Home| Analytics for Chemistry, Biology and Production: | |||
| Multi Komponenten Analyse (MKA) ist nichts anderes als absolut “normale” Spectroskopie, — nur, 'Sie' verzeiht keinen Fehler den du machst ! P. Forster | |||
|
Home |
The author of this page is independent and has no commercial intention in mind ! | This Page in English. | |||||
| For the first moment,
I can give you only a very rudimentary description of what real MCA will be: noch nicht mehr ins Deutsch zurück übersetzt![1] |
|||||||
| Spectral comparison is performed using MCA,[2,
18], a simple least-squares regression algorithm which compares a test/sample spectrum
with a file of standards, and constructs the least-squares fit from a linear combination. The proportions of each
spectrum are converted into component concentrations. Combined with the RFE it is certainly one of the most powerful tools a spectroscopist can use. It may be hard to belief, but it is equally true, that almost every spectroscopist has to learn his business from the basis again. We experienced during the first year, and were running nearly into every pitfall you can or you can’t think of. We have now succeeded to carry out MCA to such a perfection, that even less trained technicians are able to apply MCA spectroscopy in the daily routine and in production, in a safe and reliable way, and they are able to test their work by interpreting the RFE. To have this great benefit of using MCA in conjunction with the RFE, it is absolutely important to keep the spectrometer in use all the time in exactly the same “very good” shape. This is easily possible with the procedure described in report: New System Suitability Test for ...... Relative Fit Error (RFE): Don’t mingle this definition of “RELATIVE FIT ERROR” with the one for the “NORMAL” Fit Error, which is reported almost in every mathematics and/or statistic book. This RFE has an absolutely different significance level than the other. The RFE played already a very important part in the report on our experiences made in the NNIR wavelength range, [18], and is well accepted in routine work of our customers. The RFE is the most important parameter of the Multi Component Analysis, as it will tell you if it is allowed to interpret the concentration results calculated by MCA, or if you did not strictly follow a spectrometric rule. The RFE is calculated from the residual spectrum. The residual at each wavelength is weighed to the noise at this wavelength, squared and summed to give the RFE. The mathematical formula is given in equation 1: 
(1)
where n is the number of wavelengths,  1to
n; abs(i) is
the residual at the wavelength i;noise(i) is the noise at the wavelength i; the number of components is equal to the number of standards. This means, that the value of the RFE of a calculated MCA should be as low as possible. The best RFE with a value of 1.0 can be interpreted in the way, that the residual spectrum (the part of the sample spectrum the MCA algorithm was not able to modeling) is from the same size and kind as the noise that was present at the moment the sample spectrum was taken. If there is only a minor mistake, for example in preparation the sample (“You think”) the value of the RFE will explode. |
|||||||
|
For References: see also under References on the page “System Suitability Test (SST)” (To give you a helping hand is also a risen, why I opened this Site!) |
|||||||
 References:[1] "Multi Component Analysis (MCA), nothing else, as absolutely "normal" Spectroscoy:" [2] "Matrix Representations and Criteria for Selecting Analytical Wavelengths for
Multicomponent Spectroscopic Analysis", [18] "Near
Near Infrared Spectroscopy for Quantitative and Qualitative Quality Control”, |
|||||||
| I will do what ever possible to serve you a vine you will remember! | |||||||
| Keep hope alive. Peter Forster | |||||||
|
Software Development & Consulting Peter Forster Neubadstrasse 88 CH-4054 Basle, Switzerland Mail to: peter.forster@p-forster.com |
This Page in English. |