Improving the Detection Limit in a Capillary Raman System for In Situ Gas Analysis by Means of Fluorescence Reduction

Sensors

Simone Rupp¹  Andreas Off¹  Hendrik Seitz-Moskaliuk¹  Timothy M. James¹  Helmut H. Telle² 

[1] Institute for Technical Physics, Tritium Laboratory Karlsruhe, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany; E-Mails:;Instituto Pluridisciplinar, Paseo Juan XXIII-1, Universidad Complutense, 28040 Madrid, Spain; E-Mail:

关键词: Raman spectroscopy;    capillary;    gas analysis;    process control;    real-time monitoring;    instrument development;    fluorescence reduction;   

DOI  :  10.3390/s150923110

来源: mdpi

【 摘 要 】

Raman spectroscopy for low-pressure or trace gas analysis is rather challenging, in particular in process control applications requiring trace detection and real-time response; in general, enhancement techniques are required. One possible enhancement approach which enjoys increasing popularity makes use of an internally-reflective capillary as the gas cell. However, in the majority of cases, such capillary systems were often limited in their achievable sensitivity by a significant fluorescence background, which is generated as a consequence of interactions between the laser light and optical glass components in the setup. In order to understand and counteract these problems we have investigated a range of fluorescence-reducing measures, including the rearrangement of optical elements, and the replacement of glass components—including the capillary itself—by metal alternatives. These studies now have led to a capillary setup in which fluorescence is practically eliminated and substantial signal enhancement over standard Raman setups is achieved. With this improved (prototype) setup, detection limits of well below 1 mbar could be obtained in sub-second acquisition times, demonstrating the potential of capillary Raman spectroscopy for real-time, in situ gas sensing and process control applications, down to trace level concentrations.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.