Polarographic method, determination

The polarographic method is applicable to the determination of inorganic anions such as bromate, iodate, dichromate, vanadate, etc. Hydrogen ions are involved in many of these reduction processes, and the supporting electrolyte must therefore be adequately buffered. 

In the application of the polarographic method of analysis to steel a serious difficulty arises owing to the reduction of iron(III) ions at or near zero potential in many base electrolytes. One method of surmounting the difficulty is to reduce iron(III) to iron(II) with hydrazinium chloride in a hydrochloric acid medium. The current near zero potential is eliminated, but that due to the reduction of iron(II) ions at about - 1.4 volts vs S.C.E. still occurs. Other metals (including copper and lead) which are reduced at potentials less negative than this can then be determined without interference from the iron. Alternatively, the Fe3 + to Fe2+ reduction step may be shifted to more negative potentials by complex ion formation. 

Electrochemical analytical techniques are a class of titration methods which in turn can be subdivided into potentiometric titrations using ion-selective electrodes and polarographic methods. Polarographic methods are based on the suppression of the overpotential associated with oxygen or other species in the polarographic cell caused by surfactants or on the effect of surfactants on the capacitance of the electrode. One example of this latter case is the method based on the interference of anionic surfactants with cationic surfactants, or vice versa, on the capacitance of a mercury drop electrode. This interference can be used in the one-phase titration of sulfates without indicator to determine the endpoint... 

The polarographic method of analysis of parathion as described here has an accuracy of = =1%, and 2 mg. of 0,0-diethyl O-p-nitrophenyl thiophosphate per 100 ml. of solution are apparently a minimum concentration for the sensitivities investigated. However, the polarograph used is equipped with resistors, so that a sensitivity of 0.003 microampere per millimeter may be used. At this sensitivity it would be possible to obtain a sufficient wave height to determine parathion at a concentration of less than 1 p.p.m. 

Mishra and Gode developed a direct current polarographic method for the quantitative determination of niclosamide in tablets using individually three different buffer systems, namely Mcllraine s buffers (pH 2.20 8.00), borate buffers (pH 7.80—10.00), and Britton Robinson s buffers (pH 2.00—12.00) as well as 0.2 M sodium hydroxide. The drug was extracted from the sample with methanol, appropriate buffer was added to an aliquot and the solution then polarographed at the dropping-mercury electrode versus saturated calomel electrode at 25°C [36], The resultant two-step reduction waves observed were irreversible and diffusion-controlled. For the quantitative determination, the method of standard addition was used. Niclosamide can be determined up to a level of 5—10 pg/mL. 

Mohamed [63] investigated the complexation behavior of amodiaquine and primaquine with Cu(II) by a polarographic method. The reduction process at dropping mercury electrode in aqueous medium is reversible and diffusion controlled, giving well-defined peaks. The cathodic shift in the peak potential (Ep) with increasing ligand concentrations and the trend of the plot of EVl versus log Cx indicate complex formation, probably more than one complex species. The composition and stability constants of the simple complexes formed were determined. The logarithmic stability constants are log Bi = 3.56 log B2 = 3.38, and log B3 = 3.32 [Cu(II)-primaquine at 25 °C]. 

Truesdale and Smith [80] also carried out a comparative study of the determination of iodate in open ocean, inshore Irish seawaters and waters from the Menai Straits, using the spectrophotometric method (with and without pre-oxidation using iodine water) and also by a polarographic method [82]. 

A variety of methods were developed for the identification and determination of the antimicrobial nitrofurans. They include LC, colorimetric and polarographic methods. Nitrofurans could be determined in animal tissues by extraction with acetonitrile, SPE and LC-UVD533. An LC-UVD method was statistically validated for the determination of nitrofuran drug residues in poultry534. 

The concentration of H2O2 generated by sodium perborate (NaB03 H20), present as bleacher in laundering powder formulations, can be determined by polarographic methods . 

A review of the methods which facilitates the rapid choice of an optimum procedure to be used for the determination of procaine and other medicinals derived from aminocarboxylic acids has have been published [28]. This review covers volumetric, optical, electrochemical and polarographic methods. 

Two polarographic methods have been developed for the determination of cohalt(II) at concentrations ranging from approximately 1 to 80 mM in an aqueous sample. For the first method [15], which is suitable for samples containing large amounts of nickel]11), the cobalt(II) is oxidized to Co(NH3)6 in an ammoniacal medium with the aid of sodium perborate, after which the cobalt(III) species is determined. A second procedure [16] entails the use of lead dioxide in an acetic acid-acetate buffer containing oxalate to convert cobalt(II) to the 0(0204)3 ion, which can be subjected to polarographic reduction. This latter approach is well suited to the determination of cobalt in the presence of copper(II), iron(III), nickel(II), tin(IV), and zinc(II), whereas the chief interferences are cerium, chromium, manganese, and vanadium. 

The polarographic method has been used to determine the stability constants and kinetic parameters of ternary complexes of Zn(II) with L-lysine, L-omithine, L-serine, L-phenylglycine, L-phenylalanine, L-glutamic acid, and L-aspartic acid as primary ligands and picoline as secondary ligand at pH 8.5 [103] and also of zinc complexation by extracellular polymers extracted from activated sludge [104]. 

Because of the importance of zinc in nutrition, sensitive methods have been devised for determining it m plant and animal materials, soils, and natural waters The polarographic method has been used with success (108, 109). 

A perfect prototype of an ideally cation-permselective interface is a cathode upon which the cations of a dissolved salt are reduced. Experimental polarization curves measured on metal electrodes fit the theory very closely. Since in dimensional units the limiting current is proportional to the bulk concentration, the polarization measurements on electrodes may serve for determining the former. This is the essence of the electrochemical analytical method named polarography. (For the theory of polarographical methods see [28]—[30].)... 

This method is the most sensitive of the polarographic methods now available and the lower limit of determination is 5 x 10-8 M. It is fairly sensitive even for substances that undergo irreversible electrode reactions. DPP is very useful in trace analyses. 

C. Ribaudo, "A Polarographic Method for the Determination of Diethylphthalate in M-8 Type Propellant Powder , PATR 1918, (Jan 1953) 7) L. Marvillet, MP 40, 273ff... 

A vitamin K deficient chick assay may be made or physicochemical techniques, including polarographic methods, spectrophotometry of pure solutions, and prothrombin time determinations, may be used. 

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... 

A review of the state of development of the various instrumental methods of analysis including polarography is presented (Ref 136). Whit-nack (Refs 24 101) also used the linear sweep polarograph to determine microgram quantities of TNT in milligram samples of warhead exudates. Brandone et al (Ref 102) determined polarographically the compn of expl mixts containing TNT... 

Aldehydes, Polarographic Method of Determin ation is discussed by M.B.Neiman, ZhAnal-Khim 2,135-46(1957)... 

The coordination of 9-hydroxy-4//-pyrido[1,2- ]pyrimidin-4-one with Ni(II), Zn(II), Co(II), and Cd(II) ions was studied by potentiometric and polarographic methods. Stability constants of complexes were also determined (93MI25). 

Prokisch et al. [85] described a simple method for determining chromium speciation in soils. Separation of different chromium species was accomplished by the use of acidic activated aluminium oxide. Polarographic methods have been applied in speciation studies on chromium(VI) in soil extracts [86]. Mi-lacic et al. [88] have reviewed methods for the determination of chromium(VI) in soils. 

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