“…Improvement in design and technology has achieved miniaturization in portable pH sensors (Hammond, Ali, & Cumming, 2005;Kassal, Steinberg, & Steinberg, 2013;Veeramani et al, 2013) by incorporating digital processing (Hammond et al, 2005) and wireless data acquisition (Kassal et al, 2013;Veeramani et al, 2013), which has greatly expanded applicability. Moreover, numerous miniaturized chemical sensors are now commercially available and applicable to practical analyses such as pH, conductivity, ionization, salinity, and multiparameters (Megahed, Hiew, Grünberg, & Constable, 2016;Sakai et al, 2018;Trefz, Lorenz, & Constable, 2018). Portability of the miniaturized devices makes them suitable for field use in developing countries because these miniaturized devices are inexpensive and consume a small amount of reagents, which leads to a reduction in chemical waste and promotes an environmentally friendly image.…”