A novel electrochemical sensor for the determination of podophyllotoxin (PPT) was prepared by modifying a PPT-imprinted membrane, which was synthesized by in situ polymerization with PPT as template, methacrylic acid ( MAA) as functional monomer and ethylene glycol dimethacrylate ( EGDMA) as cross linking agent at the molar ratio of PPT/ MAA/ EGDMA as 1 : 2 : 100, on glassy carbon electrode ( GCE) followed by eluting PPT from the modified GCE with methanol/ acetic acid (1: 1, V/ V). The properties of the electrochemical sensor modified with PPT-imprinted membrane were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS). Under the optimum conditions, it was found that the response of peak currents was linear to the concentration of PPT in range of 1. 0 - 120 μmol/ L with the detection limit of 0. 47 μmol/ L. The sensor not only showed high selectivity, but also exhibited good stability and reproducibility. The sensor was satisfactorily applied to the determination of PPT in podophyllum hexandrum and human serum samples with the relative standard deviation (RSD) below 3. 9% and recovery ranging from 95. 0% to 103. 3% .

The catalytic effect of ruthenium on the oxidation reacti on of methylene blue (MB) was investigated and applied for the determination of ruthenium(Ⅲ) by the kinetic spectrophotometry in the sulfuric acid medium at 90±0.5℃. The optimum reaction conditions, kinetic parameters and r eaction mechan ism were studied. The linear ranges for the determination of ruthenium (Ⅲ) were 0.0～1.2 and 1.2～5.6 μg/L with a detection limit of 0.05 μg/L . Almost no foreign ions more than 50-fold concentration of Ru(Ⅲ) I nterfered with the determination. The method, which was of high sensitivity, good selectivity and stability, was s uccessfully applied for the determination of trace ruthenium in some ores and m e tallurgical products, the RSD (n=8) was 1.3%～2．2％ and the recovery was between 99% and 105%.