ABSTRACT
Quantitative measurements should utilize properly tested and documented procedures. An analytical procedure does not give the answer to the analytical question directly; it only provides the measured value of an "indicating quantity". The quantification by resin spot test methods is based on the fact that the indicating quantity is obtained by the measurement or estimation of the intensity of coloration of ion exchanger phase or of the dimension of the spot produced on the solid ion-exchanger carrier. Semiquantitative methods may be defined as analytical techniques which provide results with comparatively higher degrees of error than quantitative ones; the limits of these errors must, of course, be known. Owing to the sensitivity and often the selectivity of spot reactions, spot colorimetry occupies an outstanding place among semiquantitative analytical methods and is quite commonly used in biomedical research as well as in environmental health programs.
