Redox-Reaction Based Spectrophotometric Assay of Isoniazid in Pharmaceuticals

Table 3

Method robustness and ruggedness expressed as intermediate precision.

Method	Nominal concentration	Robustness			Ruggedness
		Reaction times*; (𝑛=3)	Volumes of FC reagent^#	Volumes; of ferricyanide^#	Interanalysts; (𝑛=3)	Interinstruments; (𝑛=3)
A	3.0	1.45	1.69	—	2.20	2.32
	6.0	1.72	1.35	—	1.74	1.92
	9.0	2.10	1.71	—	2.44	2.57
B	1.0	1.72	—	1.59	1.78	2.12
	1.5	1.84	—	1.61	2.11	1.62
	2.0	2.12	—	1.72	1.07	2.54

∗Reaction times were 10 ± 2 min for both methods. ^#Volumes of FC regent added were 2 ± 0.2 mL for method A; volumes of ferricyanide added were 1.5 ± 0.1 mL for method B.