Quantitative Analysis

Essential FTIR implements the most important techniques in Quant, developed in collaboration with some of the world's most expert practitioners of Chemometrics. These field-testes tools are used world-wide in critical enviromental, forensic, industrial and military applications.

  • Partial Least Squares (PLS)

    PLS is a very versatile technique used for liquid, solid and vapor phase samples.

    An advantage of PLS is that the method does not have to know about all possible constituents in a mixture. The standards used in the model need to incorporate the range of possible samples found in the field, but does not require spectra of pure compounds, as needed in CLS. Another advantage is that the full spectrum can often be used, it is not always necessary to indentify analysis regions for each compound in the PLS model.

    The PLS manual can be downloaded here: PLS_for_eFTIR.pdf

    The data that goes along with the manual's tutorial is here: setup_eftir_pls_tutorial.exe

  • Classical Least Squares (CLS)

    CLS is often used for the analysis of complex mixtures of gases (vapor phase samples), for instance combustion processes.

    CLS requires spectra of pure compounds of known concentrations, known as a 'standard' or 'calibration' spectrum. In some cases you may need only one standard for a given compound, if the concentration vs. absorbance curve is linear. Often, however, the absorbance will fall off at higher concentrations, so the calibration curve is not linear. In this case, for a more accurate measurement, it is necessary to provide more calibration spectra at a range of concentrations.

    Essential FTIR's CLS implementation is based on the 'multi-band weighting' technique combined with standard-bracketed interpolation, providing robust and sensitive concentration measurements.

    The CLS manual can be downloaded here: CLS_for_eFTIR.pdf

    The data that goes along with the manual's tutorial is here: setup_eftir_CLS.exe

  • Beer's Law Univariate Quantitative Analysis

    This is the analysis often taught in College Organic Chemistry courses.

    It is simpler than PLS and CLS, but is appropriate for many applications. It is called 'univariate' because it accounts for only one variable at a time, as opposed to CLS and PLS, which are multivariate techniques. The 'one variable' is the concentration of one compound. It can measure mixtures but it has no provision for subtracting or factoring out interferents and unknowns. The analyst must identify regions of the spectra in which only a given analyte absorbs with no inteference from other components in a mixture.

    Beer's Law Quant is included in the 'Core' and 'Complete' version of eFTIR.

Spectral Identification

  • Library Search

  • Library Search is included in the 'Core' and 'Complete' version of eFTIR. Click this link for more information about Library Search and Spectral Libraries: librarySearch.html

  • Quality Control Compare

  • QC Compare is often used to test incoming materials. It answers the simple question: "Is this or is this not the material it is supposed to be?". QC Compare is included in the 'Core' and 'Complete' version of eFTIR.