Inlab routine pro electrode

The pH of hydrolysates and unmodified chitosan was measured using a pH/mV/ISE Meter (Seven Multi™ model S40 Mettler Toledo, Columbus, OH, USA) equipped with InLab Routine Pro electrode (Mettler Toledo, Columbus, OH, USA).

The free o-NCO of the grafted TDI were hydrolyzed following the method of Abushammala [49 (link)]. 100 mL of DMSO were transferred to a 200 mL beaker before being acidified to a pH of 2.47 ± 0.01 using 2 mL of 2 M HCl. The carbamated CNCs, after washed with DMSO, were transferred to the beaker. The pH started to increase because of isocyanate hydrolysis to amine groups. The hydrolysis was complete when no further increase in pH was observed (a maximum of 1 h). The degree of substitution of isocyanates (DS_NCO) was calculated based on the final pH value upon hydrolysis using the below equation, which was developed by the authors and published somewhere else [49 (link)]. All pH measurements were recorded at a temperature of 25 ± 0.5 °C using a SevenEasy S20-KS pH meter equipped with InLab^® Routine Pro electrode (Mettler Toledo, Giessen, Germany). CNCs-TDN is used to refer to the carbamated CNCs after hydrolysis.
$$D{S}_{NCO}=\frac{mmolNCO}{mmolCNCHydroxyls}=\frac{-24.3p{H}^4+290.3p{H}^3-1302.0p{H}^2+2598.7pH-1946.0}{3*\left(massCNCs/162\right)}*100$$