Table 2: A comparison between existing methods and the proposed method in this paper.

Instrumental methodExtractionClean-upMDLReference

HPLC-UVAqueous methanolAnionic SPE30[6]
CE-UVAqueous methanolAnionic and cationic SPE150[8]
HPLC-FLDAqueous methanolAnionic SPE6[9]
HPLC-UVAqueous methanolAnion SPE200[13]
HPLC-MSAqueous methanolAnion SPE400[13]
HPLC-MS/MSMethanol/acetone (Extraction with PLE)200[11]
HPLC-UV-MS/MSAqueous methanolOnline SPE0.3[15]
HPLC-MS/MSAqueous methanol63[10]
HPLC-MS/MSMethanol9This paper

HPLC: high performance liquid chromatography; UV: ultraviolet detection; CE: capillary electrophoresis; FLD: fluorimetric detection; MS: mass spectrometry; MS/MS: tandem mass spectrometry; SPE: solid phase extraction; PLE: pressure liquid extraction.