在线萃取流动注射分光光度法测定二羟基苯磺酸钙中微量对苯二酚

用在线萃取-流动注射分光光度法(FISP)测定了作为杂质与2,5-二羟基苯磺酸钙共存的对苯二酚。专门设计并制作了与流动注射分光光度测定单元组合在一起的在线萃取流路,对苯二酚用乙醚萃取进入有机相并在此相中于其吸收峰297.5 nm波长处测定其吸光度,通过萃取基体成分,即2,5-二羟基苯磺酸钙的干扰,由于其在乙醚中不溶解而得以消除。对苯二酚的吸光度与其相应浓度在3.5×10-6~5.0×10-4mol.L-1之间呈线性关系,相关系数达0.999 4。该方法的检出限为2.53×10-6mol.L-1。应用此方法分析了来自不同批次的3个试样,所得结果的RSD在0.69%~1.65%之间,且其值与药典法所测得结果相符。     

Comparison of slurry sampling and microwave-assisted digestion for calcium, magnesium, iron, copper and zinc determination in fish tissue samples by flame atomic absorption spectrometry

The development of a slurry sampling method for the determination of calcium, copper, iron, magnesium and zinc in fish tissue samples by flame atomic absorption spectrometry is described. In comparison with microwave-assisted digestion, the proposed method is simple, requires short time and eliminates total sample dissolution before analysis. Suspension medium was optimized for each analyte to obtain quantitative recoveries from fish tissue samples without matrix interferences. Nevertheless, iron recoveries higher than 46% were not found. Treatment of samples slurried in nitric acid by microwave irradiation for 15-30 s at 75-285 W permitted to achieve efficient recoveries for calcium, iron, magnesium and zinc. Further improvement in the matrix effects for iron determination was accomplished by the use of an additional step of short microwave-assisted suspension treatment. However, standard addition method was required for calcium and copper determination, being necessary hydrochloric acid as suspension medium for the last one. Although copper could not be determined in the certified reference material using microwave-assisted digestion, the accuracy of the slurry sampling method was verified for all the investigated analytes. Detection limits were 22.8 ± 8.0, 0.884 ± 0.092, 5.07 ± 0.76, 35.5 ± 0.7 and 1.17 ± 0.04 μg g⁻¹ for calcium, copper, iron, magnesium and zinc, respectively. The standard deviations obtained using slurry sampling method and microwave-assisted digestion were not significantly different, and the mean relative standard deviation of the over-all method (n = 3) of the slurry sampling method for different concentration levels was below 12%.     

Effects of amino acids on crystal growth of CaC2O4 in reverse microemulsion

Crystal growth of calcium oxalate (CaC2O4) in bulk aqueous solution, reverse microemulsion of p-octyl polyethylene glycol phenylether (OP)/iso-octyl alcohol (IOA)/cydohexane/water and above microemulsions containing different kinds of amino acids, such as aspartic acid (Asp), tyrosine (Tyr) and tryptophan (Trp) were studied. The results indicated that different crystallization types of the crystals, which were calcium oxalate monohydrate (COM), calcium oxalate dihydrate (COD) and calcium oxalate trihydrate (COT), existed in bulk aqueous solution. But CaC2O4 growth mainly paralleled with (1 01) plane of COM in reverse microemulsion because of the induction of surfactant at water/oil interface. After adding amino acids into microemulsions, the growth of CaC2O4 crystals mainly influenced by the varieties of amino acids and the pH values of the amino acid aqueous solution. When pH values of the solutions was higher than isoelectric points of amino acids, CaC2O4 crystal paralleled with (1 01) plane of COM more easily with the addition of Trp, Tyr, Asp in turn; however, when pH of the solutions was lower than isoelectric points of Trp, CaC2O4 crystal growth paralleled with (020) face of COM. It is obviously that amino acids, pH values of the solutions and surfactant played important roles in the process of crystal growth of CaC2O4 in the microemulsions. The formation mechanism of CaC2O4 was also discussed in different microemulsions at last.     

Formation of CaF and AlF in the arc plasma and spectrochemical determination of Ca and Al

Summary The influence of chemical reactions in d.c. arc plasma on the atomic emission determination of traces has been investigated. The effect of added NH₄F on the intensity of spectral lines of Ca and Al was examined. A decrease of the spectral line intensities of Ca and Al in the presence of NH₄F occurred, if the sample had not been mixed in the electrode with NH₄F. The AlF band spectrum, transition A ¹ X ¹ , was observed in absorption of the arc radiation. Further, the axial intensity distribution of Ca, Al, Ga and Ag spectral lines and of the head of the green system of CaF band, has been measured. The depressive effect of fluorine on spectral line intensities of Ca, Al, Ga and Ag has to be connected with the processes in plasma. It is suggested that the formation of fluoride radicals could take part in this effect.

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Bildung von CaF und AlF im Bogenplasma und spektrochemische Bestimmung von Ca und Al

Zusammenfassung Der Einfluß von chemischen Reaktionen im Lichtbogenplasma auf die spektrochemische Spurenanalyse wurde erörtert. Die Wirkung einer Zugabe von Ammoniumfluorid auf die Intensitäten der Spektrallinien des Calciums und Aluminiums wurde untersucht. Wenn die Probe nicht in der Elektrode mit NH₄F gemischt war, wurde eine Intensitätserniedrigung von Ca- und Al-Spektrallinien in Anwesenheit von NH₄F beobachtet. Das AlF-Bandenspektrum, Übergang A ¹ X ¹ , wurde in Absorption der Bogenstrahlung beobachtet. Die Axialverteilung der Linienintensitäten von Ca, Al, Ga und Ag wie auch der Intensität der Kante des grünen Systems der CaF-Banden wurde untersucht. Die depressive Wirkung des Fluors auf die Linienintensitäten von Ca, Al, Ga und Ag sollte mit den Vorgängen im Plasma in Zusammenhang gebracht werden. Es kann vorausgesetzt werden, daß die Bildung der Fluoridradikale bei diesem Effekt eine Rolle spielt.

     

Economic feasibility study of polyelectrolyte-enhanced ultrafiltration (PEUF) for water softening

In polyelectrolyte-enhanced ultrafiltration (PEUF), a water-soluble anionic polyelectrolyte (in this study sodium polystyrene sulfonate or PSS) is added to hard water. The calcium and magnesium bind to the polymer which has a high enough molecular weight to be rejected by an ultrafiltration membrane. The permeate is softened water. Economically, the PSS needs to be recovered from the retentate for reuse. Three methods of recovery developed in this study were addition of NaCl, Na₂CO₃ or HCl to PEUF to regenerate PSS. Of the three PEUF processes considered, NaCl/PEUF as compared to Na₂CO₃/PEUF and HCl/PEUF provided the best scheme for the water softening process. PEUF is shown in this study to be competitive with lime softening at low flow rates. The PEUF process is more expensive than ion exchange for a stream containing only hardness ions. However, PEUF becomes nearly comparable with ion exchange for a stream containing hardness ions as well as bacteria, viruses and pyrogen. The cost comparisons are based on fully continuous operations and include treatment of waste streams from each process.     

Low water/methanol permeable Nafion/CHP organic-inorganic composite membrane with high crystallinity

High methanol crossover is one of the main issues of the polyelectrolyte in direct methanol fuel cells (DMFCs). In order to decrease methanol crossover, we introduced a new method that crystallinity control was performed with incorporating CHP (calcium hydroxyphosphate) into Nafion solution. As a result, crystallinity in the composite membranes increased with CHP content compared to cast Nafion accompanying the formation of new crystalline peaks in the original amorphous region of Nafion. On the other hand, water uptake content, methanol sorption/desorption permeability and methanol crossover in the composite membranes remarkably decreased. We conclude that an increase in crystallinity due to the strong interfacial adhesion between Nafion and CHP can suppress the methanol crossover.     

Solvent‐Polymeric ISEs Tailored for Measurements in Solutions Containing Tetrabutylammonium,Cesium, and Calcium Ions

Ion‐selective electrodes are described, with membranes tailored for measurements of tetrabutylammonium ions in aqueous and formamide solutions, and for measurements of cesium and calcium ions in the presence of tetrabutylammonium. It is shown that reliable measurements of cesium ions are possible when a correction is introduced for interference from tetrabutylammonium, using Nikolsky selectivity coefficient. A novel membrane composition is described which ensures high selectivity to calcium ions over tetrabutylammonium.     

Modelling of electrolyte mixtures with application to chemical equilibria in mixtures—prototypes of blood''s plasma and calcification of soft tissues

Modelling of the biologic solutions has a great importance for basic physicochemical backgrounds of the living processes, mechanism of the diseases and drugs action, etc. The modelling of the chemical equilibria in solution that served as a prototype of the blood plasma with application to calcification of the tissues is performed. The concentrations of molecular–ionic forms containing calcium and hydrogen cations and phosphate anions in the range of ionized-calcium and total phosphorus concentrations from 0.5 to 3.0 mM and at the solution pH of 7.1–7.8 were calculated. The activities of the ionized species were described in approach to Debye–Hückel's theory. The full set of the equilibria taking into consideration dissociation of the water, phosphoric acid, formation of both inert and ionic calcium phosphates was considered. The states of calcium hydrophosphate dihydrate CaHPO₄·2H₂O (CHPD), calcium phosphate Ca₃(PO₄)₂ (CP), calcium hydrophosphate-phosphate dihydrate Ca₄H(PO₄)₃·2H₂O (CHPPD) and hydroxyapatite Ca₃OH(PO₄)₃ (HA) with respect to the boundary of the region in which they crystallise were determined. A criterion has been introduced to characterize the degree of salt supersaturation with respect to crystallisation, which is based on the concentration distance between the states of a salt in solution and at the boundary of its crystallisation. This criterion is used to provide a quantitative characteristic of the supersaturation of the phosphates and their tendency to crystallise in blood's plasma. It was established that the most soluble of the phosphates, CaHPO₄·2H₂O, is undersaturated and the other phosphates are supersaturated with respect to crystallisation. Thus, this phosphate does not take part in the calcification, and this is the source for ionized calcium in a blood plasma from the soft tissues. The role of the other phosphates in calcification of the soft tissues is decreased in the series HA>CP>CHPPD. The dependencies of the supersaturation of the solution on the pH and on the concentrations of calcium and phosphorus in a mixture are discussed.     

Investigation on NIR, coating mechanism of PS-b-PAA coated calcium carbonate particulate

Particulate calcium carbonate is treated by polystyrene (PS)/polyacrylic acid (PAA) block copolymer with varied amount. Coating efficiency is obtained by measuring the dissolve curve. The results of near-infrared (NIR) analysis reveal the thickness and structural information of the surface polymer layer. The alignment of PS-b-PAA chain on and the interaction of carboxyl with the calcite surface are deduced on the basis of X-ray photoelectron spectroscopy (XPS) results.     

Direktbestimmung von Cu, Fe, Zn, Ca, Mg und Na im Serum mittels ICP-Emissionsspektralanalyse

Zusammenfassung Die Anwendung der ICP-Emissionsspektralanalyse für die direkte Bestimmung von Cu, Fe, Zn, Ca, Mg und Na in menschlichem und tierischem Blutserum wird beschrieben. Aufgrund der hohen Anregungstemperatur in einem Plasma treten dabei die von der konventionellen Atomabsorptionsspektroskopie her bekannten chemischen Interferenzen nicht auf, so daß mit geringen Probenmengen (max. 1 ml Serum für den Nachweis dieser 6 Elemente) ein sehr empfindlicher und sehr gut reproduzierbarer Nachweis möglich ist.

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Direct determination of Cu, Fe, Zn, Ca, Mg, and Na in serum by means of ICP-emission spectrometry

Summary The application of ICP-emission spectroscopy for the determination of Cu, Fe, Zn, Ca, Mg and Na in human and animal serum is described. Due to the very high excitation temperature in a plasma the well known chemical interferences in atomic absorption spectroscopy do not appear in this technique. It is possible to carry out very sensitive and very well reproducible measurements on very small amounts of the sample (the total sample consumption for the determination of the above mentioned six elements is less than 1 ml).