Table 1.

Calibration-free ISEs Based on the PEDOT:PEDOT-S Back Contact^a

electrode type: charged	K+ ISE	Ca2+ ISE
slope (mV/dec)	57.2 ± 0.2	28.5 ± 0.3
detection limit (μM)	1.68 ± 0.18	0.45 ± 0.01
$\text{log}{K}_{\text{A},\text{B}}^{\text{pot}}$	−3.53 ± 0.02 vs Na+	−3.82 ± 0.01 vs Mg2+
	−4.13 ± 0.21 vs Ca2+	−5.26 ± 0.12 vs K+

^aCharacterization of a batch of three calibration-free ISEs over three replicate calibrations. The Ca²⁺ ISE (n = 9) and the K⁺ ISE (n = 9) were calibrated versus an Ag/AgCl reference electrode under optimized solution conditions.