Chiral analysis of milnacipran by a nonchiral HPLC--circular dichroism: improvement of the linearity of dichroic response by temperature control.
The determination of the enantiomeric excess (e.e.) of a basic drug has been investigated in LC using a nonchiral stationary phase and a circular dichroism (CD) detector in order to avoid expensive chiral columns. The CD detector records both dichroic (Deltaepsilon) and UV (epsilon) signals at the same wavelength and calculates the anisotropy factor (g=Deltaepsilon/epsilon), which is linearly related to the e.e. The enantiomeric and chemical composition of a chiral drug can be simultaneously determined on a nonchiral HPLC support. However, the g factor from the CD signal is temperature dependent. Indeed, the temperature has an influence on the stability of the CD signal and the linear regression between g factor and the e.e. of 1R,2S-enantiomer. So, a decrease in temperature gives rise to an improvement of the above-mentioned linearity correlation. After optimization of chromatographic parameters (porous graphitic carbon-based column, methanol/ phosphate buffer as mobile phase) and selection of CD wavelength, a linear regression of g factor versus e.e. of 1R,2S-enantiomer was obtained at temperature-controlled CD detection and an LOQ of 94% was found. The enantiomeric composition of milnacipran was determined with good accuracy.
Lecoeur-Lorin
Marie
M
Institut de Chimie Organique et Analytique (ICOA), CNRS FR 2708, UMR 6005, Université d'Orléans, Orléans, France.
Delépée
Raphaël
R
Ribet
Jean-Paul
JP
Morin
Philippe
P
D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods; D002942:Circular Dichroism / Q000295:instrumentation / Q000379:methods; D003521:Cyclopropanes / Q000032:analysis*; D016014:Linear Models; D000078764:Milnacipran; D008968:Molecular Conformation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D013696:Temperature; D013997:Time Factors
D003521:Cyclopropanes; D000078764:Milnacipran