The modified carbon paste electrode (CPE) responding simultaneously to lead(II), copper( II), and mercury(I1) ions has been constructed by incorporating humic acid (HA) into the graphite powder with Nujol oil. Simple immerging of the electrode into the measuring solution containing these metal ions led to the chemical deposition of the ions onto the electrode through the complexation of the ions with HA Cyclic and differential pulse voltammetry (DPV) characterized the modified electrode's surfaces. Several cyclings of the potential regenerated the electrode (from more positive than the stripping potential of reduced Hg to more negative than the reduction of Pb(I1)-ion). which was then used for another deposition. After five deposition/measurement/regeneration cycles. the peak current of voltammograms of the analyte decreased slightly The response reproduced with a 5.1% relative standard deviation. We also applied the differential pulse technique to the previouslv mentioned system. Here, the detection limit for Pb(I1). Cu(I1). and Hg(I1) ions were 5.0 x 10-9'hM. 8.0 X lo-' M. and 8.0 x with KCI. we could not observe any interference by other metal ions on the determination of the test ions in aqueous solution. Satisfactory results were acquired for the determination of the test metal ions in certified standard urine reference material SRM's 2670 (trace elements in urine).
The skin of Vitis coignetiae Pulliat (meoru) grown wild in the Republic of Korea was analyzed for anthocyanins via HPLC coupled to ESI-MS/MS in positive ion mode. Chromatographic separation was conducted via RP HPLC using a C(18) column, with a 50-min gradient from 0 to 80% methanol in water containing 0.5% formic acid. A total of 18 anthocyanins were identified. Among them, nine compounds were newly determined by comparing the retention time (t(R)) and mass fragmentation patterns with those of the previously reported anthocyanins for other grape varieties: malvidin hexose, peonidin 3-galactoside, malvidin 3-galactoside, cyanidin, petunidin, petunidin 3-(6''-coumaroyl)-5-diglucoside, peonidin, malvidin, and malvidin 3-(6''-coumaroyl)-5-diglucoside. The antioxidant activity of the V. coignetiae Pulliat anthocyanins was determined via 2,2-diphenyl-2-picrylhydrazyl radical scavenging and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation assays in a range of concentration from 25 to 500 mg/L. The capacity increased with concentration. The IC(50) values, defined as the concentration of sample required to scavenge 50% of free radicals, were calculated as follows: 189.63+/-11.31 mg/L and 141.29+/-6.70 mg/L for 2,2-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, respectively. The antioxidant activity of the V. coignetiae Pulliat anthocyanins is substantially higher than that of ascorbic acid and is similar to the effects of the extracts obtained from other grape varieties.
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