Preservation of commonly applied fluorescent tracers in complex water samples

Abstract

Water sample preservation and pre-treatment are important steps for achieving accurate and reproductive results from tracer tests. However, this is particularly challenging for complex water mixtures prior to fluorescence analysis. In this study, the interference of iron and calcium precipitation with nine commonly applied conservative tracers, uranine, eosin, 1aEuronaphthalene sulfonate, 1,5-naphthalene disulfonate, 2,6-naphthalene disulfonate, 4aEuroamino-1-naphthalene sulfonate, 6aEurohydroxy-2-naphthalene sulfonate, 1,3,6-naphthalene trisulfonate, and 1,3,6,8-pyrene tetrasulfonate, was investigated in batch experiments. In general, the observed results are influenced by precipitates. A technique consisting of pH adjustment and centrifugation is described for preserving samples and avoiding the impact of these precipitates on the tracer test results.