Table 1.

Measurement results of caffeine RM purity %.

Analyte	HPLC-DAD (M1)	UV/Vis spectrophotometer (M2)
Caffeine	99.905	99.860
	99.909	99.790
	99.940	99.905
	99.854	99.810
	99.899	99.928
	99.901	99.714
	99.872	99.827
	99.902	99.812
	99.971	99.887
	99.920	99.886
	99.900	99.730
	99.868	99.842
	99.961	99.800
	99.914	99.877
	99.904	99.764
	99.866	99.915
	99.970	99.753
	99.857	99.755
	99.882	99.908
	99.869	99.880
Mean	99.903	99.832
SD	±0.036	±0.066

HPLC-DAD = high-performance liquid chromatography coupled with diode array detection; M1 = Method 1; M2 = Method 2; RM = reference material; SD = standard deviation; Vis = visible.