Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Chemical analysis
Patent
1996-04-03
1999-08-03
Kemper, Melanie A.
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Chemical analysis
702 85, 73 103, 356303, 2502521, G01N 2127
Patent
active
059337923
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the standardization of spectrometers generating an optical spectrum of a sample.
It has always been desired to be able to manufacture spectrometers which generate the same spectra when exposed to the same sample. However, due to the extreme sensitivity of spectrometers to the optical properties of the samples and, to the other optical elements of the spectrometers, this has proven impossible.
The optimal instrument would be an instrument of which identical copies could be manufactured and the measurements of which, in addition, never drifts. This means that the same calibration may be used throughout the life time of the instrument and, which is equally important, that calibrations may be developed on any instrument and may be freely transferable to all other instruments. The best alternative to this instrument would be a method of standardizing all instruments into a well defined state in which the above interchangeability of calibrations was possible.
As it will be impossible to manufacture identical spectrometers, work has been done in the field of attempting to standardize the instruments and, therefore, decrease the work load required by subsequent spectrometers, once a first spectrometer has been fully calibrated.
Ruhl (WO 93/03341) has worked with the concept of determining the spectrum of an etalon as well as the development of a calibration on a master instrument and subsequently transferring the etalon and the calibration to a field instrument which will seemingly require no further calibration. In this reference, the spectrum of the sample alone and the sample together with the etalon are subtracted in order to generate the spectrum of the etalon alone. On the basis of this etalon spectrum and a reference spectrum of the etalon, the spectrum of the sample is corrected accordingly.
However, the method of Ruhl generates a number of strictly individual references (etalons) which all have to be introduced into the master instrument. In order to generate additional slave instruments, the master instrument must exist and should, which is not possible, be exactly the same each time additional etalons are introduced and each time a new calibration is developed. If the master instrument is not exactly the same each time, the old calibration will not suit the new slave instruments or the new calibration will not suit the old slave instruments. The only solution is a re-measurement of all etalons in all slaves. Thus, the method of Ruhl does not solve the above task completely, as the method of this reference does not provide complete interchangeability of calibrations and more or less complete standardization of the instruments.
The method of Ruhl, due to the position of introduction of the etalon, corresponds to performing a determination of the background spectrum. This means that this method does not take into account the difference in light absorption when e.g. a sample holding cuvette is replaced. This is preferably avoided, as this will typically influence the operation of the spectrometer.
Also others have worked in the field of changing the state of an instrument in order to avoid a demanding re-calibration of the instrument: Yongdong Wang et al.: "Improvement of Multivariate Calibration through Instrument Standardization", Anal. Chem. 1992, 64, pp 562-64, Shenk et al. U.S. Pat. No. 4,866,644, Pittaro et al. U.S. Pat. No. 5,341,206, Maggard U.S. Pat. No. 5,243,546 and Ganz EP-A-0 560 006.
These methods either describe how to transform an instrument from its present state to its initial state or how to transform the present state of one instrument to the present state of another instrument. However, none of these methods describe how to transform an instrument to a well defined state--and preferable a state into which any number of instruments may be transformed.
However, a method of the above type is, in fact, provided by the present invention of which a first aspect relates to a method for standardizing a spectrometer generating an optical spectrum from a sample, c
REFERENCES:
patent: 5121337 (1992-06-01), Brown
patent: 5272345 (1993-12-01), Durham et al.
patent: 5545895 (1996-08-01), Wright et al.
patent: 5592402 (1997-01-01), Beebe et al.
Andersen Hans Villemoes
Hansen Per Waaben
Kjaer Lisa
Ridder Carsten
Foss Electric A/S
Kemper Melanie A.
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