Separation and determination of protocatechuic aldehyde and protocatechuicacid in Salivia miltorrhrza by capillary electrophoresis with amperometricdetection

Capillary electrophoresis with amperometric detection was applied to separa te and determine protocatechuic aldehyde and protocatechuic acid in Salivia miltorrhrza preparations. The electrode used was a 0.3 mm diameter carbon disk electrode fixed in a wall-jet with amperometric detection. Under the o ptimum conditions, the two analytes were separated completely within 8 min. Excellent linearity was obtained in the concentration ranges of 0.25-100.0 mug ml(-1) and 0.50-100.0 mug ml(-1) for protocatechuic aldehyde and proto catechuic acid, respectively. The detection limits were 0.10 mug ml(-1) of protocatechuic aldehyde and 0.25 mug ml(-1) of protocatechuic acid, which w ere found to be lower than those of other methods that determine protocatec huic aldehyde (3,4-dihydroxybenzaidehyde) and protocatechuic acid (3,4-dihy drobenzoic acid) simultaneously. The mean recoveries of protocatechuic alde hyde and protocatechuic acid were 97.4% and 103.3%. This method has been su ccessfully applied to monitor these two components in real samples such as Salivia miltorrhrza and its two traditional Chinese medicinal preparations.