Determination of inorganic acids by ion chromatography with n-tetradecylphosphocholine (zwitterionic surfactant) as the stationary phase and pure water as the mobile phase

A new ion chromatographic (IC) system, in which n-tetradecylphosphocholine (TDPC, a phosphobetaine type of zwitterionic surfactant) was used as the stationary phase, pure water as the mobile phase, and conductivity as the method of detection, has been developed for the determination of inorganic acids. Five model acids, HCl, HNO₃, HClO₄, H₂SO₄, and H₃PO₄, were separated to baseline and eluted in the order H₃PO₄ > HCl > HNO₃ > H₂SO₄ > HClO₄. When peak areas were plotted against the concentrations of the acids in samples, linear calibration curves were obtained. Ultimate determination limits were approximately 1 mmol L^–1, but the discrimination of the method between solutions of different concentration was better than 10 μmol L^–1 for those model analytes. Salts of divalent cations could also be separated, but they were eluted faster than the acids. No separation was observed for the salts of monovalent cations. This newly proposed approach is applicable to the simultaneous determination of the inorganic acids (produced by reactions of NO_x, SO_x, and HCl with water) in aerosols.     

Determination of arsenic,selenium and mercury in an estuarine sediment standard reference material using flow injection and atomic absorption spectrometry

A flow-injection analysis atomic absorption spectrometric (FIA-AAS) method was developed for the determination of trace amounts of arsenic, selenium and mercury in a proposed estuarine sediment standard reference material (SRM 1646a). The samples were prepared in two manners: a) A wet digestion procedure with HNO₃, H₂SO₄, and HClO₄ using a reflux column and b) A microwave-oven digestion procedure utilizing HNO₃, H₂SO₄, and HCl for As and Se, and HNO₃ for Hg. Microwave-oven digestion provides results comparable to those found by reflux column digestion and reduces the sample preparation time by a factor of 10. The proposed method employing the microwave-oven digestion procedure coupled with FIA-AAS for As and Se, and FIA-CVAAS for Hg, has detection limits of 0.15 ng As/ml, O.17 ng Se/ml and 0.15 ng Hg/ml.On leave from the Defense Metallurgical Research Laboratory, Hyderabad, India     

Study the effect of inorganic salts on the chemically polymerized aniline films using quartz crystal microbalance

The chemical oxidation of aniline with ammonium peroxydisulfate to form polyaniline (PANI) films has been studied in different aqueous acid mediums such as HCl, HNO₃, and H₂SO₄. The yield and the growth rate of the PANI film deposition were measured using the quartz crystal microbalance (QCM) technique. The effect of different salts such as KCl, NaNO₃, and K₂SO₄ and their concentration on the yield and the growth rate of the film formation are investigated. The yield of PANI film deposition depends on the acid used and the type of salts as well as their concentrations. When HCl and HNO₃ were used as media, the addition of salts with the same anion has no effect. However, when H₂SO₄ was used as media, the addition of salts with the same anions as the medium enhances the yield of PANI film deposition. The UV–visible spectra of the produced PANI films in the absence and presence of the salts are also studied. Copyright © 2007 John Wiley & Sons, Ltd.     

Storage and stability of inorganic and methylmercury solutions

Summary The storage behaviour of mercurychloride and methylmercury chloride solutions in deionized water and in seawater stored in polyethylene (PE), pyrex glass and teflon (PTFE) containers at various concentration levels (4 ppb, 50 ppt, natural seawater concentrations) was studied using various preservatives and container pretreament procedures. For PE bottles, the best results are obtained, after pretreatment of the bottles with an acidified KMnO₄ solution, with a 0.05% (v/v) H₂SO₄+0.02% (w/v) KMnO₄ preservative. However, the solution becomes heterogeneous rather fast, due to the formation of a MnO₂ precipitate. Acidified (pH 1 with HNO₃) deionized or seawater samples stored in pyrex glass BOD-bottles (analyses are carried out in these bottles too) or teflon containers are stable with respect to inorganic mercury for at least 1 month. Instead of acidification an oxidant such as BrCl can also be used to stabilize the solution. Methylmercury solutions (80 ppt) in deionized water (pH 6) and stored in teflon containers are stable for at least 1 month. In glass bottles, the solution should be acidified to pH 1. Methylmercury seems to be unstable in acidified seawater samples (pH 1 with HNO₃); after 2 weeks about 60% of the methylmercury is converted into inorganic mercury.     

Critical comparison of wet and dry digestion procedures for trace metal analysis of meat and fish tissues

The efficiency of four methods of digestion was evaluated for trace metal analysis of pork meat and carp fish tissues. Two methods of dry and two methods of wet ashing were compared in terms of calculated variances. Mixtures of HCl+HNO₃ were applied for wet ashing of the samples at 100 °C, while dry ashing with or without H₂SO₄ at 450 °C were the alternative methods. The digests were subsequently analysed for Pb, Cd, Cu and Zn by graphite furnace atomic absorption spectrometry. Analysis of variance and Student's t-test were performed separately for meat and fish analytical results. Wet digestion with a (1+1) mixture of HCl+HNO₃ has given better recovery and repeatability for almost all metals than a (9+1) mixture of HCl+HNO₃. Also between the dry ashing methods, the use of H₂SO₄ has given better results than ashing of the tissues without H₂SO₄.     

Speciation in strongly acidic metastable solutions of oxotungstate(vi) compounds

The ionic composition of long-lived metastable aqueous solutions of oxo compounds of tungsten(IV) with pH ≤ 1 was studied by spectrophotometry. The nature of some isopolytung-states formed in these solutions in the presence of various inorganic acids (HCl, HClO₄, HNO₃, H₂SO₄, and H₂SeO₄) was established.     

Thin-Layer chromatography of inorganic ions. VIII. A study of the acetone-phosphoric acid eluent system

Summary We present a study of the migration of inorganic ions on thin layers of silica gel, employing acetone and phosphoric acid mixtures as solvents. According to the trend of R _F values with increasing percentage of acid, the ions can be assigned to four groups with: zero or low mobility, gradually increasing mobility, elevated or characteristic mobility. This behaviour is related to that already observed with acetone — HCl, HNO₃, H₂SO₄ systems and explained chiefly on the basis of solubility and of the tendency to anionic or neutral complex formation. Finally, interesting separations obtained with this eluent are presented.This work has been in part supported by C.N.R. of Italy     

Studies on the extraction behaviour of zirconium from mixed aqueous media with TBP

A systematic study is presented on the extraction of Zr(IV) by tri-n-butylphosphate from H₂SO₄, HNO₃, HCl and HBr solutions as well from binary mixtures of H₂SO₄ and halogen acids. It has been found that Zr(IV) extraction is appreciably increased by addition of halogen acid to sulphuric acid solutions. On the other hand, the presence of water-miscible alcohols and acetone was found to enhance Zr(IV) extraction from HCl and HNO₃ solutions. An investigation of extracted Zr complexes from pure acids and mixed aqueous media enabled an explanation of the observed enhancements. In the light of the obtained results, an extraction mechanism is suggested.     

Solvent extraction of hafnium(IV)

^{175, 181}Hafnium(IV) was extracted by HDBP in 2-ethylhexanol from 1–10M solutions of HClO₄, HCl and HNO₃, and 1–8M H₂SO₄. As with low polar organic phase diluents, the acidity dependence of the distribution ratio of Hf, D, passes through a minimum for HClO₄, HCl, and H₂SO₄ whereas only an increase of D can be observed with increasing HNO₃ concentration. From the slope analysis the following complexes were found to be extracted (HDBP=HA): HfA₄ at <4M HClO₄ and <5M HCl, lg K_extr=9, HfX₄(HA)₄ (X=ClO ₄ ⁻ , Cl⁻ or NO ₃ ⁻ ) at >5M HClO₄, >7M HCl and 1–10M HNO₃, Hf(SO₄)A₂(HA)_3–4 at <3M H₂SO₄, and Hf(SO₄)₂ (HA)₄ at >6M H₂SO₄. Coextraction of sulphate with hafnium from H₂SO₄ solutions was evidenced in experiments with macro concentrations of Hf(IV) and³⁵SO ₄ ²⁻ . Part XX: Coll. Czech. Chem. Commun., 40 (1975) 3617.     

Mechanical degradation of filter polymer materials: Polyphenylene sulfide

Polyphenylene sulfide (PPS) is known as a material resistant to high temperature and chemicals; however, there are arguments on the durability of PPS non-woven fabrics to chemicals, such as nitric acid (HNO₃), sulfuric acid (H₂SO₄), and hydrochloric acid (HCl). Therefore, this work aims at investigating the degradation of PPS non-woven fabrics in HNO₃, H₂SO₄ and HCl, and at confirming acid durability of PPS non-woven fabrics. In addition, this paper also studies the interaction among these three acids by measuring the retention of strength in binary or tertiary mixtures of these three acids. A discussion has been made on the acceleration/retardation of PPS degradation by the interactive effects, and also on the chemistry related to the degradation by these acids. Furthermore, there is a linear relationship between the nitric acid concentration and the proportion of carbon in the remaining PPS structures after 100 h of acid exposure. Also, this proportion of carbon is a good indicator of the retained strength in PPS fabrics.     

Carbon–carbon bond fission on oxidation of primary alcohols to carboxylic acids

α-Carbon–carbon bond cleavage is shown to be a general side reaction accompanying the oxidation of unbranched primary alcohols to the corresponding carboxylic acids using HNO₃, CrO₃/H₂SO₄/H₂O/acetone, CrO₃/CH₃COOH, PDC/DMF, H₅IO₆/CrO₃, KMnO₄/H⁺, KMnO₄/HO^?, NiCl₂/NaClO, TEMPO/PhI(OAc)₂. Therefore, the product formed is always contaminated with a carboxylic acid containing one carbon atom less. Systems such as PhI(OAc)₂/TEMPO or H₅IO₆/CrO₃/CH₃CN reduce to a minimum the content of this impurity. Temperature, the order of reagent addition, and additives such as oxalic acid or cerium salts produce a profound effect on the formation of the undesirable impurity during the Jones oxidation of primary alcohols.     

Quecksilberbestimmung in Wasser-, Fisch-, Pflanzen- und sedimentproben mit Hilfe der Atom-Absorptions-Spektroskopie

Zusammenfassung Quecksilber wurde in Flußwasser, Fischen, Pflanzen und Sedimenten durch Atom-Absorptions-Spektroskopie bestimmt. In Wasserproben wurden die Hg-Verbindungen mit H₂SO₄ aufgeschlossen und mit KMnO₄ oxidiert. Nach der Beseitigung des entstandenen MnO₂-Niederschlags bzw. des überschüssigen Permanganats mit HONH₃Cl wurde das Quecksilber mit SnCl₂ reduziert, durch einen Luftstrom in eine Vorlage mit bidest. Wasser+H₂SO₄ +KMnO₄ eingeleitet und damit angereichert. Quecksilber wurde nach Zusatz von SnCl₂ mit Hilfe eines Luftstroms in die Meßzelle eingeleitet und gemessen. Fisch-, Pflanzen- und Sedimentproben wurden mit H₂SO₄+HNO₃ aufgeschlossen und das Hg mit KMnO₄ allein (beim Fisch) oder KMnO₄+K₂S₂O₈ (bei Pflanzen und Sediment) oxidiert. Bei diesen Analysen wurden der MnO₂-Niederschlag und das überschüssige KMnO₄ ebenfalls mit HONH₃Cl beseitigt. Die Bestimmung wurde in einem geschlossenen System durchgeführt. Bei diesem System sind die Nachweisempfindlichkeit und die Reproduzierbarkeit besser als beim offenen System. Der mittlere relative Fehler beträgt 13,7% für Wasser, 1,9% für Fisch, 4,9% für Pflanzen und 5,6% für Sediment. Die Wiederfindung des Quecksilbers beträgt 91–122%.

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Determination of mercury in water, fish, plant and sediment samples by atomic-absorption spectroscopy

Summary Organic and inorganic Hg-compounds in water samples were decomposed with H₂SO₄ +KMnO₄. Precipitated MnO₂ and excess of permanganate were destroyed with HONH₃Cl. Mercury was reduced by SnCl₂ and driven by an air stream into an absorption solution containing KMnO₄ and H₂SO₄. This solution was treated with SnCl₂, and mercury was aerated into the measuring cell. Fish, plant and sediment samples were digested with H₂SO₄ +HNO₃. For the oxidation of all forms of mercury to Hg(II) ions, KMnO₄ was added to the fish samples and KMnO₄+K₂S₂O₈ to the plant and sediment samples. Precipitated MnO₂ and excess of permanganate were destroyed with HONH₃Cl, too. Mercury was determined by using a closed, recirculating air stream. Sensitivity and reproducibility of the closed-system were better than those of the open-system. The coefficient of variation was 13.7% for water, 1.9% for fish, 4.9% for plant and 5.6% for sediment samples. Recovery rate of mercury ranged from 91 to 122%.

     

Extraction of tungsten and rhenium by basic or neutral extractants in xylene from mineral acidic media

Extraction of WO ₄ ^2– and ReO ₄ ^– by Adogen-381, tricaprylmethylammonium chloride, Hyamine 10-X, trioctylphosphine oxide or dibenzylsulphoxide in xylene from HNO₃, HCl or H₂SO₄ acid medium was investigated. Based on the separation factors obtained, the separation of ReO ₄ ^– from WO ₄ ^2– was elucidated. ReO ₄ ^– was separated from WO ₄ ^2– in high radiochemical purity: >99.9% by three successive extractions and strippings using Adogen-381 from HCl or HNO₃ acid medium.     

Determination of plutonium in environmental samples by controlled valence in aniion exchange

The title method was successfully used for collecting^239,249Pu from 200 litres of seawater by coprecipitation with 16 g FeSO₄·7H₂O under redcing conditions witout filtering. The plutonium is leached by concentrate HNO₃+HCl from the coprecipitate and the solid particles. The precipitate is heated at 400°C and digested in aqua regia. Na₂SO₃ and NaNO₂ have been applied to obtain the Pu⁴⁺ valence state in 0.5–1N HNO₃ for different samples. Plutonium and thorium are coadsorbed on anionic resin from 8N HNO₃. The column is eluted with 8N HNO₃ containing fresh NaNO₂ to keep the Pu⁴⁺ state for uranium decontaination. The system of the column is changed from 8N HNO₃ to concentrated HCl with 50 ml concentrated HCl containing a few milligrams of NaNO₂. Furtheer decontaimination of torium was achieved by elution with concentrated HCl instead of 9N HCl. The plutonium is successfully stripped by H₂O, NaOH, 2N HNO₃ and 0.5N HNO₃ containign 0.01M NaNO₃. The chemica yield of plutonium for a 2001 seawate sample is 60–80%. The resolution of the electroplated thin source is very good.     

Decomposition of organoarsenic compounds for total arsenic determination in marine organisms by the hydride generation technique

The conditions necessary for the complete decomposition of six organic arsenic compounds, namely methylarsonic acid (MMAA), dimethylarsinic acid (DMAA), trimethylarsine oxide, tetramethylarsonium iodide, arsenocholine bromide (AsC) and arsenobetaine (AB), were investigated. The degree of decomposition of the arsenic compounds was monitored using a hydride generation (HYD) technique, because the response from this system depends strongly on the chemical species of arsenic, with inorganic arsenic (the expected product from these decomposition experiments) giving a much more intense HYD signal than the organic arsenic compounds. The arsenic compounds were decomposed by heating them with three types of acid mixture, namely HNO₃? HClO₄, HNO₃? HClO₄? HF, or HNO₃? HClO₄? H₂SO₄. Both MMAA and DMAA were decomposed completely using any of the mixed acids at a decomposition temperature of 200 °C or higher. The HNO₃? HClO₄? H₂SO₄ mixture was the most effective for decomposing AsC and AB, which are the most difficult compounds among all types of organic arsenic compound to decompose and render inorganic. The complete decomposition of AB was only achieved, however, when the temperature was 320 °C or higher, and the sample was evaporated to dryness. When the residue from this treatment was examined by high‐performance liquid chromatography combined with inductively coupled plasma atomic emission spectrometry, all of the arsenic was found to be present as arsenic(V). The optimized conditions (HNO₃? HClO₄? H₂SO₄ at 320 °C) for decomposing AB were then used to determine the total amount of arsenic in marine organisms known to contain AB. Copyright © 2005 John Wiley & Sons, Ltd.     

Extraction of some elements of the groups IV b and VI b with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) from aqueous mineral acid solutions

Solvent extraction of Cr(VI), Mo(VI), W(VI) and Hf(IV) with 1-phenyl-3-methyl-4-caproyl-pyrazolone-5 (PMCP) in methyl isobutylketone (MIBK), xylene and chloroform (CHCl₃) from mineral acid solutions was studied. Chromium(VI) is not extracted from any of the acids studied (HCl, H₂SO₄ and HClO₄). Molybdenum(VI) is quantitatively extracted by the reagent in xylene and CHCl₃ from HClO₄ and HNO₃ solutions. It is also extracted quantitatively by the reagent in MIBK from HCl, HNO₃ and H₂SO₄ solutions but the participation of the diluent as extractant is considerable. Tungsten(VI) is quantitatively extracted in xylene from 9M HClO₄ solution. MIBK used as diluent also affects its extraction with PMCP. Hafnium(IV) is not extracted from H₂SO₄ solutions while it extracts more than 99% at 3M HNO₃ and above. The extracted species likely are: MoO₂(PMCP)₂, WO₂(PMCP)₂ and Hf(PMCP)₄, respectively.     

Accurate and precise reference method for the determination of chromium in high-alloy steel

Methods for determining chromium in high-alloy steels based on potentiometric titration after oxidation of chromium(III) to chromium(VI) with peroxodisulphate were studied using different dissolution procedures, viz., dissolution in HClHNO₃ and fuming with H₂SO₄H₃PO₄, dissolution in HClHNO₃ and fuming with HClO₄, dissolution in HClHNO₃HF in a microwave oven, fusion in sodium peroxide in a zirconium crucible and dissolution in dilute H₂SO₄ and oxidation with H₂O₂. A back-titration was used with dichromate after addition of solid ammonium iron (II) sulphate.The dissolution procedures were tested on 24 certified reference materials (0.01–3.3% C, 10–325% Cr). All procedures except the second gave good results for samples with ? 0.8% C. For samples with ? 0.8% C, the third and fourth procedures gave significantly higher values and better precisions, and gave the best results for all samples. The relative standard deviations were, with few exceptions, below 0.2%.     

Electrochemical hydride generation for the determination of hydride forming elements by atomic fluorescence spectrometry

The determinations of As, Bi, Ge, Sb and Se were performed by atomic fluorescence spectrometry following their electrochemical hydride generation. An electrochemical hydride generator based on a screw-thread seal arrangement, working in a continuous flow mode was used. The effects of cathode material, shape and area of material, catholyte, sample flow rate, applied current, catholyte solution concentration and interference of transition metals on signal intensity were studied. Five kinds of materials including lead, graphite, copper, tungsten and platinum with different shapes were tested as cathode materials. The signal obtained from a 3-dimensional electrode was higher than that from a 2-dimensional electrode under the same conditions. The signal intensity of Ge in HNO₃ medium within a narrow concentration range of 0.05–0.10 mol L^− 1 was stronger than that in other acidic medium, such as HCl and H₂SO₄. However, the signal intensity of Ge was rapidly decreased with HNO₃, HCl and H₂SO₄ concentration increasing, and then reached approximately zero. In general, limits of detection and a precision were improved using a graphite cathode in H₃PO₄ medium. The analysis of the reference materials showed good agreement with the certified values for As, Bi, Ge, Sb and Se. The method was successfully applied in the determination of As, Bi, Ge, Sb and Se in traditional Chinese medicine samples.     

Interaction parameters and (solid + liquid) equilibria calculation for KCl–H2O–HCl–C2H5OH,K2SO4–H2O–H2SO4 and K2SO4–H2O–C2H5OH mixed solvent-electrolyte systems

This work deals with the prediction and experimental measurements of the (solid + liquid) equilibrium (SLE) in acid medium for industrial purposes. Specific systems including KCl–ethanol–water–HCl and K₂SO₄–water–H₂SO₄ were analyzed. At first, a critical discussion of SLE calculations was given, based on the well-known UNIQUAC extended and LIQUAC models. Two new proposals were derived, considering the explicit necessity of a new reference state for SLE calculations for the studied (solvents + acid) mixtures. The solubility of KCl in water–ethanol–HCl mixed solvents was measured in the temperature range of 300.15 to 315.15 K using an analytical gravimetric method. These results combined with some other experimental data reported in the open literature let us to propose a set of parameters for the new models. They included the interaction parameters between ethanol and the H⁺ ion. The prediction capability of the new models, for calculations in acid medium, was illustrated. Experimentally, it was observed that the (K₂SO₄ + water + H₂SO₄) system presented the unusual behavior of increasing K₂SO₄ solubility with an increase in the sulfuric acid concentration. This was accurately predicted by the newly proposed models.     

Liquid-liquid extraction of 233Pa(V) with Aliquat 336</p> </p>

Summary The extraction of protactinium with Aliquat 336 (methyl-tri-caprylyl ammonium chloride) in toluene, cyclohexane and chloroform from HCl, HNO₃, H₂SO₄, HClO₄, HF and mixed HCl-HF media was investigated by radioactive tracer technique. Distribution ratios of protactinium between the aqueous solution and the organic phase were determined as a function of shaking time, concentrations of acid in aqueous solution phase, extractant concentration and type of diluents in the organic phase. Aliquat 336 can almost quantitatively extract protactinium from strong HCl solution. At the same time, small amounts of HF in HCl solutions have a strong effect on Pa distribution.</p> </p>