Development of the photoacoustic rapid-scan FT-IR-based method for measurement of ink concentration on printed paper.

Photoacoustic rapid-scan FT-IR spectroscopy was used to collect spectra of paper samples printed with mineral- and vegetable-oil-based inks at different concentrations. Partial least-squares (PLS) analysis and principal component analysis (PCA) were combined to form a model that, with data collected in the 3600-3200, 3000-2800, and 1800-1000 cm-1 spectral regions, enables one to predict the concentration of ink in printed samples. Prediction is statistically robust provided the selected optical path difference (OPD) velocities are within the range 0.05-1.00 cm/s.