Differential pulse voltammetric determination of P(V) following adsorptive accumulation of alpha-[PMo(12)O(40)](3-) on a polypyrrole-modified glassy carbon electrode.
On the basis of the formation and pre-concentration of an alpha-Keggin-type [PMo(12)O(40)](3-) complex, a novel voltammetric method was developed for the determination of trace levels of P(V). The alpha-[PMo(12)O(40)](3-) complex was formed by heating a 5x10(-4) M Mo(VI)-0.2 M HCl-40% (v/v) CH(3)CN system containing a trace amount of P(V) at 70 degrees C for 30 min. During the electrochemical polymerization of pyrrole in the alpha-[PMo(12)O(40)](3-) solution, the alpha-[PMo(12)O(40)](3-) complex was accumulated into the polypyrrole film on a glassy carbon electrode. The differential pulse voltammetric peak current due to the alpha-[PMo(12)O(40)](3-) complex incorporated in the polypyrrole film was linearly dependent on the P(V) concentration in the range of 5x10(-9)-5x10(-7) M; a detection limit of 2x10(-9) M was achieved.
Potentiometric evaluation of antioxidant capacity using polyoxometalate-immobilized electrodes
Abstract The voltammetric behaviour of polyoxometalates (POMs) is greatly affected by acid and solvent conditions. POMs can be immobilized on an electrode surface by various cationic conducting polymers prepared via in situ electro-oxidative polymerization. In the present study, the effects of acid and organic solvent concentrations on POM immobilization on the surface of a glassy carbon electrode (GCE) were investigated with cyclic voltammetry. Several Keggin-type POMs, such as [PMo 12 O 40 ] 3− , [PVMo 11 O 40 ] 4− , [PVW 11 O 40 ] 4− and [SVMo 11 O 40 ] 3− , were examined with three types of conducting polymers, polypyrrole (PPy), poly(3,4‑ethylenedioxythiophene) (PEDOT) and polyaniline (PAni). In addition, the voltammetric behaviour of the POM-immobilized electrodes was investigated under various conditions. Finally, the most appropriate POM-immobilized electrode was selected as a redox probe to potentiometrically evaluate antioxidant activity. The antioxidant activities of several typical antioxidants contained in food and beverages were evaluated using an appropriate PMo 12 O 40 -immobilized electrode under the optimized conditions, and the results were compared with those obtained from two well-known spectroscopic methods: the oxygen radical absorbance capacity (ORAC) and 2,2‑diphenyl‑1‑picrylhydrazyl (DPPH) radical assays.
Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat
In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C10−C18 fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C4−C18 fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.