Pulse polarographic detection

Takana et al. [344] used high performance liquid chromatography on an anion exchange column with differential pulse polarographic detection to determine thiosulphate and tri, tetra-, penta- and hexathionates in trade effluents. The method is accurate to within 10% at the 0,001 1 mM concentration range. 

Elferink, F. van der Vjjgh, W.J. Pinedo, H.M. On-line differential pulse polarographic detection of carboplatin in biological samples after chromatographic separation. Anal.Chem., 1986, 58, 2293-2296... 

Differential pulse polarographic detection of catalytic [183] reduction of perchlorate or nitrate by solvent extracted phosphomolybdate... 

A pulse polarographic system for detection of the dicarboxylic acid in the presence of nalidixic and hydroxynalidixic acids was devised by Koss and Warner.(45) The reduction potential in the system used was -.54V vs. SCE. 

The pulse polarographic determination of chlordiazepoxide and its metabolites in plasma has also been described [191]. Chlordiazepoxide and its metabolites are extracted from serum buffered to pH 9.0 followed by a TLC separation, elution, and final quantitation in 0.5 M H2S04. The detection limit of the assay of 0.05-0.1 ng of each compound per milliliter of serum using a 2-mL sample is sufficiently useful for pharmacokinetic studies. 

Pulse polarographic studies have been described using a microcell of 0.5 mL capacity, which analyzed two 1,4-benzodiazepines, with the lowest detection limit reported to date being 10-20 ng/mL of blood [199]. Detailed construction of the cell and electrode assembly was also described (shown in Fig. 26.16). Further miniaturization of this type of three-electrode cell is not practical hence further increases in sensitivity will have to rely on electrochemical detector flow cells of microliter capacity such as those used in conjunction with liquid chromatography (see Chap. 27). 

Eletrochemical detection has been used for the detection of synthetic dyes. Fogg et al. (226) described a method for the qualitative and quantitative determination of several synthetic dyes using polarographic detection. The system was a stationary mercury drop electrode operated in the differential-pulse mode. Ashkenazi et al. (131) used fast-scan square-wave voltammetry for the polarographic detection of five synthetic dyes. The voltametric mode was observed to be much faster than the differential-pulse method. Another advantage is that the experimental measurement produces, in addition to the peak current, the redox potential of the dye, which can serve to identify the analyte further. 

The detection of products derived from the N-oxygenation of C=N functionalities presents many problems, which illustrate difficulties that are associated with the isolation, identification and quantification of small amounts of water-soluble metabolites. Spectrophotometric methods19 as well as differential pulse polarographic techniques20 previously used to determine oximes, nitrones and N-oxides frequently lack sensitivity and/or specificity. Improved analytical methods for the quantification of these N-oxy compounds include chromatographic techniques taking into account the chemical peculiarities of the individual N-oxygenated C=N functionalities. These procedures usually require the chemical synthesis of authentic material for comparison with data obtained with the isolated metabolites, and also for the construction of calibration curves. 

Hemmi et al. [ 11 ] has described a differential pulse polarographic procedure for the determination of nitrate in environmental samples such as silage, grass, plants, snow and water. This method utilizes the catalytic reaction between nitrate and uranyl ion in the presence of potassium sulfate. The differential pulse polarographic peak is proportional to the nitrate ion concentration from 1 to 50 pmol/1. The detection limit for nitrate in water is 8 x 10 7 mol/1. Using this procedure, between 1 and 70 mg/g nitrate was found in vegetation samples. 

Anodic stripping voltammetry has been used to determine total arsenic spedes . Pulse polarographic methods have been applied to aqueous and non-aqueous solutions of methyl- and dimethylarsenic adds at concentration levels down to 0.1 /rg/ml . These arsenicals are electroactive in aqueous buffers and in non-aqueous media in which the acidic supporting electrolyte, guanidinium porchlorate, is employed. A direct method of analysis, based on differential pulse polarography, is reported. Detection limits of roughly 0.1/xg/ml (for MMAA) and 0.3p[Pg.190]

Commercial electrochemical detectors whose cells are directly connectable to the postcolumn efflux of the HPLC apparatus are available from a number of manufacturers. This method of detection is comparable in sensitivity to detection by absorption spectroscopy when the amperometric circuit is operated as a DC pulse polarograph. 

This paper investigates the differential pulse polarographic, dc and square wave voltammetric determination of selected antibiotics, antibacterials and anticonvulsants at mercury and solid electrodes. The results of these determinations are compared and contrasted with rival analytical methods based on high performance liquid chromatography with ultraviolet detection. 

It is important in evaluating this situation to remember the context. In the 50 s fundamental work on pulse polarography decreased polarographic detection limits from about 10 M (dc) to about 10 m (dp). The advent of solid-state circuitry and the beginning of an applications literature for pulse polarography set... 

Betso and McLean [11] have described a differential pulse polarographic method for the determination of acrylamide and acrylic acid in polyacrylamide. A measurement of the acrylamide electrochemical reduction peak current is used to quantify the acrylamide concentration. The differential pulse polarographic technique also yields a well-defined acrylamide reduction peak at 2.0 V versus SCA (reduction potential), suitable for qualitatively detecting the presence of acrylamide. The procedure involves extraction of the acrylamide monomer from the polyacrylamide, treatment of the extracted solution on mixed resin to remove interfering cationic and anionic species, and polarographic reduction in an 80/20 v/v) methanol/water solvent with tetra-n-butylammonium hydroxide as the supporting electrolyte. The detection limit of acrylamide monomer by this technique is less than 1 ppm. 

The differential pulse polarogram of a 10 ug/ml methanolic solution of acrylamide showed a well-defined and well-resolved peak. The differential pulse polarographic acrylamide reduction current is directly proportional to concentration as shown in Table 7.24. The polarographic detection limit for acrylamide is less than 1 pg acrylamide/cm. ... 

The realization that current sampling on a step pulse can increase the detection sensitivity by increasing the faradaic/charging ratio is the basis for the development of various pulse voltammetric (or polarographic) techniques. Also, the pulses can be applied when it is necessary and can reduce the effect of diffusion on the analyte. Figure 18b. 11 shows the waveform and response for three commonly used pulse voltammetric techniques normal pulse voltammetry (NPY), differential pulse voltammetry (DPV), and square-wave voltammetry (SWV). 

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