FTIR calibration curves

TGA - coupled - FTIR calibration curves for "low boiling point" components... 

Figure 6.21 summarises the results described above. The deomposition products shown in this figure for a CPC, system B sample, were also measured for the CPC, system A samples, only differences in the measured intensities of released water (quantitatively determined with the aid of a MS calibration curve) and ammonia (quantitatively determined with the aid of a FTIR calibration curve) were found ... 

A Nicolet 7000 FTIR instrument was used for the infrared studies with 120 scans accumulated for all samples. The materials used for the FTIR study were prepared as follows samples of polymers of low glass transition temperatures which were soluble in THF were prepared by the deposition of a polymer solution onto an NaCl window. For moderately high glass transition temperature polymers soluble in THF, samples were prepared by solution casting onto a glass plate. Thin films of polymer samples insoluble in THF were compression molded at 150 to 200 C (depending on the sample). An FTIR calibration curve was obtained from ethyl acrylate copolymers which had previously been neutralized completely with perchloric acid. This curve was used to determine semiquanti-tively the percent proton transfer in the blends. 

A calibration curve is prepared, using absorbance versus concentration plot, so that the concentration of the unknown component can be determined. But quantitative analysis for a complex system like vulcanised rubber or a blend of two or three components, is not possible. The use of computers with the FTIR spectrometer, increases the rapid scanning capability, data processing for analysis of chemical or physical structural changes in polymers as a function of time over the entire mid-IR frequency. 

The intensity of the incident radiation (/q) and the intensity of the transmitted radiation (/) can be measured by the base-line method illustrated in Fig. 10. In the FTIR spectrometer, the computer is capable of converting the transmittance into absorbance, subtracting the background or the solvent interference from the sample spectrum, generating a calibration curve, and calculating the unknown concentration. 

Using spreadsheets to calculate unknown concentrations, and their standard deviations from the calibration curve, p. 481 Spectrometers (components) for UV, visible, and IR regions, p. 483 FTIR spectrometers, p. 499 Spectrometric error, p. 501 Fluorometry, p. 505 Optical sensors and fiber optics, p. 511... 

The linear relation between the IR absorption and the sample concentration makes calibration of the TGA - coupled - FTIR possible, for the determination of the total amount of components released during a TGA experiment. Quantitative MS component determinations are more complicated (due to more parameters) than quantitative FTIR component determinations but it might be possible if at least a part of the calibration curve is linear. 

The limitations for quantitative determinations of single components (both by the FTIR and the MS) were investigated by measuring calibration curves for the following pure components ... 

Carbon-13 NMR was used as the reference method to enable comparison of FT-Raman and FTIR spectroscopies as isotacticity determination methods. Calibration curves relating Raman scattering and IR absorption ratios to the carbon-13 NMR results are presented. The repeatability for both FT-Raman and FTIR measurements was comparable to that of carbon-13 NMR analysis and there was good correlation between between carbon-13 NMR and FT-Raman/FTIR results. The reliabilities of the three methods are statistically evaluated and compared. 9 refs. 

The molecular interactions were evaluated by FTIR spectroscopy. As an example, Figure 5 shows the FTIR spectrum of the insoluble PP residue from the extracted blend, after modification by BMI. Typical absorption bands of PS occur in the PP spectrum at 1601 cm and 699 cm caused by absorption of the skeleton oscillations of the benzene ring and the absorption of the aromatic substitution on it. This indicates that PS chains are grafted onto the PP molecules. Hence, no absorption band occurs in the FTIR spectrum of the unmodified PP/PS blend. For quantification of the grafting, the PS content was estimated from the area under the peaks at 1601 cm and 699 cm using a calibration curve. The amount of the grafted PS strongly depends on the BMI, but not as much on the DCP content. For example, at 1 wt% of BMI in the blend up to 2.5 wt% of... 

Fourier Transform Infrared Spectroscopy Fourier transform infrared spectroscopy (FTIR) coupled with an in situ probe is a powerful technique for instantaneously monitoring chanical species including monomers in a water-soluble polymerization matrix. Monomer concentrations can be determined from a partial least square (PLS) calibration curve estabhshed from a sales of reference samples with known monomer concentration generated by HPLC analysis. The determination of residual monomer is limited only by the sensitivity of the detector. Calihration curves are product and formula specific. 

After the analyses of the calibration standards is complete, the GC/FTIR is calibrated by generating the selective reconstruction chromatograms for each analyte and the internal standard from the frequency ranges in Table 6. These GC peaks are integrated and calibration curves for each analyte are obtained. 

Concentrations of phenols IV and V were estimated from the sharp phenol -OH FTIR absorption at 3620-3650 cm, based upon calibration curves for each specific phenol. Concentrations of the completely unhindered phenols (I-III) could not be measured by this method as the phenolic OH of these compounds was a broad IR absorption at -3400 cm. This was obscured by corresponding absorption of the alcohol and hydroperoxide oxidation products from the PP. 

The curve-fitting calibration technique is a process whereby sample spectra are modeled as linear combinations of constituent spectra. This procedure is better suited for the analysis of a mixture of known components than for complex biopolymers such as lignin. Nevertheless, ongoing successful work throughout the world on the calibration of FTIR data with those of wet chemistry demonstrates that FTIR spectroscopy can be a powerful tool for quantitative (or at least semi-quantitative) lignin analysis. 

Fig. 9 Steps for automated determination of metastable zone using ATR-FTIR and FBRM. While automatically collecting the IR spectra for calibration, the metastable limit is determined using FBRM. Then the model for relating the IR spectra to solution concentration is constructed using multivariate analysis such as principal component regression (PCR) or partial least squares (PLS). Using this model, the solubility curve can be obtained from the IR spectra of saturated slurry.

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