Applicability of laser-induced Raman microscopy for in situ monitoring of imine formation in a glass microfluidic chip

Abstract

Laser-induced Raman microscopy has been used to illustrate its applicability for the in situ monitoring of imine formation reaction in a glass microfluidic chip. In order to monitor the diffusion process in a micro channel, the Raman spectra were measured at various points along the channel with a constant flow rate of 2.7 mul min(-1). Time-dependent Raman spectra were also measured without flow in order to monitor the variation of Raman peaks to a complete conversion. The disappearance of the C=O stretching peak at 1700 cm(-1) of the reactant, benzaldehyde, and the appearance of the Raman peak for the product, an imine, at 1628 cm(-1) were successfully monitored. In addition, the intensity increases of three phenyl stretching modes in the 1550-1630 cm(-1) region were also observed. The increase in Raman intensity for this vibrational mode is caused by an effective pi-electron conjugation between two phenyl rings through the -C=N - bridging group of the product. Laser-induced Raman microscopy enables us to monitor in situ product formation and to obtain detailed structural information in a glass microfluidic chip. Copyright (C) 2003 John Wiley Sons, Ltd.