In this study, a quantitative analysis of nitrate in aqueous solution was performed through the combination of an oxazine170 perchlorate⁻ethyl cellulose (O17-EC) membrane with aluminum-containing compounds. Aluminum of Devarda's alloy (DA) or a clay hydrotalcite (HT) was employed for the reduction of nitrate to produce ammonia, and the produced ammonia was detected by the O17-EC membrane. The method of combining the O17-EC membrane with aluminum compounds has showed a broad detection range of nitrate. That is, the DA was combined with the O17-EC membrane and showed the linear nitrate detection ranges of 1⁻10 mM and 10⁻100 mM, while the O17-EC membrane immobilized with the clay HT showed a linear detection range of 0.1⁻1 mM nitrate. The visual color transition of the nitrate-sensing membranes at different nitrate concentrations was clearly observed under sunlight or irradiation of a light-emitting diode (LED) at an excitation wavelength of 470 nm (LED470).
Keywords: Devarda’s alloy; Nitrate detection; clay hydrotalcite; colorimetric and ratiometric fluorescence detection; oxazine–ethyl cellulose membrane.