Development of stability indicating HPTLC method for estimation of antihypertensive drug combination nifedipine and valsartan

Figures & data

Figure 1. Chemical structure of nifedipine.

Figure 2. Chemical structure of valsartan.

Figure 3. Overlay of absorbance spectra of NIF and VAL.

Figure 4. Densitogram of NIF and VAL.

Table 1. Regression analysis of the calibration curve.

Parameters	NIF	VAL
Linearity (ng/band)	120–320	900–2400
Correlation coefficient (r^2)	0.997	0.995
Slope of regression equation	11.846	1.296
Standard deviation of slope	1.096	0.074
Intercept of regression	2111.8	351.1

Table 2. Summary of validation parameter.

Parameters	NIF	VAL
Linearity (ng/band)	120–320 ng/band	900–2400 ng/band
Detection limit(ng/band)	35.01	287.62
Quantitation limit (ng/band)	106.1	871.60
Accuracy (%)	98.3–100.14%	98.47–100.12%
Precision (% RSD)
Intra-day (n = 3)	1.14–1.85	1.54–1.81
Inter-day (n = 3)	1.09–1.90	1.02–1.45
Instrument precision (% RSD)
Scanner (n = 6)	0.62	0.87
Injection (n = 6)	0.89	0.85
Specificity	Specific	Specific

Figure 5. Densitogram of base (0.1 N NaOH) hydrolysed sample of VAL and NIF.

Figure 6. Densitogram of acid (1 N HCl) hydrolysed sample of VAL and NIF.

Figure 7. Densitogram of dry heat degraded sample of VAL and NIF.

Figure 8. Densitogram of photolytic degraded sample of VAL and NIF.

Figure 9. Densitogram of oxidative stress degraded sample of VAL and NIF.

Table 3. Forced degradation study.

		% of drug found		Rf values of degradation products
Condition	Time	NIF	VAL	NIF	VAL
Acid 1 M HCl, (70–80°C)	1 h	75.45	87.23	0.45, 0.54	0.18
Base 0.1 M NaOH, (70–80°C)	1 h	78.34	89.12	0.44	0.12
Oxidative degradation 3% H2O2, (70–80°C)	1 h	83.86	78.26	0.49	0.13
Dry heat (70–80°C)	2 h	92.67	98.67	0.51	–
Photolytic (RT)	24 h	88.37	99.12	0.53	–

Table 4. Analysis of synthetic mixture.

	Amount of drug applied (ng/band)		Amount of drug found (ng/band)		%Amount of drug ± S.D (n = 3)
Synthetic mixture	NIF	VAL	NIF	VAL	NIF	VAL
	240	1600	239.92	1576.48	99.96 ± 0.76	98.52 ± 0.70

Note: Synthetic mixture contains nifedipine 30 mg and valsartan 80 mg.