Nitrophenyl glucoside hydrolysis as a potential time-temperature integrator reaction

Hydrolysis of p-nitrophenyl β-d-glucopyranoside (NPG) in borate buffer, pH 11.0, has been investigated as a potential chemical time-temperature integrator (TTI) reaction. The yellow nitrophenolate ion produced on hydrolysis was shown to be highly stable and to follow first order kinetics of formation. The temperature coefficient of the reaction rate (z-value) was found to be 21.7 (± 1.2) °C over the range 91.0–121.1 °C. Glucose formed on hydrolysis was unstable, apparently undergoing caramelisation to brown pigments. The latter compounds were shown not to interfere with the measurement of nitrophenolate absorbance. It was concluded that NPG hydrolysis was a reaction with significant potential for application as a chemical TTI.