Optimized and validated spectrophotometric determination of two antifungal drugs in pharmaceutical formulations using an ion-pair complexation reaction

Peer review under responsibility of Taibah University.

Figures & data

Fig. 1 Chemical structure of the studied antifungal drugs.

Fig. 2 Absorption spectra of the ion-pair complexes of 10 and 16 μg mL⁻¹ SER and MCO with 1.0 × 10⁻³ mol L⁻¹ BCP reagent against a reagent blank.

Fig. 3 Absorption spectra of the ion-pair complexes of 14 and 18 μg mL⁻¹ SER and MCO with 1.0 × 10⁻³ mol L⁻¹ BPB reagent against the reagent blank.

Fig. 4 Absorption spectra of ion-pair complexes of 20 and 24 μg mL⁻¹ SER and MCO with 1.0 × 10⁻³ mol L⁻¹ MO reagent against reagent blank.

Fig. 5 Effect of the pH of the acetate buffer solution on ion-pair complex formation between 14 μg mL⁻¹ SER and BCP, BPB and MO reagents (1.0 × 10⁻³ mol L⁻¹).

Fig. 6 Effect of the volume of the BCP, BPB and MO reagents (1.0 × 10⁻³ mol L⁻¹) on ion-pair complex formation with 14 μg mL⁻¹ MCO.

Fig. 7 Job’s method of continuous variation plot for the reaction of SER with dyes: BCP, BPB and MO, [drug] = [dye] = 5.0 × 10⁻⁴ mol L⁻¹.

Scheme 1 Proposed reaction mechanism for the ion-pair complex formation between SER and BPB.

Table 1 Statistical analysis of the calibration graphs and analytical data in the determination of SER and MCO using the proposed methods.

Parameters	SER			MCO
	BCP	BPB	MO	BCP	BPB	MO
Wavelengths λmax (nm)	410	416	427	408	415	426
pH	3.0	3.0	4.0	3.0	3.0	3.0
Beer’s law limits (μg mL^−1)	1.0–10	1.0–18	2.0–20	1.0–18	1.0–16	2.0–24
Molar absorptivity ɛ, (L/mol^−1 cm^−1) × 10^4	1.612	1.870	1.602	1472	3.33	1.482
Sandell’s sensitivity (ng cm^−2)	31.07	26.78	31.26	32.55	14.39	32.33
log Kf	4.962 ± 0.342	4.817 ± 0.279	5.026 ± 0.326	4.947 ± 0.251	5.156 ± 0.178	4.89 ± 0.273
Regression equation^a
Intercept (a)	0.0029	−0.0028	−0.0005	−0.0034	−0.0037	0.0039
Slope (b)	0.0311	0.0383	0.0319	0.0379	0.0713	0.00298
Correlation coefficient (r)	0.9994	0.9998	0.9998	0.9995	0.9998	0.9997
LOD (μg mL^−1)^b	0.21	0.29	0.55	0.25	0.28	0.57
LOQ (μg mL^−1)^b	0.70	0.97	1.83	0.83	0.93	1.90
Mean ± SD	100.10 ± 1.09	99.95 ± 1.24	100.05 ± 1.20	99.86 ± 1.02	100.04 ± 0.95	99.90 ± 0.92
RSD%	1.09	1.24	1.20	1.02	0.95	0.92
RE%	1.15	1.30	1.26	1.07	0.997	0.97
t-test^c	0.60	0.74	0.63	0.42	0.16	0.38
F-test^c	1.84	1.42	1.52	1.27	1.41	1.56

a A = a + bC, where C is the concentration in μg mL⁻¹ and A is the absorbance units.

b LOD, limit of detection; LOQ, limit of quantification; ɛ, molar absorptivity.

c The theoretical values of t and F at P = 0.05 are 2.571 and 5.05, respectively.

Table 2 Intra-day and inter-day precision and accuracy data for SER obtained using the proposed methods.

Method	Added (μg mL^−1)	Intra-day				Inter-day
		Recovery %	Precision RSD%^a	Accuracy RE%	Confidence limit^b	Recovery%	Precision RSD%^a	Accuracy RE%	Confidence limit^b
BCP	2.0	100.10	0.79	0.10	2.002 ± 0.017	99.70	0.68	−0.30	1.994 ± 0.014
	6.0	99.50	1.17	−0.50	5.97 ± 0.073	99.30	0.84	−0.70	5.958 ± 0.053
	10	100.40	1.28	0.40	10.04 ± 0.135	99.40	1.50	−0.60	9.94 ± 0.156
BPB	4.0	99.70	0.62	−0.30	3.988 ± 0.026	100.50	0.56	0.50	4.02 ± 0.024
	10	99.30	0.96	−0.70	9.93 ± 0.100	99.60	0.95	−0.40	9.96 ± 0.099
	16	100.20	1.65	0.20	16.032 ± 0.278	99.40	1.160	−0.60	15.904 ± 0.194
MO	5.0	99.60	0.81	−0.40	4.98 ± 0.042	99.40	0.75	−0.60	4.97 ± 0.039
	10	100.30	1.65	0.30	10.03 ± 0.174	99.70	1.10	−0.30	9.97 ± 0.115
	20	99.70	1.92	−0.30	19.94 ± 0.402	99.50	1.75	−0.50	19.9 ± 0.366

a Mean of six determination, RSD%, percentage relative standard deviation; RE%, percentage relative error.

b Confidence limit at 95% confidence level and five degrees of freedom (t = 2.571).

Table 3 Intra-day and inter-day precision and accuracy data for MCO obtained using the proposed methods.

Method	Added (μg mL^−1)	Intra-day				Inter-day
		Recovery %	Precision RSD%^a	Accuracy RE%	Confidence limit^b	Recovery %	Precision RSD%^a	Accuracy RE%	Confidence limit^b
BCP	4.0	99.80	0.78	−0.20	3.992 ± 0.033	99.40	0.68	−0.60	3.976 ± 0.028
	10	99.10	1.35	−0.90	9.91 ± 0.140	99.80	0.94	−0.20	9.98 ± 0.098
	16	100.20	1.80	0.20	16.032 ± 0.303	99.50	1.32	−0.50	15.92 ± 0.221
BPB	4.0	99.60	0.54	−0.40	3.984 ± 0.023	100.20	0.46	0.20	4.008 ± 0.019
	10	99.70	1.26	−0.30	9.97 ± 0.132	99.10	0.94	−0.90	9.91 ± 0.098
	16	99.20	1.94	−0.80	15.872 ± 0.323	99.90	1.24	−0.10	15.984 ± 0.208
MO	6.0	100.50	0.70	0.50	6.03 ± 0.044	99.40	0.55	−0.60	5.964 ± 0.034
	12	99.60	1.15	−0.40	11.952 ± 0.144	100.30	0.89	0.30	12.036 ± 0.112
	24	100.20	1.70	0.20	24.048 ± 0.429	99.70	1.40	−0.30	23.928 ± 0.352

a Mean of six determination, RSD%, percentage relative standard deviation; RE%, percentage relative error.

b Confidence limit at 95% confidence level and five degrees of freedom (t = 2.571).

Table 4 Application of the standard addition technique for the determination of SER and MCO in dosage forms using the proposed methods.

Sample	Taken (μg mL^−1)	BCP		BPB		MO		Official method [2]
		Added (μg mL^−1)	Recovery^a (%)	Added (μg mL^−1)	Recovery^a (%)	Added (μg mL^−1)	Recovery^a (%)
Dermofix cream	2.0	–	99.60	–	98.70	–	100.10
		2.0	99.10	2.0	99.50	4.0	99.70
		4.0	99.80	6.0	100.30	10	100.60
		8.0	100.40	10	100.50	16	99.20
		12	98.80	14	99.20	22	100.30
		14	99.00	18	99.60	26	99.50
Mean ± SD			99.45 ± 0.599		99.63 ± 0.674		99.90 ± 0.525	99.50 ± 0.73
RSD%			0.602		0.677		0.525
V			0.359		0.455		0.276
t-value^b			0.12		0.29		1.0
F-value^b			1.09		1.17		1.90
Miconaz cream	2.0	–	99.10	–	100.40	–	99.20
		2.0	100.40	2.0	100.20	4.0	100.80
		4.0	99.00	6.0	99.10	10	99.50
		8.0	98.50	10	99.60	16	99.30
		12	99.50	14	99.20	22	100.60
		14	99.80	18	99.40	26	99.90
Mean ± SD			99.38 ± 0.668		99.65 ± 0.536		99.88 ± 0.68	99.64 ± 0.46
RSD%			0.668		0.536		0.68
V			0.446		0.287		0.462
t-value^b			0.72		0.03		0.654
F-value^b			2.11		1.36		2.19
Micoban cream	2.0	–	99.60	–	99.30	–	99.10
		2.0	99.10	2.0	98.90	4.0	99.70
		4.0	99.80	6.0	99.00	10	99.50
		8.0	98.70	10	99.40	16	98.60
		12	98.60	14	99.20	22	99.40
		14	99.30	18	98.50	26	99.30
Mean ± SD			99.18 ± 0.48		99.05 ± 0.327		99.27 ± 0.383	99.08 ± 0.67
RSD%			0.48		0.327		0.383
V			0.23		0.107		0.147
t-value^b			0.27		0.09		0.55
F-value^b			1.95		4.20		3.06

a Average of six determinations.

b The theoretical values of t and F are 2.57 and 5.05, respectively, at the confidence limit at the 95% confidence level and five degrees of freedom (p = 0.05).