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Tracing Anthropogenic Wastes: Detection of Fluorescent Optical Brighteners in a Gradient of Natural Organic Matter FluorescenceDixon, Laura Kellie 09 November 2009 (has links)
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.
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[en] METROLOGICAL AND INSTRUMENTAL EVALUATION CONTROL OF WHITE SAMPLES TREATED WITH FLUORESCENT WHITENING AGENTS / [pt] CONTROLE METROLÓGICO E INSTRUMENTAL DA AVALIAÇÃO DE AMOSTRAS BRANCAS TRATADAS COM ALVEJANTE ÓTICOJENNIFER KATHRIN GAY 21 June 2004 (has links)
[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.
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