A fiber optic fluorometer utilizing a double-fiber optic probe
was constructed. The absolute fluorescence signal and effective
collection efficiency are approximately one fifth those of typical
cuvette fluorometers and agree with those predicted by theory. A
quinine sulfate calibration curve shows linearity from a detection
limit of 10 pg/mL to 10 μg/mL. Single- and double-fiber probe
configurations were also compared. The double-fiber configuration
provided better detection limits due to its superior signal-to-background
ratio.
A discussion of sensor methodology for the monitoring of
reaction intermediates is presented and a simple kinetic model for
predicting the time dependent response of such sensors is developed.
Two possible mechanisms for the Fujiwara reaction with chloroform are
discussed. The effect of pyridine, water, and base concentrations on
reaction kinetics was evaluated to develop single-phase Fujiwara
reagent mixtures for both fluorometric and spectrophotometric
determinations of chloroform. A unique "continuous-exposure"
apparatus allowing vapor phase transport of chloroform from an
aqueous sample to a conventional cuvette was constructed. The
spectrophotometric detection limit for chloroform is 11 ng/mL and the
method was shown to be suitable for the analysis of tap water.
Two fiber optic chemical sensors (FOCS) for the detection of
chloroform were developed. An aliquot of the optimized fluorometric
reagent solution is held in contact with the fiber optic probe within
a light-tight enclosure and is isolated from a bulk sample by a
trapped headspace. One FOCS utilizes 1.3 mL of reagent held in a
reservoir and the other utilizes a 10-μL drop of reagent suspended on
the sensing tips of the fiber optic probe. Chloroform vapor from the
sample migrates into the FOCS and reacts with the reagent to produce
a fluorescent reaction intermediate which is monitored at 590 nm; the
rate of increase in the fluorescence signal is related to chloroform
concentration. Both FOCSs give detection limits better than 0.1
ng/mL. The response and total measurement times are comparable for
the two FOCSs, and the duration of the linear response is limited by
inner-filter effects. The response to a number of volatile GPHHCs
including the trihalomethanes are reported. Analyses of tap water
for chloroform with the reservoir FOCS and GC/MS were in excellent
agreement. / Graduation date: 1992
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36270 |
| Date | 17 May 1991 |
| Creators | Louch, Jeff |
| Contributors | Ingle, James D. Jr |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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