New pencil graphite electrodes for potentiometric determination of fexofenadine hydrochloride and montelukast sodium in their pure, synthetic mixtures, and combined dosage form

Table 1 Response characteristics and the validation data of the constructed sensors

Parameter	FEX.Mol	MON.Co	The combined sensor
Parameter	FEX.Mol	MON.Co	FEX	MON
Slope ± SD (mV.decade⁻¹)	− 59.23 ± 0.05	28.43 ± 0.09	− 59.05 ± 0.70	28.64 ± 0.22
Intercept (mV)	435.1	− 45.6	439.2	− 44.3
Correlation coefficient	0.9991	0.9998	0.9999	0.9998
Response time (seconds)	20	27	29	32
pH range	(2–4.5)	(5–9.5)	(2–4.5)	(5–9.5)
Linearity range (mol L⁻¹)	(1.00 × 10^–2–1.00 × 10^–5)	(1.00 × 10^–2–1.00 × 10^–5)	(1.00 × 10^–2–1.00 × 10^–5)	(1.00 × 10^–2–1.00 × 10^–5)
Life time (days)	69	45	45
Recovery ^a %	99.84 ± 0.51	100.92 ± 0.21	99.76 ± 0.50	100.55 ± 0.71
Repeatability ^b	1.59	1.18	1.70	1.63
Reproducibility ^c	1.73	0.29	1.91	1.99
Lod^d (M)	1.4 × 10^–8	2.1 × 10^–8	2.5 × 10^–8	1.9 × 10^–8
Loq (M)	4.3 × 10^–8	6.3 × 10^–8	7.6 × 10^–8	5.9 × 10^–8

^aAverage of three determinations
^bRepeatability: the intraday precision (n = 3 × 3), average of three concentrations (5*10^–5, 5*10^–4 and 5*10^–3 mol L⁻¹) were repeated three times within the day
^cIntermediate precision: the interday precision (n = 3 × 3), average of three concentrations
(5*10^–5, 5*10^–4 and 5*10^–3 mol L⁻¹) were repeated three times on two consecutive days
^dLod 3.3 SD of intercept/ slope, LOQ = 10*SD/ slope

ISSN: 2661-801X