Refractive index detection food analysis

Refractive index monitors are used in food analysis, for detecting carbohydrates, alcohols, and other substances with weak or no UV absorption. 

Fig. 11.4.3. Analysis of common food sugars. Chromatographic conditions column, Spherisorb S5 NH2 (250x4.6 mm) mobile phase, acetonitrile-water (75 25) flow rate, 2.0 ml/min detection, refractive index. Reproduced from Macrae (1982), with...

Generally speaking, most inorganic anions and cations have weak absorption in UV-Visible spectral region. Thus, only selected ions can be determined by UV detection. Therefore other detection techniques such as amperometry, spectrometry, and refractive index are used for food analysis. The best detection limit is offered by mass spectrometry because of the reduction of chemical noise especially in complex matrices. 

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