Potentiometric titration of milligram amounts of organic acids with an interfacial voltaic cell for end-point detection

A small interfacial (antimony scratch) cell is shown to be satisfactory for indicating end-points in microtitrations of 28 organic acids, as well as pharmaceutical preparations. The method is simple and rapid and end-points are sharp. Recoveries were 98.0–101.9% for sample weights of 0.6–4 mg.     

Determination of uranium in the presence of iron and plutonium by Ti(III) reduction and biamperometric titration

A method is described for the determination of uranium in the presence of iron and plutonium. Ti(III) is used as the reductant in a mixture of H₂SO₄ and HNO₃. Fe(II) and Pu(III) are selectively oxidized by the nitrous acid generated in the reaction between Ti(III) and HNO₃. The U(IV) is determined by titration with K₂Cr₂O₇ using biamperometry to detect the end point. The method is applicable to a variety of nuclear materials encountered at different stages of the nuclear fuel cycle and has no bias. The precision of the method is evaluated at different levels from 100 microgram to 100 milligram. The method is simple, rapid and convenient.     

Potentiometric titration of plutonium

In the potentiometric titration of plutonium(III), it has been customary to take the equivalence point as the inflection point on a plot of potential vs. volume of titrant.¹ That the stoichiometric end point corresponds to the inflection point does not seem to have been theoretically demonstrated, however. The purpose of this letter is to suggest that these points may not correspond in the potentiometric titration of plutonium(III). Mound Laboratory is operated by Monsanto Research Corporation for USERDA under contract No. EY-76-C-04-0053.     

Potentiometric titration of Co(II) in presence of Co(III)

A potentiometric titration for cobalt(II) determination in the presence of Co(III) based on the oxidation of Co(II) with Na₂CrO₄ in ethylenediamine medium and back-titration of the oxidant excess with (NH₄)₂Fe(SO₄)₂ in acid medium is described. The titration is monitored with a Pt indicator electrode and carried out until the greatest jump of potential from one drop of titrant appears. A RSD smaller than 1.5% has been obtained for 50–300 μmol Co(II). The method proposed was applied in the analysis of a new type electroless copper plating solutions containing Co(II)-ethylenediamine complex compounds as reducing agents. Cu(II), Co(III) and Cr(III) do not interfere in the determination of Co(II).     

Potentiometric determination of uranium in the presence of plutonium in H2SO4 medium

The potentiometric determination of uranium is widely carried out in phosphoric acid medium to suppress the interferences of plutonium by complexation. Owing to the complexity of the recycling plutonium from the phosphate based waste involving manifold stages of separation, a method has been proposed in the present paper which does not use phosphoric acid. Uranium and plutonium are reduced to U/IV/ and Pu/III/ in 1M H₂SO₄ by Ti/III/, and NaNO₂ is chosen to selectively oxidize Pu/III/ and the excess of Ti/III/. The unreacted NaNO₂ is destroyed by sulphamic acid and excess Fe/III/ is added following dilution. The equivalent amount of Fe/II/ thus liberated is titrated against standard K₂Cr₂O₇. R.S.D. obtained for the determination of uranium /1–2 mg/ is 0.3% with plutonium being present upto 4.0 mg.     

Potentiometric titration of lignosulfonic acids

The conditions of potentiometric titration of lignosulfonic acids allowing quantitative determination of strongly and weakly acidic functional groups in lignosulfonates were determined.     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titration of diprotic systems

 The approximate nature of Gran’s method of linearization of potentiometric titration curves applied to diprotic systems has been thoroughly investigated. A function involving pH and titrant volume V (which is linearly dependent on V and becomes zero at the first equivalent point of titration of a weak diprotic base with a strong monoprotic acid) has been critically examined and validated by means of widely extended simulated experiments. Accurate experimental confirmation of the theoretical expressions has been obtained by performing many real titrations of the primary standard Na₂CO₃ with HCl. This particular application, analytically significant itself, can be a prototype of analogous applications. Received: 25 March 1996/Revised: 15 November 1996/Accepted: 19 November 1996     

Potentiometric titration of metal ions in ethanol

The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented.     

Potentiometric titration of p-Aminobenzoic acid and α-naphthylamine with NaNO2 solution in presence of HCl

Analytical and Bioanalytical Chemistry - p-Aminobenzoic acid and α-Naphthylamine have been determined potentiometrically in presence of HCl against a standard solution of NaNO2 using bright...     

Potentiometric titration in a low volume of solution for rapid assay of uranium: application to quantitative electro-reduction of uranium(VI)

A simple, inexpensive PC based potentiometric titration technique for the assay of uranium using low volumes of sample aliquot (25–100 μL) along with all reagents (total volume of solution being less than 2.5 mL) is presented. The technique involves modification of the well known Davies and Gray Method recommended for assay of uranium(VI) in nuclear materials by introducing an innovative potentiometric titration device with a mini cell developed in-house. After appropriate chemical conditioning the titration is completed within a couple of minutes with display of online titration plot showing the progress of titration. The first derivative plot generated immediately after titration provides information of end point. The main advantage of using this technique is to carry out titration with minimum volumes of sample and reagents generating minimum volume of wastes after titration. The validity of the technique was evaluated using standard certified samples. This technique was applied for assay of uranium in a typical sample collected from fuel reprocessing laboratory. Further, the present technique was deployed in investigating the optimum conditions for efficient in situ production of U(IV). The precision in the estimation of uranium is highly satisfactory (RSD less than 1.0%).     

Potentiometric determination of iron with DTPA in the presence of a large amount of aluminium

Potentiometric determination of iron with DTPA at pH 1.6 (platinum and calomel electrodes) permits determination of iron in the presence of aluminium up to an Al:Fe ratio of 70. Aluminium is determined indirectly by addition of excess of DCTA, adjustment to pH 5, and back-titration with iron(III) chloride.     

Potentiometric titration of permanganate with resacetophenone oxime

Milligram amounts of permanganate can be titrated with resacetophenone oxime (4-acetylresorcinol oxime) as a reducing titrant in the presence of phosphoric acid (0.5 M). The stoichiometry between permanganate and the oxime is 3:1 (MnO₄^-:oxime). The titration is successful in the presence of large amounts of dichromate or vanadate or moderate amounts of cerium(IV).     

Direct complexometric determination of magnesium in the presence of uranium, iron and aluminium

Conditions for the direct complexometric determination of magnesium in the presence of uranium, iron and aluminium are described. The method is based on the masking of uranium by hydroxylamine, and of iron and aluminium by triethanolamine. Methylthymol Blue is used as indicator for the EDTA titration of magnesium at pH 10.     

A method for recording X-ray diffraction patterns of milligram quantities of particulates

A method for recording X-ray diffraction patterns of milligram quantities of particulates has been developed. The resulting diffraction patterns are similar to patterns obtained by standard methods. Application of this method to analysis of airborne particulates in the vicinity of a lead smelting operation has demonstrated the practical use of the method. Sample sizes as low as 1.1 mg have produced useful diffraction patterns.     

Production of milligram quantities of affinity tagged-proteins using automated multistep chromatographic purification

A new chromatography system, AKTAxpress (GE Healthcare, Amersham Biosciences, Uppsala, Sweden) has been designed to meet the demand for high-throughput purification of proteins in structural genomics and drug discovery. The system offers a number of automated multistep purification protocols for affinity-tagged proteins. All protocols start with affinity chromatography followed by combinations of desalting, ion exchange chromatography and gel filtration. As an option, tag removal can be included in the purification protocols. Up to 16 proteins can be purified per day and the yield can be as high as 50 mg of each protein at > 90% purity. To highlight the versatility of the system, this paper presents several case studies; purifications of hexahistidine- and glutathione S-transferase-tagged proteins using different protocols, automated on-column tag cleavage and optimization studies for a hexahistidine-tagged kinase.     

Photometric titration of arsenate with thorium nitrate on the microgram and milligram scale

Summary A method is described for the photometric titration of arsenate with thorium nitrate using pyrocatechol violet as indicator. The method works at a low pH level and is therefore not subject to the most cationic interferences. Alkali salts do not affect the determination even at high concentrations if present as halides, nitrates or perchlorates. This makes the method particularly suitable for the analysis of arsenic in organic and inorganic compounds after decomposition.

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Zur photometrischen Titration von Arsenat mit Thoriumnitrat im Mikrogramm- und Milligrammbereich

Zusammenfassung Ein Verfahren zur photometrischen Titration von Arsenat mit Thoriumnitrat gegen Brenzcatechinviolett als Indicator wird beschrieben. Die Titration erfolgt bei niedrigem pH-Wert und wird deshalb von den meisten Kationen nicht beeinflußt. Außerdem stören auch hohe Konzentrationen an Alkalisalzen nicht, wenn diese als Halogenide, Nitrate oder Perchlorate vorliegen. Deshalb ist das Verfahren insbesondere zur Analyse von anorganischen und organischen Arsenverbindungen nach Aufschlüssen geeignet.

     

Potentiometric titration of heterocyclic nitrogen bases in non-aqueous media

Pyridine, quinoline, isoquinoline, acridine, alpha-picoline, beta-picoline, gamma-picoline and 2,6-lutidine have been titrated potentio-metrically (calomel and glass electrodes), with chlorosulphonic acid in methyl ethyl ketone-acetic acid (1:1) medium, with an error of less than 1%.     

Potentiometric titration of gold in ores with potassium iodide

Summary A direct potentiometric titration method for the determination of gold in ores and alloys is described. It is based on the reduction of Au(III) with iodide ions yielding accurate and reproducible results. Detection limit and sensitivity were 0.06 and 0.032 mg/l Au, respectively. The linear response range was between 0.1 and 120 mg/l Au. The method can be used for the routine assay of gold in different kind of samples.