Determination of Microamounts of Phenols by Thermal Lens Spectrometry

Abstract

The conditions for unified spectrophotometric determination of phenols (using phenol, resorcinol, and pyrogallol as model substances) in batch mode by their azo coupling with p-nitrophenyldiazonium were optimised. The detection limits are 50–120 ng ml^–1. The data were used in the search for the optimum conditions for thermal lens determination of the test phenols. The main disadvantage of thermal lens determination of phenols by this procedure is a high blank signal. To decrease the blank signals, the concentration of the reagent was decreased by a factor of 40. The detection limits of the test phenols are 2–9 ng ml^–1, the linear calibration range is two orders of magnitude. The relative standard deviation (3–8%) is similar to that of spectrophotometric determination.