Multivariat least-squares methods applied to the quantitative spectral analysis of multicomponent samples

Journal Article · Tue Jan 01 00:00:00 EST 1985 · Appl. Spectrosc.; (United States)

DOI:https://doi.org/10.1366/0003702854249376· OSTI ID:5951942

Haaland, D M; Easterling, R G; Vopicka, D A

In an extension of earlier work, weighted multivariate least-squares methods of quantitative FT-IR analysis have been developed. A linear least-squares approximation to nonlinearities in the Beer-Lambert law is made by allowing the reference spectra to be a set of known mixtures, The incorporation of nonzero intercepts in the relation between absorbance and concentration further improves the approximation of nonlinearities while simultaneously accounting for nonzero spectra baselines. Pathlength variations are also accommodated in the analysis, and under certain conditions, unknown sample pathlengths can be determined. All spectral data are used to improve the precision and accuracy of the estimated concentrations. During the calibration phase of the analysis, pure component spectra are estimated from the standard mixture spectra. These can be compared with the measured pure component spectra to determine which vibrations experience nonlinear behavior. In the predictive phase of the analysis, the calculated spectra are used in our previous least-squares analysis to estimate sample component concentrations. These methods were applied to the analysis of the IR spectra of binary mixtures of esters. Even with severely overlapping spectral bands and nonlinearities in the Beer-Lambert law, the average relative error in the estimated concentration was <1%.

• Research Organization: Sandia National Laboratories, Albuquerque, New Mexico 87185
• OSTI ID: 5951942
• Journal Information: Appl. Spectrosc.; (United States), Vol. 39:1
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
QUANTITATIVE CHEMICAL ANALYSIS
ESTERS
INFRARED SPECTRA
COMPUTER CALCULATIONS
EQUIPMENT INTERFACES
LEAST SQUARE FIT
CHEMICAL ANALYSIS
MAXIMUM-LIKELIHOOD FIT
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
SPECTRA
SPECTROSCOPY
400104* - Spectral Procedures- (-1987)