355. Reversible Detection of Trace Hydrazines by an Evanescent Wave Fiber Optic Sensor

Agricultural Ammonia Monitoring Technology

“…Because this effect was more pronounced in the TBS sensor than TEB film, water may be associating with both the polymer and the dye molecules as both TBS and TEB sensors contain approximately the same w/o of the various components. Also, in other work we have shown that the baseline signal in the presence of constant humidity background stabilizes to a constant value (not shown) once the sensor equilibrates with its surroundings (10)(11)(12). A heated sensor configuration, as discussed above, solves the problem of humidity sensitivity.…”

“…Once optimal sensor formulations were established and characterized, we screened a variety of colorimetric dyes to determine which were best suited for ammonia detection. Dye selection was based on our previous experience with fiber optic chemical sensors for N 2 H 4 and NH 3 (10)(11)(12). 2 mL of solution was cast onto a glass slide (1 in 2 ) using a pipette.…”

Chemical Threat Point Sensors Based on Infrared Spectrophotometry and Adsorptive Preconcentrators

“…The rationale for using a preconcentrating thin film to increase the local concentration of the target analyte is shown in Figure 3. This strategy is well-known and has been discussed by many authors, including us, in relation to polymer films for piezoelectric, surface acoustic wave, optical and IR gas sensors (4,(6)(7)(8)(9)(10)(11)(12)(13) The attraction of this approach is that, if suitable sorbents can be identified, the analysis pathlength according to Beer's Law and the overall device size, can be reduced considerably. For example, with a partition coefficient of 10 5 , a 10 micron thick film could provide the equivalent SNR of a 1 m gas cell.…”

“…These procedures produce film thicknesses of several microns to 0.1 micron, respectively. Work involving the performance of commercial polymers has been reported elsewhere (3,4,13). Here, we discuss some key aspects of the fluorinated epoxies, which are relatively new polymer sorbents.…”