Polarographic, differential pulse

The cathodic cyclization of several types of A -(5-oxoalkyl)pyridinium salts in 1 M sulfuric acid afforded quinolizine derivatives. For example, compound 256, prepared from 4-methylpyridine, gave a diastereomeric mixture of quinolizines 257 and 258. Differential pulse polarographic studies allowed a mechanism to be proposed, which is outlined in Scheme 53 <2003EJ02919>. 

Figure 2.1. Differential pulse polarographic verification of sunlight-induced bromate production in chlorinated seawater. Curve (a) polarogram from untreated seawater, seawater immediately after chlorination to 4.9 ppm, or chlorinated seawater kept in the dark for 4 h at 40 °C. Curve (b) polarogram from chlorinated seawater exposed to full sunlight for 70 min. Curve (c) standard 1.0 x 10-6 M sodium bromate in seawater, offset with respect to curves (a) and (b). Polarograms were recorded at 25 °CandpH 8.35 SCE saturated calomel electrode. From [19]...

Stolzberg [143] has reviewed the potential inaccuracies of anodic stripping voltammetry and differential pulse polarography in determining trace metal speciation, and thereby bio-availability and transport properties of trace metals in natural waters. In particular it is stressed that nonuniform distribution of metal-ligand species within the polarographic cell represents another limitation inherent in electrochemical measurement of speciation. Examples relate to the differential pulse polarographic behaviour of cadmium complexes of NTA and EDTA in seawater. 

Studies using a differential-pulse polarographic technique, which is recommended in place of classical direct current polarography, yielded the following results. For... 

AG Fogg, AM Summan. Further differential-pulse polarographic and visible spectrophotometric studies of the degradation of permitted synthetic food coloring matters without the addition of ascorbic acid accelerated heat degradation studies. Analyst 109(6) 743-747, 1984. 

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. 

Brooken et al39 described a sensitive differential pulse polarographic assay for phenytoin in blood. It involves extraction of phenytoin into chloroform followed by nitration. The analysis of the nitro derivative is then accomplished. 

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. 

Bundy KJ, Berzins D. 1998. Differential pulse polarographic analysis of lead and chromium content in Louisiana waters. Environ Geochem Health 20 45-51. 

Differential Pulse Polarographic Peak Potentials at the Dropping Mercury Electrode (18,19)... 

Moore DE, Fallon MP, Burt CD. Photo-oxidation of tetracycline—a differential pulse polarographic study. Int J Pharm 1983 14 133-142. 

A highly sensitive differential pulse polarographic method has been developed for the determination of trace levels of sulfa drugs after diazotization and coupling with AM-naphthylethylenediamine dihydrochloride. For the coupled diazo product of sulfacetamide, at pH 1.6 and with 0.01 M KH2PO4 as base electrolyte, the peak current at -0.070V versus SCE is increased linearly in the concentration range... 

Ladanyi E, Stalder K. 1986. Differential pulse-polarographic determination of formaldehyde in lung surfactant. Bioelectrochem Bioenerg 15 89-93. 

Moore, D.E., Fallon, M.P., and Burt, C.D., 1983, Photo-oxidation of tetracycline a differential pulse polarographic study, Int. J. Pharm. 14, 133-142. 

Figure 7.3.9 Potential program for several drops in a differential pulse polarographic experiment. The 10-100 mV potential change late in the drop lifetime is the pulse height, AE.

Figure 7.3.10 Events for a single drop of a differential pulse polarographic experiment.

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... 

If this is too difficult to understand, do not worry about it. The important facts to remember are (f) if a electrode reaction is reported to be irreversible the polarographic wave or peak will often be less well formed than for a reversible process (n) irreversibility causes classical dc and normal pulse polarographic waves to be less steep but has little effect on their height Hi) on the otherhand irreversibility broadens and lowers the height of the differential pulse polarographic peak but the area under the peak is little affected. 

The simplicity of the differential pulse polarographic method lies in the fact that the peak height is proportional to the analyte concentration (Fig. 15.33). If adequate resolution... 

A differential pulse polarographic method for the determination of prednisolone in tablets is described. The method is more sensitive than dc polarography and the measurement of diffusion current is greatly simplified. Sorenson phosphate buffer pH 5.6 was used as the supporting... 

Zereini F, Alt F, Messerschmidt J, von Bohlen A, Liebl K, Piittmann W (2004) Concentration and distribution of platinum group elements (Pt, Pd, Rh) in aiibome particulate matter in Frankfurt am Main, Germany. Env Sci Technol 38 1686-1692 Zereini F, Alt F, Messerschmidt J, Wiseman C, Feldmann 1, von Bohlen A, Muller J, Liebl K, Piittmann W (2005) Concentration and particle size distribution of toad-specific heavy metals in urban airborne particulate matter. Env Sci Technol 39 2983-2989 Zhao Z, Preiser H (1986) Differential pulse polarographic determination of trace levels of platinum. Anal Chem 58 1498-1501... 

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