Methods and apparatus for improving the long-term stability of spectroscopic quantitative analyses

摘要

The long-term stability of the analytic accuracy of spectroscopic measurements is often limited by wavelength axis instabilities of the hardware. A dedicated optical element called the inverse sample element (4) is inserted into the path of the measurement light. The optical response of the inverse sample element (4) is determined from the spectral response of the average sample (3) in such a way that wavelength axis instabilities of the instrument hardware cause opposite and nearly cancelled amplitude effects in the resulting absorbance spectrum. The inverse sample element (4) can be movable or permanently mounted inside the instrument and is preferably made from a thin-film structure.