A dual wavelength method was developed for the field detection of optical brighteners (OBs), fluorescent laundry additives used as indicators of anthropogenic wastes. The method was quantitative for OBs under variable levels of fluorescent colored dissolved organic matter (CDOM). Based on excitation at 300-400 nm and 440 and 550 nm emission, the method assumed a constant ratio of fluorescence due to CDOM alone, even if absolute amplitude varied. Concentrations of OBs were computed as the difference between the observed 440 nm emission and the expected CDOM fluorescence at 440 nm, as extrapolated from the 550 nm fluorescence and established CDOM fluorescence ratio. Real-time inner filter corrections were based on absorption modeled from 550 nm fluorescence and from exponential relationships at alternate wavelengths. The effects of temperature and dissolved oxygen on CDOM fluorescence and computed OB were quantified but were minimal because effects were comparable between the two fluorescence regions. Assumptions on the locally conservative behavior of CDOM were supported in field surveys of sewered and non-sewered areas. Varying water masses were detected, but OB quantities were detected that did not co-vary with fluorescence alone. Eleven geographic regions of peninsular Florida and sources of OBs were sampled to evaluate the method under a broader range of CDOM and to conduct an extensive detergent spike analysis. Fluorescence data were collected as EEMs and subjected to PARAFAC modeling, isolating eight spectral factors that could sufficiently describe all samples. There were no visible regions of the spectra that were unique to detergents or OBs, but a previously unreported peak in the UV (<230 / 284 ex / em) was tentatively identified as a detergent surfactant and should be pursued as a potential complementary indicator of anthropogenic wastes. Limits on EEM fluorescence measurements were identified: maximum linear range, maximum turbidity, and sensitivity to assumptions. A sub-sampling technique of EEM data approximated the filter fluorometer readings, was used to optimize the dual wavelength method, validated the method with spike recoveries, and presented alternative approaches.

[pt] A avaliação de artigos brancos tratados com alvejantes ópticos, como eles são comuns em substratos têxteis, plásticos e de papel, é uma tarefa que tradicionalmente resulta em muitas divergências entre avaliações visuais realizadas em uma cabine padronizada e avaliações instrumentais realizadas com espectrofotômetros de refletância. Mesmo entre as avaliações visuais ou entre as avaliações instrumentais são encontradas diferenças muito além do aceitável. Uma das principais causas é a fluorescência dos alvejantes ópticos que é influenciada pela quantidade de radiação UV em relação com a radiação na faixa visível do espectro. O trabalho apresentado analisa as diferentes formas de avaliação, principalmente do ponto de vista da qualidade da distribuição espectral de potência do simulador de luz do dia. No caso das avaliações visuais, são testadas diferentes lâmpadas fluorescentes. Para as avaliações instrumentais, a calibração e o ajuste de UV em conjunto com as diferentes aberturas de medição são analisados. O objetivo é aprimorar os aspectos metrológicos da avaliação e contribuir para a sua padronização a fim de garantir a maior reprodutibilidade de resultados, um procedimento importante e almejado por todos os segmentos industriais que utilizam os alvejantes ópticos. / [en] The evaluation of white objects treated with fluorescent whitening agents, such as they are commonly found on substrates like textiles, plastics and paper, is a task that traditionally leads to frequent controversy between the visual evaluations performed in a standardized light booth and the instrumental evaluations performed on reflectance spectrophotometers. Even between visual or instrumental evaluations the differences encountered are far beyond the acceptable. One of the main reasons is the fluorescence of the optical brightening agents that is influenced by the amount of UV radiation in relation to the amount of radiation in the visible range of the spectrum. The work presented analyses the different forms of evaluation, mainly from the point of view of the quality of the daylight simulators´ spectral power distribution. In the case of the visual evaluations, different fluorescent lamps are tested. For the instrumental evaluations, the UV calibration and adjustment are analyzed together with the different measurement apertures. The objective is to improve the metrological aspects of the evaluation and contribute to its standardization with the aim to guarantee better reproducibility of results, an important procedure that is desired by all the industrial segments that use optical brighteners.