Voltammetric determination of phytochelatins using copper solid amalgam electrode.

Voltammetric determination of synthetically prepared phytochelatins (gamma-Glu-Cys)(2)Gly (PC(2)) and (gamma-Glu-Cys)(3)Gly (PC(3)) has been studied using new type of copper solid amalgam electrode. The determination, based on the formation of cuprous complexes in buffer pH 8.1, is suitable for concentrations of PC in the range 10-100 nmol l(-1). Reproducibility, employing electrochemical cleaning of the electrode surface, was statistically evaluated. The achieved limit of detection (2.1-2.6x10(-9) mol l(-1) for DCV measurement) together with the robust character of the electrode offer its use for detection of PCs in separated extracts of real samples.

Voltammetry on mercury and carbon electrodes as a tool for studies of metallothionein interactions with metal ions.

Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gamma-Glu-Cys)2-Gly were studied as examples of animal and plant metallothioneins. Using hanging mercury electrode, cathodic stripping voltammetry after adsorptive accumulation of the Cd(II)-SR complex at different potentials, is suitable for estimating changes occurring in metal coordination due to the presence of metal ions such as Zn2+, Cu2+, Hg2+ or excessive Cd2+. Conditions under which similar behaviour can be observed for both CdMT and Cd-pentapeptide complex are specified. On carbon electrodes, detailed study of reduction processes of Cd(II)-SR complexes is prevented by occurrence of a large catalytic current; oxidation processes are more suitable for study at these electrodes. Carbon composite paste electrode (10% SiO2) allows deposition of Cd(II)-SR complex during its reduction, as was demonstrated with Cd-cysteine, CdMT or Cd-pentapeptide complex. After deposition, oxidation peak of the uncomplexed Cd2+ ions and one or two oxidation peaks corresponding to a formation of the RS-Cd(II) complex are observed. Also, similarly as on Hg electrode, it was observed that excessive Cd2+ or Zn2+ ions influence oxidation peaks of the RS-Cd(II) complex formation. Combination of measurements on mercury electrode and composite paste electrode is recommended for studies of metallothionein interactions with metal ions or other metal complexes.

Determination of cyadox and its metabolites in plasma by adsorptive voltammetry.

Adsorptive stripping voltammetry was combined with separation of the surfactants by gel chromatography or solvent extraction for determination of the growth promotor, cyadox, and its metabolites in the plasma from pig blood. The procedure permits determination of the substance at concentrations from units to hundreds of ng per ml of plasma. The accuracy of the results was checked by comparison with radiochemical measurements.

[Pulse polarographic determination of piperacillin (Pipril) in serum and urine]. / Pulspolarografische Bestimmung von Piperacillin (Pipril) im Serum und Urin.

Two pulse polarographical methods for determination of the half-synthetic penicillin derivate piperacillin in serum and in urine are described. 3.7 X 10(-5) mol/l (20 micrograms/ml) can yet been proved in serum with the direct pulse polarographical determination. 1.85 X 10(-6) mol/l (1 microgram/ml) can quantitatively be determined after preceded hydrolysis. Both the methods are diffusion standards being well developed which can be evaluated in an adequate manner. The piperacillin concentrations determined by pulse polarography agree to the levels of the agar diffusion test. The precision is some reduced by the separations incorporated. Inspite of the hydrolysis, the pulse polarographical method of determination will offer more prompt and reliable results.

A new procedure for estimation of nitrovin and carbadox residues and their metabolites in food of animal origin.

In order to establishe the length of the protective period for which the animals are given food without chemical growth stimulators before slaughter two methods are proposed permitting wide use in sanitary control: 1/ A highly sensitive method of pulse-polarography has been worked out for the estimation of widely used growth stimulator nitrovin residues/ 1.5-bis/5-nitro2-furyl/1.4-pentadiene-3-on amidinohydrazone / and its metabolites. In the tissues of the experimental animals examined were found residues at a level of about 50 ppb. The limit of sensitivity of the procedure used is 10 ppb. 2/ Based upon double-electron reduction of the quinoxaline circle a simple and sufficiently sensitive polarographic method was worked out for the estimation of carbadox residues / quinoxaline-1.4-N-dioxide-2-methylcarbazate/and its main metabolite / quinoxaline-2-carboxylic acid/. With the sensitivity of the method of 0.1 ppm excretion curves were designed and residue levels were determined in tissues of pigs fed up to 56 days of age by feed containing 20 - 50 ppm of carbadox.