Gimena Acosta, Silvia Arce, Claudia Ortega, Luis D. Martínez and María R. Gomez Pages 197 - 204 ( 8 )
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.
Capillary electrophoresis, dynamic pH junction, normal stacking mode, on-line preconcentration, phenolic compounds.
Química Analítica. INQUISALCONICET. Departamento de Farmacia, Chacabuco y Pedernera. San Luis. Argentina. (5700).