Chemometrics explained...
Evaluation & interpretation of chemical analyses with mathematical methods
How high is the pH value? What is the temperature at a heating wire? Which area does a peak cover in a chromatogram? – In the chemical field, these questions are examples of so-called "univariate" problems, i.e. "one-to-one correlations". The pH value depends only on the concentration of hydronium ions, the temperature of the heating wire depends only on the current intensity, and the peak area in a chromatogram is directly related to the concentration of an analyte.
In reality, such clear correlations are rarely found. More likely are "multivariate" problems. How much milk a cow gives depends, among other things, on her age, the amount of feed, the water supply, the type of feed, the ambient temperature or her state of health. A very rustic example of a measured variable with many influencing factors. But which variable has which influence? – When transferring this question to chemical-technical problems, usual analytical methods reach their limits and bring chemometrics into play: chemometrics is the combination of instrumental chemical analysis with mathematical and statistical models. The main field of application of chemometrics is spectroscopy. Statistical methods such as principal component analysis (PCA) or multiple linear regression (PLSR) are applied to spectroscopic measured values. In this way, multivariate problems can also be solved and, for example, quantitative statements about complex mixtures can be made on the basis of a single spectrum.
NIR spectrometers
Spectra recorded with near-infrared spectrometers are more difficult to interpret analytically due to the strong band overlap. Therefore, the use of chemometric models is mandatory for their evaluation. For applications in the field of plastics recycling, asbestos screening and narcotics analysis, users can rely on established methods and are immediately ready to measure (MicroNIR OnSite-W, microPHAZIR Asbestos, NIR Lab).
Users involved in quality control and process analysis are provided with powerful programs in the form of MicroNIR Pro software (for 1700ES, OnSite-W, PAT-L, PAT-U and PAT-W) or the Thermo-Method Generator (for microPHAZIR GP and microPHAZIR Rx), which enable them to build their own models using all common chemometric methods.
Chemometrics tool for mobile Raman spectrometers
Conventional Raman handhelds can usually only identify pure substances. However, the mobile Raman spectrometer TruScan RM, equipped with the chemometrics add-on TruTools – can also solve more complex problems, such as quantitative analyses.