, tested according to Ph. Eur., heavy

Supelco

Hydrogen chloride – ethanol solution, ~1.25 M HCl, for GC derivatization, LiChropur^™

Supelco

Hydrogen chloride – methanol solution, ~1.25 m HCl (T), for GC derivatization, LiChropur^™

Sigma-Aldrich

L-Aspartic acid, BioUltra, ≥99.5% (T)

SAFC

L-Aspartic acid

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Potassium fluoride, anhydrous, powder, ≥99.9% trace metals basis

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Formamide, ACS reagent, ≥99.5%

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Magnesium oxide, ≥99.99% trace metals basis

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Acetic acid, ≥99.5%, FCC, FG

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Methanol, suitable for HPLC, gradient grade, 99.93%

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Magnesium oxide, nanopowder, ≤50 nm particle size (BET)

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Phthaldialdehyde, for fluorescence, ≥99.0% (HPLC)

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Hydrochloric acid, 36.5-38.0%, BioReagent, for molecular biology

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Formamide, BioReagent, ≥99.5% (GC), for molecular biology