Chloride potentiometric determination

The oxidizing agents used include gold chloride (potentiometric determination of the end point of the extremely slow oxidation) (Karrerefal, 1938) ceric sulfate (determination of the end point of the almost immediate reaction, with diphenylamine as indicator) (Kofler, 1941) lead tetraacetate (Kofler, 1941) but mostly ferric chloride in presence of a Fe -complex-forming compound, such as a,a -dipyridyl (Emmerie and Engel, 1938). The red color produced in this reaction is used for colorimetric determination. 

Satake et al. reported the use of a coated wire electrode sensitive to procaine and other local anesthetic cations, and their application to potentiometric determination [73]. Electrodes were constructed from a copper wire (0.8 mm diameter), coated with a PVC membrane comprising a mixture of the drug-tetraphenylborate ion-pair, dioctyl phthalate, polyvinyl chloride, and tetrahydrofuran. Potential measurement was made with respect to a Ag-AgCl reference electrode. The electrodes showed linear responses with a Nemstian slope for procaine over the concentration range investigated. The method was used for analyses of the drug in pharmaceutical preparations. 

Hamada et al. used a poly (vinyl chloride) matrix membrane ion-selective electrode for the analysis of procaine [76]. Procaine flavianate (10 mg, prepared by precipitation from an equimolar mixture of procaine hydrochloride and flavianic acid), was mixed with PVC powder (150 mg), dioctyl phthalate (370 mg), and tetrahydrofuran (4 mL). This mixture was used to produce membranes (3 cm diameter), from which discs were cut to prepare ion-selective electrodes. The electrodes were used in conjunction with a double-junction Ag-AgCl (KNO3) reference electrode for the potentiometric determination of procaine hydrochloride at 25°C. 

The potentiometric determination of bromide anions with ion-selective electrodes is possible with commercial electrodes that are commonly based on solid Ag2S—AgBr ion conductor membranes [148-150]. Recently, a novel liquid film sensor has been proposed by Ganjali etal. [151] Determination of bromide was reliable without significant interference from common ions such as chloride and iodide, and was reported down to a micromolar level. The electroactive species in the liquid membrane... 

Chlorides were determined by potentiometric titrations performed on distilled water dilutions. Carbonates and bicarbonates were either determined by titration or by calculation from pH measurements. Sulfates were determined by the gravimetric method utilizing BaS04 precipitation. 

The composition of the THF complexes of the lanthanide trichlorides is established by dissolution of a weighed amount of each compound in water and determination of chloride potentiometrically with aqueous silver nitrate. Analysis for the lanthanide is effected by titration with disodium ethylenediaminetetraacetate using xylenol orange indicator after appropriate buffering of the solution.The IR spectra of all the trichlorides show intense bands at 1020 and 880 cm" (see below), indicative of coordinated THF. ... 

When electrolyte concentrations are not too great, it is often useful to swamp both samples and standards with a measured excess of an inert electrolyte. The added effect of the electrolyte from the sample matrix becomes negligible under these circumstances, and the empirical calibration curve yields results in terms of concentration. This approach has been used, for example, in the potentiometric determination of fluoride ion in drinking water. Both samples and standards are diluted with a solution that contains sodium chloride, an acetate buffer, and a citrate buffer the diluent is sufficiently concentrated so that the samples and standaids have essentially identical ionic strengths. This method provides a rapid means of measuring fluoride concentrations in the part-per-million range with an accuracy of about 5% relative. 

The calcium and sodium activity coefficients were determined at 25.0 - 0.1 C with an Orion electrode (model 92-32) and a Radiometer electrode (model G502 Na), respectively. A saturated calomel electrode was used as the reference. Calibration curves were obtained using CaCl or NaCl solutions before and after each measurement. The CaCl2 and NaCl concentrations were measured by potentiometric determinations of the chlorides with silver nitrate and with a silver electrode. 

Electrodes suitable for the potentiometric determination of surfactants are either specially designed liquid or solid membrane electrodes or ion-selective electrodes that in addition to being selective to a particular ion, also quantitatively respond to surfactants. For example, a nitrate ion-selective electrode responds to anionic surfactants, a calcium ion-selective electrode is sensitive to quaternary ammonium salts, and a barium ion-selective electrode can be used for assaying polyethoxylates [43], In some cases it is possible for one to perform potentiometric determination of a counter-ion, e.g. one can titrate alkylpyridinium chloride or bromide salts with silver nitrate solution using silver wire as an indicator electrode [38]. 

Chlorides are determined in all types of waters particularly by argento-metry or by mercurimetry. For turbid or intensively coloured solutions, a potentiometric indication of the end point is used. 

G. B. Marshall and D. Midgley, Potentiometric Determination of Sulphite by Use of Mercury(I) Chloride-Mercury(II) Sulphide Electrodes in Flow Injection Analysis and in Air-Gap Electrodes. Analyst, 108 (1983) 701. 

The acid ionization constants of dibenzepine HCl and opipramol HCl were determined potentiometrically in aqueous solutions at 25 °C. The values pKi = 8.275 and pKi = 3.451 respectively, were obtained for the acid ionization constants at zero ionic strengfli. The value pKi = 8 was obtained for opipramol at Bie ionic strength I = 0.01. The effect of ionic strength on Bie ionization constant, as adjusted with sodium chloride, was determined."... 

Coeuee and Gunaratna [36] reported on the potentiometric determination of free chlorine in water using a silver/silver chloride electrode following a gas diffusion separation using a acceptor stream buffered at pH 4.5. 

The application of the copper selective electrode for detemination of copper in nickel, cobalt and zinc plating baths gives good results. In good agreement with very small values of selectivity coefficients of copper electrode towards Zn +, Co " and Ni " " the interferences do not occur even in the presence of very large excess of ions mentioned. Addition of thiosulphate efficiently removes interferences of chloride ions, and creates favourable conditions for copper determination. Results of potentiometric determination of copper are close to those obtained spectrophotometrically. 

The samples were equilibrated by stirring for 10 hours in a thermostat. The potassiun content was determined with the use of a type C Zeiss Jena Model III flame photometer and gravimetrically as KCIO, phosphate ion was determined by a complexi-metric titration with MgCl2 using Eriochrome Black T as indicator (1), chloride was determined by potentiometric titration with AgNO, and NH was determined by the Kjeldahl method. 

Keywords Poly(vinyl) chloride, potentiometric sensors, polymer membrane, liquid contact electrodes, solid-state electrodes, determination of anti-inflammatory drugs, pharmaceutical... 

Bromide, iodide, cyanide, and especially, sulfide ions strongly interfere with the potentiometric determination of chloride ions. Fortunately, these ions are seldom present in disturbing concentration in certain water samples. The solid-state ion-selective electrodes are not sensitive to oxidizing agents however, their function is influenced by strong reducing agents. 

Fusion with sodium carbonate is a very useful method for the fusion of polymers that, upon ignition, release acidic vapours, e.g., PE containing traces of chlorine or PVC, both of which, upon ignition, release anhydrous hydrogen chloride. To determine chlorine accurately in the polymer in amounts down to 5 ppm, hydrogen chloride must be trapped in a solid alkaline reagent (e.g., sodium carbonate). In this method, PE is mixed with pure sodium carbonate and ashed in a muffle furnace at 500 "C. The residual ash is dissolved in aqueous nitric acid, and then diluted with acetone. This solution is titrated potentiometrically with standard silver nitrate. 

A potentiometric determination of saccharin was proposed by Fatibello-Filho et al. [86]. In this method, saccharin was potentiometrically measured using a silver wire coated with a mercury film as the working electrode. With this, the main difficulty was the presence of a precipitate (mercurous saccharinate) that could adsorb on tube walls and the electrode surface. To avoid these undesirable effects, a relocatable filter unit was placed before the flow-through potentiometric cell and a surfactant was added to the carrier solution (Figure 24.12). The same investigation team reported the construction and analytical evaluation of a tubular ion-selective electrode coated with an ion pair formed between saccharinate anion and toluidine blue O cation incorporated on a poly(vinyl chloride) matrix [87]. This electrode was constructed and adapted in a FIA system. The optimum experimental conditions found were an analytical path of 120 cm, an injection sample volume of 500 pL, a pH of 2.5, a flow rate of 2.3 mL/min, and a tubular electrode length of 2.5 cm. 

Mohamed GG, Ali TA, El-Shahat ME, Al-Sabagh AM, Migahed MA, Khaled E (2010) Potentiometric determination of cetylpyridinium chloride using a new type of screen-printed ion selective electrodes. Anal Chim Acta 673 79-87... 

Add a known volume ofo oaM.AgNOj solution (in excess) and boil the solution until the silver chloride has coagulated. Filter through a conical 5 cm. funnel, ensuring that the filter-paper does not protrude above the r m of the funnel. Wash the silver chloride and the filter-paper several times with a fine jet of distilled water. To the united filtrate and washings add i ml. of saturated ferric alum solution. The solution should be almost colourless if it is more than faintly coloured, add a few drops of concentrated nitric acid. Then titrate with 0 02M-ammonium thiocyanate solution until the permanent colour of ferric thiocyanate is just perceptible. (Alternatively the chloride may be determined potentiometrically.)... 

This experiment describes a semester-long project in which the concentration of several ions in a fresh water aquarium are monitored. Ions that are monitored using potentiometric electrodes include H+ (pH electrode), Gh (chloride electrode), HG03 (GO2 electrode), NH4+ (NH3 electrode), and N03 (NH3 electrode). Nitrate concentrations were determined following its conversion to ammonia. 

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