Calibration of a Fourier transform infrared spectrometer for hydrogen peroxide vapour measurement

A new method is described to calibrate a Fourier transform infrared (FTIR) spectrometer for the measurement of hydrogen peroxide (H2O2) vapour. A stream of nitrogen gas is bubbled through a 90% weight-to-weight solution of aqueous H2O2 to create a stream of vapour comprising of nitrogen, water and hydrogen peroxide. The vapour exiting the H2O2 bubbler is then measured by the FTIR spectrometer and then bubbled through a water bubbler which captures the H2O2, enabling the average concentration of the H2O2 vapour leaving the H2O2 bubbler to be determined. The average concentration obtained using the FTIR spectrometer is compared to the average concentration obtained from the H2O2 stored in the water bubbler to obtain a scaling factor and create a valid reference spectra at a known concentration. An advantage of using the average concentration to determine a scaling factor is that a stable concentration of H2O2 vapour is not required to obtain a valid reference spectra, which makes the calibration more robust and therefore more repeatable. The approach also has the advantage of being recursive, in that the initial reference spectra can be used to obtain new improved reference spectra. Calibration results are presented for H2O2 vapour concentrations in the range of 20–500 ppm. A good linear calibration curve was obtained with a coefficient of determination (R2) of 0.9998, and results which suggest an achievable resolution of ±3% of the reference vapour concentration.