DETERMINATION OF PPB-LEVEL CO, CO2, CH4, AND H2O IN HIGH-PURITY GASESUSING MATRIX-ISOLATION FT-IR WITH AN INTEGRATING SPHERE

Parts per billion-level CO, CO2, CH4, and H2O are determined in high-p urity argon and nitrogen gases bq using matrix isolation Fourier trans form infrared spectrometry with an integrating sphere. A linear respon se was observed in the corrected absorbance vs concentration of CH4 an d H2O in both matrices. While a linear response was also observed for CO and CO2 in argon matrix, a nonlinear response was found in nitrogen matrix. The latter is probably due to internal vibration-phonon inter action. Addition of argon into the nitrogen matrix resulted in a linea r response. Comparison with gas-phase FT-IR shows that the combination of the matrix isolation FT-IR technique with an integrating sphere al lows an enhanced sensitivity with a reduced sample volume.