A method of using a spectrometer to produce corrected diamond Attenuated Total Reflectance (ATR) spectral data includes acquiring, using the spectrometer, an initial set of ATR spectral data for a sample pressed into contact with a diamond ATR crystals; numerically matching, using the spectrometer, a pressure dependent diamond artefact reference spectrum to a corresponding pressure dependent diamond artefact in the initial set of ATR spectral data; and numerically subtracting out the numerically matched pressure dependent diamond artefact reference spectrum from the initial set of ATR spectral data to yield a corrected set of ATR spectral data for the sample for output by the spectrometer.