Photoinduced potentiometric response of poly(vinyl chloride)/spirobenzopyran/crown ether composite memberanes modified with urease

Photoresponse of the poly(vinyl chloride) membranes, which contain spirobenzopyran and crown ether, covered with a urease layer was studied in the presence and absence of urea. In the absence of urea, UV light irradiation induced more than 160 mV of membrane potential change, whereas the photoresponse decreased with an increase in the concentration of urea in the solution. The effects of such operating variables as crown loading and pH and ionic strength in the aqueous phase on the potentiometric response were also elucidated in the presence of urea. The results were explicated using the fact that the local concentration on NH₄⁺ and H⁺ ions changed as a result of the urease‐catalyzed decomposition reaction of urea.