Electrophoretic Behaviour of 34 Organic Acids on Impregnated Strips

Abstract

Electrophoretic behaviour of 34 organic acids on calcium sulphate impregnated papers has been studied. The 19 binary separations in aqueous sodium chloride and sodium sulphate solutions and distilled water have been achieved.     

Chromatographic Studies of 34 Organic Acids on Papers Impregnated with Hydroxides of Aluminium and Cadmium

Abstract

Papers impregnated with aluminium hydroxide and cadmium hydroxide have been used for the chromatographic separation of organic acids exist in various biological materials, soil and water. The following important separations: cinnamic acid from hippuric acid; benzoic and m-nitrobenzoic acids from gallic, β-naphthalene acetic, β-naphthoxy acetic, phthalic, quinic and salicylic acids; and salicylic acid from citric, cis-aconitic, malic, quinic, tartaric and trans-aconitic acids can be achieved in common electrolytes (Cd(NO₃)₂, KI, NaCl, NH₄Cl) solution.

Hydroxides¹ show amphoteric behaviour i. e. they may exchange either cations or anions depending upon the pH of the solution, and t h i s may be shown by the following ionic equilibria.     

Quantitative Separation of Citric Acid From Trichloroacetic Acid on Plates Coated with Calcium Sulphate Containing Zinc Oxide

Abstract

Thin-layer chromatographic behaviour of ten acids on coating of calcium sulphate containing ammonium molybdate, aluminium oxide, calcium carbonate, copper sulphate, ferric chloride, magnesium sulphate, phthalic anhydride, titanium oxide, zinc oxide etc. has been studied. Quantitative separation of citric acid from trichloroacetic acids has been achieved on calcium sulphate containirig zinc oxide in ethyl acetate. Herbicide, trichloroacetic acid can be separated from plant growth regulators such as indole-3-acetic, β-naphthaleneacetic and β-naphthoxy acetic acids and from other organic acids.     

Separation of Some Herbicides by Two Dimensional Thin Layer Chromatography on Calcium Sulphate

Abstract

Two dimensional thin layer chromatography is being used for the last forty years¹ and now it has became an important tool for the separations of varying complexity. Various coating materials such as alumina, cellulose, kieselgel G, silica gel, silufol and polyamide have been used and studied for the separation of organics such as alkaloids, amino acids, carbohydrates, fatty acids, glycopeptides, glycolipids, lipids, phospholipids, pigments, protiens, peptides, pesticides, steroids and inorganics such as oxy acids of phosphorus, metal ions. Our previous work^{2′3′4′5′6} shows that calcium sulphate coated paper and glass plates have a great separation potential for herbicides containing carboxyl group. Therefore now an attempt is made to test the separation potential of calcium sulphate alone and calcium sulphate containing aluminium oxide active neutral, calcium carbonate and p-dimethylaminobenzaldehyde for some nerbicides by two dimensional thin layer chromatography. The results obtained are discxissed in this paper.     

Thin-Layer Chromatographic Studies of 30 Organic Acids on Calcium Sulphate

Abstract

Thin layer chromatographic behaviour of 30 organic acids on coatings of calcium sulphate and calcium sulphate containing charcoal, p-dimethyl-aminobenzaldehyde, flyash, silica gel G etc. has been studied. Farm chemicals: plant growth regulators (benzoic, cinnamic, gallic, β-naphthalene acetic, β-naphthoxy acetic and indole-3-acetic acids) and herbicides (phenoxy acetic acid) have been separated from one another and from several other organic acids.     

New Inexpensive and Selective Sorbent Phases for Rapid Thin Layer Chromatographic Analysis of Metal Ions

Abstract

New sorbent phases have been developed by impregnating silica gel G with different inorganic salts for the analysis of metal ions by thin layer chroma to graphy in carboxylic acids media. Thin layers prepared from silica gel G impregnated with ammonium chloride or barium nitrate show the unusual selectivity towards metal ions in comparison to the thin layers prepared from plain silica gel G or silica gel impregnated with silver nitrate or aluminium nitrate. Many qualitative separations     

Improved Calcium Ion-Selective Electrode Based on a Neutral Carrier

Abstract

The performance of a liquid-membrane electrode using a synthetic, neutral carrier in o-nitro-phenyl-n-octyl-ether as membrane component in a PVC matrix, in the presence of sodium tetra-phenyl-borate, is described. Selectivities, working range, lifetime and anion interference are discussed. The electrode makes possible the measurement of calcium ion activities in the range 10^?1M to 10^?6M in unbuffered and in the range 10^?1M to 10^?8M in calcium buffered systems respectively. The selectivities of calcium over protons, magnesium, sodium and zinc are 25,000, 26,000, 2,800 and 7,100, respectively, and are far superior than those reported for other calcium sensors.     

A Calcium Ion-Selective Electrode Based on a Neutral Carrier

Abstract

The performance of a liquid-membrane electrode using a synthesized ligand in p-nitroethylbenzene as membrane component is described. Selectivities, working range, lifetime, pH-dependence, and dependence on the dielectric constant of the membrane solvent are discussed. The electrode makes possible the measurement of calcium ion activities in the range of 10^?1 M to 10^?5 M In unbuffered systems with a selectivity of calcium over sodium and magnesium of 175 and 33,000 respectively. The selectivity constants of the cell discussed are heavily influenced by the dielectric constant of the membrane solvent.     

Direct Spectrophotometric Determination of Calcium in Human Serum and Cerebrospinal Fluids with Amino G Acid Chlorophosphonazo

ABSTRACT

A novel spectrophotometric method based on amino G acid chlorophosphonazo (AGCPA) has been developed for measuring calcium in human serum and cerebrospinal fluids. The effects of experimental factors including pH, reagent concentrations, and interfering species on calcium determinations were investigated. In a neutral reaction media of pH 7.0, AGCPA reacts rapidly with calcium to form a stable and greenish blue complex, whose absorption maximum is at 670 nm. The molar absorptivity (?) of the complex is 7.2x10⁴ 1 mol^?1cm^?1, and the molar ratio of calcium to AGCPA in the complex is found to be 1:2. Beer's law is obeyed over the range 0.02-0.8 μg ml^?1 of calcium. No interferences were observed from the commonly coexisting species present in serum and cerebrospinal fluids. Compared to the reported and currently often used methods based on o-cresolphthalein complexone, arsenazo III and methylthymol blue, the proposed method in this work provides better analytical characteristics such as high sensitivity, good selectivity and neutral reaction media. In addition, the present method is simple and can be applied to the direct determination of calcium in human serum and cerebrospinal fluid samples with satisfactory results.     

Interfacial Shear Rheology of Calcium Naphthenate at the Oil/Water Interface and the Influence of pH,Calcium, and in Presence of a Model Monoacid

In this article, the interfacial shear rheological properties of calcium naphthenate with a model tetraacid at the chloroform/xylene-water interface has been investigated as a function of aqueous pH, calcium concentration and monoacid concentration. The experiments are carried out using an interfacial rheology system with an electro commutated motor, direct strain oscillation and a biconical bob geometry. The model tetraacid used, BP10, has previously been shown to have similar bulk and interfacial properties as a narrow group of tetraprotic, so-called Arn acids, and these acids are known to be responsible for formation of hard deposits during oil recovery. A great increase in the elastic modulus was observed around pH 6.2, which is in agreement with observations from oil fields with calcium naphthenate deposition problems. The gel strength and elastic nature is highest around the gelation onset, believed to be due to a bilayer-like conformation of the tetraacid generating a densely packed interface with high cross-linking density and possible film growth. As a function of calcium concentration, both a reduction of the gel strength and slower gel formation was observed when decreasing the calcium concentration from 10 to 4 mM. Myristic acid, a linear C14 fatty acid, was employed as a model for indigenous monoacids and the influence onto the viscoelastic properties of the Ca²⁺-TA film was studied as a function of myristic acid concentration at pH 8.0 and 6.5. A great reduction of both the gel strength and elasticity was obvious in the range of 100 to 1000 higher monoacid than tetraacid concentration. This is however typical indigenous acid concentrations for an acidic crude oil, and may indicate that indigenous monoacids have the ability to act as indigenous inhibitors towards formation of calcium naphthenate. This could explain why some Arn-containing acidic crude oils have deposition problems while others do not. Moreover, all parameters should be taken into account when predicting the deposition risk for a given crude oil, such as concentrations of Ca²⁺, Arn, monoacids and other indigenous acids.     

新型钙离子选择电极测定血清中总钙

本文研制成一种新型开链酰胺的PVC膜钙离子选择电极。应用于临床,测定了85个血清样品中的总钙,其结果与AAS法和比色法的测定结果相一致,该电极在对血清的测量中显示出良好的重现性、稳定性和准确性。     

肽钙螯合物VGLPNSR-Ca的结构表征及在Caco-2单细胞层的促钙吸收性能

以Val-Gly-Leu-Pro-Asn-Ser-Arg（VGLPNSR）和氯化钙为原料制备了肽钙螯合物VGLPNSR-Ca.采用紫外光谱（UV）、X射线衍射（XRD）、扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）、高分辨质谱等手段对VGLPNSR-Ca的结构特性进行了分析，并通过体外Caco-2单细胞层模型模拟研究了VGLPNSR-Ca在肠道中的促钙吸收能力.紫外光谱、X射线衍射、扫描电子显微镜分析结果显示，VGLPNSR-Ca形成了一个稳定的肽钙螯合物.红外光谱表明VGLPNSR-Ca的螯合位点主要为氨基的氮原子和羧基的氧原子，结合高分辨质谱分析，VGLPNSR与钙离子的螯合反应主要由氮端Val、碳端Arg及氨基酸Asn参与.根据上述分析结果预测了VGLPNSR-Ca的分子结构.此外，VGLPNSR-Ca在Caco-2单细胞层中的钙吸收率为31.97%，是氯化钙的钙吸收率的2倍多，证明了VGLPNSR-Ca能有效提高钙的生物利用率.     

A Neutral Carrier Membrane Calcium-Sensitive Electrode with Wide Working pH Range

Abstract

A poly(vinyl chloride) (PVC) membrane calcium-sensitive electrode based on a new type of synthetic carrier 1,7-di[2-(1-phenylazo)naphtyl]-1,4,7-trioxaheptan is introduced. This electrode exhibited Nernstian response over the concentration range 1.0×10^?1 - 3.0×10^?8 mol/L Ca²⁺ with a slope of 28.8 mV/pCa in calcium ion buffer solutions. The detection limit for calcium ion was 1.0X10^?8 mol/L. The response time varied from 10 to 30 seconds. The working pH range for the electrode was 3.5 - 12.3 when the concentration of Ca²⁺ was 10^?3 mol/L. The lifetime of the electrode was proved to exceed 8 months. It was applied successfully in the determination of calcium ion in river water, mineral water and cosmetic. A method for the determination of total calcium in urine was developed.     

The Crystal Structures of Two Calcium(II) Complexes with Pyrazine- 2,6-Dicarboxylate and Water Ligands

The structure of catena-{bis[(μ-aqua)(diaqua)(pyrazine-2,6-dicarboxylato-O,N-μ-O')](calcium(II)} consists of dimeric units composed of two calcium(II) ions, two ligand molecules and six water molecules. The calcium ions are bridged by two bidentate oxygen atoms, each donated by one carboxylic group of the ligand. The Ca(II) ion is also coordinated by one oxygen atom of the second carboxylate group and the hetero-ring nitrogen atom belonging to the same ligand molecule. Both calcium ions in a dimer are bridged to the Ca(II) ions in adjacent dimers by a pair of water molecules forming infinite molecular ribbons. In addition, each Ca(II) ion is coordinated by three water molecules; one of them is used for bridging the adjacent dimer. The coordination polyhedron around the Ca(II) ion is a pentagonal bipyramid with two apices above and one apex below the equatorial plane. The same molecular pattern is observed in the structure of catena-{bis[(μ-aqua)(diaqua)(pyrazine-2,6-dicarboxylato-O,N-μ-O')](calcium(II)} dihydrate which, in addition, contains two solvation water molecules per unit cell. In both compounds the molecular ribbons are held together by extended systems of hydrogen bonds.     

The Crystal and Molecular Structure of a New Calcium(II) Complex with Pyridine-2,6-DiCarboxylate,Water and Nitrate Ligands

Crystals of {catena-[μ-aqua-O]bis[μ-pyridine-2,6-dicarboxylato-O,N-O']} {[monoaqua-nitrato, O-calcium(II)] [diaqua-calcium(II)]} contain dimeric units composed of two calcium(II) ions and two ligand molecules, in which the calcium ions are bridged by two bidentate oxygen atoms, each donated by one carboxylic group of the ligand. The Ca(II) ion is also coordinated by one oxygen atom of the second carboxylate group and the hetero-ring nitrogen atom belonging to the same ligand molecule. The dimers form molecular chains through protons situated at the symmetry centers halfway between the non-bridging carboxylate oxygen atoms. In addition, both calcium ions in the dimer are bridged to calcium ions in adjacent dimers - each by a pair water oxygen molecules giving rise to two-dimensional molecular sheets. Coordination of the Ca ion in the dimer is completed either by two water oxygen atoms or by one water oxygen atom and an oxygen atom donated by a nitrate group. The molecular sheets are held together by an extended system of hydrogen bonds.     

The Crystal Structures of Two Polymorphic Forms of a Calcium(II) Complex with Pyridine-2,6-Dicarboxylate,Water and Nitrate Ligands

The calcium (II) complex: catena-mono(μ-pyridine-2,6-dicarboxylato-O:O:N;O') (diaqua-O)mono (nitrato-O:O)calcium(II) exists in two polymorphic forms. Each contains molecular ribbons in which adjacent Ca(II) ions are bridged by monodentate oxygen atoms donated by one carboxylate group of the pyridine-2,6-carboxylate ligand. Apart from this bridging oxygen atom, the Ca(II) ion is coordinated by two carboxylate oxygen atoms contributed by a different carboxylate group of the ligand molecule, the heteroring nitrogen atom, two water oxygen atoms and two oxygen atoms of a nitrate group giving rise to a distorted pentagonal bipyramid as a coordination polyhedron. The structures of the polymorphic modifications differ in the way in which the nitrate ligands are oriented with respect to the equatorial planes of the adjacent Ca(II) coordination polyhedra: the trans mode in the α-form; the cis mode in the β-form. In both forms, hydrogen bonds operate between the carboxylate oxygen atoms, water oxygen atoms and nitrate oxygen atoms.     

Determination of Calcium and Magnesium in Cardiac and Skeletal Muscle by Atomic Absorption Spectroscopy Using Stoichiometric Nitrous Oxide-Acetylene Flame

Abstract

A highly sensitive technique is reported for the determination of calcium and magnesium contents in demoisturized, defatted and     

Molecular Chains in the Crystals of a Calcium(II) Complex with Pyridine-3,5-Dicarboxylate (Dinicotinate) and Water Ligands

The crystal of pentaqua (catena-pyridine-3,5-dicarboxylato-O,O) calcium(II) contain zigzag molecular chains composed of Ca ions linked by two bridging oxygen atoms, each donated by one carboxylate group [Ca-O1 2.353(2) Å, Ca-O3^III 2.334(1) Å]. The Ca ions, the ligand molecules and one water oxygen atom coordinated by each metal ion [Ca-O5 2.410(2) Å] are coplanar. The coordination of the Ca ion is completed by four other water oxygen atoms situated above and below the plane of the chain [Ca-O6 2.475(1) Å, Ca-O7 2.371(2) Å]. The coordination number of the calcium(II) ion is seven. The water molecules act as donors in a system of hydrogen bonds.     

Influence of Calcium Sources on Microbially Induced Calcium Carbonate Precipitation by Bacillus sp. CR2

Stimulation of microbially induced calcium carbonate precipitation (MICCP) is likely to be influenced by calcium sources. In order to study such influences, we performed MICCP using Bacillus sp. CR2 in nutrient broth containing urea, supplemented with different calcium sources (calcium chloride, calcium oxide, calcium acetate and calcium nitrate). The experiment lasted 7 days, during which bacterial growth, urease activity, calcite production and pH were measured. Our results showed that calcium chloride is the better calcium source for MICCP process, since it provides higher urease activity and more calcite production. The influences of calcium sources on MICCP were further studied using Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. These analyses confirmed that the precipitate formed was CaCO₃ and composed of predominantly calcite crystals with a little amount of aragonite and vaterite crystals. The maximum yield of calcite precipitation was achievable with calcium chloride followed by calcium nitrate as a calcium source. The results of present study may be applicable to media preparation during efficient MICCP process.     

The π Complexation of Calcium inside the meso-Octaethylporphyrinogen Tetraanion Cavity

A possible binding cavity for alkali and alkaline earth metal ions: The synthesis and structural characterization of the complex shown, which was obtained from meso-octaethylporphyrinogen and calcium metal, shows that the porphyrinogen functions as a binucleating ligand with four η³-azaallyl binding sites for two calcium cations.