Capillary electrophoresis-UV analysis using silica-layer coated capillary for separation of seven phenolic acids and caffeine and its application to tea analysis

Abstract This work presents an innovative silica-layer coated capillary with comparison study of the and fused-silica for separation seven phenolic acids viz . p -hydroxyphenylacetic acid (PHPA), -coumaric (PCA), -hydroxybenzoic (PHBA), caffeic (CFA), (3,4-dihydroxyphenyl)acetic (DHPA), gallic (GLA), 2,3,4-trihydroxybenzoic (THBA), together caffeine (CF), by electro-chromatography (CEC) micellar electrokinetic chromatography (MEKC), respectively. The running buffer was 25.0 mM borate at pH 9.0, addition 50.0 sodium dodecyl sulfate MEKC mode. non-coated could not separate all CEC or MEKC. achieved using both had plate number N ≥ 2.0 × 10 4 m −1 resolution R s 1.6 adjacent pairs peaks. also able to GLA THBA which are structural isomers. Although mode provided comparable efficiency selectivity, reduced EOF led longer time. linear calibration range were different but coefficients determinations (r 2 ) > 0.9965. precisions relative migration times peak area ratios analyte internal standard 0.1–1.8% 1.8–6.8%, There no statistical differences in three capillaries. It applied analysis brewed tea tyramine as standard. samples diluted prior CEC. less than 15 min. Caffeine, detected quantified. Caffeine contents 10.8–15.0 2.6–4.8 mg g dry leaves, p- Coumaric only one a content 0.4 Percent recoveries spiked 90 ± 9 106 13%, Article highlights Silica-layer is first reported simultaneous non-MEKC analysis. Performance between coated, capillaries compared. Plate number, resolution, reproducibility, electroosmotic flow mobility investigated. Graphical abstract