On-Line Preconcentration Method Using Normal Stacking Mode and Dynamic pH Junction for the Quality Control of Herbal Medicines Containing Related Phenolic Compounds

GIMENA ACOSTA; SILVIA ARCE; CLAUDIA ORTEGA; LUIS DANTE MARTINEZ; MARIA ROXANA GOMEZ

CURRENT ANALYTICAL CHEMISTRY

BENTHAM SCIENCE PUBL LTD

Lugar: Oak Park; Año: 2014 vol. 10 p. 197 - 204

1573-4110

An on-line preconcentration capillary electrophoresis (CE) methodology, which combines a normal stacking mode (NSM) with a dynamic pH junction technique, is introduced in this paper. A systematic study of the parameters (concentration and pH value of background electrolyte, composition of sample matrix, injection pressure and time, separation voltage and temperature) affecting on-line concentration of seven related phenolic compounds were investigated and optimized. Under the optimum focusing conditions, about 54-fold improvement in the detection sensitivity was obtained compared with usual hydrodynamic sample injection (0.5 psi, 5 s) without detriment in separation efficiency. In particular, the concentration limits of detection (LOD) (S/N = 3) for the phenolic compounds obtained after preconcentration were from 6.0 to 11.0 ng mL-1 with UV detection without any pretreatment procedure. The proposed method has been validated with RSD values between 1.13% and 1.98% for migration times and between 1.28% and 4.65% for peak areas. Developed NSM-dynamic pH junction method was applied to determination of related phenolic compounds in labeled Melissa officinalis medicinal herbal products commercialized in our country.