Polarographic procedures

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-... 

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. 

In a polarographic procedure of A.M. Wild, Chem Ind 1963(20), 819-20 CA 59, 3710(1963), Lead Dinitroresor-cinate, LSt, NC (varnish), and Tetracene are detd from their mixts in the following manner. Weigh accurately contents of cap into a tared microsinter, extract NC with dry acetone, dry the residue and weigh. Extract Ba nitrate using minimum amt of cold w, wash the residue with ale, dry and reweigh. Extract LSt with 0.01 M HCl at RT using 20 ml of acid in four... 

Reliable instruments for differential pulse polarography are available commercially at reasonable cost. The method has thus become the most widely used polarographic procedure. 

Carbon disulfide, for example, can be determined by dpp in water, in concentrations as low as 1 / g CS2/I, using a purging step to preconcentrate the CS2 in ethanol/diethylamine with the subsequent formation of diethyldithiocarbamate. The polarographic procedure is substantially more sensitive than other reported methods. ... 

Electroanalytical techniques Polarographic procedures are described for acesulfame-K, cyclamate, and saccharin. Cyclamate was decomposed by heating with sodium nitrite and the sulfate liberated is... 

A polarographic procedure for determining the acetaldehyde content of port wines was developed by Almeida (1950). His results (Table VII) are generally lower than those obtained earlier in port wines by Teixeira Jfinior (1940) using the Jaulmes and Espezel procedure. A summary of the methods for determination of aldehydes was given by Mestre and Campllonch (1942). 

The procedure of Kuta and Quackenbush [121] can be modified for the determination of relatively simple organic peroxides such as benzoyl peroxide, para-tert-huty perbenzoate and lauroyl peroxide in PS, and would no doubt be suitable for the determination of other types of peroxides. In these procedures a suitable weight of polymer is dissolved in toluene and then an equal volume of 0.6 M lithium chloride in methanol is added. Precipitated polymer is removed by centrifuging and peroxides in the filtrate are determined by cathode-ray polarography. Polymerisation additives, styrene monomer or antioxidants in the polymer do not interfere in the polarographic procedure. A procedure for the determination of down to 20 ppm para-tert-hu.ty perbenzoate in PS is given next. 

The development of electrochemical applications in pharmaceutical analysis (and to a somewhat lesser degree in food control) was chiefly based on potentiometric titrations, but chiefly on DC polarography and, soemtimes, on coulometric procedures. This phase culminated toward the end of the 1950 s when it became evident that the DC polarographic procedures are not sensitive and selective enough to be applied to all the following problems of pharmaceutical analysis[5] ... 

Residual amounts of styrene and acrylonitrile monomers usually remain in manufactured batches of styrene-acrylonitrile copolymers and acrylonitrile-butadiene-styrene terpolymers (ABS), As these copolymers have a potential use in the food packaging field, it is necessary to ensure that the content of both of these monomers in the finished copolymers is below a stipulated level. In a polarographic procedure [9, 10] for determining acrylonitrile (down to 2 ppm) and styrene (down to 20 ppm) monomers in styrene-acrylonitrile copolymer, the sample is dissolved in 0.2 M tetramethylammonium iodide in dimethyl formamide base electrolyte and polarographed at start potentials of -1.7 V and -2.0 V, respectively, for the two monomers. Excellent results are obtained by this procedure. Table 5.3 shows the results obtained for determinations of acrylonitrile monomer in some copolymers by the polarographic procedure. 

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. 

Yoshiaki Miura has published [1] a procedure for the determination of iron and copper in aluminum alloys, using ethylenediamine tartrate (EDT) and potassium pyrophosphate as base electrolyte. As a result of this investigation, polarographic procedures using ethylenediamine tartrate complexes have been developed for the determination of iron (ferrous), nickel, cadmium, and copper, as well as for mixtures of the latter three elements. 

In a polarographic procedure for determining acrylonitrile (down to 2 ppm) and styrene (down to 20 ppm) monomers in styrene-acrylonitrile copolymer, the sample is dissolved in 0.2 M tetramethyl ammonium iodide in dimethyl formamide base electrolyte... 

A cadiode-ray polarographic procedure is described which determines hydro-quinone, substituted benzoquinone and anthraquinone inhibitors in styrene monomer in amounts down to 5 ppm. 

Cathode ray polarograph complete with dropping mercury electrode polarographic cells (10 cm ) and thermostated (at 75 C) water baA. The sensitivity of the procedure for determining hydroquinone depends on the cleanness of the capillary used in the dropping mercury electrode. A new capillary should be used when any decrease in sensitivity in the polarographic procedure is noted. 

Table 7.27 shows the results obtained in determinations of acrylonitrile monomer in some copolymers by the polarographic procedure. Comparison of ftiese results with those obtained by the dodecyl mercaptan procedure show that acrylonitrile contents some 30 per cent higher are obtained by the latter method. 

The acrylonitrile and styrene monomer contents of several copolymers were determined by the polarographic procedure. The styrene monomer content of these samples was also determined by a procedure involving evaluation by ultraviolet spectroscopy at 292 nm of solutions of the samples in carbon tetrachloride. The results obtained (see Table 7.28) show that styrene contents determined by the two procedures are in good agreement with each other. 

A polarographic procedure was suggested for the determination of traces of lanthanum in lanthanum-gadolinium oxysulphide (Gao et al. 1983). Steeman et al. (1977) described pulse polarographic determination of traces of europium in rare-earth oxides. Cerium in rare-earth oxides was determined by stripping voltammetry (likova et al. 1983). Klinov and Ladeishchikov (1986) have developed a y-activation procedure for the determination of traces of neodymium and yttrium in La203 and 76467. Uwamino et al. (1984) and... 

Provided that a suitable sample size is taken for analysis, the azeotropic distillation-polarographic procedure can be used for determining acrylonitrile in extractants in concentrations down to 1 ppm or a little lower. Thus, it is seen from Table 11.1 that approximately 90% of the added amounts of acrylonitrile is recovered when the procedure is applied to 500 ml of a 0.75 ppm solution of acrylonitrile in the distilled-water extractant. The method can be used for achieving a similar level of sensitivity in the determination of acrylonitrile in the other aqueous alcoholic or oily extractants for plastics recommended by the British Plastics Federation [4] and the FDA [3]. This level of sensitivity is quite adequate for the examination of extractants that have been brought into contact with styrene-acrylonitrile copolymers under the British Plastics Federation and FDA extractability-test conditions. 

Lingane (147) has devised a systematic polarographic procedure for the determination of lead, copper, tin, nickel, and zinc employing... 

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