When the OH absorption intensity is high, a staight backgrount between 3700 and 3100 cm-1 results in a satisfactory integration (blue area on curve).
However, when the OH intensity is low, residual curvature in the background can make an arbitrary straight background a poor choice. In this example, the same range used above produces a poor result by including negative area (red) that should not be included in the integration.
The same curve with a background chosen by subjective interaction with the program. This produces a more realistic integration.
The same curve with a different subjective background chosen to be curved. This produces a signficantly greater area included in the integration. In our experience, better, more reproducible water contents are obtained with subjective baselines than with any systematic curve-fitting procedure we have tried.