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Reproducibility of working electrodes in voltammetry
Josypčuk, Bohdan ; Heyrovský, Michael
In voltammetry the working electrode is the source of signal from which the due information is gained. A transition from the dropping mercury electrode to any kind of stationary electrode is inevitably accompanied by worsened reproducibility of measurements, the transition to the hanging mercury drop electrode is accompanied by a certain instrumental complication. When solving a concrete task, the precision of reproducibility of measurements often becomes the decisive factor for selecting a particular type of working electrode, or for taking voltammetry as the method of choice. This work is the beginning of a wider study which includes comparison of different working electrodes and finding of optimal conditions guaranteed reproducible measurements of various electrode processes (reduction, oxidation, accumulation, adsorption and catalysis).
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Electrochemical behavior of alkali metal alcoholates on mercury
Heyrovský, Michael
In chemistry in general, and in organic chemistry and biochemistry in particular, sodium borohydride is a frequently used reducing agent of medium strength. If we follow the products of borohydride reduction by an electrochemical method, we may be surprised by the appearance on the polarization curves of current due to catalytic evolution of hydrogen.
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Recyclation and Transformation of Homocysteine as a Part of Detoxication Processes in the Cell
Přistoupilová, K. ; Přistoupil, T. ; Šenholdová, Z. ; Navrátil, Tomáš ; Heyrovský, Michael
The presented metabolic pathways explain how the transformation of homocysteine affects the detoxication processes in the human cell. On the one hand homocysteine is recycled to methionine; on the other hand it is transformed to cysteine. Both pathways are connected by B12 vitamin. Their relation to the thiodiglycolic acid (TDGA), which represents a part of the detoxication processes, is demonstrated on the scheme. The changes in TDGA concentration in urine were found to depend on the changes in redox equilibria (of vitamin B12, folic acid, homocysteine). Key Words: Thiodiglycolic acid, TDGA, vitamin B12, folic acid, metabolic pathways, homocysteine, detoxication.
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Změny koncentrace TDGA v moči jako možný marker metabolismu thiosloučenin
Přistoupilová, K. ; Přistoupil, T. I. ; Šenholdová, Z. ; Navrátil, Tomáš ; Heyrovský, Michael ; Fenclová, Z.
The new simple voltammetric method we described recently, proved already to be useful in determining thiodiglycolic acid (TDGA) levels in urine samples of people influenced by some chemicals, victuals and pharmaceuticals. The present pilot study is a continuation of our previous work devoted to test general feasibility of the method. We concentrated upon time dependent quantitative changes of TDGA excretion into urine of selected volunteers. The TDGA level in all morning samples was the highest in comparison with samples collected during the day. The TDGA level was dependent on the health condition of each person involved. However, a further marked increase of TDGA in the morning urine was observed individually, in general when vitamin B12 had been administered in the evening the day before. Vitamin B12 is known to play an important role in the metabolism of one- and two-carbon units, of homocysteine and of sulfhydryls in general. Certain differences in excretion course of TDGA.
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