Laser-Based Fluorescence Eem Instrument for<i>In-Situ</i>Groundwater Monitoring

Taylor, Todd A.; Jarvis, George B.; Hong, Xu; Bevilacqua, Anthony C.; Kenny, Jonathan E.

doi:10.1080/10739149308543769

Cited by 14 publications

(5 citation statements)

References 12 publications

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“…When a two-fiber probe is dipped into a solution sample for fluorescence measurement, the signals detected are the total signals, integrated from some minimum value of r , r min , to some effective r max , which is dependent on fiber dimension, probe geometry, and the absorption by sample at both excitation and emission wavelengths . An angle of 22° between the two fibers has been used to maximize the efficiency of dip-in measurement. , For subsurface measurements in a cone penetrometer, however, there are two differences: first, r min is greater than or equal to the window thickness and second, the “effective” depth is very small because only a thin layer of sample in close contact with the window can be excited and the fluorescence detected. The 22° may not be the “optimum” angle for the measurements across a window due to the thickness of the window.…”

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confidence: 99%

Improved Two-Fiber Probe for in Situ Spectroscopic Measurement

1996

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A simple two-fiber probe has been modified and improved for in situ spectroscopic measurements that utilize frontsurface geometry. The efficiency of the probe for fluorescence measurement across a window is improved by maximizing the overlap of the light cones of the two fibers at the outside surface of the window where the sample is in contact with the window. This is achieved by polishing the ends of the fibers at predetermined angles and using different probe geometries. Improvement factors up to 14 have been obtained for fluorescence of phenol in distilled water, anthracene in 75% methanol, and the solutions mixed with sands and clay. The improved twofiber probe can be used for fluorescence as well as phosphorescence, Raman, and infrared (reflectance) spectroscopic measurements.

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confidence: 99%

Improved Two-Fiber Probe for in Situ Spectroscopic Measurement

1996

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“…Two optical bers were situated such that the angle between them was 228, the calculated optimal angle for dip-in m easurements. 5,12 This angle was achieved by aligning the bers with a printed template, taping them in place, and applying epoxy (Hysol, 608 Clear Epoxy, Dexter Corporation, Seabrook, NH) just behind the distal ber ends. The two-ber probe was then epoxied into a cylindrical plastic housing, which both protected thebers and made them easier to hold in a clamping system during uorescence measurements.…”

Section: Experim Entalmentioning

confidence: 99%

“…8,9 The possibility of attaching reagents to the distal surfaces ofbers has resulted in the development of ber-optic chemical sensors. 10 The ability to deliver and collect light in inaccessible 11,12 or hazardous areas has rendered the use of optical bers invaluable. Remote sensing has become increasingly important with the advent of subsurface -ber-optic characterization techniques.…”

Section: Introductionmentioning

confidence: 99%

Fiber-Optic Quantum Counter Probe for Incident Excitation Energy Correction in Fluorescence Measurements

Hart

Jones

2001

Appl Spectrosc

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Excitation-power correction of uorescence spectra is essential for meaningful interpretation of analytical data. In particular, uorescence m easurements obtained using optical bers require special consideration due to the possibility of variations in the light intensity delivered to the sample or the incident excitation energy. A quantum counting ber-optic probe has been developed to sim ultaneously and independently collect uorescence spectra of both analytes and a quantum counter. The probe consists of excitation and emission bers angled to maximize distal cone overlap and a third ber positioned at a greater angle to allow excitation of rhodamine B, which is af xed to its distal end with a polymer. The uorescence of the quantum counter af xed to the ber was linear with incident 266 nm excitation energy over the measured range 1.2 3 10 14 photons per exposure to 1.2 3 10 15 photons per exposure at 266 nm. The corrected uorescence signals were im mune to adverse condition experiments such as laser power reduction and launch berlaser beam misalignment, while the uncorrected signals suffered greatly. The concentration calibration generated using the beroptic quantum counter method showed an improvement in the correlation coef cient, r 2 5 0.950, compared with the calibration generated using uncorrected data, r 2 5 0.906. Different types of adverse conditions were tested including power attenuation, power increase, and ber launch misalignment; the prediction erro rs were between 287% and 366% for the uncorrected data compared with prediction errors between 29% and 15% when using the ber-optic quantum counter method.

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“…One alternative to chromatography is fluorescence spectroscopy. , Molecular fluorescence measurements can be rapidly and inexpensively performed in either an in situ or remote fashion. − Many environmentally important hydrocarbon contaminants are naturally fluorescent and detectable at the ppb level; − therefore, no sample preconcentration or derivatization is required. Unfortunately, the broad nature of fluorescence bands and the large number of fluorescent natural compounds prohibit complete analyte selectivity with both excitation- and emission-based measurements.…”

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Single-Measurement Excitation/Emission Matrix Spectrofluorometer for Determination of Hydrocarbons in Ocean Water. 2. Calibration and Quantitation of Naphthalene and Styrene

1996

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An excitation/emission matrix imaging spectrofluorometer was employed for quantitation of two fluorescent compounds, naphthalene and styrene, contained in ocean water exposed to gasoline. Multidimensional parallel factor (PARAFAC) analysis models were used to resolve the naphthalene and styrene fluorescence spectra from a complex background signal and overlapping spectral interferents not included in the calibration set. Linearity was demonstrated over 2 orders of magnitude for determination of naphthalene with a detection limit of 8 parts per billion. Similarly, nearly 2 orders of magnitude of linearity was demonstrated in the determination of styrene with an 11 ppb limit of detection. Furthermore, the synthesis of the EEM spectrofluorometer and the PARAFAC analysis for unbiased prediction of naphthalene and styrene concentration in mixture samples containing uncalibrated spectral interferents was demonstrated.

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Laser-Based Fluorescence Eem Instrument forIn-SituGroundwater Monitoring

Cited by 14 publications

References 12 publications

Improved Two-Fiber Probe for in Situ Spectroscopic Measurement

Improved Two-Fiber Probe for in Situ Spectroscopic Measurement

Fiber-Optic Quantum Counter Probe for Incident Excitation Energy Correction in Fluorescence Measurements

Single-Measurement Excitation/Emission Matrix Spectrofluorometer for Determination of Hydrocarbons in Ocean Water. 2. Calibration and Quantitation of Naphthalene and Styrene

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