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Tungstate as complex‐forming reagent facilitating separation of selected polyphenols by capillary electrophoresis and its comparison with borate
Author(s) -
Jáč Pavel,
Polášek Miroslav,
Batista Ana I. V.,
Kaderová Lenka
Publication year - 2008
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200700598
Subject(s) - chemistry , capillary electrophoresis , tungstate , chromatography , reagent , chlorogenic acid , rutin , vitexin , molybdate , polyphenol , apigenin , nuclear chemistry , inorganic chemistry , flavonoid , organic chemistry , antioxidant
Abstract A novel electrophoretic BGE containing tungstate as complex‐forming reagent is suitable for the separation of polyphenols. Similar to molybdate‐containing BGE reported earlier ( cf. M. Polášek, et al.., Talanta 2006, 69 , 192) addition of tungstate to BGE affects significantly migration of compounds/ligands with vicinal –OH groups due to the formation of negatively charged complexes involving W(VI) as central ion. Baseline separation of mixtures of flavonoids (apigenin, luteolin, hyperoside, quercetin, and rutin) and phenolic acids (chlorogenic and p ‐coumaric acid) was achieved within 15 min with optimized BGE of pH 7.4 containing 50 mM N ‐(2‐hydroxyethyl)piperazine‐2′‐(2‐ethanesulfonic acid) (HEPES), 2.2 mM tungstate, and 25% v/v of methanol. The separation was performed in a 75 cm (effective length 42 cm)×75 μm id uncoated fused‐silica capillary at 30 kV with spectrophotometric detection at 275 nm. The calibration curves were rectilinear for 25–175 μg/mL of all analytes (cinnamic acid as the internal standard). The LODs ranged from 1.8 to 6 μg/mL for all analytes except for chlorogenic acid. Intraday precision ( n = 6) of migration times (RSD ≤ 1.2%) and peak areas (RSD ≤ 5.6%) was evaluated. The tungstate‐based BGEs can be alternatively utilized for the analysis of polyphenols at considerably lower pH than with conventional alkaline borate‐based BGEs.