Selected wavelength chromatograms

The effectiveness of mass selective detection in the SIM(MIM) mode and selected wavelength chromatograms (SWC) in FT-IR-detection depends on efficient sample clean-up. In raw extracts the risk of co-eluting substances which remain indiscri-minative from chiral volatiles increases with the complexity of flavouring and fragrance extracts to be analyzed. 

FIG. 4 Expanded Selective Wavelength Chromatogram (602-899 cm-1) of Total AromaMca... 

Two-component mixtures can be quantitatively analysed without a calibration chromatogram or calibration graph. Solutions of identical concentration are prepared of each pure compound and the UV spectra are recorded. If the wavelength at which the spectra lines intersect is chosen for detection (isosbestic point), then the peak area is identical with the mixing ratio of the sample, on condition that the UV detector used shows high stabiUty and excellent reproducibility of the selected wavelength (at least to 0.2 nm). 

The detector is set to measure the complexed metal band at a pre-selected wavelength. The results appear in the form of a chromatogram, essentially a plot of the time the band was retained on the column versus the signal it produces in the detector. Each metal in the sample can be identified and quantified by comparing the chromatogram against that of a standard solution. 

In uv absorbance detection, it is often useful to be able to detect different peaks in the chromatogram at different wavelengths. This may be because certain solutes have only a small absorptivity at the wavelength selected. At other times, a wavelength change can be used to edit out unwanted peaks. It is also useful to be able to record the spectrum of each component this can tell us the optimum detection... 

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