{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,4]],"date-time":"2026-02-04T16:24:24Z","timestamp":1770222264828,"version":"3.49.0"},"reference-count":19,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2015,9,11]],"date-time":"2015-09-11T00:00:00Z","timestamp":1441929600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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\u2014including the capillary itself\u2014by 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.<\/jats:p>","DOI":"10.3390\/s150923110","type":"journal-article","created":{"date-parts":[[2015,9,15]],"date-time":"2015-09-15T03:46:33Z","timestamp":1442288793000},"page":"23110-23125","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":17,"title":["Improving the Detection Limit in a Capillary Raman System for In Situ Gas Analysis by Means of Fluorescence Reduction"],"prefix":"10.3390","volume":"15","author":[{"given":"Simone","family":"Rupp","sequence":"first","affiliation":[{"name":"Institute for Technical Physics, Tritium Laboratory Karlsruhe, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany"}]},{"given":"Andreas","family":"Off","sequence":"additional","affiliation":[{"name":"Institute for Technical Physics, Tritium Laboratory Karlsruhe, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany"}]},{"given":"Hendrik","family":"Seitz-Moskaliuk","sequence":"additional","affiliation":[{"name":"Institute for Technical Physics, Tritium Laboratory Karlsruhe, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany"}]},{"given":"Timothy","family":"James","sequence":"additional","affiliation":[{"name":"Institute for Technical Physics, Tritium Laboratory Karlsruhe, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany"}]},{"given":"Helmut","family":"Telle","sequence":"additional","affiliation":[{"name":"Instituto Pluridisciplinar, Paseo Juan XXIII-1, Universidad Complutense, 28040 Madrid, Spain"}]}],"member":"1968","published-online":{"date-parts":[[2015,9,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/0924-2031(94)00050-Q","article-title":"Remote Raman spectroscopy for process control","volume":"9","author":"Marteau","year":"1995","journal-title":"Vib. 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