Attenuated total reflectance infrared microspectroscopy of coal

The measurement of i.r. microspectra utilising an attenuated total reflecti on (ATR) objective is described. The ATR objective contains a small crystal about 100 mu m in diameter which must contact the coal surface. This allow s i.r. spectra to be measured from standard polished petrography blocks, wi thout further preparation. The spectra obtained are similar to normal absor ption spectra, unlike specular or diffuse reflection spectra. The spectra r eflect the changes in coal structure with rank typically seen with macro i. r. methods. A silicon crystal gave better results than a germanium crystal because it has a greater depth of penetration into the sample. (C) 2000 Els evier Science Ltd. All rights reserved.