Ion-chromatographic determination of phosphates in castables

A procedure for the determination of orthophosphate and condensed phosphates in castables is proposed. The sample is calcined with sodium carbonate and leached with deionized water. After removing the interfering components from the matrix by cation-exchange, the sample solution is subjected to ion-chromatographic determination with gradient elution and conductivity detection. Recoveries are within 84–89% with a relative standard deviation of less than 3.6%.     

Ion-chromatographic determination of fluorine in texas lignite

Summary Samples of approximately 1.0 g were taken from three Texas lignite cores and mineralized in oxygen bombs. The residue was dissolved in distilled water to a total volume of 50 ml. The resulting solutions were analyzed for fluoride by ion chromatography and with a fluoride-sensitive electrode. The results obtained with these two methods were in good agreement. The pH of solutions prepared from mineralized lignite samples must be adjusted to fall into the range 4 to 12 before fluoride is determined by ion chromatography. The calibration curve is linear to 10 mg/l F^– (in solution). Twenty g/l of F^– (in solution) corresponding to 1 mg/kg of dry lignite can still be determined. Ion chromatography has higher sensitivity for fluoride than fluoride-sensitive electrodes and provides at the same time information about other anionic species. The fluorine concentrations in the three cores varied from 10 to 140 mg/kg (dry lignite). Layers of clay interspersed between the lignite seams had higher fluorine concentrations than the lignite.

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Ionen-chromatographische Bestimmung von Fluor in Braunkohle aus Texas

Zusammenfassung Braunkohlenproben von etwa 1 g wurden in der Sauerstoffbombe mineralisiert, der Rückstand in Wasser gelöst und die Lösung mit Hilfe der Ionen-Chromatographie und mit einer fluoridsensitiven Elektrode auf Fluorid untersucht. Die mit beiden Methoden erhaltenen Ergebnisse stimmten gut überein. Vor der Ionen-Chromatographie müssen die Lösungen der mineralisierten Proben auf pH 4–12 eingestellt werden. Die Eichkurve verläuft bis 10 mg/l F^– linear. Noch 20 g/l F^– (in Lösung), entsprechend 1 mg/kg trockener Braunkohle, können bestimmt werden. Die Ionen-Chromatographie weist eine höhere Empfindlichkeit auf als fluorid-sensitive Elektroden und bietet darüber hinaus Information über andere Anionen. Die untersuchten Fluoridkonzentrationen lagen zwischen 10 und 140 mg/kg (trockene Braunkohle). Zwischengelagerte Lehmschichten wiesen höhere Fluorgehalte auf.

     

Ion-chromatographic determination of chromium (VI)

Summary A simple ion-chromatographic method has been developed for the selective determination of chromium (VI) using UV-photometric detection. The anion exchanger was based on a matrix of a 2-hydroxyethyl-methacrylate copolymer; the mobile phase consisted of phosphate buffer and sodium perchlorate. The relative standard deviation was 2.26%. Application was made to waste waters of the metallurgical industry.     

The determination of fluoride by titration with calcium chloride

A new method for the determination of fluoride ions is described. Precipitation is effected with an excess of standard calcium chloride and, after standing overnight, the unconsumed calcium ions are back-titrated with ethylenediamine tetra-acetic acid (EDTA) using Eriochrome Black T as indicator. Halides, sulphate, phosphate and arsenate do not interfere under the recommended conditions. The method is applicable over the range 5-65 mg of fluoride ion.     

Ion-chromatographic determination of iodide in sea water with UV detection

A highly sensitive and selective ion-chromatographic procedure with UV detection at 227 nm was developed for the determination of trace amounts of iodide. The procedure utilizes 0.1M NaOH as eluent, which enables the determination of 1–100 g I^–1 I^– with a precision of ca. 6%. 1000-fold amounts of other anions such as fluoride, chloride, phosphate, sulphate, bromide, nitrite and nitrate do not interfere. The method has been applied to determine iodide in sea water samples from the Indian coast.     

Ion-chromatographic determination of trace anions with direct sample injection

The influence of the sample volume on the ion-chromatographic determination of anions was examined using various separation columns. Unlike conventionally used columns, Akvilain Al columns exhibit higher capacity factors for weakly retained anions. Thus, increasing the injected sample volume does not result in the masking of peaks of weakly retained anions by the negative system peak. The determination of anions at a level of several Μg/L is possible over a wide pH range. A double-loop system was used to eliminate the effect of residual ions in water used for the preparation of calibration solutions.     

Computer-controlled potentiometric determinations,illustrated by the determination of uranium,fluoride and chloride

Summary The computer system described is suitable for automation of many operations in a classical (wet) analytical laboratory. Programs and procedures are given for high-accuracy redox titrations (e. g. the determination of uranium) and for determination of F- and Cl-by means of ion-selective electrodes.

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Zusammenfassung Ein Computersystem wurde beschrieben, das sich für die Automatisierung analytischer Verfahren eignet. Programm und Arbeitsweise für Redox-Titrationen höchster Präzision (z. B. die Bestimmung von Uran) und für Bestimmungen von Fluorid und Chlorid mittels ionen-selektiver Elektroden wurden angegeben.

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Presented at the International Symposium on Microchemical Techniques 1977, Davos, May 1977.     

Ion-chromatographic determination of seven common anions in electronic-grade, water-miscible solvents

An ion-chromatographic method has been developed to determine seven common anions in electronic-grade acetone, isopropyl alcohol, methanol, and N-methyl-2-pyrrolidone (NMP), solvents whose cleanliness is vital to the manufacturing of semiconductor devices. The system requires only a pump, conductivity detector, and switching valve as hardware. A calibration study was conducted first, by preparing and analyzing 11 concentrations (between 0.3 and 6.0 ng/g) in deionized (DI) water. Subsequently, a spiking study was performed by spiking each solvent at each of nine concentrations (between 50 and 500 ng/g). Dilutions of 1-100 (w/w) were prepared and analyzed. For each anion, recovered concentrations were estimated using the appropriate calibration curve. For each recovery curve, uncertainties in predicted concentrations were between +/-20 and +/-150 ng/g (except for phosphate in acetone), at 95% confidence. Recoveries were between 82% and 112% for all anions in all solvents, except for nitrite and nitrate in acetone, nitrite in methanol, and fluoride in N-methyl-2-pyrrolidone.     

Ion-chromatographic determination of carbocisteine in pharmaceuticals based on non-suppressed conductimetric detection

A novel method for the determination of carbocisteine (S-CMC), a mucolytic and expectorant drug with an acidic amino acid structure, was developed and validated, using non-suppressed ion-chromatographic system with conductimetric detection, and anion or cation exchange columns. Among the various combinations of column type and eluent composition tested, a cation exchange column with a 0.25 mM tri-fluoroacetic acid (TFA) as eluent in isocratic mode at 1.2 ml/min gave the best results. S-CMC was very well separated from all common amino acids (resolution > 2.6). The retention time was 3.5 min and the asymmetry factor 1.1. A linear calibration curve from 17 to 400 microg/ml (r = 0.99994), with a detection limit of 0.14 microg (5.6 microg/ml-25 microl injection volume) and a precision of 1.5% R.S.D. (100 microg/ml, n = 3) was achieved. The proposed method was applied for the determination of S-CMC content in intensely colored commercial formulations (syrups). No interference from excipients was found and the only pretreatment step was the appropriate dilution with the mobile phase. Recovery from standard additions was ranged from 96.0 to 104.9% and precision (R.S.D., n = 3) 1.8-3.6%.     

New leading electrolyte for the direct determination of chloride and other anions in analytical isotachophoresis.

In a number of experiments it was shown that the dithionate ion possesses a higher effective mobility than the chloride ion in aqueous solution, thus enabling the direct and simultaneous isotachophoretic determination of chloride and other anions. Using an acid-base titration, we found only one pKa value for dithionic acid, which is in contrast to the two pKa values stated in the literature. Based on this pKa value, theoretical calculations and the experimentally observed effective mobility of the dithionate ion indicate a higher effective mobility compared to the chloride ion from pH 3. Taking into account the physico-chemical properties of the dithionate, its unrestricted use as isotachophoretic leading ion was confirmed. Based on the dithionate ion, new electrolyte systems for the determination of chloride were used. One system was optimised for the determination of chloride and other low-molecular-mass anions and applied to the analysis of waste water and drinking water. The water samples were analysed in parallel by ion chromatography and compared with the isotachophoretic results.     

Supramolecular fluoride and chloride anions

The Cambridge Structural Database has been searched for supramolecular anions of the form H_nX_n + 1⁻ where X is fluorine (n = 1 to 6) and chlorine (n = 1 to 5); no credible evidence was found for comparable bromine or iodine species. Several structural isomers have been identified, and an experimental measure has been developed which seems to distinguish between two-centre and three-centre bonded species. There are also examples of suprafluoride and suprachloride anions as ligands in organometallic complexes. Most of these anions have not been previously described.     

Energetics of halogen bonding of group 10 metal fluoride complexes

A study is presented of the thermodynamics of the halogen-bonding interaction of C(6)F(5)I with a series of structurally similar group 10 metal fluoride complexes trans-[Ni(F)(2-C(5)NF(4))(PCy(3))(2)] (2), trans-[Pd(F)(4-C(5)NF(4))(PCy(3))(2)] (3), trans-[Pt(F){2-C(5)NF(2)H(CF(3))}(PR(3))(2)] (4a, R = Cy; 4bR = iPr) and trans-[Ni(F){2-C(5)NF(2)H(CF(3))}(PCy(3))(2)] (5a) in toluene solution. (19)F NMR titration experiments are used to determine binding constants, enthalpies and entropies of these interactions (2.4 ≤ K(300) ≤ 5.2; -25 ≤ ΔH(o) ≤ -16 kJ mol(-1); -73 ≤ ΔS(o) ≤ -49 J K(-1) mol(-1)). The data for -ΔH(o) for the halogen bonding follow a trend Ni < Pd < Pt. The fluoropyridyl ligand is shown to have a negligible influence on the thermodynamic data, but the influence of the phosphine ligand is significant. We also show that the value of the spin-spin coupling constant J(PtF) increases substantially with adduct formation. X-ray crystallographic data for Ni complexes 5a and 5c are compared to previously published data for a platinum analogue. We show by experiment and computation that the difference between Pt-X and Ni-X (X = F, C, P) bond lengths is greatest for X = F, consistent with F(2pπ)-Pt(5dπ) repulsive interactions. DFT calculations on the metal fluoride complexes show the very negative electrostatic potential around the fluoride. Calculations of the enthalpy of adduct formation show energies of -18.8 and -22.8 kJ mol(-1) for Ni and Pt complexes of types 5 and 4, respectively, in excellent agreement with experiment.     

Properties of nickel-cobalt-diamond composite coating deposited from a chloride electrolyte

Effect of electrolysis modes and electrolyte composition on physicomechanical properties of nickel-cobalt-diamond composite electroplated coatings deposited from a chloride electrolyte with introduction of an ultradispersed diamond suspension was studied and the possibility of replacement of wear-resistant chromium coatings with these composite coatings was demonstrated.     

Properties of composite nickel-cobalt-aluminum oxide coating deposited from chloride electrolyte

Effect of the cathodic current density, pH value, electrolyte temperature, and concentration of aluminum oxide introduced into the electrolyte on the wear, microhardness, and internal stresses in nickel-cobalt-aluminum oxide composite electrolytic coatings was studied. It is shown that the coatings under consideration can be used instead of chromium coatings.     

Ion-chromatographic determination of the constant of ion exchange of aliphatic hydrazines and amines on silica-gel-based sulfocationites

Based on studies of the ion-chromatographic retention of 16 aliphatic amines and hydrazines on Diasorb-130-Sulfo and Nucleosil 5 SA, the relevant ion-exchange constants were calculated. The selectivities of the retention of these compounds were compared. The mass-spectrometry detection was used after the chromatography separation. The characteristics of the mass spectra of the aliphatic amines and hydrazines were discussed. Optimum conditions of detection were determined.     

Multiple potentiometric system for continuous determination of chloride, fluoride, nitrate and ammonia in natural waters

Summary A flow-through system for the simultaneous determination of chloride (30–150 ppm), fluoride (0.08-0.4 ppm), nitrate (5–20 ppm) and ammonia (0.05-0.5 ppm) in water was developed. Solid-state chloride and fluoride electrodes, a nitrate PVC membrane electrode with solid silver contact and a gassensing ammonia ORION 95-10 electrode were employed. The air-segmented sample stream is mixed with appropriate buffering solutions before entering the measuring cells. Mean accuracy of the determinations is usually better than ± 10%.

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Multiples potentiometrisches System zur kontinuierlichen Bestimmung von Chlorid, Fluorid, Nitrat und Ammoniak in natürlichen Wässern

Zusammenfassung Ein Durchflußsystem wurde entwickelt zur gleichzeitigen Bestimmung von Chlorid (30–150 ppm), Fluorid (0,08-0,4 ppm), Nitrat (5–20 ppm) und Ammoniak (0,05-0,5 ppm). Folgende Elektroden wurden eingesetzt: Festkörperelektroden für Chlorid und Fluorid, PVC-Membranelektrode für Nitrat und die ORION 95-10 Gassensor-Elektrode für Ammoniak. Der Luft-segmentierte Probestrom wird vor Eintritt in die Meßzellen mit geeigneten Pufferlösungen gemischt. Die mittlere Genauigkeit beträgt ±10%.

     

Pyrohydrolytic separation technique for fluoride and chloride from radioactive liquid wastes

A rapid method for simultaneous determination of fluorine and chlorine in radioactive liquid wastes with ion chromatography after pyrohydrolysis separation was proposed for routine analysis. The elements were separated from radioactive liquid wastes by pyrohydrolysis and were subsequently determined with ion chromatograpy. Total time taken to determine these elements is about 45 min including 30 min for the pyrohydrolysis and 15 min for ion chromatography. The results of recovery tests ranged 95% or above. The limits of detection for F and Cl are 0.5 and 0.8 mg kg⁻¹, respectively.