Derivative Pulse Polarography Research Articles

Determination of traces of molybdenum and tungsten by extraction and polarography of their salicoylhydroxamates

Molybdenum and tungsten salicoylhydroxamates have been extracted into methyl isobutyl ketone or a mixture of chloroform and isobutyl alcohol from 1.5 M hydrochloric acid and subjected to DC and derivative pulse polarography (DPP) after addition of methanolic lithium chloride solution, phosphoric acid and water in defined proportions. Molybdenum gives two DC waves with E 1 2 at −125 and −525 mV and a sharp DPP peak at −75 mV, whereas tungsten shows a single DC wave at −840 mV and a DPP peak at −850 mV. The two metals can be determined down to the sub-ppm level.

Polarography of Metal Hydroxamates. Individual and Simultaneous Determination of Tungsten and Molybdenum Using Benzo- and Cinnamohydroxamic Acids

Abstract Methods for the determination of traces of tungsten have been developed by directly subjecting the organic extracts of its benzo- and cinnamohydroxamic acid complexes to d. c. and derivative pulse polarography. Well defined waves and peaks are obtained in a ternary solvent mixture containing the extract, methanolic lithium chloride and aqueous phase. The methods are highly selective and allow determination of the metal in the ppm range. A procedure has also been developed for the simultaneous determination of tungsten and molybdenum using their benzohydroxamates. Effects of acids and solvents on the system have been studied and the probable mechanism of reduction of the complexes has also been discussed.

Reduction and tensammetric pulse-polarographic currents of polynucleotides

The behaviour of electrochemically reducible single-strand polynucleotides (poly(adenylic acid)) and poly(cytidylic acid)) was studied by the differential (derivative) pulse polarography (DPP) and by other methods. Measurements were performed with the help of the dropping mercury electrode under various conditions specified by the pulse width, pulse amplitude, drop time etc. For the faradaic and tensammetric DPP peaks the diagnostic criteria were proposed which make it possible to classify even very small DPP peaks of double helical polynucleotides.

Determination of nitrilotriacetic acid in water by derivative pulse polarography at a hanging mercury drop electrode

Determination of nitrilotriacetic acid in water by derivative pulse polarography at a hanging mercury drop electrode

Properties of DNA modified with N-methyl-N-nitrosourea.

The initial effect of N-methyl-N-nitrosourea (MNU) on double-stranded calf thymus DNA was studied by means of derivative pulse polarography, kinetic formaldehyde method and spectrophotometric denaturation curves. In the first 30 min of the reaction it was found that, at a molar ratio MNU : DNA P = 20 : 1, changes in the pulse-polarographic behaviour of DNA took place, while no changes in Tm were detected. A higher reactivity of DNA with formaldehyde was observed in the same time interval, when a higher ratio MNU : DNA P (50 : 1) was used. The increase of the pulse-polarographic peak that was observed at room temperature and slightly acid pH, or at neutral pH and elevated (premelting) temperature was explained by a local destabilization of the double helix.

Pulse-polarographic analysis of nucleic acids and proteins

Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and d.c. and a.c. polarography in connection with the dropping mercury electrode. It was shown that natural ribonucleic acids, as transfer, ribosomal and viral RNAs yield derivative pulse-polarographic peaks; from their heights and potentials conclusions can be made about their content of ordered structure in solution, similarly as in the case of deoxyribonucleic acids studied earlier. Synthetic single-stranded polyribo-cytidylic acid yields a well developed peak, whereas in the double-helical complex with polyriboguanylie acid it is inactive when using either derivative pulse polarography or d.c. polarography. Well developed peaks were obtained also with albumin (a protein containing reducible−S−S− groups), while only an inflex was observed on the d.c. polarogram. Proteins were also studied in media containing cobalt (Brdička's solution) or nickel and it was shown that derivative pulse polarography due to its high sensitivity and accuracy enables us to carry out the measurements even in less common media than Brdička's solution. This fact could be exploited in clinical chemistry as well as in the investigation of the nature of catalytic currents of proteins. The currents of double-helical polynucleotides obtained by means of normal pulse polarography exhibit a marked dependence on the initial potential and cannot represent a reliable indicator of structural changes of biopolymers in solution. They can however, be used in studies of the influence of the polynucleotide adsorption at different potentials on the subsequent reduction.

Pulse-polarographic analysis of nucleic acids and proteins

Nucleic acids and proteins were studied by means of derivative and normal pulse polarography, and d.c. and a.c. polarography in connection with the dropping mercury electrode. It was shown that natural ribonucleic acids, as transfer, ribosomal and viral RNAs yield derivative pulse-polarographic peaks; from their heights and potentials conclusions can be made about their content of ordered structure in solution, similarly as in the case of deoxyribonucleic acids studied earlier. Synthetic single-stranded polyribo-cytidylic acid yields a well developed peak, whereas in the double-helical complex with polyriboguanylie acid it is inactive when using either derivative pulse polarography or d.c. polarography. Well developed peaks were obtained also with albumin (a protein containing reducible−S−S− groups), while only an inflex was observed on the d.c. polarogram. Proteins were also studied in media containing cobalt (Brdička's solution) or nickel and it was shown that derivative pulse polarography due to its high sensitivity and accuracy enables us to carry out the measurements even in less common media than Brdička's solution. This fact could be exploited in clinical chemistry as well as in the investigation of the nature of catalytic currents of proteins. The currents of double-helical polynucleotides obtained by means of normal pulse polarography exhibit a marked dependence on the initial potential and cannot represent a reliable indicator of structural changes of biopolymers in solution. They can however, be used in studies of the influence of the polynucleotide adsorption at different potentials on the subsequent reduction.

Polarographic studies on the N-benzoylphenylhydroxylamine complex of tin and pulse polarographic determination of trace quantities of tin after extraction

A polarographic investigation on the N-benzoylphenylhydroxylamine (BPHA) complex of tin has been made in a mixture of chloroform and methanol. From the studies it has been confirmed that the complex is formed by tetravalent tin. A tentative mechanism of the oxidation of tin(II) in presence of BPHA has been suggested. Moreover, a rapid, sensitive and specific method of determination of tin in trace quantities by derivative pulse polarography has been developed. The chloroform extract can be directly subjected to polarography after addition of requisite quantities of water and methanolic lithium perchlorate. Effect of different supporting electrolytes on the system has been studied. By the described method 7×10−7 M to 2×10−5 M tin can be determined without interference from large quantities of the elements commonly associated with tin and also from a large number of other elements and complexing agents.

Determination of some monoazo compounds by derivative pulse polarography

The determination of some monoazo compounds by derivative pulse polarography has been investigated. The effect of pH is studied, and the optimum pH was determined to give the highest sensitivity. The detection limit is ca. 1×10−5 M. Response is linear up to 8×10−4 M.

Structural transitions of polyadenylic acid due to protonation: the influence of the length of single strands on the polarographic behaviour of the double-helical form.

Transition of single-stranded poly(A) into its double-helical protonated form was followed by means of derivative pulse polarography, spectrophotometry, and other methods. It was found that properties of protonated poly(A) depended on the length of single strands from which the protonated double helix was formed. In contrary to longer poly(A) transition of short single-stranded molecules (s(20),w lower than about 3) caused practically no decrease in the pulse-polarographic current. It was concluded that the formation of the protonated double helix of poly(A) did not result in the inaccesibility of the reduction sites (located in the vicinity of the surface of the molecule) for the electrode process, as it was in DNA-like double-helical polynucleotides. The current changes observed in the course of transition of longer poly(A) were explained as due to slower transport of long double-stranded molecules to the electrode.

Polarographic Study of Lead-Tropolone Complexation

Abstract A.C., D. C. and derivative pulse polarography of lead-tropolone complexes has been studied. It has been shown that the application of usual treatments for complexation in d. c. polarography are invalid in this system, where the irreversible wave in presence of the ligand is a composite step. It seems generally advisable to apply derivative pulse or a.c. polarography before using non-reversible d.c. steps for evaluation of K and p.

Determination of Traces of Copper, Lead, and Cadmium in Cobalt by Derivative Pulse Polarography

Abstract A derivative pulse polarographic method is described for determining traces of copper, lead and cadmium in cobalt and its compounds without separation. In hydrochloric acid medium the detection limits are respectively about 0.02, 0.04 and 0.1 ppm in metallic cobalt when analysing 2 M cobalt solutions. The procedure was applied to the analyses of synthetic and commercially available cobalt samples and showed a satisfactory sensitivity and precision at various concentrations levels of the three impurities.