A disposable single-use optical sensor for potassium determination based on neutral ionophore

Potassium disposable optical sensor based on transflectance and cromaticity measurements

“…The values of the selectivity coefficients (SSM method), as log K opt K,j obtained using membranes with the composition indicated above are −4.27 Li(I); −1.99 Na(I), −3.13 Ca(II), and −2.99 Mg(II) and are of the same magnitude order as the values previously described for the same sensor working in absorbance mode [26]. This membrane exhibits sufficient potassium selectivity against the usual concomitant ions in natural waters to make determination possible.…”

“…The sensing zone of the disposable sensor in contact with an aqueous solution containing potassium ions holds an ionexchange equilibrium [26], in which barred species are in membrane phase (Eq. (5)), assuming the formation of a 1:1 potassium complex:…”

“…The ion activities ratio a H + /a K + in aqueous phase is related to the equilibrium constant K exch and the experimental parameter α eff through the response function [26,29] (Eq. (6)):…”

“…The composition of the membrane used here was the same as with the previously described sensor for potassium [26]. The values of the selectivity coefficients (SSM method), as log K opt K,j obtained using membranes with the composition indicated above are −4.27 Li(I); −1.99 Na(I), −3.13 Ca(II), and −2.99 Mg(II) and are of the same magnitude order as the values previously described for the same sensor working in absorbance mode [26].…”

“…As the chromoionophore cannot be fully protonated (1 − α ∼ = 0.9) at the working pH (9.0), we use an effective α value, α eff [26]. This α eff value is evaluated by the optical property measured, which in the case of absorbance is…”