Sensitivity improvement of circular dichroism detection in HPLC by using a low‐pass electronic noise filter: Application to the enantiomeric determination purity of a basic drug

Abstract

The quality control of chiral drugs requires the determination of their enantiomeric purity. Nowadays, circular dichroism (CD) spectroscopy is gaining increasing importance in pharmaceutical analysis because of the commercially available CD detector in liquid chromatography. The separation of the two enantiomers of a basic drug (efaroxan) was achieved by high performance liquid chromatography using an amylose-derivated column with both UV and CD detections. A baseline-resolved separation (resolution: 5) was obtained after optimization of the mobile phase composition with hexane-ethanol-diethylamine (90:10:0.05; v/v/v). The use of a commercial low-pass electronic noise filter of the CD signal has improved the signal-to-noise ratio by a factor twelve and allowed the quantitation of each enantiomer in the 1.25-300 microg ml(-1) concentration range. The CD linear calibration curve, expressed in terms of stereoisomer height ratio versus concentration ratio, was plotted over the 0.4-6% range. A correlation coefficient greater than 0.999 was obtained by least-squares regression and the limit of detection for the distomer/eutomer ratio was estimated at 0.14%. Although the method validation showed good repeatability on the retention times (RSD < 0.9%), on the peak height ratios (RSD < 8.7%) of each enantiomer only up to 99.2% enantiomeric purity was achieved.

Chiroptical fingerprints to characterize lavender and lavandin essential oils

“…polarimetric and circular dichroism (CD) detectors [2][3][4] , were developed [5] and are nowadays routinely used in HPLC on chiral support to identify and differentiate chiral molecules [6] . Moreover, chiroptical detectors can be applied to the determination of enantiomeric ratios on chiral stationary phases (CSPs) with baseline [7] or partial separation [8,9] , but also on achiral support [10][11][12][13] , to preparative purposes [14,15] , and to the assignment of absolute configurations [16][17][18] . They have sometimes been used to characterize complex mixtures focusing on chiral components [19] , because the analysis is simplified by hiding achiral molecules, which are not sensed by chiroptical detection.…”

Microscale methodology for structure elucidation of natural products

“…Chiracel®, Chirex® or Pirkle-type columns), gives signed peak intensities of resolved of enantiomers whose integrals identify both optical purity (enantiomeric excess, %ee) and the sign of Δε for the major enantiomer. [xlvi] Conversely, CD-detected HPLC with achiral columns can be used for determination %ee of known molecules with well-characterized g values by simultaneous measurement of CD and UV spectra, ratioing of the ε and Δε signals and comparison with g values of the pure compound. [xlvii],[xlviii],[xlix] HPLC with CD detection has been used in quantifying enantiomeric ratios for a variety of synthetic molecules, and has potential applications to natural products analysis, particularly with compounds that exist as non-racemic mixtures of enantiomers.…”

Synthesis and Quantitative Analysis of Diastereomeric Linked Ester Conjugates With Remote Stereocenters Using High‐Field NMR and Chiral HPLC

“…Diastereomeric homogeneity of the target conjugates depends on both the er of the starting compounds as well as on the stability of the constituents that could racemize throughout the linking procedure. The requirements to homogeneity of the target prodrug are stringent; the desired level is usually set at molar 0.1% content of the undesired stereoisomer . This value has to be at least as high as the limit of quantitation (LOQ) for an assured analysis.…”

“…The requirements to homogeneity of the target prodrug are stringent; the desired level is usually set at molar 0.1% content of the undesired stereoisomer. 27 This value has to be at least as high as the limit of quantitation (LOQ) for an assured analysis. Works where high-performance liquid chromatography (HPLC) [27][28][29][30][31] or capillary electrophoresis 32,33 (CE) have been used describe particular efforts made in order to improve stereochemical analysis.…”

“…27 This value has to be at least as high as the limit of quantitation (LOQ) for an assured analysis. Works where high-performance liquid chromatography (HPLC) [27][28][29][30][31] or capillary electrophoresis 32,33 (CE) have been used describe particular efforts made in order to improve stereochemical analysis. Chiral HPLC has been routinely used for the determination of er of enantiomeric compounds, but less often used for the analysis of diastereomers with remote stereocenters.…”