title: Comparison of the use of volume fractions with other measures of concentration for quantitative spectroscopic calibration using the classical least squares method.
abstract: Since the commercial development of modern near-infrared spectroscopy in the 1970s, analysts have almost invariably used units of weight percent as the measure of analyte concentration, due largely to the historical precedent from other analytical methods, including other spectroscopic techniques. The application of the CLS algorithm to a set of binary and ternary liquid mixtures reveals that the spectroscopic measurement sees the sample differently; that the measured absorbance spectrum is in fact sensitive to the volume fraction of the various components of the mixture. Because there is not a one-to-one relationship between volume fraction and other measures of analyte concentration, nor is the relationship linear, this has important implications for the application of both the CLS algorithm and the various other, more conventional, calibration algorithms that are commonly used.
authors.affiliation: Mark Electronics, 69 Jamie Court, Suffern, New York 10901, USA. hlmark@nearinfrared.com
authors.forename: Howard
authors.initials: H
authors.lastname: Mark
authors.forename: Ronald
authors.initials: R
authors.lastname: Rubinovitz
authors.forename: David
authors.initials: D
authors.lastname: Heaps
authors.forename: Paul
authors.initials: P
authors.lastname: Gemperline
authors.forename: Donald
authors.initials: D
authors.lastname: Dahm
authors.forename: Kevin
authors.initials: K
authors.lastname: Dahm
mesh_terms: D000465:Algorithms; D002138:Calibration; D002725:Chloroform / Q000737:chemistry; D006536:Heptanes / Q000737:chemistry; D016018:Least-Squares Analysis; D008752:Methylene Chloride / Q000737:chemistry; D015999:Multivariate Analysis; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D014050:Toluene / Q000737:chemistry
chemical_list: D006536:Heptanes; D014050:Toluene; C028618:n-heptane; D008752:Methylene Chloride; D002725:Chloroform