Standardization of fluorescence excitation-emission-matrices in aquatic milieu

Abstract

Fluorescence excitation-emission-matrices (EEM) are a useful tool for water quality monitoring. Recent publications show the potential of the method for real time drinking water control. However, in fluorescence measurements there is still a need for standardization to make data interpretation comparable. In this work a standardization procedure based on excitation and emission correction as well as normalization and optional inner filter effect correction is presented. By measurements of humic acid and tryptophan standards with two different spectrometers (LS 50 and LS 55 by PerkinElmer) the procedure application leads to comparable fluorescence intensities with relative standard deviations (median) of 6.6-8.4% and 10.6-12.0%, respectively. These small differences are not avoidable even if all possible correction methods are implemented and constant measurement conditions are given. The used BAM kit for emission correction induced good agreement in peak shape not only for single wavelengths but also for the whole EEM. As a consequence it is necessary to use identical equipment and identical experimental conditions in order to apply this method in fields of water quality control if small changes of fluorescence intensities are relevant for data assessment.