Development of on-site chiral switching micro columns

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Recently, the racemization of optically-active and bioactive compounds or the role of D-amino acids etc. in vivo have been cleared. Additionally, the importance of chiral separation is increasing because the measurement of optical purity of chiral drug substances becomes important due to the side-effect problem etc., Meanwhile, the downsizing analytical devices are rapidly advanced. Only the separation system in the downsizing device is hardly improved because, in most case, the separation and flow systems are integrated in the same system.In this study, A micro column that is able to change the elution order of enantiomers by photo-irradiation was developed.Two photo-responsive chiral stationary phases (CSP(1) and CSP(2)) with an azobenzene moiety were prepared using D-and L-valine, respectively. Prepared stationary phases were continuously packed into a UV-permeable polymer-coated fused silica capillary tubing (100 mm, i.d.) with 20 cm of length, respectively, and used as a micro column. When 3,5-dinitrobenzoyl-D,L-leucine isopropyl ester and 3,5-dinitrobenzoyl-D,L-alanine methyl ester were used as test samples, the samples were eluted in this order, D-form and L-form, after a UV light was irradiated to only the part of CSP(1) in the column. Continuously, when a UV light was irradiated to the part of CSP(2) after a visible light was done to the CSP(1), the elution order became L-form and D-form. It can be seen that the reversible change in the retention order was caused by the reduction of the enantio-of the enantio-selectivity of the stationary phase by the UV light irradiation.