Logit linearization of analytical response curves in optical disposable sensors based on coextraction for monovalent anions

The general equation resulting from the logistic transformation is discussed considering the stoichiometric factors for monovalent anions, and the linearization of the theoretical fit to experimental data was checked for two real cases. The strategy was applied to the determination of chloride and nitrate using disposable sensors for different types of waters (tap, well, stream, rain, snow and sea), validating the results against a reference procedure. This new linear calibration proposed for anion determination increases the linear dynamic range up to six orders of magnitude. The main advantage is that it is possible to directly quantify samples with very different analyte contents in a fast and simple way. The methods are easy to use and eliminate the need for prior treatment of the sample.