Clip-on adapter for simultaneous inline Raman and fluorescence spectroscopy inside semitransparent plastic pipes

We present an adapter developed to clip a standard Raman probe (d = 9.5 mm) on semitransparent tubes (d_OD = 0.25″ = 6.35 mm), thus allowing inline spectroscopic measurements in continuous microflow reactor systems. The clip-on adapter can be placed at any position along a fixed or flexible tube, enabling real-time monitoring and control of chemical reactions in the micro-reactor. In addition to Raman scattering, which is detected in reflection mode, the Raman laser (λ = 532 nm) also excites fluorescence, detected at a 90° angle relative to excitation. The simultaneous application of Raman and fluorescence spectroscopy is demonstrated by analyzing various vegetable oil mixtures of sunflower and olive oil. The influence of integration time and total flow rate on the signal intensity was investigated on the example of olive oil. Acid-catalytic esterification of ethyl acetate serves as a typical use case for non-contact inline Raman monitoring in a microflow reactor.