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PubMed2004

Equilibrium studies on chromium(III) complexes of salicylic acid and salicylic acid derivatives in aqueous solution.

The complexes of chromium(III) ion formed by salicylic acid, SA(H(2)L), and its derivatives (H(2)L): 5-nitrosalicylic acid (5-NSA), 5-sulphosalicylic acid (5-SSA) were investigated by means of potentiometry and spectroscopy, at 25 degrees C and in ionic strength of 0.1 M KNO(3) and 0.1 M KCl, respectively. Over the acidic pH range, the coordination of Cr(III) ion to SA and its derivatives in 1 : 1 mole ratio occurs, CrL(+) type complex is formed. In the excess of ligand, the coordination of the second ligand molecule is somewhat hindered; as a result CrL(HL) type complex occurs. Their existences were verified and their formation constants were determined. At near neutral pH, CrL(OH) and CrL(HL)(OH)(-) type hydroxo complexes formed by hydrolytic equilibria and their formation constants were also defined. The stabilities of Cr(III) complexes of SA and its derivatives decrease in the following order: SA>5-SSA>5-NSA. The formation constants of Cr(III) complexes of SA and its derivatives are in comparable ranges with the corresponding complexes of the 2,x-dihydroxybenzoic acid (2,x-DHBA) of Cr(III) ion. The stabilities of SA complexes for V(IV), Cr(III) and Fe(III) ions that have similar ionic radii, increase in the order VOL<CrL(+)<FeL(+). It is worthwhile noting that the binding ability of Cr(III) to salicylate ion is four orders of magnitude higher than to transferin, which is a blood serum protein and is associated with insulin action.

Chromium↗
PubMed2005

Formation constants of chromium(III), scandium(III) and yttrium(III) complexes of some hydroxy naphthoic acids.

The complexes of chromium(III), scandium(III) and yttrium(III) formed by 1-hydroxy-2-naphthoic acid (1,2-HNA: H2L) and 3-hydroxy-2-naphthoic acid (3,2-HNA: H2L) were investigated by potentiometry and spectroscopy at 25+/-0.1 degrees C and at an ionic strength of 0.1 M KNO3 in 50% ethanol-water (v/v) medium. The stoichiometries of these three M(III) complexes formed with these hydroxy-naphthoic acids and with hydroxo ion were defined and their formation constants were determined and compared. Thus, the removing capacities of these ligands could be examined by calculating the equilibrium concentration of Cr(III) that exists in the discharge water of various industries since Cr(III) ions are the main pollutants present during waste water treatment in our city, Bursa.

Chromium↗
PubMed2000

Use of ion-selective electrodes for blood-electrolyte analysis. Recommendations for nomenclature, definitions and conventions. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Scientific Division Working Group on Selective Electrodes.

This paper will familiarize the reader with the terms used to describe the behavior of ion-selective electrodes, particularly in relation to their use in clinical chemistry for determination of blood electrolyte cations. It serves as an introduction to a series of papers dealing with important cations in blood, namely calcium, sodium, and potassium. The detailed relationships between the ion activity determined by means of ion-selective electrode potentiometry in undiluted specimens, and the total substance concentration measured by flame atomic-emission spectrometry are described by flow chart and equations. Adoption of a convention for reporting results is recommended. The Working Group on Selective Electrodes has taken into account recent revisions of IUPAC recommendations on nomenclature and selectivity coefficient determinations for ion-selective electrodes, and benefited from the experience of a member of the WG, who was also involved in the IUPAC discussions. Nomenclature for determined quantities follows previous IUPAC/IFCC joint recommendations.

Electrodes↗
PubMed2003

Multimethod characterization of the interaction of aluminum ion with alpha-ketoglutaric acid in acidic aqueous solutions.

It has recently been reported that aluminum plays a very important role in reducing the activity of Krebs-cycle enzymes and glutamate dehydrogenase in rat brain homogenate. Therefore, it is necessary to identify the aluminum binding ability with the pivotal substrate alpha-ketoglutarate in biological systems. The interactions of aluminum with alpha-ketoglutarate were studied with pH-potentiometry, cyclic voltammetry, UV-vis, 1H, 27Al-NMR and Raman spectra multi-analytical techniques in acidic aqueous solution to measure the stoichiometries and stability constants of the complexes and its keto-enol tautomerism. The alpha-ketoglutarate was found to bind Al in a bidentate manner at the carboxylate and carbonyl moieties. The mononuclear 1:1 (AlLH(-1), AIL+, AlHL2+) and 2:1 (AlL2-, AlL2H(-2)3-) species, and dinuclear 2:1 (Al2L4+) species were found in acidic aqueous solution. Meanwhile, Al can promote alpha-KG tautomerize to its enolic-structure compounds in solutions. These findings may help to further understand the influence of Al on GDH enzyme reactions in biological systems.

Aluminum↗
PubMed2005

Electrochemical study of the assisted transfer of silver ion by 1,5-cyclooctadiene at the 1,6-dichlorohexane/water interface.

The transfer of Ag+ ion across a polarized 1,6-dichlorohexane/water interface assisted by an alkene or olefin ligand, 1,5-cyclooctadiene (COD), was studied by cyclic voltammetry. Even if COD was absent from the organic phase, Ag+ ion gave a reversible voltammetric wave, and the formal potential of the non-assisted ion-transfer at the 1,6-dichlorohexane/water interface was determined from the reversible half-wave potential. By the addition of COD to the organic phase, the reversible half-wave potential shifted to more negative potentials with increasing concentration of COD. The concentration dependence of the half-wave potential revealed that the transfer of Ag+ ion is assisted by the formation of 1:1 and 1:2 Ag+-COD pi-complexes in 1,6-dichlorohexane with overall formation constants of (2.1 +/- 0.2) x 10(3) M(-1) and (7.8 +/- 1.0) x 10(3) M(-2), respectively. The formal potential and the formation constants coincide well with those obtained by the potentiometry of Ag+ ion in aqueous and organic media with a Ag electrode.

Alkadienes↗
PubMed1982

Antibiotic compounds and enamel demineralization. An in vitro study.

Discoloration, pigmentation and even caries-like lesions have been reported in teeth subsequent to per oral administration of antibiotics. The present in vitro study examines the possible medicament/tooth reaction by exposing plane, polished enamel surfaces to aqueous solutions or oily suspensions of various commonly used penicillin compounds, or to solutions of tetracycline sodium. The teeth were examined by visual inspection, microhardness tests, scanning electron microscopy and microradiography. pH and [Ca2+] of the test solutions were analyzed by potentiometry. Surface or subsurface lesions and a decline in microhardness were found in (most) enamel specimens exposed to aqueous solutions of the medicaments. Similar changes were found in test specimens immersed in deionized water, while saliva, oily suspensions of the medicaments and aqueous solutions made from ordinary Ca-penicillin had no adverse affect on the enamel. The most serious destruction was seen in enamel specimens submerged in watery solutions made from effervescent (citrate-containing) Ca-penicillin, or from tetracycline. A slight decline in pH was observed in the aqueous solutions during the experiment. The calcium ion concentration did not increase parallel to enamel destruction.

Dental Enamel↗
PubMed1996

The need for protein containing quality control materials for blood pH and electrolyte analyzers.

In clinical chemistry quality control refers to monitoring of precision and accuracy of the performance of analytical methods. Calibration solutions and (matrixed) control solutions are used in transferring accuracy between definitive method, reference method and field methods. For this purpose aqueous (protein-free), protein-containing and serum-based types of quality control materials having different matrices are available. Here are presented differences in behaviour between aqueous (protein-free) and protein-containing materials. Potentiometry with an electrochemical cell is an often used field method to determine pH and activity of electrolytes with an Ion-Selective Electrode (ISE). Basically, measured e.m.f.'s of calibrators and sample are translated into the activity of the ionic species of the sample by means of the Nernst equation. Besides the standard e.m.f. (E(zero)) of the electrochemical system, the measured e.m.f. includes the ISE-membrane e.m.f. (EISE) and depends on electrolyte type and its concentration and Eij depends on the composition and geometry of the salt bridge. Both EISE and Eij depend on the sample matrix. Protein-containing samples cause a negative bias on the e.m.f. at the liquid junction and a positive bias at the ISE. When EISE and Eij are compared to the mV span of the reference interval, the effects are large for Ca2+, Na+ and Cl-. Exactly the same effects exist for H+, K+, Li+ and Mg2+ but the inaccuracy is less critical for these ions. It may be concluded that only protein containing controls can detect an error that occurs only with measurements on plasma specimens. In practice this means that calibration is checked with protein-free solutions, but that measurements in plasma are best checked with protein-containing solutions.

Acid-Base Equilibrium↗
PubMedDate not supplied

Assessment of a commercial pH electrode used with blood.

With the recent development of ion selective electrodes, potentiometry has entered a new era of usefulness ranging from pollution control to the investigation of single cells. Routine use of these sensors in the clinical environment is severely restricted due to errors associated with the reference electrode. Due to the Nernstian response of the potentiometric sensors the entire reference and ion selective electrodes are housed within a thermostatically controlled heater assembly. A clinically based thermostatically controlled combined ion selective/reference electrode system is discussed and a simple algorithm is presented to correct for the additional liquid junction potential encountered when monitoring biological solutions.

Blood Gas Analysis↗
PubMed2003

Serum fluoride levels in a group of Egyptian infants and children from Cairo city.

In this study, the authors investigated fluoride levels in the serum of infants and children (n = 296) and in the breast milk from nursing mothers (n = 60) in Cairo city. Their goal was to evaluate the necessity and safety of implementing a fluoride supplementation program. The authors used an ion-selective electrode to assay fluoride by direct potentiometry. Also, 2- to 12-yr-old participants underwent clinical dental examinations to detect caries and/or fluorosis. The serum fluoride levels of infants were significantly lower than levels found in preschoolers and school-age children. Serum fluoride correlated positively with age; it was significantly lower during the 1st than 2nd yr of infancy (p = 0.005). Breast or formula feeding did not influence serum fluoride status; the fluoride levels in mothers' milk reflected the serum levels of their own infants. Dental examinations revealed that 81% of the children had caries, whereas there was no evidence of fluorosis. Serum fluoride levels did not vary with the presence or absence of dental caries and did not correlate with the number of decayed, missing, or filled teeth. Gender did not influence serum fluoride expression, and the percentile values were unrelated to height, weight, or head circumference. These findings suggest the necessity and safety of improving the fluoride consumption levels of infants and children in Cairo city. Wider-scale studies are needed to obtain better insight into the problem.

Breast Feeding↗
PubMed1999

Influence of coprecipitation and interactions with anionic surfactants on the activity of plant phospholipase D.

The effects of two surfactants (sodium dodecyl sulfate and sodium dodecyl dioxyethylene sulfate) of similar structure but differing water solubility (of their calcium salts) on the enzymatic activity of cabbage phospholipase D have been studied. The solubility difference is insignificant because the two surfactants activate phospholipase D similarly. To elucidate the mechanism of their influence on the enzyme, the phase behavior in the reaction media and the interactions of the surfactants with the enzyme were investigated by potentiometry and by light scattering and UV spectroscopy. Calcium dodecyl dioxyethylene sulfate (which is more soluble in water than calcium dodecyl sulfate) precipitates in the presence of phosphatidylcholine, the substrate of the enzymatic reaction. In the reaction media phospholipase D was involved into a precipitate consisting of calcium salts of the surfactants and phosphatidylcholine that might be interpreted as its immobilization. In addition, the surfactants were adsorbed on the enzyme, unfolding the globular enzyme molecule due to electrostatic repulsion between adsorbed surfactant anions. The observed increase in the functional activity of phospholipase D is accounted for by transfer to an optimal tertiary structure for the enzyme molecule in the course of consecutive conformational transitions induced by the surfactants.

Brassica↗
PubMed1999

[Synthesis and investigation of protonation properties and lipophilicity of some new quinazolone-3-carboxylic acid derivatives].

Several new quinazolone-carboxylic acid derivatives as potential NMDA and AMPA receptor antagonists have been synthesized, and the protonation properties and lipophilicity of some representative molecules have also been studied. The protonation macroconstants (logK) of 4(3H)-quinazolone (Q0) and two 2-methyl-4-oxo-3H-quinazoline-3-carboxylic acids (Q1, Q2) were determined by pH-potentiometry. The acid-base chemistry of Q1 and Q2, where protein-bindings take place in an overlapping fashion, was described in terms of protonation microconstants (logk) as well. Microspeciation was carried out by UV-pH titration and deductive method. Microspeciation revealed remarkable differences between the two homologue compounds (Q1 and Q2), namely insertion of a second methylene moiety into the aliphatic acid side-chain reversed the predominantly zwitterion-involved protonation pathway into neutral form-involved one. Lipophilicity of our molecules was described by the octanol-water partition coefficients. The apparent partition coefficients of Q1 and Q2 were determined by shake-flask method and converted into true logP values using the protonation microconstants. The unexpected differences between their true logP values were explained, similarly to the different protonation pathways with conformational preferences and formation of intramolecular interactions. Out of the other 15 monoprotic quinazolone compounds the lipophilicity of 10 molecules (Q8-Q17, experimental set) was determined by RP-TLC method with the help of a calibration set consisting of 12 standard molecules, five quinazolones (Q3-Q7, determined by shake-flask method) and seven pyrido[1,2a]pyrimidines (PP1-PP7). The obtained logP values proved mostly the expected structure-property relationships. These physico-chemical investigations are pieces of predictive information for the pharmacokinetics of our compounds. These are also discussed in the paper.

Carboxylic Acids↗
PubMed2001

Capillary ion electrophoresis of endogenous anions and anionic adulterants in human urine.

Normal human urine contains many anions and cations. Ionic concentrations in urine have classically been determined by spectrophotometry of color reactions, flame emission spectrophotometry, atomic absorption spectrophotometry, high performance liquid chromatography, or potentiometry with ion-specific electrodes. Capillary ion electrophoresis (CIE) is a form of capillary electrophoresis which uses the differential electrophoretic mobility of ions to perform a separation of an ionic mixture. Various salts can be added to urine specimens to abnormally elevate ionic concentrations and interfere with either immunoassay urine drug screening procedures or gas chromatographic/mass spectrometric confirmation techniques. Application of CIE for the direct detection of endogenous anions and anionic adulterants in human urine specimens was the purpose of this investigation. CIE was performed using a Waters Quanta 4000 Capillary Electrophoresis System with either direct or indirect ultraviolet absorption detection at 254 nm. CIE of 30 random normal urine specimens and 21 urine specimens suspected of adulteration was performed. Duplicate aliquots were assayed by CIE and by colorimetric technique for nitrite. Sixteen specimens had elevated concentrations of nitrite and/or nitrate. The correlation coefficient between nitrite CIE and colorimetric results was 0.9895. Three specimens had detectable concentrations of chromate and were suspected of being adulterated with "Urine Luck," an adulterant found to contain chromate. Two specimens suspected of being adulterated with bleach were found to only contain chloride, sulfate, and phosphate. CIE is applicable to forensic analysis of urine anion concentrations. CIE can easily quantitate numerous endogenous anions and offers a method to detect and/or confirm anion adulteration of urine specimens.

Adult↗
PubMed1979

[The complexing ability of gangliosides for Ca2, I. Influence of mono- and divalent cations and of acetylcholin (author's transl)].

The binding of Ca2 to single ganglioside species (GGtet1NeuAc, GGtet2aNeuAc, GGtet 3aNeuAc), to their free, reducing sialyl-oligosaccharides and to ganglioside mixtures from chicken brain was investigated by means of ion-sensitive electrodes (potentiometry). Unlike the sialyl-oligosaccharides and free N-acetylneuraminic acid, gangliosides were found to possess two different modes of binding for Ca2, depending on the total concentration of Ca2. This was mainly indicated by a release of up to 75% of previously bound Ca2 after raising the total Ca2-concentration above a critical level of about 5--9 X 10(-5)M. Addition of acetylcholin (9mM), Li, K, and Na, respectively, caused a release of Ca2 from ganglioside-Ca2-complexes (0.1mM Ca2, 0.1mM ganglioside-NeuAc) in the sequence: acetylcholin : Li : K : Na = 4 : 3 : 1 : 1 composed on molar basis (9mM).

Acetylcholine↗
PubMed2001

[Electrochemical methods of control of iodine contents in drinks].

The simple and express methods of determination of iodide ions (0.01-0.20 mg/decimeter3) in iodine-enriched drinks by potentiometry and inversion voltamperometry were developed. The studies on influencing a storage time hermetically packaged carbonated beverages, a storage time of the depressurized drinks, stuff of ware on the contents of iodine in drinks are held.

Carbonated Beverages↗
PubMed1964

Life and space.

The studies dealing with the detection of life on planets and in space will have two periods. The first period will be associated with the application of automatical devices, which will detect living creatures, whereas the second, more late, period will be concerned with the investigations provided by man himself. In these studies one should proceed from the idea of life on the Earth, and, consequently, look for living creatures containing no water, no carbon dioxide, etc. only after obtaining negative results in searching for creatures similar to those living on the Earth. The whole course of "chemical evolution" on the Earth proves the necessity of the detection on other planets of heterotrophic microorganisms at first, and only afterwards to look for specialized forms, i.e. chemo- and photoautotrophs. It is usually underestimated that as a result of adaptation to certain ecological conditions existing on planets living creatures may appear, which will distinctly differ in their biological properties from terrestrial forms. At present there is no faultless investigation which is able to prove to existence of cosmobionts in meteorites. The appropriate experiments convince us that soil bacteria. may penetrate into the central parts of meteorites, which have been lying in the ground. Samplings at high altitudes with the aid of aerostats or the rockets are difficult to provide because of the possibility of pollution of samples by terrestrial microbes. It is therefore necessary to elaborate special devices and new methods for sampling. The most perfect instrument for the detection of microorganisms will be a device, which will record the multiplication rate of microbes in the liquid media simultaneously by means of different methods: manometry, nephelometry, potentiometry and the determination of radioactive carbon dioxide which is extracted during the breakdown of organic substances.

Atmosphere↗
PubMed1963

Perspectives for the development of exobiology.

In the majority of the papers dealing with the status and prospects of the development of exobiology a theoretical analysis predominates. More attention should be given to the discussion of methods and experiments carried out at the present time or planned for the near future. In investigating life in the cosmos, we attach considerable interest to detection of compounds specific to living beings, in particular, organic compounds of phosphorus, porphyrins, amino nitrogen and others. In searching for microorganisms on other planets and in interplanetary space the greatest danger is that, as a result of errors in technique, the investigator will detect earthly microorganisms which have invaded and reproduced in the nutrient mediums used. Information on the vitality of microbes detected in the ground taken in the zone of eternal frigidity, in big pieces of rock salt, in meteorites, etc. confirms these apprehensions. Initially, search for heterotrophic bacteria should be carried out, then for phototrophic, denitrifying, sulfate-reducing, nitrogen-fixing microorganisms, as well as bacteria oxydizing sulfur, iron, methane and hydrogen. Instruments for detection of cosmobionts can be based on nephelometry, potentiometry, manometry and on the use of carbon labelled compounds and added to the nutrient medium. Investigations elucidating the influence of low and high temperatures, vacuum, and radiation on living cells are possible to carry out on earth and therefore are most accessible to exobiology. They give interesting results and in some degree make it possible to approach the study of the conditions to which life would be exposed in space. The sterilization of space ships is of paramount importance for further exobiological investigations. Under space conditions microbes will not completely perish on the space ship surface and, therefore, careful sterilization is necessary. The assertion that earth microbes, having reached the lunar surface, will not be able to develop is not free of objections. To carry out sterilization so that space ships will not contain dead bodies of microbes is impossible. Therefore, the wish expressed sometimes that "carcasses" of microbes should not be conveyed onto other planets is practically unrealizable.

Containment of Biohazards↗
PubMedDate not supplied

Protonation and complex formation of 5-sulfosalicylate in NaCl, CaCl2 and MgCl2 aqueous media. Speciation in synthetic seawater.

The binding capacity of 5-sulfosalicylic acid (ssa) towards cationic macro-components of natural waters has been investigated in different ionic media (NaCl, MgCl2 and CaCl2 aqueous solutions) and in the ionic strength range 0 < or = I < or = 1 mol dm-3. In order to contribute to the speciation of this multi-sites ligand, measurements have been carried out also in a synthetic seawater (SSWE) containing the major components of seawater (Na+, K+, Ca2+, Mg2+, Cl- and SO4(2-)). Measurements have been performed by potentiometry ([H+]-glass electrode), at t = 25 degrees C. A critical analysis on the experimental and literature data is also given.

Benzenesulfonates↗
PubMedDate not supplied

On the complex formation equilibria between iron (III) and sulfate ions.

The equilibria have been investigated at 25 degrees C in 3 M NaClO4 using potentiometry, glass and redox Fe3+/Fe2+ half-cells, and UV optical absorptiometry. The concentration of the reagents was chosen in the intervals: 10(-4) < or = [Fe(III)] < or = 5.10(-3) M, 0.01 < or = [SO4(2-)]tot < or = 0.65 M. The value of [H+] was kept at 0.1 M or more to reduce the hydrolysis of the Fe3+ ion to less than 1%. Auxiliary constants, corresponding to the formation of Fe(II)-sulfate complexes and to the association of H+ with SO4(2-) ions, were taken from previous determinations. The experimental data could be explained with the equilibria [formula: see text] Equilibrium constants at infinite dilution, log beta 101 degrees = 3.82 +/- 0.17, log beta 102 degrees = 5.75 +/- 0.17 and log beta 111 degrees = 3.68 +/- 0.35, have been evaluated by applying the specific interaction theory.

Ferric Compounds↗