A sensitive optode membrane for berberine using conjugated polymer as sensing material.

A new optode membrane for the sensitive determination of berberine based on fluorescence quenching of a conjugated polymer, poly(2,5-dimethoxy-phenyldiacetylene) (PDPA), is proposed. Incorporated in a membrane composed of plasticized poly(vinyl chloride) (PVC), the conjugated polymer exhibits better stability than those small sensing molecules regarding its excellent optical properties and lipophilic characteristics. Moreover, upon the introduction of a negatively charged lipophilic additive (tetraphenylborate salt) into a PVC membrane, the optode displayed enhanced sensitivity. In addition, satisfactory analytical sensing characteristics for determining beberine were obtained in terms of the selectivity, reversibility and reproducibility with a detecting range of between 7.5 x 10(-7) mol l(-1) and 7.5 x 10(-4) mol l(-1). The optode membrane has been applied to determine berberine in commercial tablets. The results showed a good agreement with those obtained by the pharmacopoeial method.