Concentrations Of Chloride Anions Research Articles

Colorimetric Detection of Cyanide with a Chromogenic Oxazine

[reaction: see text] We have designed a chromogenic oxazine for the colorimetric detection of cyanide. Indeed, the [1,3]oxazine ring of our compound opens to form a 4-nitrophenylazophenolate chromophore in response to cyanide. This quantitative chromogenic transformation permits the detection of micromolar concentrations of cyanide in water. Furthermore, our chromogenic oxazine is insensitive to the presence of large concentrations of fluoride, chloride, bromide, or iodide anions, which are generally the principal interferents in the colorimetric detection of cyanide.

Ramified gold deposits at the gas ∣ liquid interface

Ramified gold films have been prepared by electroless deposition at the surface of aqueous mixtures of hydrogen tetrachloroaurate and potassium chloride, covered by a positively charged dimethyldioctadecylammonium monolayer. We show that increasing the concentration of chloride anions in the subphase induces a progressive modification of the morphology of the gold deposits, from compact to finely ramified patterns. Both the nature of the dissolving electrode and the presence of the positively charged surfactant monolayer have a profound effect on the structure and the growth mechanism of such ramified deposits.

Nitrite-catalase interaction as an important element of nitrite toxicity.

It was established that nitrite in the presence of chloride, bromide, and thiocyanate decreases the rate of hydrogen peroxide decomposition by catalase. The decrease was recorded by the permanganatometric method and by a method of dynamic calorimetry. Nitrite was not destroyed in the course of the reaction and the total value of heat produced in the process was not changed by its presence. These facts suggest that nitrite induces inhibition of catalase with no change in the essence of the enzymatic process. Even micromolar nitrite concentrations induced a considerable decrease in catalase activity. However, in the absence of chloride, bromide, and thiocyanate inhibition was not observed. In contrast, fluoride protected catalase from nitrite inhibition in the presence of the above-mentioned halides and pseudohalide. As hydrogen peroxide is a necessary factor for triggering a number of important toxic effects of nitrite, the latter increases its toxicity by inhibiting catalase. This was shown by the example of nitrite-induced hemoglobin oxidation. The naturally existing gradient of chloride and other anion concentrations between intra- and extracellular media appears to be the most important mechanism of cell protection from inhibition of intracellular catalase by nitrite. Possible mechanisms of this inhibition are discussed.

Short-chain carboxylates in high-temperature ore fluids of W-Sn deposits in south China.

The Xihuashan, Dangping and Piaotang deposits in the Jiangxi Province, south China can be considered as typical high-temperature hydrothermal quartz vein-type W-Sn mineralization, that is temporally and spatially related to Mesozoic S-type granite. Microthermometric studies of fluid inclusions in various minerals from these deposits were conducted to obtain homogenization temperature and salinity data. Major organic and inorganic aqueous components of the fluid inclusions were extracted by a crush-leaching, and concentrations of short-chain carboxylate (formate, acetate, propionate, oxalate), fluoride, chloride and sulfate anions in the leachates were determined using ion chromatography. The results indicate the presence of formate and acetate as well as minor amounts of oxalate and propionate in leachates, and the dominance of formate over other carboxylates. The molar ratio of acetate to formate appears to be a potential indicator of the redox state for the ore fluid system. Oxygen and hydrogen isotopic data show that inclusion water in quartz is mainly magmatic in origin. It is postulated that the dissolved carboxylate anions in the ore fluids for the deposits probably were generated by the breakdown of kerogen in “primitive sedimentary rocks” during the formation of S-type granites. The possibility of inorganic synthesis of the carboxylate species in a C-H-O system can not be excluded.

Aggregation Kinetics and Fractal Structure of γ-Alumina Assemblages

Suspensions of a variety of different aluminum oxides have previously been shown to require very high concentrations of chloride and nitrate anions (>0.5 M) to induce rapid aggregation. This high stability has been accredited to the presence of surface forces considered to be due to the formation of highly charged Al13 polymeric species at slightly acidic pH's and aluminum oxyhydroxide gel formation under alkaline conditions. The effect of this stability on the structure of the resulting aggregates is investigated here using well-established static light-scattering techniques. Power law behavior of scattered light intensity as a function of scattering wave vector is observed in all cases and is suggestive of fractal structure. The fractal dimensions obtained fall within the expected range of 1.8 to 2.3 observed for colloidal aggregates but do not appear to follow the typical observations for colloids destabilized by indifferent electrolytes where lower fractal dimensions are associated with rapid (diffusion-limited) aggregation and higher fractal dimensions with slower (reaction-limited) aggregation. Indeed, relatively constant fractal dimensions (2.10 to 2.25) are observed over the range of salt concentrations at which the slow to rapid aggregation rate transformation occurs with, if anything, a slightly higher fractal dimension observed for higher aggregation rates. The presence of specifically binding sulfate anions appears to negate the strong near-distance repulsive forces leading to rapid aggregation at low (1 to 2 mM) sulfate concentrations. Significantly lower fractal dimensions (1.85 to 1.91) are observed for aggregates formed by destabilization using sulfate ions than obtained when chloride or nitrate are used with, again, an apparent slight increase in fractal dimension upon increasing aggregation rate.

Extraction of Thallium with Butyl Acetate

ABSTRACT Experimentally obtained extraction isotherms of the system thallium-sulfuric acid-sodium chloride-butyl acetate are presented. The influence of the sulfuric acid and chloride anion concentrations on the extraction equilibria of thallium was investigated. An increase in the acidity of the aqueous phase results in steeper extraction isotherms, and the amount of thallium extracted generally increases. The influence of chloride anions on the equilibrium is more complex. It was found that the extraction equilibria is not influenced by the chloride ion concentration, provided that the Cl/T1 ratio in the aqueous phase is ⩾ 4. If this ratio is less than 4, the concentration of chloride anions significantly influences the extraction isotherms. The results obtained are discussed in terms of the composition of the complex in the organic phase. An apparent reaction constant equation is proposed for the prediction of the extraction equilibria.

Increased Tissue Neutral Endopeptidase 24.11 Activity in Spontaneously Hypertensive Hamsters

The purpose of this study was to determine whether tissue neutral endopeptidase (NEP) 24.11 activity, a membrane-bound metalloenzyme widely distributed in the peripheral circulation that cleaves and inactivates vasodilator peptides, is increased in spontaneously hypertensive hamsters relative to genetically/age-matched normotensive hamsters. Mean arterial pressure and heart rate were 163 ± 11 mm Hg and 312 ± 7 beats/min in spontaneously hypertensive hamsters and 99 ± 3 mm Hg and 302 ± 10 beats/min in normotensive hamsters, respectively (mean ± SEM). NEP 24.11 activity is significantly increased in the kidney, cheek pouch, and spinotrapezius muscle, and significantly decreased in the heart and aorta of spontaneously hypertensive hamsters relative to controls ( P < .05). Lung and brain NEP 24.11 activity is similar in both groups. Renal NEP 24.11 activity increases and to a similar extent in spontaneously hypertensive and normotensive hamsters as chloride anion concentration in the assay buffer is increased. Substituting citrate for chloride anion significantly attenuates renal NEP 24.11 activity. Taken together, these data indicate that NEP 24.11 activity in spontaneously hypertensive hamsters is increased in two organs that contribute appreciably to peripheral vascular resistance, skeletal muscle, and kidney. We suggest that the spontaneously hypertensive hamster is a suitable model to study the role of skeletal muscle and renal NEP 24.11 in regulating vasomotor tone in essential hypertension.

Chloride-dependent sarcoplasmic reticulum Ca2+ release correlates with increased Ca2+ activation of ryanodine receptors

The mechanism by which chloride increases sarcoplasmic reticulum (SR) Ca2+ permeability was investigated. In the presence of 3 microM Ca2+, Ca2+ release from 45Ca(2+)-loaded SR vesicles prepared from procine skeletal muscle was increased approximately 4-fold when the media contained 150 mM chloride versus 150 mM propionate, whereas in the presence of 30 nM Ca2+, Ca2+ release was similar in the chloride- and the propionate-containing media. Ca(2+)-activated [3H]ryanodine binding to skeletal muscle SR was also increased (2- to 10-fold) in media in which propionate or other organic anions were replaced with chloride; however, chloride had little or no effect on cardiac muscle SR 45Ca2+ release or [3H]ryanodine binding. Ca(2+)-activated [3H]ryanodine binding was increased approximately 4.5-fold after reconstitution of skeletal muscle RYR protein into liposomes, and [3H]ryanodine binding to reconstituted RYR protein was similar in chloride- and propionate-containing media, suggesting that the sensitivity of the RYR protein to changes in the anionic composition of the media may be diminished upon reconstitution. Together, our results demonstrate a close correlation between chloride-dependent increases in SR Ca2+ permeability and increased Ca2+ activation of skeletal muscle RYR channels. We postulate that media containing supraphysiological concentrations of chloride or other inorganic anions may enhance skeletal muscle RYR activity by favoring a conformational state of the channel that exhibits increased activation by Ca2+ in comparison to the Ca2+ activation exhibited by this channel in native membranes in the presence of physiological chloride (< or = 10 mM). Transitions to this putative Ca(2+)-activatable state may thus provide a mechanism for controlling the activation of RYR channels in skeletal muscle.

Tissue angiotensin I-converting enzyme activity in ageing hamsters with and without cardiomyopathy

The purpose of this study was to determine tissue angiotensin I-converting enzyme (ACE) activity in ageing hamsters with and without cardiomyopathy, and the factors that regulate its activity in vitro. We found that ACE activity was significantly increased in the heart and significantly decreased in the lung of ageing hamsters with hereditary cardiomyopathy in comparison to age/genetically-matched controls ( P < 0.05). Kidney and cheek pouch ACE activity was similar in both groups. Lisinopril inhibition curves of tissue ACE activity were similar in ageing hamsters with and without cardiomyopathy. In both groups, tissue ACE activity was dependent on chloride anion concentration in the assay buffer. Substituting citrate for chloride abrogated, in part, this response. We conclude that cardiomyopathy is associated with significant changes in cardiac and lung ACE activity in ageing hamsters in comparison to age/genetically-matched controls. However, regulation of tissue ACE activity in vitro is similar in both groups.

In Vitro Characterization of Sodium Glycocholate Binding to Cholestyramine Resin

Cholestyramine resin in a bile acid sequestrant which binds with bile salts in the intestinal lumen to increase the fecal excretion of bile salts and, thus, lower blood serum cholesterol. In order to gain a better understanding of the lowin vivopotency of cholestyramine,in vitroequilibrium binding studies, water sorption studies, and resin capacity measurements were performed using cholestyramine and the bile salt sodium glycocholate. Equilibrium binding and water sorption studies entailed equilibrating cholestyramine (1.0–20 mg/mL) with solutions which varied in glycocholate anion concentration (0.20–16.5 mM) and chloride anion concentration (15–150 mM). The resin's practical specific capacity for glycocholate was lower than the practical specific capacity for chloride. This difference suggests that the rigid, bulky bile salt was pore excluded from 10% of the resin's ionogentic sites. A fundamental parameter called the capacity‐corrected molar selectivity coefficient,KCl‐GC−, was postulated to describe the underlying binding phenomena and was determined by measuring the free glycocholate and chloride anion concentrations;KCl‐GC−ranged from 9.8 (±0.7) to 18.6 (±0.2) and depended on the square of the free chloride concentration. The capacity‐corrected molar selectivity coefficient was larger than the molar selectivity coefficient due to pore exclusion of glycocholate. A more simple method to calculate the capacity‐corrected molar selectivity coefficient which required less data gave similar values to the more rigorous method (r2= 0.955).

A new anion-sensitive biosensor using an ion-sensitive field effect transistor and a light-driven chloride pump, halorhodopsin

A new biosensor sensitive to chloride anion using a light-driven chloride pump protein, halorhodopsin (hR), and an ion-sensitive field effect transistor (ISFET) has been developed. Membrane vesicles of halophilic bacteria containing hR were immobilized in the matrix of polyvinylbutyral resin on the surface of the ISFET. The gate voltage of this device changed in the min time scale under yellow light illumination. The response for chloride anion increased according to the increase of chloride anion concentration in the bulk aqueous phase. In the dark, the gate potential did not change even in the presence of chloride anion. These chloride-dependent gate potential changes of the hR-ISFET indicate that the chloride pumping by hR is active on the ISFET and that ISFET detects the light-dependent chloride transport by hR.

Chloride anion concentration as a determinant of renal vascular responsiveness to vasoconstrictor agents

1. The role of chloride concentration in modulating vasoconstrictor responses of the rat isolated kidney, perfused with Krebs-Henseleit solution, to angiotensin II (AII), arginine vasopressin (AVP) and phenylephrine (PE) was investigated. 2. Reduction of perfusate chloride from a high (117 mM) to low (87 mM) concentration, by substitution of sodium chloride with a mixture of sodium salts of propionate, acetate and methanesulphonate, reduced responsiveness to all three vasoconstrictors, the change for AII being most pronounced. 3. For AII, reduced vasoactivity with low chloride was evident both in terms of the threshold dose and on the linear part of the dose-response curve but not for the maximum response. This attenuating effect of low chloride on the vasoconstrictor response to AII was reversed when perfusion with high chloride was reinstituted. Continuous perfusion with high chloride progressively increased the vasoconstrictor effect of low doses of AII for successive dose-response curves. 4. In addition to reducing responses on the linear part of the dose-response curve for both AVP and PE, low chloride also reduced the maximum vasoconstrictor response to PE, whereas the threshold dose for the two agonists was unchanged. In contrast to the enhanced pressor response to AII, during continuous perfusion with high chloride, tachyphylaxis occurred with AVP and PE. 5. The ability of chloride to modify renal responsiveness to vasoconstrictor agents may contribute to the increase in renal vascular resistance and decrease in glomerular filtration rate (GFR) which occurs during infusion of hyperchloremic solutions into the renal artery and explain the need for chloride as the anion accompanying sodium in salt-sensitive hypertensive models.

Tissue angiotensin I-converting enzyme activity in spontaneously hypertensive hamsters

The purpose of this study was to measure angiotensin I-converting activity in heart, kidney, lung and cheek pouch tissue homogenates of spontaneously hypertensive and normotensive hamsters. We also determined inhibitor sensitivity and the effects of chloride anion concentration on kidney angiotensin I-converting activity in these animals. We found no significant differences in angiotensin I-converting activity between hypertensive and normotensive hamsters in all tissues tested. Inhibitor sensitivity of kidney angiotensin I-converting activity with captopril and lisonopril was similar in both groups. Finally, kidney angiotensin I-converting activity increased significantly in both groups as chloride anion concentration in the assay buffer increased. Substituting chloride anion for citrate abrogated the increase in angiotensin I-converting enzyme activity.

Thermodynamic characterization of cytochrome c at low pH : Observation of the molten globule state and of the cold denaturation process

Several reports have pointed out the existence of intermediate states (both kinetic and equilibrium intermediate) between the native and the denatured states. The molten globule state, a compact intermediate state in which the secondary structure is formed but the tertiary structure fluctuates considerably, is currently being studied intensively because of its possible implication in the folding process of several proteins. We have examined the thermal stability of horse cytschrome c at low pH between 2.0 and 3.2 and different potassium chloride concentrations by absorbance of the Soret band, far and near-ultraviolet circular dichroism (u.V. c.d.) and tryptophan fluorescence using a multidimensional spectrophotometer. The concentration of potassium chloride ranged from 0 m to 0.5 m. The experimental thermal denaturation curves show that: (1) the helical content of cytochrome c remains stable at higher temperature when the concentration of salt is increased; whereas (2) the extent of ordering of the tertiary structure is weakly dependent on salt concentration; and (3) for cytochrome c, the stabilization of the molten globule state is induced by the binding of anions. Other salts such as NaCl, LiCl, potassium ferricyanide (K 3Fe(CN) 6) and Na 2SO 4 may also be used to stabilize the molten globule state. The thermodynamic analysis of the denaturation curves of c.d. at 222 nm and c.d. at 282 nm shows that, whereas a two-state (native and denatured) transition is observed at low-salt concentration, the far and near-u.v. c.d. melting curves of cytochrome c do not coincide with each other at high-salt concentration, and a minimum of three different thermodynamic states (IIb, intermediate or IIc, and denatured) is necessary to achieve a sufficient analysis. The intermediate state (called IIc) is attributed to the molten globule state because of its high secondary structure content and the absence of tertiary structure. Therefore, at low pH, cytochrome c is present in at least four states (native, IIb, IIc and denatured) depending on the salt concentration and temperature. The thermodynamic parameters, i.e. the Gibbs free energy differences ( ΔG), the enthalpy differences (Δ H), the midpoint temperatures ( T m ) of the transition (IIb → intermediate (IIc) → denatured) are determined. We also give estimates of the heat capacity differences (Δ C p) from the temperature dependence of the enthalpy differences. The enthalpy change and the heat capacity difference of the IIc → denatured transition are non-zero. The number of charges (protons or chloride anions) released upon transitions are determined by analysing the pH and chloride anion concentration dependence of the Gibbs free energy. At low salt concentration, these values are in good agreement with a microcalorimetric study and can also explain a cold denaturation process at sub-zero temperature, which was first observed for cytochrome c in the present study. Finally, the phase diagram of cytochrome c at low pH proposed previously by Ohgushi and Wada is re-examined in view of the present data.

Effects of chloride on chicken iodopsin and the chromophore transfer reactions from iodopsin to scotopsin and B-photopsin

Spectroscopic properties of chicken iodopsin were investigated in correlation with the concentration of chloride in digitonin extracts. When chloride in the extract was depleted by extensive dialysis, chloride-depleted iodopsin (absorption maximum, 512 nm) was formed. It was converted to chloride-bound iodopsin (absorption maximum, 562 nm) by the addition of chloride in the extract. There existed an equilibrium between two forms of iodopsin with a dissociation constant of 0.8 mM chloride. The chromophore-transfer reaction from iodopsin to scotopsin or B-photopsin, the protein moiety of chicken rhodopsin or chicken blue-sensitive cone pigment, respectively, in digitonin extract was also investigated in correlation with the concentrations of chloride, other monovalent and divalent anions, and detergent. The chromophore of chloride-depleted iodopsin was easily transferred to scotopsin in the extract, resulting in formation of rhodopsin. On the other hand, chloride-bound iodopsin was fairly stable even in the presence of scotopsin, indicating that the reaction is inhibited by binding of chloride to iodopsin. The chromophore-transfer reaction to B-photopsin was also observed from chloride-depleted iodopsin but not from chloride-bound iodopsin. The reaction was observable in the 10% digitonin extract as well as in the 2% digitonin extract. The reaction was also observed when 25 mM Na2SO4 was present in the mixture instead of NaCl, but was not when 67 mM NaNO3 was present. All these facts suggest that the chloride binding site of iodopsin does not accept a divalent anion such as SO4(2+), but does accept a monovalent anion such as Cl- or NO3-, which causes inhibition of the chromophore transfer.

The Critical Condition for the Initiation of Localized Corrosion of Mild Steel Used for Nuclear Waste Package

ABSTRACTThe general corrosion rate of mild steel is so small in neutral water environments that adequately provided corrosion allowance can ensure the requirement of one thousand years’ integrity of geological disposal package of high-level nuclear wastes. In alkaline water environments, however, mild steels can passivate themselves and often undergo localized corrosion in much the same manner stainless steels do in neutral water environments. This paper describes a study of localized corrosion behavior of the mild steel conducted to assess the long-term performance of the disposal packages. The critical potentials for pitting and crevice corrosion and critical pH for general corrosion-to-passivity transition were determined for neutral and alkaline water environments. Effects of temperature, pH, and chloride and other anion concentrations on the critical potentials and the critical pH were discussed. The initiation and propagation behavior of crevice corrosion was also analyzed under potentiostatic conditions.

Aluminum Anodization in a Basic Ambient Temperature Molten Salt

Aluminum anodization has been studied in the basic ambient temperature molten salt . The anodization process was studied as a function of chloride anion concentration. Two different anodization processes are observed with onset potentials of approximately −1.1 and 0 V. The more cathodic anodization involves formation of the tetrachloroaluminate anion and exhibits a limiting current controlled by diffusion of chloride to the electrode surface. The number of chlorides required for each Al anodized was determined to be . The more anodic anodization shows no diffusion control. A value for the diffusion coefficient of chloride was obtained which is lower than previously reported; the difference involves using an n value of 1, rather than . No reduction of the tetrachloroaluminate anion was observed even at elevated temperatures.

Prescribed fire in Arizona chaparral: Effects on stream water quality

Prescribed fire in Arizona chaparral can be used to obtain temporary improvements in forage supplies and a mosaic of uneven-aged stands of chaparral to reduce risks of widespread wildfires. A paired-watershed study demonstrated that prescribed fire had a negligible effect on the ionic composition of streamflow from a chaparral watershed that had been converted by means of a herbicide to grasses, forbs, and scattered shrubs. Before the prescribed fire, nitrate concentrations from the converted watershed were about 10 × greater than those from the control watershed because of nitrate release associated with the conversion process. The fire did not cause further increases in nitrate concentration. Concentrations of sulfrte, bicarbonate, and chloride anions and of calcium, magnesium, sodium, and potassium cations were not affected by the fire. Electrical conductivity and pH also were not influenced. Seasonal fluctuations in ionic concentrations coincided with seasonal variations in rainfall and streamflow. Nitrate concentrations increased during periods of high streamflow, but other anions and all cations decreased during periods of high flow. Electrical conductivity and pH remained relatively constant during the study.

Simultaneous water and solute movement through an unsaturated soil following an increase in recharge

Playa lakes have been promoted as potential point sources of recharge to the High Plains aquifer, but information about recharge rates is only available for the Southern High Plains, where soils and substrate differ significantly from the Central High Plains. The goal of this study is to determine the degree to which functioning playas contribute to recharge of the aquifer in the Central High Plains. This is accomplished through a multifaceted study across a single 34–43 day-long playa hydroperiod, combining physical and geochemical evidence to measure fluid flux through the playa and geochemical evidence of fluid flux through the nearby interplaya. The hydroperiod resulted in increased matric potential and decreases in chloride and other anion concentrations in the vadose zone beneath the playa, and increases in groundwater levels downgradient, likely indicating recharge to the aquifer over the course of the short event. Anion concentrations are significantly higher in the interplaya compared with the playa, while fluid flux estimates are significantly higher beneath the playa. The fluid fluxes determined in this study are consistent with estimates from elsewhere in the High Plains region. The combination of physical and geochemical data decreased the uncertainty and improved the overall conclusion that recharge rates are higher beneath the playa than the interplaya, providing evidence that playas in the Central High Plains function similarly to those in the Southern High Plains.

Short-term changes in the base neutralizing capacity of an acid Adirondack lake, New York

Concern and controversy over the effects of acidic deposition on low ionic strength surface waters has led to much discussion on the nature and extent of proton transformations within acid sensitive ecosystems1–4. The source of base neutralizing capacity (BNC) within acid surface waters has been attributed to atmospheric deposition of H2SO4 (or SO2)5,6 or HNO3 (ref. 7), as well as production of soluble organic acids from soils8. Unfortunately many of these studies have failed adequately to characterize aluminium, which is often a very significant component of BNC in acidic waters9. We have evaluated the nature of short-term changes in the BNC of an acidic clearwater lake. Our results suggest that much of the variation in hydrogen ion and aluminium BNC can be attributed to changes in nitrate concentration, rather than to variations in sulphate, chloride, or organic anion concentrations.