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.