Use of Alizarin Red S as an Ion-Pair Reagent for the Spectrophotometric Assay of Fexofenadine in Pharmaceuticals and in Spiked Human Urine

Table 5

Robustness and ruggedness.

		Robustness		Ruggedness
Method	FFH taken, μg mL^−1	Parameters interchanged		Interanalysts; (%RSD), (𝑛=3)	Interinstruments (%RSD), (𝑛=3)
		Volume of HCl/ethanolic KOH*	Reaction time**
A	4.00	1.84	2.24	1.96	1.84
	6.00	1.68	1.87	2.04	1.68
	8.00	2.02	2.32	2.18	2.02
B	1.00	1.12	—	1.78	1.97
	2.00	1.24		1.96	2.28
	3.00	1.58		2.29	2.56

*In method A, the volumes of 0.1 M HCl were 4.8, 5.0, and 5.2 mL, and in method B the volumes of ethanolic KOH added were 1.4, 1.5, and 1.6 mL. **In method A, the reaction times were 8, 10, and 12 min.