Determination of Lycopene, α-Carotene and β-Carotene in Vegetable Juice by Liquid Chromatography/Atmospheric Pressure Chemical Ionization-Mass Spectrometry

Lycopene, α-carotene and β-carotene in canned vegetable juice were determined by high performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) with selected ion monitoring (SIM). The extracted carotenoids were separated on a C-18 reversed phase column with methanol as the mobile phase and cholesterol benzoate as an internal standard (IS). In order to obtain good repeatability, only the peak portion of analytes eluted from the LC column was introduced into the APCI interface by using an auto switching valve. In the positive mode, lycopene, α-carotene and β-carotene were monitored at m/z 537 and IS was monitored at m/z 369. The limit of detection was 1ng (s/n=4) and the recoveries of lycopene, α-carotene and β-carotene were 85.1%, 80.0% and 82.8%, respectively.This SIM determination using LC/APCI-MS allows the analyte in samples to be determined without the influence of co-existing substances which cause problems in LC-UV chromatography.