Trading Wavelength for Absorbance Resolution: Predicting the Performance of Array Detection Systems

Mid-infrared spectra of liquid mixtures measured at 4 cm⁻¹ resolution and near-infrared spectra of synthetic natural gas samples measured at 2 cm⁻¹ resolution were convoluted to determine the effect of low resolution on multicomponent analyses of these samples. The resolution of the liquid samples could be degraded to almost 100 cm⁻¹ before significant effects on the quantitative results were observed. The minor components in the natural gas samples were sensitive to degrading the resolution; however, the major components, methane and ethane, and the BTU values were unaffected until the resolution was degraded to over 100 nm (∼600 cm⁻¹ at 1225 nm). The convoluted spectra were also displayed across a simulated array detector to determine the effect of the number of pixels on quantitative analysis. Excellent results were obtained on the convoluted spectra of both the liquid and gas mixtures with 32 elements. The liquid samples could be analyzed with as few as 8 pixels.