Infrared determination of barium, strontium, sodium and potassium sulphates by the pellet technique

Methods are proposed for the infrared determination of barium, strontium, sodium and potassium sulphates by the pellet technique. The semimicro sample is mixed with 300 mg of potassium bromide, the pellet is formed, and the peak heights are determined at the appropriate peak. Barium and strontium sulphates are measured at 983 and 993 cm(-1), respectively. Sodium and potassium sulphates are both measured at 619 cm(-1). Barium and strontium sulphates can be determined in the presence of each other in ratios from 1:20 to 20:1 from the measurements at 983 and 993 cm(-1). Carbonates or nitrates do not interfere with any of the procedures.     

Spectrophotometric study of the reactions of arsenazo III with alkaline-earth metals

Arsenazo III is used as a spectrophotometric reagent for alkaline-earth metals. The molar absorptivities of the calcium, strontium and barium complexes at 650 nm are 4.40 x 10(4), 4.00 x 10(4) and 3.65 x 10(4) l.mole(-1).cm(-1) respectively. The interference of magnesium is eliminated at pH 5-6. The use of sodium sulphate as masking agent permits the determination of small amounts of calcium, strontium and magnesium in the presence of barium. The alkaline-earth ions can be determined in the presence of each other at pH 4.2 at the 2-10 mug level. Some organic solvents such as dioxan, acetone and ethanol increase the sensitivity and selectivity in acidic medium. The stability constants have been measured and the structure of the complexes is discussed.     

一种新的测定锶的高选择性光工法的研究: 用新显色剂DBC-偶氮氯膦测定合金及海水中的锶

研究了新型显色剂二溴-氯偶氮氯膦与锶的显色反应及锶的分析, 发现锶能与这一显色剂在酸性条件下生成一种稳定的蓝紫色配合物, 在丙酮、EATA和硫酸钠存在下, 采用双波长分光光度法可有效地解决钙, 钡, 镁, 铁等三十余种元素的干扰, 用本方法测定了海水、氧化镁试剂和硅铁合金中的锶, 取得满意结果.     

A new selective metallochromic reagent for the detection and chelatometric determination of calcium

A new reagent, Calcichrome, which gives a highly sensitive colour reaction with calcium ions in alkaline solution, has been synthesised. Neither barium, strontium nor magnesium react with the reagent, which is therefore proposed as a selective spot-test reagent for calcium. In addition, Calcichrome may be used as a metallochromic indicator for the accurate complexometric titration of calcium in the presence of at least twelve-fold amounts of barium. Trans-1:2-diaminocyclohexane-N:N:N':N'-tetra-acetic acid is used as titrant since it is the only complexan available which is sufficiently selective in its reactivity towards calcium and barium.     

Amperometric titration of calcium,strontium and barium and their mixtures in presence of large amounts of alkali metal salts

Trace amounts of alkaline earth metals are titrated with triethylenetetraaminehexaacetic acid; lead(II) is added as indicator and the current is measured by square-wave polarography. At pH 13.3, calcium, strontium and barium give a common end-point corresponding to the total content of alkaline earth ions. Copper and cadmium interfere but small concentrations of Ni, Al, Mg, Zn, Mn(II) and Fe(III) are tolerated. The alkaline earth metals can be determined in the presence of 1000-fold amounts of lithium and 10⁵- fold amounts of sodium or potassium ions.     

The rapid determination of barium in bone by atomic absorption spectrophotometry

A rapid and precise method for the determination of barium in bone is presented. Barium as the nitrate is directly separated from calcium by co-precipitation with added strontium using fuming nitric acid. Atomic absorption measurements are made at 553.6 nm using a nitrous oxide-acetylene flame in the presence of strontium and potassium, and being free from noise due to the emission of CaOH. In order to improve accuracy and speed a radioactive tracer is used.     

Radiation Chemical Studies of Protein Reactions: Effect of Alkaline-Earth Metals on the Breaking of Secondary Bonding in Protein

The radiation protective effect of the breaking of secondary bonding in protein was examined with alkaline-earth metals such as magnesium chloride, calcium chloride, strontium nitrate, and barium chloride, and alkaline metals and heavy metals such as lithium chloride, sodium chloride, potasium nitrate, ferrous chloride, ferric sulfate, nickel sulfate, aluminum nitrate, and zinc sulfate. An empirical equation for the viscosity change was obtained.     

Determination of semimicro amounts of calcium in the presence of other alkaline-earth metals

Cyclam tetraacetic acid (CTA) is used to determine semimicro quantities of calcium in the presence of other alkaline-earth metals in natural and synthetic water samples. End-point detection is achieved amperometrically with Zn(en)(2+)(3) as the indicator. Magnesium and barium do not interfere. In the presence of strontium, two distinct end-points are obtained when its concentration is comparable with that of the calcium. If the concentrations are substantially different, calcium and strontium appear to be titrated together.     

Use of 2, 3, 4-trihydroxyacetophenone in the spectrophotometric determination of calcium

A critical examination of the calcium-2,3,4-trihydroxyacetophenone system in an aqueous medium is presented. This system showed a broad absorbance maximum at 540 nm (?₅₄₀ = 3.55 × 10³ liters/mole-cm). The spectrophotometric determination of calcium can be effected at pH 11.2 to 12.0 in the optimum calcium concentration range of 2.5 to 9 ppm if the concentration of 2,3,4-trihydroxyacetophenone corresponds to 4 ml of 8 × 10^?3M reagent in a final volume of 25 ml. Absorbance measurements must be made within the interval of 15 to 60 min. Beer's law is followed at 540 nm for 0.5 to 10 ppm of calcium (1-cm cell). Among the ions commonly occurring with calcium, the following were found to cause an error of +2% at a calcium concentration of 5 ppm: vanadate, chromate, manganese (II), uranyl (10 ppm) and molybdate and zirconate (60 ppm); an appreciable error from strontium, barium, and iron (III) (even at 1 ppm) and an error from magnesium due to partial co-precipitation of calcium with magnesium hydroxide.     

Determination of calcium in lithium salts

Two procedures are described for the determination of traces of calcium in lithium salts. In both procedures the calcium is titrated with very dilute EDTA and the end-point is determined fluorometrically with Calcein as indicator. This titration is carried out in the presence of the lithium salt in one procedure; in the other, a preliminary separation of the calcium is made on the chelating exchange resin, Dowex A-1.     

The separation of niobium from tantalum by extraction with tributyl phosphate and determination of niobium as the thiocyanate complex

A method is proposed for the rapid extraction and separation of microgram amounts of niobium(V). The niobium is extracted quantitatively by 100 % TBP from 7.7-9.4 M (initial) hydrochloric acid and determined spectrophotometrically as the thiocyanate in TBP-acetophenone solution. Beer's Law is obeyed at 430 mmu over the range 0.8-9.0 mug ml . The system is stable for 72 hr. Caesium, calcium, strontium, barium, aluminium, titanium(IV), zirconium(IV), cerium(TV), fluoride, thiocyanate and oxalate do not interfere (1 mg). Niobium(V) can be determined in a niobium(V)-tantalum(V) mixture. The method is accurate and reproducible to within +/-2%.     

Flow injection spectrophotometric determination of calcium in rain and snow with chlorophosphonazo III

Summary A spectrophotometric flow injection technique for the determination of calcium based on its color reaction with chlorophosphonazo III(CPA-III) is described. The complex formation of CPA-III with calcium ions was carried out in the presence of 0.01 mol/l oxalate at pH 2.8. Most of the common foreign ions did not interfere. Only strontium, barium and rare earth metals interfered. Under the optimum conditions, the calibration curve was linear up to 1.2 ppm calcium and the detection limit was 0.01 ppm for a sample volume of 120 l. The relative standard variations for 0.4 and 1.0 ppm calcium were 0.354 and 0.352%, respectively. The method was successfully applied to the determination of calcium in rain and snow.     

Change in ionization of barium in calcium and direct determination of barium in calcium by flame atomic absorption spectrometry using the Ba ion resonance line

Partial pressures of barium at various concentrations of calcium are calculated, and degree of ionization of barium in the nitrous oxide-acetylene flame are determined experimentally and theoretically using the Saha equation. The ionization of barium (50 μg ml^?1 ) in the presence of 10000 μg ml^?1 of calcium was about one third of the theoretically expected value. Using the ion resonance line of barium permits the direct determination of barium down to 3 ppm in calcium matrices by atomic absorption spectrophotometry.     

1,5-bis(dicarboxymethylaminomethyl)-2,6- dihydroxynaphthalene as a selective spectrofluorimetric reagent for calcium

1,5-Bis(dicarboxymethylaminomethyl)-2,6-dihydroxynaphthalene (BDDN) forms fluorescent complexes with aluminium, barium, beryllium, calcium, magnesium and strontium. All the complexes have 2:1 metal :ligand ratios. Barium, calcium, magnesium and strontium exhibit maximal fluorescence at pH 11.7, with excitation and emission maxima at 385 and 445 nm respectively. Aluminium and beryllium show maximal fluorescence at pH 5.8 and 5.2 respectively, the excitation and emission maxima being at 370 and 405 nm. The formation of the calcium complex provides a highly sensitive and selective determination of calcium in the range 10/2-500 ng. The fluorescence measurement of calcium should be made within 5 min of mixing the solutions because of the instability of the reagent at the given pH. Potassium cyanide may be used as a masking agent and ter- or quadrivalent cations should be removed by preliminary extraction with 8-hydroxyquinoline in chloroform at pH 6.0. In such conditions, of 33 cations studied, only magnesium (>20 ng), strontium (>70 ng) and barium (>150 ng) caused interference in the determination of 300 ng of calcium. Among 16 anions examined, only EDTA interfered seriously.     

Atomic absorption spectrometric determination of calcium and other metallic elements in some animal protein sources

The phosphorus content of some animal protein sources was determined in order to identify the sample with the highest phosphorus content for use as a pilot sample. Varying concentrations of strontium and lanthanum were added to solutions of the ashed pilot sample for the determination of calcium and magnesium using flame atomic absorption spectrophotometry operated on the air-acetylene mode. At least 3000 ppm of strontium or lanthanum was required to completely overcome the interference of phosphate ion, PO(4)(3-), and give peak values for calcium. The presence of strontium or lanthanum did not affect the amount of magnesium obtained from the analyses. Based on this, a procedure is proposed and the results obtained by this procedure for calcium are more enhanced than those obtained without the addition of strontium or lanthanum for the same samples whereas comparable results were obtained for all other elements whether strontium or lanthanum was added or not. The method gives more accurate results and is reproducible. The coefficients of variation calculated using one of the samples were 0.58% for magnesium, 3.12% for zinc; 0.44% for calcium, 11.06% for lead, 22.22% for nickel, 3.53% for manganese and 3.50% for iron at the concentration levels found in that sample. Recoveries of spiked calcium, magnesium and zinc were quantitative. Also, for selected elements, results from the procedure compared well with those from chemical analysis.     

Study of the Ternary Systems M (II)(NO3)2–LiNO3–H2O ( M (II)?5?Mg, Ca, Sr, Ba) at 25°C

 The isothermal solubility diagrams of four aqueous systems containing lithium nitrate and nitrates of group IIA metals – magnesium, calcium, strontium, and barium – were studied at 25°C. No double salt formation was observed. The results were compared with similar nitrate and chloride systems. Some trends in the shape of the phase diagrams were observed. Hydration analysis was applied to the solubility branches, rendering information about ionic processes in saturated solutions. Further, the ratio of activity coefficients of the saturating solid phase in ternary and binary solutions (γ/γ₀) was obtained.     

Determination of tributyltin in toluene extract from sea water by graphite furnace atomic absorption spectrometry with a new matrix modifier

A new matrix modifier composed of calcium and chromium[VI] was proposed for the determination of tributyltin (TBT) in toluene extract from sea water containing sediment by graphite furnace atomic absorption spectrometry (GFAAS). Fourteen inorganic and organic compounds (barium, calcium, chromium[VI], lanthanum, magnesium, nickel, palladium, strontium, calcium-chromium[VI], calcium-strontium, nickel isocaprylate, 5%-, 10%-aqueous solution of ascorbic acid and toluene-saturated solution of ascorbic acid) as a matrix modifier were comparatively studied and a matrix modifier composed from 5 microg of calcium and 1 microg of chromium[VI] was found to give the best performance. The interference effects of co-existing elements in sea water containing sediment (aluminium, iron, magnesium, sodium and strontium) were studied. TBT in eight toluene extracts was determined by GFAAS with the proposed matrix modifier. The relative standard deviation was 3.0% for 63 ng ml(-1) of TBT (n = 11). The recoveries were 88-104%. The characteristic mass was 7 pg. The linearity range was 0-250 ng mg(-1).     

Separation and determination of radiostrontium in calcium carbonate matrices of biological origin

Radiostrontium is concentrated in the shells of mollusks and other animals due to the isomorphic substitution of strontium for calcium in the calcium carbonate shell matrix. Radiochemical separation of strontium from such matrices is difficult because of the chemical similarity between strontium and calcium. This paper describes a technique using a commerically-available, solid-phase extractant to separate Sr-89 and Sr-90 from high concentrations of Ca²⁺. The extractant removes Sr(NO₃)₂ from acidic nitrate media, and strontium activities are determined via conventional -counting techniques. This method has been used to process mollusk shells collected from contaminated reactor cooling ponds at the Savannah River Site and Chernobyl Nuclear Power Plant.     

Study of the Ternary Systems M(II)(NO3)2–LiNO3–H2O (M(II) 5 Mg, Ca, Sr, Ba) at 25°C

Summary.  The isothermal solubility diagrams of four aqueous systems containing lithium nitrate and nitrates of group IIA metals – magnesium, calcium, strontium, and barium – were studied at 25°C. No double salt formation was observed. The results were compared with similar nitrate and chloride systems. Some trends in the shape of the phase diagrams were observed. Hydration analysis was applied to the solubility branches, rendering information about ionic processes in saturated solutions. Further, the ratio of activity coefficients of the saturating solid phase in ternary and binary solutions (γ/γ₀) was obtained. Received April 13, 2001. Accepted June 15, 2001     

Spectrophotometric determination of lithium ion using a water-soluble octabromoporphyrin in aqueous solution

A water-soluble porphyrin, (2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin; H(2)obtpps(4-)) was synthesized and developed for the determination of lithium ion in aqueous solution. The octabromo groups lower the basicity of the porphyrin by their electron-withdrawing effect, and enable the porphyrin to react with the lithium ion in alkaline solution to form the lithium complex along with a shift of absorption maximum: lambda max/nm (logepsilon/mol(-1) dm(3) cm(-1)) of the lithium porphyrin are 490.5 nm (5.31) and 734 nm (4.36). Sodium and potassium ions did not react with the porphyrin. The equilibrium constant for the reaction Li(+)+Hobtpps(5-)right harpoon over left harpoon[Li(obtpps)](5-)+H(+) was found to be 10(-8.80) and the conditional formation constant of the [Li(obtpps)](5-) at pH 13 is 10(4.21). The above results were applied to the determination of lithium ion in aqueous solution. The interference from transition and heavy metal ions was masked by using N,N'-1,2-ethanediylbis[N(carboxylmethy)glycinato]magnesium(II) ([Mg(edta)](2-)) solution. Absorbance at 490 nm was measured against a blank solution. A calibration graph was linear over the range of 0.007-0.7 mug cm(-3) (1x10(-6)-1x10(-4) mol dm(-3)) of lithium(I) with a correlation factor of 0.967. Lithium ion less than ppm level was determined spectrophtometrically in aqueous solution. The proposed method was applied to the determination of lithium in human serum and sea water samples.