Quantification of the concentration of aliphatic alcohols by an infrared technique

Abstract

A quantitative infrared assay for long-chain primary aliphatic alcohols in the presence of oil is described. Absorbances of samples dried for 24 h in vacuo over phosphorus pentoxide and dissolved in trichlorotrifluoroethane, are measured in a 10-mm Infrasil cuvette between 4 000 and 3 000 cm^–1. Absorbance for the O–H bond stretching is measured at 3 660 cm^–1 in dilute solutions (concentrations below 0.05 M). The presence of oil reduces the response, but this effect can be eliminated provided that the final concentration of the oil is less than 0.5%m/m and that it is counterbalanced by the reference solution.