The advantages and disadvantages of attenuated total reflectance, ATR, infrared spectroscopy

摘要

Fourier transform infrared spectroscopy, FT-IR, is a powerful analytical technique for the rapid qualitative and quantitative analysis of lubricants and additives. However, the transmission of infrared radiation through opaque samples is impossible and variations in path length when capillary films of lubricant are used can be problematical. Specifically, thicker films exhibit more intense absorption in accordance with Beer's law. Attenuated total reflectance spectroscopy is a surface technique that facilitates the acquisition of spectra from lubricant samples containing molybdenum disulfide, graphite, and other solid additives. It is also extremely useful for the routine analysis of oils and thickeners. Moreover, since the procedure results in a constant depth of penetration of the infrared radiation, cell path length issues are virtually eliminated. Disadvantages of the technique include poor resolution of analytes possessing a weak extinction coefficient especially when the analyte is present at low concentration.