What is mid infrared (MIR) spectrometry in relation to soil analysis?
Spectrometry is the combination of spectroscopy and chemometric (multivariate statistical) methods, in order to identify and/or quantify chemical species. Infrared radiation light and heat energy in a continuous distribution of varying wavelengths, with frequencies in the near infrared (NIR) range 16600 to 4000 cm-1 (600-2500 nm) and in the mid infrared (MIR) range 4000 to 500 cm-1 (2500 to 20,000nm). Frequencies in the NIR are generally overtone and combination bands from the fundamental vibrations seen in the MIR. When this radiation is focused onto a sample, the molecules in the sample will increase their vibrational energy by absorbing specific frequencies depending on the molecular geometry, bond strengths and atomic masses. The resulting radiation is thus modified, resulting in a spectrum or “signature” of the molecular composition with peaks at the absorbing frequencies. In practice, for soils, this is most conveniently and rapidly done using diffuse reflectance, where the incom
