Paper based sensors were tested for sensitivity using ammonium hydroxide solution. 5 mM stock solution were prepared and three solution were added in 2 mL vials. Sensors were then exposed to various amounts of diluted ammonium hydroxide solution in the vial and their TBN compound sensitivities were determined by a distinct colaor chage from yellow to blue-purple. The steady-state paper sensor response to the vapor with its known concentration was obtained after adding varying volumes in the vial (Fig. 9.). The vapor concentration of ammonia Cg (ppm) inside the vial was calculated using the equation :
in which C1 (wt.%) is concentration in the liquid, V1 (µL) ammonium hydroxide solution volume in the vial, d (g/mL) the density, R the gas constant, T (K) temperature, P0 (atm) the pressure in the vial, Vc (I) the vial volume and M the molecular weight.
The color change effect can be seen in Fig. 9. The lowest detectable limit was with 1 µL of ammonium hydroxide, equivalent to 63 ppm NH3. Different coating formulations were also used to test several levels of volatile ammonia. The combinations of coating weight and the dye were 6 g/m2 coat weight and 0.5 part dye, 20 g/m2 coat weight and 1 part dye (Fig. 9.). In all measurement the color change was very distinct and uniform in all samples. In case of the diatom containing coating formulation, the color change was also stable and remained in the observed level for about 5 days. We do not expect any interference with other gases in the experiments.
Paper based sensors were tested for sensitivity using ammonium hydroxide solution. 5 mM stock solution were prepared and three solution were added in 2 mL vials. Sensors were then exposed to various amounts of diluted ammonium hydroxide solution in the vial and their TBN compound sensitivities were determined by a distinct colaor chage from yellow to blue-purple. The steady-state paper sensor response to the vapor with its known concentration was obtained after adding varying volumes in the vial (Fig. 9.). The vapor concentration of ammonia Cg (ppm) inside the vial was calculated using the equation :in which C1 (wt.%) is concentration in the liquid, V1 (µL) ammonium hydroxide solution volume in the vial, d (g/mL) the density, R the gas constant, T (K) temperature, P0 (atm) the pressure in the vial, Vc (I) the vial volume and M the molecular weight.The color change effect can be seen in Fig. 9. The lowest detectable limit was with 1 µL of ammonium hydroxide, equivalent to 63 ppm NH3. Different coating formulations were also used to test several levels of volatile ammonia. The combinations of coating weight and the dye were 6 g/m2 coat weight and 0.5 part dye, 20 g/m2 coat weight and 1 part dye (Fig. 9.). In all measurement the color change was very distinct and uniform in all samples. In case of the diatom containing coating formulation, the color change was also stable and remained in the observed level for about 5 days. We do not expect any interference with other gases in the experiments.
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