Methods and apparatus for improving the long-term stability of spectroscopic quantitative analyses
OwnerRalf Marbachinventor
Life of this patent
Estimating the term…
Abstract
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.
Claims19
A method for improving the long-term stability of spectroscopic quantitative analyses performed on a population of samples, comprising the steps of:
- A) measuring a sample spectrum of one of said samples and a reference spectrum, by using measurement light and a spectroscopic instrument;
- B) computing an absorbance spectrum from said sample spectrum and said reference spectrum;
- C) inserting an inverse sample element into the path of said measurement light during either the measurement of said sample spectrum or the measurement of said reference spectrum, removing said inverse sample element out of said path of said measurement light during one of said measurements of said sample spectrum and said reference spectrum, the spectral response of said inverse sample element being determined from the spectral response of the average of said population of samples so that wavelength axis instabilities of said spectroscopic instrument cause opposite and nearly cancelled amplitude effects in a relevant wavelength range of said absorbance spectrum;
- and
- D) applying a computer algorithm to said absorbance spectrum to estimate the value of a property of interest;
- whereby the long-term accuracy of said quantitative analyses is improved and the need for calibration maintenance is reduced.
A method for improving the long-term stability of spectroscopic quantitative analyses performed on a population of samples, comprising the steps of:
- A) measuring a sample spectrum of one of said samples and a reference spectrum, by using measurement light and a spectroscopic instrument;
- B) applying a noise-filtering algorithm to said reference spectrum to obtain a filtered reference spectrum, wherein said noise-filtering algorithm is a smoothing algorithm;
- C) computing an absorbance spectrum from said sample spectrum and said filtered reference spectrum;
- and
- D) applying a computer algorithm to said absorbance spectrum to estimate the value of a property of interest;
- whereby amplitude effects caused by wavelength axis instabilities in said reference spectrum are prevented from propagating into said absorbance spectrum.
An optical element for improving the long-term stability of spectroscopic quantitative analyses performed on a population of samples, comprising:
- A) means for positioning said optical element into the path of the measurement light of a spectroscopic instrument;
- and
- B) means for shaping the spectral response of said optical element to be essentially proportional in a relevant wavelength range to a response spectrum selected from the group consisting of the spectral response of the average of said population of samples and the inverse of the product of the spectral responses from said spectroscopic instrument and said average of said population of samples.
Dependencies are inferred from the claim text.