Adsorptive polarographic analysis

A sensitive method for the estimation of different surface active compounds (tetraalkylammonium salts, dextrans, crude oil components) in water is based on the measurements of the depression of the electrocapillary curve under conditions where the transport of the compound to the dropping Hg-electrode is accelerated by stirring of the solution being examined[12] The detection limit is in the range of 10-100 jjg 1 More details on "adsorptive polarographic analysis" are given in[13]. 

The presence of other kinds of limiting current and adsorption effects pose a hazard to precise and accurate polarographic analysis. 

F. Cullen, M. P. Brindle, and G. J. Popariello, Automated polarographic analysis in pharmacy, J.Pharmac.Sci., 62 1708 (1973). Kalvoda, Adsorptive accumulation in stripping voltammetry. Anal. Chim.Acta, 138 11 (1982). 

The accumulation effect can be exploited also for adsorptive stripping analysis of polarographically reducible surface active compounds. As an example, the local anaesthetic Percaine Ciba (Table 1) can be mentioned the obtained peak belongs to the reduction of the adsorbed compound (Figure 3). Other examples of adsorptive accumulation of electroactive compounds are the Ge (Figure 5) and Cu surface active complexes mentioned in Table 1. In the case of the adsorbable complexes mentioned the method is suitable mainly for metals where the amalgam formation is complicated or where the solubility of the metal in mercury is low. 

ScHLEiCH C and Henze G (1990a) Trace analysis of germanium. Part 2. Polarographic behaviour and determination by adsorptive stripping voltammetry. Fresenius J Anal Chem 338 145-148. 

Square wave polarography/voltammetry Electrocapillary curve methods Polarographic adsorption analysis... 

Polarographic adsorption techniques and tensammetric methods (for further details the reader should consult two recent review papers ) are non-specific and mostly do not permit analysis of mixtures of substances, and thus, the results correspond only to the overall content of the surface active pollutants present in the water sample. Often, however, the determination of the surface activity of water is more important than the determination of... 

Adsorption of polymers, in general, on the electrode surface is the main property of these (most) electroinactive organic compounds that has been used in their polarographic determination. The polarographic adsorption analysis, the state of which was quite recently reviewed embraces two different methods dc polarographic maximum suppression and ac polarography. 

Pipette 0.4 ml of serum and mix by gentle stirring with 1 ml of O.lN potassium hydroxide solution. Allow the denaturation to take its course at 20 C (at best in a tempered water bath) for exactly 45 min. Then add 1 ml of 20% sulfosalicylic acid solution, mix intimately, and allow to stand at room temperature for exactly 10 min. Then filter the entire sample through a paper filter with a low adsorptivity of proteins (suitable are, e.g., Whatman No. 1, VEB Niederschlag No. 388 h, Schleicher Schuell No. 575 resistant). The filtration procedure must always be performed in a standard way (the same sort of paper, same size of the filter, same volume of liquid filtered, filtration never repeated), and the filtrate must be clear. If the filtration fails, the entire analysis must be repeated. The filtrate can be stored, if necessary, at 4°C for 24-48 hr without any change in polarographic activity. 

R. Kalvoda, Polarographic adsorptive analysis and tensammetry of adsorbable molecules. Pure and Applied Chem., in print. 

The aim of the present work is the study of the adsorptive accumulation of surface active compounds on the electrode surface in polarographic stripping analysis, where, during the stripping pro-cess, the desorption peak is recorded using differential pulse polarography (DPP). 

The adsorptive accumulation of some alkaloids, local anaesthetics, surfactants and metal complexes in stripping analysis using differential pulse polarographic procedure is described. The combination of this stripping method with liquid chromatography is possible. 

Less ambiguous conclusions can be reached if the polarographic characteristics obtained under conditions which exclude adsorption and the effect of protolytic equilibria are compared. We therefore carried out such an analysis for the half-wave potential of the first wave formed by these compounds in the polarography of dimethyl-formamide solutions. In fact, under these conditions, we were able to observe the transmission of the substituent effect in the first series, which in accordance with the views expressed earlier indicated decrease of conjugation (p = +0.1). The polarographic data can thus be explained if a nonplanar conformation of the hydrazone molecules is adopted. 

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