Kinetic behavior of polymer-coated long-period-grating fiber-optic sensors.
A new method of analysis employing the time-dependent response of long-period-grating (LPG) fiber-optic sensors is introduced. The current kinetic approach allows analysis of the time-dependent wavelength shift of the sensor, in contrast to previous studies, in which the LPG sensing element has been operated in an equilibrium mode and modeled with Langmuir adsorption behavior. A detailed kinetic model presented is based on diffusion of the analyte through the outer protective membrane coating into the affinity coating, which is bound to the fiber cladding. A simpler phenomenological approach presented is based on measurement of the slope of the time-dependent response of the LPG sensor. We demonstrate the principles of the kinetic methods by employing a commercial Cu+2 sensor with a carboxymethylcellulose sensing element. The detailed mathematical model fits the time-dependent behavior well and provides a means of calibrating the concentration-dependent time response. In the current approach, copper concentrations below parts per 10(6) are reliably analyzed. The kinetic model allows early-time measurement for low concentrations of the analyte, where equilibration times are long. This kinetic model should be generally applicable to other affinity-coated LPG fiber-optic sensors.
Widera
Justyna
J
Contribution from Innovative Scientific Solutions, Inc, Dayton, Ohio 45440, USA.
Bunker
Christopher E
CE
Pacey
Gilbert E
GE
Katta
Viswanath R
VR
Brown
Michael S
MS
Elster
Jennifer L
JL
Jones
Mark E
ME
Gord
James R
JR
Buckner
Steven W
SW