Pulse polarographic determination of nitrosamines: Part 2. Methods for the Determination of N-Nitrosodiphenylamine and N-Nitrosodibutylamine

Differential pulse polarographic methods are reported for the determination of N-nitrosodiphenylamine and N-nitrosodibutylamine in aqueous media. Optimum conditions for analysis were obtained with acetate buffer (pH 3.74) and 0.01 M H₂SO₄, where reduction peak separations were of the order of 300 mV and 200 mV, respectively. Detection limits were approximately 3×10^-8 M for each compound. Methods for the extraction of these nitrosamines from iso-octane to aqueous solutions were quantitatively examined.     

Potentiometric determinations with the silver sulfide membrane electrode : Part I. Determination of cyanide

The possibilities of the silver sulfide membrane electrode for the determination of cyanide are described; determinations by multiple standard addition and titration have been studied, and interferences have been checked. The determination of cyanide in solutions containing various metal complexes, and the evolution method for separation of hydrogen cyanide are discussed. Automatic titration can be used for samples containing 1 p.p.m. cyanide, and the standard addition method for 1 p.p.b. cyanide.     

Automated polarographic analysis : Part I. Design of flow-through cells and deaeration unit

The design of polarographic flow-through cells for automated analysis of discrete samples is discussed. A simple way of fitting the DME capillary into the cell is described, and the problems associated with the use of a mercury pool counter electrode are discussed. A platinum wire or gauze counter electrode downstream from the DME is more satisfactory. The reference electrode may be placed outside the flow cell, e.g. in the mercury waste bottle. A new method for the deaeration of sample solutions is also described; argon is bubbled through the solutions in the sample cups just before aspiration. The effect of various experimental parameters on the deaeration is described. Pump stoppage during sample shifts is advantageous. The adaptation of the deaeration method to commercial samplers is explained. The application of the proposed automated system for the determination of chlordiazepoxide is discussed.     

New techniques in radiochemical determinations using polarographic methods

This work was undertaken as part of a research program on the development of new radio-chemical procedures. The techniques used are those of standard polarographic practices. Radio-isotopes that can be polarographically reduced to the zero oxidation state amalgamate with the mercury, are removed from the solution, and the radioactivity determined. Reproducible curves of activity vs. Ede are found to be in every way analogous to polarograms obtained under the same experimental condition. The requirements necessary for any radio-ihotope to be determined quantitatively by this method are that the radio-isotope be polarographically reduced to the zero oxidation state and that no other radio-isotope be polarographically reduced at the same potential. This type of analysis has been successfully applied to several radio-isotopes and mixtures of radio-isotopes.     

Determination of sulphhydryl compounds in physiological fluids by liquid chromatography with polarographic detection

Summary A polarographic detector with a horizontal, fast dropping mercury electrode has been applied for the determination of thiols in physiological fluids. To establish suitable detection conditions first some basic studies on the polarographic behaviour of penicillamine, glutathione and cysteine were performed. This type of detection shows a high selectivity and reasonably low detection limits for sulphhydryl compounds. Detection limits of 6×10^–7 mol l^–1 for penicillamine and cysteine and 8×10^–7 mol l^–1 for glutathione were found. A good linearity has been observed over a concentration range of three orders. The detector has successfully been applied to the determination of penicillamine in urine and serum samples.

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Bestimmung von Sulfhydrylverbindungen in physiologischen Flüssigkeiten durch Flüssigkeits-Chromatographie mit polarographischer Detektion

Zusammenfassung Ein polarographischer Detektor mit horizontaler, schnell tropfender Quecksilberelektrode wurde zur Bestimmung von Thiolen in physiologischen Flüssigkeiten angewendet. Zur Feststellung geeigneter Bedingungen wurden zunächst grundlegende Untersuchungen zum polarographischen Verhalten von Penicillamin, Glutathion und Cystein durchgeführt. Das Verfahren bietet hohe Selektivität und niedrige Nachweisgrenzen (6 · 10^–7 mol/l für Penicillamin und Cystein, 8 · 10^–7 mol/l für Glutathion). Linearität besteht über drei Größenordnungen. Der Detektor wurde mit gutem Erfolg für die Penicillaminbestimmung in Harn und Serum verwendet.

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Dedicated to Prof. Dr. H. Weisz on occasion of his 60th birthday

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On leave from the Technical University of Gdansk     

Potentiometric determinations with the silver sulfide membrane electrode : Part II. Determination of Sulfur Compounds

A simple, sensitive and fast titrinetric method for sulfur determinations with the silver sulfide membrane electrode is described. Sulfide and sulfate can be determined in one sample. A sensitive sulfate determination is possible after reduction with hydrogen iodide—sodium hypophosphite—acetic acid. Other inorganic sulfur compounds can also be determined. Sparingly soluble metal sulfides can be determined after treatment with strong acid. A reduction with Raney nickel is suitable for the estimation of elementary sulfur and organic sulfur compounds; combustion of the samples in an oxygen flask may be necessary. The methods outlined are applied to the determination of sulfur in steel, some petroleum products and aerosols. When different methods are used, different kinds of sulfur compounds present in an unknown sample can be distinguished.     

Studies on the precise differential polarographic determination of elements of nuclear interest : Part I. Determination of europium and ytterbium in lithium chloride and lithium iodide electrolytes

Differential polarographic determination of the europium content of solutions of LiI and LiCl can be made within the concentration ranges of 50 to 500μg Eu/g with varying presion. Comparative techniques can give precisions of the order of 0.1% or even better; the accuracy depends on the reference material used for the standardisation of the method.     

Automated polarographic analysis: Part II. Response time and precision studies

A systematic study of various experimental parameters which may influence the response time and precision of an automated polarographic system is described. The effects of segmented streams, flow rate, pump stop during sample shifts, debubbler position, current damping, scale expansion, sampling rate and type of deaerating gas are discussed. Low response times are favoured by the use of segmented streams, a high aspiration rate, a short distance between the debubbler and the working electrode and a low current damping, while the best precision is obtained by using scale expansion, pump stop during sample shifts, a low sampling rate and argon gas for deaeration. Under optimized conditions a standard deviation of 0.3 % was obtained.     

Investigations on Bioanalytical Chemistry Part I. On Differential Pulse Voltammetry of Bilirubin

Abstract

The electrochemical behaviour of the bilirubin in many kinds of supporting electrolytes on a glassy carbon electrode (GCE) and a hanging mercury drop electrode (HMDE) was investigated by means of anodic or cathodic differential pulse voltammetry. The influences of different methods of pre-treatment of the glassy carbon electrode was also discussed. In Na₂B₄.O₇-KH₂PO₄ buffer solution, the linear range was 2×10^?9-1×10^?9 mol/l and the detection limit was 3.3×10^?9 mol/l by anodic differential pulse voltammetry at GCE. A linear relationship holds between the peak current and the concentration of bilirubin in a concentration range of 1×10^?9-4×10^?7 mol/l with good precision and accuracy, and the limit of detection was 2×10^?10 mol/l, when cathodic differential pulse adsorption voltammetry at HMDE was used.     

Analytical applications of triethylenetetraminehexaacetic acid : Part I. the influence of TTHA on the polarographic reduction of some metal ions

The influence of triethylenetetraminehexaacetic acid (TTHA) on the d.c. and square-wave polarographic curves of Cu(II), Pb(II), Cd(II), Ni(II), Co(II), Zn(II), Fe(III), Bi(III), Sb(III), As(III) and In(III) has been investigated in several supporting electrolytes over the pH range 1–13. The E_{$\text{1}\text{2}$} and E_p values with and without a 10-fold excess of TTHA are compared. Some analytical applications are suggested.     

The CuII−CuI−Cu0(Hg) system in the presence of benzotriazole: Part I. A polarographic investigation

A polarographic investigation of Cu^II electroreduction from solutions of benzotriazole (BTA) of pH from 1 to 3 at a dropping mercury electrode shows the presence of two successive adsorption waves of equal height (waves Ic and IIIc) due, respectively, to the formation and to the subsequent dissolution of an adsorbed film of a Cu^I compound. The dependence of the half-wave potential of wave IIIc, which is polarographically reversible, upon pH and BTA concentration indicates that the adsorbed film has the composition [Cu^I(BTA^?)], where BTA^? denotes the deprotonated anionic form of benzotriazole. Moreover, the maximum height of wave IIIc indicates that this film is one monolayer thick. A third cathodic wave (wave IIc), lying between waves Ic and IIIc, stems from the reduction to the metal state of the Cu^II ions diffusing from the bulk solution. Copper(0) oxidation at dropping amalgam electrodes in BTA solutions yields two successive adsorption waves (waves Ia and IIa). Wave Ia is due to the same electrode process, Cu⁰ (Hg)+BTA?Cu^I(BTA^?)+H⁺+e, responsible for the cathodic wave IIIc. On the other hand, wave IIa is due to the formation of roughly two adsorbed monolayers of [Cu^I(BTA^?)] upon that formed along wave Ia.     

Differential pulse polarographic determination of ofloxacin in pharmaceuticals and biological fluids

A sensitive method is described for the determination of ofloxacin in its pure form, dosage forms and biological fluids. The proposed method depends upon the polarographic activity of ofloxacin in Britton Robinson buffers, whereby a well-defined cathodic wave is produced over the pH range 4.1-10.3. The wave was characterized as being irreversible, diffusion-controlled with limited adsorption properties. The current-concentration relationship was found to be rectilinear over the range 5x10(-5)-5x10(-4) M and 1x10(-5)-5x10(-4) M using the DC(t) and DPP modes respectively, with a minimum detectability (S/N=3) of 3x10(-7) M. The proposed method was successfully applied to the determination of ofloxacin in tablets and biological fluids. The results obtained were found to be in agreement with those obtained by a reference method.     

GC-LRMS法测定啤酒中3种N-亚硝胺化合物

用气相色谱-低分辨率质谱(GC-LRMS)联用法测定了啤酒中的3种亚硝胺.通过与脱亚硝基化试剂(HBr+HAc)作用,脱去亚硝基生成相应的二级胺,再与对甲苯磺酰氯反应,然后进行GC-LRMS分析.与原N-亚硝胺化合物相比,有效地改善了N-亚硝胺的色谱行为,衍生化后目标化合物的检测限降低了1～2个数量级(低至0.05μg...     

Determination of telmisartan in human blood plasma: Part I: Immunoassay development

Telmisartan is an angiotensin II receptor antagonist and a known drug against high blood pressure. In this report, the development of a new and rapid analytical technique, an enzyme-linked immunosorbent assay (ELISA) for the determination of telmisartan in human blood plasma is described. The immunoassay is based on a conversion of 4-(N-methylhydrazino)-7-nitro-2,1,3-benzooxadiazole (MNBDH) to 4-(N-methylamino)-7-nitro-2,1,3-benzooxadiazole (MNBDA), which is detected by fluorescence spectroscopy. The limit of detection was 0.1 ng/mL, the limit of quantification was 0.3 ng/mL and the working range extended from 0.3 ng/mL to 300 ng/mL.     

Determination of boron in nuclear materials by isotope dilution technique. Part I

Summary The application of the mass-spectrometric stable-isotope dilution technique for the determination of microgram and submicrogram quantities of boron in nuclear materials is described. An adequate amount of spike solution (enriched in¹⁰B) is added to the sample and the mixture is treated chemically to ensure isotopic equilibration. Boron is then separated as methyl borate by distillation from phosphoric acid and converted into sodium tetraborate suitable for isotopic analysis by surface ionization in a mass spectrometer. The results for boron content in a standard boric acid solution, reagents, ammonium diuranate, uranium dioxide, sintered pellets of UO₂ and uranyl nitrate are given. Owing to the simplicity, accuracy and high precision a possible application of the method would be its use for routine boron determinations in a natural uranium processing plant and/or as a standard method for intercomparison with other analytical methods.

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Zusammenfassung Die Anwendung der massenspektrometrischen Isotopenverdünnungsmethode auf die Borbestimmung im Bereich von Mikrogramm und darunter in Reaktormaterialien wurde beschrieben.Eine entsprechende Menge von angereichertem¹⁰B wird einer Probe zugegeben und die Mischung zur Herstellung des Isotopengleichgewichtes chemisch behandelt. Das Bor wird dann als Methylborat durch Destillation aus der phosphorsäurehaltigen Lösung abgetrennt und zum Zweck einer massenspektrometrischen Isotopenanalyse in Natriumtetraborat umgesetzt.Der Borgehalt in H₃BO₃-Standardlösungen, Reagenzien, Ammoniumdiuranat (ADU), UO₂, gesinterten UO₂-Pastillen und Uranylnitrat wird angegeben. Wegen der Einfachheit, Genauigkeit und Empfindlichkeit könnte diese Methode sowohl für die routinemäßige Borbestimmung bei der Herstellung von Brennstoffelementen mit natürlichem Uran als auch für die Standardisierung analytischer Methoden angewandt werden.

     

Determination of carbonate in the presence of hydroxide : Part I. Analysis of first-derivative potentiometric curves

Mathematical consideration of the course of neutralization of a solution containing a moles of a strong base (e.g. sodium hydroxide) and a moles of a salt of a weak dibasic acid (e.g. sodium carbonate) with a strong acid (e.g. hydrochloric acid) shows that the first derivative of the titration curve should contain three maxima. The first, corresponding to neutralization of most of the hydroxide, is small (with height proportional to a^{$\text{1}\text{2}$}), displaced slightly from the equivalence point, and disappears for a less than 0.01 mol l^-1. The second corresponds to the conversion of most of the CO₃^2- to HCO₃^- and its height is almost independent of a. The third corresponds to the conversion of HCO₃^- to H₂CO₃, with height proportional to a^{$\text{1}\text{2}$}. The two minima are independent of a and of the dissociation constants of the weak acid. These conclusions were examined experimentally and were extended to the titration of hydroxide contaminated with a small amount of carbonate.     

The controlled potential coulometric and controlled potential polarographic determinations of substituted nitrobenzene compounds in dimethylsulfoxide

The n-values for the reduction of the isomers of nitrophenol and nitrobenzoic acid and for several other nitro compounds were determined in dimethylsulfoxide by controlled potential coulometry. A procedure is given in which one μmole of nitro compound may be determined in less than 8 min with an error of approximately ±l%. The associated background currents were quantitatively evaluated, and electrolysis conditions for their minimization were discussed. A procedure and results are given for the controlled potential polarography of these nitro compounds in dimethylsulfoxide.