Pulse polarograph

Explain the reason for including the time-consuming oxygen removal step in pulse-polarographic measurements of tin ion in juice samples. 

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. 

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. 

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

Commercial processor-based electrochemical instruments are available in two forms. In the first configuration, a general-purpose laboratory or personal computer is interfaced to the analog instrumentation. In the other approach, the package is integrated in such a way that the processor is dedicated to the electrochemical experiments. Several dedicated, processor-based pulse polarographs... 

The development of a simple fast-scan polarographic method for the determination of the A4-3-ketosteroid flurandrenolone in pharmaceutical preparations has been reported [134]. The polarographic peak due to the reduction of the carbon-fluorine bond is measured in ointments and creams to determine concentrations as low as 0.01 % w/w. Pulse polarographic procedures have been described for progesterones [135], A4-3-ketosteroids [136], hydrocortisone [137], and flucytosine [138] in pharmaceutical preparations. Recent studies have illus-... 

A pulse polarographic method to determine dantrolene sodium and its major metabolites in urine after ethyl acetate extraction has been reported [181]. The ethyl acetate is brought to a residue and the dantrolene plus the total extract-able metabolites are analyzed for reduction of the azomethine linkage at -0.86 V in a DMF-acetate buffer (pH 4.0). The nitro compounds are simultaneously determined in the same media as dantrolene equivalents from the reduction of the nitro group at -0.26 V (see Fig. 26.13). The difference between the two determinations represents the metabolites not containing the nitro group. Levels as low as 0.1 fig/mL can be determined for either functional group. 

Polarographic methods have been extremely useful for the determination of the urinary excretion of the 1,4-benzodiazepines. An assay that employs selective solvent extraction and acid hydrolysis of diazepam and its major metabolites, iV-desmethyldiazepam and oxazepam, to their respective benzophe-nones has been employed to measure the urinary excretion of diazepam [183]. A pulse polarographic assay has been reported that will measure the urinary excretion of bromazepam following a single 12-mg dose [184]. The assay employs selective extraction of bromazepam and the 2-amino-5-bromobenzoyl-pyridine metabolite from the deconjugated metabolites, 3-hydroxybromazepam and 2-amino-3-hydroxy-5-bromobenzoylpyridine, into separate diethyl ether fractions. The residues of the respective extracts are dissolved in phosphate buffer (pH 5.4) and analyzed by pulse polarography, which yields two distinct... 

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). 

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. 

Pulse Polarographic Determination of Trinitroglycerin in Explosives , BullSocChemBelg 86 (1-2), 17-21 (1977) 136) J. Yinon, Analy-... 

Pulse Polarographic Determination of Trinitro-glycerin in Explosives , BullBelg 86 (12), 17—21 (1977) CA 86,192063 (1977) [Reported is a quant pulse polarographic technique for the measurement of NG with a reproducibility of 0.5%] 2) W.L. RoUwitz D.J. King, Funda-... 

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. 

This problem was addressed by Brikmann and Loss [38] and solved later by Galvez and Sema [39]. More recently, a compact expression as a function of the ratio (f2/0 for the pulse polarographic wave when the two species are initially present in the solution was obtained [40, 41]. Under these conditions, the current can be expressed as... 

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. 

Polarographic AC and pulse polarographic techniques as well as stripping analysis are effective tools for the determination of trace levels of metal ions. Table 3.1 provides a comparison of the sensitivity and usefulness of the various methods.12,21 23 For metal ions, stripping voltammetry usually is the method... 

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

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