New methods, sensors, and devices based on redox indicators were developed to
monitor redox conditions in anoxic and anaerobic laboratory systems and the subsurface
environment. The primary application was monitoring redox conditions
during the dechlorination of tetrachioroethene (PCE) to ethene (ETH) in packed
columns and microcosm bottles containing an enriched...
The development and optimization of a fluorometric reaction
rate method for the determination of aluminum is described.
Modifications to existing instrumentation permit automatic
monitoring and reporting of measurement conditions. Automatic
correction of measured analytical signals is provided if monitored
parameters deviate from optimum values. A computer controlled
standard addition procedure...
An automated multielement flame atomic fluorescence (AF) spectrometer based on microcomputer control was constructed to determine four elements simultaneously. The instrument employs a multiple exit slit monochromator where the light from various exit slits is directed to a single detector with a mirrored funnel. Each element is excited to fluoresce...
The concentration of chlorophyll in natural bodies of water is
commonly determined as a means to rapidly estimate the phytoplankton
biomass. The literature gives numerous warnings, however, as to the
problems involved with accurately determining chlorophyll
concentrations. The author's work at Crater Lake, Oregon enticed him
to explore critically the...
A practical and versatile instrument has been developed both to
optimize the chemistry of bio- and chemiluminescence reactions and to
measure ultra-trace quantities of associated analytes. The instrument
consists of a pneumatic flow injection system linked to a detection cell and a
signal processing and readout system. The disk-like cell...
An automated instrument based on a single-board microcomputer
was developed for use in voltammetric analyses. Operator input of
numerous experiment parameters allows any type of voltammetric
analysis to be implemented and multiple scans to be run unattended.
A three operational amplifier potentiostat is used to control
the cell voltage and...
Two related techniques, based upon ion-exchange solid phase extraction, have been
developed for the determination of arsenic speciation. The inorganic arsenic species
arsenite (As(III)) and arsenate (As(V)) are separated by anion-exchange and detected with
graphite furnace atomic absorption spectrophotometry (GFAAS) with a nickel matrix
modifier. The first separation technique, which...
The development and optimization of a single-phase derivatization
technique for small ring aromatics in water are presented. Also
described are the design, optimization and application of a remote
reaction chamber for fiber optic sensing.
Aqueous solutions of the major aromatic compounds in gasoline are
derivatized to o-nitrosophenol-Cu complexes with a...
A novel, portable, filter fluorometer was developed for the determination of chloroform and TCE at environmentally-relevant levels when coupled with improved sampling techniques and reagents. Reagents selective for the TCE or chloroform convert these toxic species into fluorescent species that can be monitored. The fluorometer is based on LED excitation...
A direct purge technique was developed for the determination of chloroform or trichloroethylene (TCE) in water samples. These volatile organic solvents are transferred from the water sample to a reagent where they are trapped and react to form products (Fujiwara chemistry) that are monitored fluorometrically. Chloroform in a water sample...