A method of analysis of and an apparatus for analysing a sample comprising the steps of: (A) examining at least one characteristic of a sample as a function of a variable parameter to obtain data, (B) normalizing the data with respect to a model, (C) making a comparison of the normalized data with reference data, and (D) determining from the comparison the quality of the sample. As a function of such determination of quality, control functions may be carried out with respect to a sample that was analyzed, such as a blend sample in a chemical processing plant.