Rapid and Sensitive Determination of Methylxanthines in Commercial Brands of Tea Using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry

Table 3

Comparison of the proposed method with some of the recently reported HPLC methods for the determination of caffeine.

Ref.	Analytical column (length mm × i.d. mm, particle size μm)	Elution type	Flow rate (mL/min)	Retention time (min)
[1]	Inertsil ODS-3v (250 × 4.6, 5)	Isocratic	1.5	5.82
[2]	PartiSphere 5 C18 (250 × 4.6, 5)	Gradient	1.0	10.95
[10]	Fused core Kinetex C18 (100 × 4.6, 2.6)	Gradient	2.2	1.79
[13]	Poroshell 120 EC-C18 (50 × 4.6, 2.7)	Isocratic	0.5	5.0
[15]	BDS HypersilGold C18 (250 × 4.6, 5)	Isocratic	1.4	8.2
[15]	Merck monolithic Rp-18 e (100 × 4.6)	Isocratic	1.4	2.6
[19]	Chromolith SpeedRod (50 × 4.6)	Isocratic	3.0	0.68
[20]	Hexyl methacrylate monolith (150 × 0.53)	Isocratic	0.041	1.16
[20]	Betasil C18 (150 × 4.6, 3)	Isocratic	0.5	15.41
[37]	Kinetex C18 (150 × 4.6, 5)	Gradient	1.0	11.71
[38]	UPLC C18 BEH (50 × 2.1, 1.7)	Isocratic	0.7	2.52
[39]	Eclipse XDB-C8 (150 × 4.6, 5)	Isocratic	1.0	2.1
[40]	Agilent TC-C18 (250 × 4.6, 5)	Gradient	0.75	38.0
[41]	BEH HILIC C18 (50 × 2.1, 1.7)	Isocratic	0.25	1.15
[42]	Eclipse C18 (250 × 4, 5)	Gradient	1.0	10.0
[43]	Scherzo SS-C18 (150 × 4.6, 3)	Gradient	0.4	12.6
[44]	Diol-HILIC (150 × 3.0, 5)	Gradient	0.3	4.1
[45]	XBridge C18 (150 × 4.6, 3.5)	Isocratic	1.0	7.16
[46]	Gemini C18 (150 × 4.6, 5)	Gradient	1.0	18.6
[47]	BEH C18 (100 × 2.1, 1.7)	Gradient	0.25	4.24
[48]	Kinetex C18 (100 × 2.1, 2.6)	Gradient	0.2	3.6
[48]	HypersilGold (50 × 2.1, 1.9)	Gradient	0.2	1.9
[49]	Titan C18 (100 × 2.1, 1.9)	Gradient	0.3	6.81
This work	Nucleodur C18 polar Tec. (50 × 2, 1.8)	Isocratic	0.5	0.46

Retention time for caffeine (min). Since it was not mentioned in some studies, the retention time of caffeine was carefully estimated from the separation chromatogram.