Stanislaw Rubel

Adsorptive voltammetry for the determination of trace amounts of aluminium in blood serum derived products

A method for the determination of aluminium in blood serum derived products is described. The samples are mineralized in an open system with a mixture of nitric and perchloric acids, followed by H2O2 addition. The determinations are carried out by adsorptive stripping voltammetry with calmagite in acetate buffer.

Potentiometric titration of trace amounts of mercury after a preliminary separation by a reduction method

Isolation and concentration of mercury by reduction of mercury(II) with acidic tin(II) chloride solution and absorption of mercury vapour in acidic permanganate solution is combined with potentiometric titration with dithiooxamide. The simple procedure is applicable to 5–100 ppb mercury in 1-dm3 samples. Recoveries from organomercurials are discussed.

A comparison of potentiometric, spectrophotometric and atomic absorption spectrometric methods for the determination of mercury in wastes

Abstract The potentiometric titration with dithiooxamide applied to mercury determinations in industrial wastes is compared with cold-vapour atomic absorption spectrometry and spectrophotometry with dithizone. The potentiometric method is shown to have adequate sensitivity and selectivity as well as economic advantages.

Potentiometric titration of trace amounts of mercury with dithiooxamide

Abstract Titration with dithiooxamide in potassium hydrogenphthalate medium (pH 5–6) is suitable for the determination of mercury in concentrations above 0.05 ppm. The precision in the range 0.05–1.0 ppm Hg is ⩾ 4%. Significant amounts of sulphate, nitrate, Zn2+, Cd2+ and Pb2+ and small amounts of Ni2+, Co2+ and Al3+ can be tolerated, but Fe3+, Cu2+ and Ag+ interfere.

Analytical application of triethylenetetraaminehexa- acetic acid: Part 2. Polarographic Investigation of the reactions of TTHA at the dropping mercury electrode

Abstract TTHA gives an anodic d.c. wave and s.w. peak corresponding to oxidation of mercury at the d.m.e. surface with formation of a Hg(II)—TTHA complex. Similar processes are known for other ligands, e.g. EDTA and DCTA, but the greater stability of the Hg(II)—TTHA complex gives a significant improvement in the shapes of the anodic wave and s.w. peak. An increase in pH shifts the E 1 2 and Ep values towards more negative values because the conditional stability constant of the Hg(II)—TTHA complex is increased. Although the half–wave potentials of the reduction wave of Hg(II)—TTHA and of the anodic wave of TTHA, are the same, other criteria for the reversibility of polarographic reactions suggest that the anodic TTHA process at the d.m.e. is not completely reversible. The temperature coefficient of the wave and s.w. peak as well as the dependence of the wave height on the square root of the mercury head prove that the process is diffusion–controlled. Supporting electrolytes are given for which the d.c. wave and the s.w. peak of TTHA are well-shaped, with linear dependence between the wave or peak height and the concentration of TTHA in the ranges 5 × 10-5–5 × 10-4 M (d.c.) and 1 0-5–1 × 10-4 M (s.w.).

Amperometric titration of calcium, strontium and barium and their mixtures in presence of large amounts of alkali metal salts

Abstract Trace amounts of alkaline earth metals are titrated with triethylenetetraaminehexaacetic acid; lead(II) is added as indicator and the current is measured by square-wave polarography. At pH 13.3, calcium, strontium and barium give a common end-point corresponding to the total content of alkaline earth ions. Copper and cadmium interfere but small concentrations of Ni, Al, Mg, Zn, Mn(II) and Fe(III) are tolerated. The alkaline earth metals can be determined in the presence of 1000-fold amounts of lithium and 10 5 - fold amounts of sodium or potassium ions.

Analytical applications of triethylenetetraminehexaacetic acid : Part I. the influence of TTHA on the polarographic reduction of some metal ions

Abstract The influence of triethylenetetraminehexaacetic acid (TTHA) on the d.c. and square-wave polarographic curves of Cu(II), Pb(II), Cd(II), Ni(II), Co(II), Zn(II), Fe(III), Bi(III), Sb(III), As(III) and In(III) has been investigated in several supporting electrolytes over the pH range 1–13. The E 1 2 and Ep values with and without a 10-fold excess of TTHA are compared. Some analytical applications are suggested.

Analytical applications of triethylenetetraminehexa-acetic acid: Part 4. amperometric titrations of metal ions☆

Abstract The behaviour of metal ions during titration with triethylenetetraminehexaacetic acid (TTHA) in several supporting electrolytes was investigated by d.c. and square-wave polarography. The composition of the complexes (M2L or ML) formed during titration is reported as well as the [M] : [L] ratio corresponding to the end-point of amperometric titration. The optimal conditions (by d.c. and s.w. detection) are given for titrations of Cu(II), Ni(II), Cd(II), Pb(II) and Zn(II) based on the reduction current of metal ions, as well as for titrations of Cu(II), Cd(II), Pb(II), Zn(II), Al(III), Ca(II) and Mg(II) based on the anodic current of TTHA. Application of the anodic current of TTHA permits determinations of polarographically inactive metals and is valuable in analysis of mixtures.

Statistical estimation of the influence of mineralization methods on the results of heavy metals determination in cereals by the DPASV method

SummaryThe elements Cd, Cu, Pb and Zn have been determined in wheat, barley and oats by differential pulse anodic stripping voltammetry after wet mineralization, mineralization by dry ashing or mineralization in a PTFE bomb. The procedures are described. The results were evaluated by BASIC programs for one dimensional data evaluation, by principal components plot and by multidimensional analysis of variance. The influences of mineralization procedures on the results are low compared with the different contents in the three cereals particularly for Cd, but also for Pb and Zn. There are no significant differences, in the Cu content.