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Figure 4. Different types of NIR instruments: a) bench-top, high-precision instruments; b) mini-spectrometers, c), d) various types of portable instruments and probes which allow measurements in situ and in vivo, of a variety of samples and at various locations
5. How does Aquaphotomics work?
In the near infrared region, the spectrum of water, or any aqueous system, for example body fuids, or even tissues will look very similar – it will be dominated by a few large absorbance bands of water – so called overtones of water and its combination bands3,6 (Figure 5). Finding the differences in such spectra using only visual observation is an impossible task.
Figure 5. Absorbance spectrum of liquid water in near infrared region (based on the data from Palmer and Williams9)
Any change of water spectra is very subtle, and analysis and extraction of information requires specifc multivariate tools10.
Multivariate analysis allows extraction of information about the water molecular conformations, i.e. water species – by fnding the specifc water absorbance bands where changes in the spectra occur in response to some perturbation (Figure 6). The places in the spectra where absorbance of