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

## TL;DR

A clip-on adapter enables real-time Raman and fluorescence spectroscopy in microflow reactors, allowing monitoring of chemical reactions in semitransparent plastic tubes.

## Contribution

The development of a clip-on adapter for simultaneous inline Raman and fluorescence spectroscopy in semitransparent plastic pipes.

## Key findings

- The adapter allows real-time monitoring of chemical reactions in microflow reactors using Raman and fluorescence spectroscopy.
- The influence of integration time and flow rate on signal intensity was studied using olive oil as an example.
- The adapter was successfully demonstrated with vegetable oil mixtures and acid-catalytic esterification of ethyl acetate.

## Abstract

We present an adapter developed to clip a standard Raman probe (d = 9.5 mm) on semitransparent tubes (dOD = 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.

The online version contains supplementary material available at 10.1007/s00216-025-06213-3.