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Quantitative Determination of F2 in Gaseous Samples by Microwave Plasma Emission Spectrometry Disclosure Number: IPCOM000127280D
Publication Date: 2005-Aug-19
Document File: 2 page(s) / 36K

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Quantitative Determination of F2 in Gaseous Samples by Microwave Plasma Emission Spectrometry



Two common analytical techniques that provide real-time for measuring F2 are mass spectrometer (MS) and UV absorption spectroscopy.  The MS sometimes cannot be applied to analyzing high-level corrosive gases, such as F2 and Cl2.  Corrosive chemicals often damage the MS instrument, results in a change in the instrument response during the measurement.  A


patent was recently awarded for using UV absorption spectroscopy to measure high level F2.  The detection limit of the UV absorption spectroscopy depends on the optical path length of the gas cell.  The longer the gas cell, the lower the detection limits.  The required length of the gas cell makes it impractical to use the UV absorption technique for measuring F2 at level below 1000 parts per million (PPM). 

We propose the use of emission spectroscopy to measure the analytes including corrosive species.  The detection limit of the emission spectroscopy ranges from a few PPM to as high as ten percent.  This technique could fill the gap between the dynamic range of the MS and the UV absorption spectroscopy.

 To obtain the emission spectrum, analyte molecules must be electronically excited by either a microwave 1,2,3 or high-voltage.4,5  These excited state species each have strong and distinctive emission profiles.  For example, F2* could be produced directly in the microwave discharge.  F2* has several emission bands ranging from 7510-4220oA.6  We can choose the strong emission bands at 6517.2 and 6102.8 oA for low- level detection and weak emission ban...