Question

How does a multivariate technique enhance selectivity?

Answer 1

There are various fields which uses multivariate technique to enhance selectivity. Raman spectroscopy and NMR spectroscopy, Infrared spectroscopy etc. Especially the entire spectroscopy field uses this techniques to interpret the final results with accuracy by using sensitivity and selectivity techniques. For example consider the following Raman spectra.

from the above figure, the spectra-to-spectra overall intensity varies siginificantly. A wide variety of approaches can be taken to normalize the spectra, to suppress the background interference, and enhance selectivity and accuracy. Quantitativee methods for Raman spectroscopy using univariate and multivariate methods are treated extensively elsewhere. In this example, a second derivative was applied to the spectra, which removes baseline variation and enhances band resolution (selectivity in signal and enhancing its resolution), followed by a univariate intensity calibration. Although limit of quantitation will vary widely depending on the analyte and matrix. The critical factor affecting every aspect of the Raman spectroscopy system is the weakness of the Raman effect. The same technique is also used in NMR spectroscopy to remove noise signals and enhances real signal resolution by scanning the sample (analyte) in a NMR tube inserted into NMR magnet by multiple times of 8 due to quadrant rule.

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