Numerical methods for comparison of oils by FTIR

ASTM standard test method D 3414-98 is used by the Environment Protection Authority, New South Wales to compare IR spectra of an oil spill with those of suspect oils. The method recommends comparison of spectra by physically overlaying scaled spectra on transparencies. With modern FT methods which provide digitised spectra, numerical methods must offer an improved approach to this task. We have investigated four point-to-point comparison statistics, namely the Euclidean distance, first derivative Euclidean distance, correlation coefficient and first derivative correlation coefficient. All four methods work well to distinguish between replicate measurements of the same sample and of different oil samples in the fingerprint region of 900-700 ern", with the first derivative methods being best