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Infrared Spectrometric Purity Control of Organic Liquids and Water
Author(s) -
Kondagula Fayaz,
Molt Karl
Publication year - 2009
Publication title -
clean – soil, air, water
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 66
eISSN - 1863-0669
pISSN - 1863-0650
DOI - 10.1002/clen.200900126
Subject(s) - impurity , phthalate , analytical chemistry (journal) , attenuated total reflection , reproducibility , chemistry , correlation coefficient , infrared spectroscopy , infrared , diamond , materials science , chromatography , optics , organic chemistry , statistics , mathematics , physics
For the purpose of purity control, spectral comparisons are performed by regressing the infrared spectrum of a potentially polluted sample on the reference spectrum of the pure compound. The resulting correlation coefficient, R , is a measure of the similarity between both spectra. It is shown that it is advantageous to transform R to Fisher's Z coefficient, especially in the case of relatively small impurities. Following this transformation, a critical value for Z can be determined by reproducibility measurements and if Z falls below this critical value for a certain sample, a contamination of the examined product will be diagnosed. As a first example, the manner in which a certain type of phthalate plasticizer containing small contaminations of another similar type can be analyzed, is described. The purity control of water is discussed as a second example. In this case, potassium hydrogen phthalate is the impurity that can be detected. All spectra are measured by multiple internal reflection using a Diamond Attenuated Total Reflectance (ATR) accessory. Impurities in the per mill range (ca. 0.1–10%) can be detected using this technique.