Chapter 4. Colorimetric Reactions

SAMPIETRO, D. A.; SGARIGLIA, M. A.; SOBERÓN, J. R.; QUIROGA, E. N.; VATTUONE, M. A.

Isolation, Identification and Characterization of allelochemicals/Natural Products

Science Publishers Inc.

Lugar: Einfield, New Hampshire, USA.; Año: 2009; p. 73 - 101

Colorimetry, the measurement of the absorption of visible light, allows a first qualitative and quantitative estimation of the phytochemicals available in a plant, soil or water sample. Colorimetric methods allow the assessment of an unknown color in reference to known colors. In practice, they provide qualitative or semiquantitative estimations rather than quantitative determinations. The instrumental progress in visible spectroscopic techniques allows the development of reliable and sensitive instruments. Colorimeters and spectrophotometers photoelectrically measure the amount of colored light absorbed by a colored sample respect to a “blank” or colorless sample reference. Modern spectrophotometers split the incident light into different wavelengths and measure the intensity of that radiation. Colorimetric measurements often involve the reaction of colorless substances under analysis with specific reagents. This allows the formation of colored complexes with absorbance maxima at wavelengths comprised in the visible light. In this chapter, general reactions of color development are provided for the qualitative and quantitative determination of phenolic compounds, terpenoids, alkaloids, lipids, carbohydrates, proteins and aminoacids  in plant samples.