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 D. Martínez and María R. Gomez
Affiliation: Química Analítica. INQUISALCONICET. Departamento de Farmacia, Chacabuco y Pedernera. San Luis. Argentina. (5700).
Keywords: Capillary electrophoresis, dynamic pH junction, normal stacking mode, on-line preconcentration, phenolic compounds.
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 was 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 for determination of related phenolic compounds in labeled
M. officinalis medicinal herbal products commercialized in our country.
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