Determination of strontium in environmental media

A procedure is described for the determination of strontium in natural materials by name photometry. An alkaline fusion of the ashed sample followed by dissolution in dilute acid gives a preliminary separation. Further separation of strontium is obtained by sorption on Dowex-50 resin from an EDTA solution at pH 5.1 followed by elution of the alkali metals with 0.5M hydrochloric acid, and of the strontium with 3M hydrochloric acid. The emission line at 460.7 mmu; is used and the intensity enhanced by the addition of s-butanol to the solution.     

Extraction with long-chain amines--VI. Separation of manganese as Mn(CNS)4-(6) complex and its complexometric determination in calcareous material

Manganese is quantitatively extracted into a benzene solution of trioctylmethyl-ammonium chloride from a solution at least 0.25M in potassium thiocyanate and at pH 2.5-7. After stripping into dilute ammonia containing triethanolamine (TEA) and hydroxylamine hydrochloride, manganese is determined by EDTA titration. Calcium and magnesium are not extracted even in traces. Iron is co-extracted with manganese and is masked with TEA during the stripping. Aluminium also does not interfere. In the aqueous phase, after the extraction of manganese, calcium or magnesium can be determined by the usual EDTA titration. The method described permits highly selective individual determination of manganese and calcium and/or magnesium in all materials rich in manganese.     

Preconcentration and determination of calcium and magnesium in brine with flow-injection systems

On-line preconcentration on a chelating resin (Dowex A-1) and elution with 0.1 M hydorchloric acid is followed by spectrophotometry based on the metal complexes formed with 1- (2-hydroxy-4-diethylamino-1-phenylazo)-2-hydroxynaphthalene-3,6-disulfonic acid. The total concentration of calcium and magnesium is determined; in a second sample, calcium is masked with a ligand buffer containing excess of barium(II) and EGTA, and magnesium is determined. The calcium concentration is measured by difference. Magnesium (1–30 μg l^?1 and calcium (8– 10 μg l^?1) in 2.5 M sodium chloride can be determined. Calcium and magnesium in analytical reagent-grade sodium chloride and potassium chloride and primary standard sodium chloride are aslo determined. The method based on the exchange between calcium ions and Mg(EDTA) is proposed to enchance the sensitivity for calcium.     

Quantitative precipitation of large amounts of sodium as sodium zinc uranyl acetate and its determination by an indirect complexometric method

Up to 40 mg of sodium can be quantitatively precipitated as sodium zinc uranyl acetate if enough reagent of appropriate composition is added to make the concentrations of zinc and uranium in the mother liquor at least 1.25 and 0.14M respectively. In practice, the reagent solution contains 100 g of uranyl acetate and 300 g of zinc acetate per litre and the volume added (ml) must be at least 15 times that of the solution to which it is added or 1.5 times the number of mg of sodium present, whichever is the greater. The triple salt can then be dissolved in water and the zinc selectively titrated with EDTA at pH 5.3, with Xylenol Orange as indicator. The uranium is masked with ammonium fluoride. Most constituents of ceramics and other silicates, including barium, strontium, magnesium, potassium, sulphate, phosphate and arsenate, do not interfere.     

A rapid complexometric scheme for analysis of iron, aluminium, calcium and magnesium in slags

A simple and rapid complexometric method has been developed for the simultaneous determination of iron, aluminium, calcium and magnesium in a single solution in slags. Phosphorous and small amounts of chromium (1.5 mg) and vanadium (1 mg) do not interfere in the titration. Titanium and manganese are suitably masked with lactic acid and tetra sodium pyrophosphate, respectively. In a suitable aliquot, iron is titrated at pH 2 with EDTA, using sulphosalicylic acid as indicator. To this solution, excess disodium 1,2-cyclohexane diamine tetra acetic acid (DCTA) is added and aluminium is titrated by titrating the excess DCTA with standard copper sulphate solution at pH 3.5, using 1-(2-pyridylazo)-2-naphthol (PAN) as an indicator. A known excess of EDTA is added, the pH is raised to 10 and calcium and magnesium are jointly titrated by titrating the excess EDTA with copper sulphate solution, using PAN indicator. The Ca-EDTA complex is demasked with ammonium oxalate at pH 5 and the released EDTA equivalent to calcium is titrated with copper sulphate solution at pH 10 with PAN indicator. Results of analysis compare favourably with certified values and values obtained by standard methods for BCS and other slags. A set of five samples can be analysed for iron, aluminium, calcium and magnesium in four hours as compared to three days by the classical conventional method.     

Comparison of secondary-ion mass spectrometry and compleximetric titration for the determination of leaching of magnesium from chrysotile asbestos

The dissolution of chrysotile asbestos in 0.05 M oxalic acid is evaluated by secondary-ion mass spectrometry and by titration of magnesium with EDTA. The results of the two methods agree closely; thus matrix effects in the utilization of sputtering depth profiles of the mass spectrometric determination do not influence the final results.     

Microbalance study of gold dissolution in alkaline sulfite-thiocarbamide electrolytes

It is shown that gold does not virtually dissolve in alkaline (pH 12.5) solutions containing either thiocarbamide or sodium sulfite. Gold dissolves in alkaline solutions simultaneously containing thiocarbamide (0.1 M) and sodium sulfite (0.5 M). The gold dissolution rate increases with the increase in the contents of thiocarbamide and sodium sulfite. The methods of microbalance and voltammetry are used in studying the mechanism of gold dissolution in a solution containing 0.5 M sodium sulfite, 0.1 M thiocarbamide, and 0.03 M KOH. The found relationships are explained based on the assumption that the gold dissolution in alkaline sulfite-thiocarbamide electrolytes affords gold sulfite complexes.     

Determination of magnesium and calcium ions in sea water by capillary type isotachophoresis

Summary A new analytical procedure for the determination of magnesium and calcium ions in sea water was developed with a capillary type isotachophoresis after adsorption on sodium form cation-exchange resin and elution with EDTA solution. Linear working curves were obtained for 3% sodium chloride solutions containing up to 2,000 mg/l of these ions, adjusted to pH 8 with 0.1 N sodium carbonate solution. A supporting electrolyte containing 0.01 M hydrochloric acid and 0.5% methyl cellulose buffered to pH 8.5 with tris(hydroxymethyl)aminomethane and a 40 cm long FEP tube as the main column were used. The proposed method was applied to the determination of magnesium and calcium ions in coastal sea water samples collected in Osaka Bay in April, 1984 and in artificial samples prepared with artificial or natural sea water.

---

Bestimmung von Magnesium und Calcium in Meerwasser mit Hilfe der Capillar-Isotachophorese

Zusammenfassung Das Verfahren beruht auf der Isotachophorese nach vorhergehender Adsorption an Kationen-Austauscher in Na-Form und Elution mit EDTA-Lösung. Für 3%ige NaCl-Lösungen mit <2000 mg/l Mg und Ca (auf pH 8 mit 0,1 N Natriumcarbonatlösung eingestellt) wurden lineare Eichkurven erhalten. Als Trägerelektrolyt diente 0,01 M Salzsäure mit 0,5% Methylcellulose, gepuffert auf pH 8,5 mit Tris(hydroxymethyl)aminomethan. Hauptsäule war eine 40 cm lange FEP-Röhre. Das vorgeschlagene Verfahren wurde zur Mg- und Ca-Bestimmung in Küstenwasser der Osaka-Bucht sowie in synthetischen Proben eingesetzt.

     

Direct determination of fluoride in aluminium reduction materials by using an ion-selective electrode

Macro amounts of fluoride in aluminium reduction materials are successfully determined with a fluoride electrode. Except for anhydrous aluminium fluoride, which requires fusion with sodium hydroxide, samples are dissolved in aqueous media. Cryolite and sodium fluorosilicatc are dissolved in boiling sodium hydroxide solution. Other materials containing fluoride, such as fluorspar and the reduction cell bath and pot-lining, require dissolution in a hydrochloric acid solution of aluminium chloride. Potential interference from large amounts of aluminium (and calcium, if present) is eliminated and pH control attained by using ammoniacal sulphosalicylate (and EDTA). The procedures are reasonably rapid. Relative errors of less than 2% and a relative standard deviation of 1% are achieved.     

A Study on the Adsorption of Benzotriazole on Copper in Hydrochloric Acid Using the Inflection Point of the Isotherm

This paper is a contribution to correlate benzotriazole (BTA) adsorption films on copper with BTA concentration in bulk solution with hydrochloric (HCl) acid. Three HCl concentrations were tested, 0.001, 0.005, and 0.01 M. Twelve BTA concentrations, from 1 × 10^–5 to 1 × 10^–1 M, were added to the HCl acid solution at four temperatures from 298 to 328 K. Commercial copper was used. Gravimetric measurements were performed after 3 h experimentation. The Frumkin isotherm gave the best fit to the experimental results. This result was based on the inflection point approach of the isotherm.     

A novel method of non-violent dissolution of sodium metal in a concentrated aqueous solution of Epsom salt

A new technique of non-violent and fast dissolution of sodium metal in a concentrated aqueous solution of Epsom salt (MgSO₄.7H₂O) at room temperature (RT) has been developed. The dissolution process is mildly exothermic but could be carried out even in a glass beaker in air under swift stirring condition. The reaction products consist of mixed salts of MgSO₄ and Na₂SO₄ as well as Mg(OH)₂ which are only mildly alkaline and hence are non-corrosive and non-hazardous unlike NaOH. A 50 mL solution having Epsom salt concentration of 2 M was found to give the optimal composition for disposal of 1 g of sodium. Supersaturated (>2.7 M), as well as dilute (<1.1 M) solutions, however, cause violent reactions and hence should be avoided. Repeated sodium dissolution in Epsom solution produced a solid waste of 4.7 g per g of sodium dissolved which is comparable with the waste (4 g) produced in 8 M NaOH solution. A 1.4 M Epsom solution sprayed with a high-pressure jet cleaner at RT in air easily removed the sodium blocked inside a metal pipe made of mild steel. The above jet also dissolved peacefully residual sodium collected on the metal tray after a sodium fire experiment. No sodium fire or explosion was observed during this campaign. The Epsom solution spray effectively neutralized the minor quantity of sodium aerosol produced during this campaign. This novel technique would hence be quite useful for draining sodium from fast breeder reactor components and bulk processing of sodium as well as for sodium fire fighting.     

The influence of complexing agents on the effectiveness of electrochemical masking with anionic surfactants in anodic stripping voltammetry

The influence of sodium dodecyl sulphate, sodium dodecyl sulphonate and sodium stearinate on the anodic stripping peaks of Tl(I), Pb(II), Cd(II), Cu(II) and In(III) was investigated. The supporting electrolytes were 0.5M sodium sulphate solution, 0.2M citrate solution (pH 3.7, 4.6 and 7.3), 0.5M tartrate solution (pH 4.4) and 0.1M solution of EDTA (pH 4.4). The composition of complex compounds forming in a solution under experimental conditions was defined. The conditions of ion reduction of metals on hanging mercury electrode during the electrolytical deposition were investigated. The investigation included an analysis of voltammetric curves of the metal ions. The obtained results suggest that "electrochemical masking" is much stronger in electrolytes containing a complexing agent than in the sodium sulphate solution. The influence of the complexing agent may not be explained in terms of the interaction between the form of the complex and the charge of the adsorbed surfactant particles; rather the complexing process is connected with indirect inhibition, i.e., by decreasing the rate of charge transfer reaction.     

Adsorption of benzotriazole on copper surfaces in a hydrochloric acid solution

The adsorption of benzotriazole (BTA) on commercial copper surfaces in hydrochloric (HCl) acid concentrations from 1 × 10^?3 to 5 × 10^?1 M was investigated using gravimetric measurements. BTA in bulk solution was tested in concentrations from 1 × 10^?5 to 1 × 10^?1 M at temperatures from 298 to 328 K. The adsorption mechanism is discussed using the objective function (OF) and in terms of applicability of the conventional isotherm models. The best fit was obtained using the Frumkin equation. The projected molecular area of BTA was calculated to elucidate inhibitor orientation in the adsorption process. Copyright © 2006 John Wiley & Sons, Ltd.     

Compleximetric titration of aluminum and zirconium in siliceous materials after alkali fusion of samples

Rapid methods for the determination of zirconium and aluminum in siliceous materials are described. Samples are decomposed by sodium carbonate—sodium borate fusion and dissolved in perchloric acid. The zirconium is titrated directly with standard EDTA solution at 90–95 ° C in 1 M perchloric acid solution with xylenol orange as the indicator. Aluminum is then complexed by boiling with an excess of EDTA and the free EDTA is back-titrated potentiometrically with standard zinc solution. Interference of titanium in the aluminum determination is prevented by lactic acid masking. The methods have been applied successfully to a wide variety of glass-ceramics, refractories and NBS minerals.     

Simple pulse-acquire NMR methods for the quantitative analysis of calcium, magnesium and sodium in human serum

Simple pulse-acquire NMR methods are presented for accurate quantitation of calcium (Ca(2+)), magnesium (Mg(2+)) and sodium (Na(+)) in human serum. Ca(2+) and Mg(2+) can be determined simultaneously by (1)H NMR via their EDTA (ethylenediaminetetraacetic acid) complexes. Spectra are acquired before and after addition of EDTA, and the difference spectrum is used for integration of the signals from the complexes relative to an internal reference. Serum sodium can also be determined through pulse-acquire (23)Na NMR by integration of the free sodium signal relative to a reference signal (Na(+)+EDTA in a coaxial capillary tube). The method shows excellent accuracy and precision for all three metal ions. Slow chemical exchange between complexed and free EDTA at the natural pH of serum does not limit the accuracy of the determination of Ca(2+) and Mg(2+), and the large errors associated with spin-echo spectral editing methods are avoided.     

Rapid isolation of carcinogen-bound DNA and RNA by hydroxyapatite chromatography.

Carcinogen-bound DNA and RNA are conveniently isolated by solvent extraction and hydroxyapatite (HAP) chromatography. Tissue is suspended in 8 M urea-0.24 M sodium phosphate-1% sodium dodecyl sulfate-10 mM EDTA, pH 6.8 (MUP-SDS-EDTA) and extracted with chloroform-isoamyl alcohol-phenol (24:1:25; CIP) to remove protein. RNA and DNA are separated by passing the aqueous solution through an HAP column; RNA is eluted with MUP, DNA with 0.48 M sodium phosphate, pH 6.8. Examples presented are: (1) calf thymus DNA that has been reacted with N-acetoxy-2-acetylaminofluorene (N-OAc-AAF), (2) isolated intact rat hepatocytes incubated with N-hydroxy-AAF and (3) livers from Sprague-Dawley rats treated with N-hydroxy-AAF.     

Complexometric determination of magnesium oxide in flyash blended cement

A complexometric titration method is proposed to determine magnesium oxide in flyash blended cement. A 0.50 g of sample was heated with hydrochloric acid for 10 min. The solution was diluted to 500 ml, and 50 ml was pipetted and heated to boiling with 2.5 ml of 5% ammonium oxalate solution. The solution was then made alkaline by ammonium hydroxide. The suspension was cooled and filtered. The filtrate was titrated by standard 0.002M EDTA solution. The concentration of MgO in sample was calculated. The flyash content of the sample was determined by British Standard method and the recovery factor (f) was calculated by the equation of f = 100/(99 - 0.315 x %FA). Concentration of MgO in sample was corrected by multiplying the recovery factor with concentration initially found by EDTA titration. The precision of the method is better with more time saving than the official methods.     

Novel applications of dipicrylamine as an extractant in the determination of alkali metals

A ten-stage mixer-settler type extraction procedure has been used for the preparation of rubidium-free caesium salts. A nitrobenzene solution of (0.11M CsDPA flows counter to a purified aqueous solution of 0.05M CsCl and 10(-3)M Cs(4)(EDTA), which removes Rb, K, Na and most other metals from the organic phase. An extraction colorimetric titration procedure for 0.2-2 mg of caesium is described, and also an indirect method for determination of potassium and sodium in admixture, based upon the difference in the ability of the two ions to replace (137)Cs(+) in a nitrobenzene solution of dipicrylaminate.     

On co-adsorption on passive iron from aqueous 1,2,3-benzotriazole and sodium phenylundecanoate

Passivation of iron and low-carbon steel in borate buffer solution (pH 7.40) was studied in the presence of 1,2,3-benzotriazole (BTA) and its equimolar mixture with sodium phenylundecanoate (SPU). As was shown BTA is an ineffective stabilizer of the passive state, while SPU has a better efficiency in this function. However, the stabilizing effect of BTA can be improved by forming its adsorption layer on the electrode surface pre-modified with SPU anions at anodic potential E = 0.2 V or by its co-adsorption with SPU. The analysis of attraction between the adsorbed particles of these inhibitors enabled to suggest that their co-adsorption on oxidized iron (E = 0.2 V) yields associates of SPU and BTA anions.     

Dissolution of calcium bilirubinate disk as a model of a gallstone by mixed solutions of 1,3-dimethyl-2-imidazolidinone and ethylenediaminetetraacetic acid

Direct dissolution agents of calcium bilirubinate gallstones were prepared by dissolving chelating agents in aqueous solutions of sodium carbonate containing polar solvent. Dissolution experiments on a calcium bilirubinate disk as a model of a gallstone were performed using a static disk method.

From the amounts dissolved in an hour using dissolution agents with various composition, the most effective conditions for dissolving calcium bilirubinate were determined as follows: (1) the higher the pH of the dissolution agent, the more calcium bilirubinate was dissolved. Thus, pH 8.4 was chosen as the best pH condition within the range of harmless usage to the human body in vivo in limited amount; (2) a combination of ethylenediaminetetraacetic acid (EDTA) as chelating agent for calcium and 1,3-dimethyl-2-imidazolidinone (DMI) as polar solvent; (3) in the mixed system of EDTA and DMI, the most effective concentrations were about 4 wt.% EDTA and about 30 wt.% DMI.

The dissolution agent satisfying the above conditions gave a dissolved amount of about 70 mg dl⁻¹ in 1 h. This amount was considerably higher than those using DMI and EDTA independently. This suggests that dissolution is due to cooperation between EDTA and DMI.