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

Table 2

Optimum HPLC and MS conditions for determination of theobromine, theophylline, and caffeine.

Items	Parameters
HPLC conditions
Column	Nucleodur C18 polar Tec. (50 × 2 mm i.d.; 1.8 μm particle sizes)
Mobile phase	Acetonitrile: water (10 : 90, v/v) with 1.0% formic acid
Flow rate	0.5 mL/min
Column temperature	70°C
Injection volume	5.0 μL
MS conditions
MS mode	ESI^+ (SIM mode)
Capillary (KV)	3.5
Extractor (V)	2
RF lens (V)	0
Cone voltage (V)	35
Source temperature (°C)	120
Desolvation temperature (°C)	300
Desolvation gas flow (L/h)	600
Cone gas flow (L/h)	60