Concentration Of Citrate Ions Research Articles

ECL sensor for selective determination of citrate ions as aprostate cancer biomarker using polymer of intrinsic microporosity-1 nanoparticles/nitrogen-doped carbon quantum dots.

Urine citrate analysis is relevant in the screening and monitoring of patients with prostate cancer and calcium nephrolithiasis. A sensitive, fast, easy, and low-maintenance electrochemiluminescence (ECL) method with conductivity detection for the analysis of citrate in urine is developed and validated by employing polymer of intrinsic microporosity-1 nanoparticles/nitrogen-doped carbon quantum dots (nano-PIM-1/N-CQDs). Using optimum conditions, the sensor was applied in ECL experiments in the presence of different concentrations of citrate ions. The ECL signals were quenched gradually by the increasing citrate concentration. The linear range of the relationship between the logarithm of the citrate concentration and ΔECL (ECL of blank - ECL of sample) was obtained between 1.0 × 10-7M and 5.0 × 10-4M. The limit of detection (LOD) was calculated to be 2.2 × 10-8M (S/N = 3). The sensor was successfully applied in real samples such as human serum and patient urine.

Synthesis of Silicon- and Carbonate-doped Biomimetic Hydroxyapatite in the Presence of Citrate Ions and its Physicochemical, Bioactivity Properties

The present study investigated the phase composition, the structural, morphological, and bioactivity properties of silicon- and carbonate-doped biomimetic hydroxyapatite synthesized by precipitation from aqueous solutions in the presence of different amounts of citrate ions. The X-ray diffraction and Fourier transform infrared spectroscopy analyses confirmed that all the samples exhibited single-phase. Base on the results of the morphological study, all the obtained samples consisted of porous agglomerated particles made up of tiny crystallites in the nanometer range. The change in structural order, as well as the decrease in particle size and degree of crystallinity result from the presence of citrate ions were revealed by X-ray diffraction, dynamic light scattering, and scanning electron microscopy analyses. Bioactivity properties of samples were studied by analyzing their bioresorbability in physiological saline (ω (NaCl) = 0.9%) and evaluating their solubility in SBF solution after a certain period of soaking time. The amount of the released Ca2+ ions was found to increase with the increasing concentration of citrate ions introduced in the synthesis process. The better solubility of material with the presence of citrate ions was beneficial in the growth of apatite on its surface that made produced material more biocompatible.

Growth of gold nanoparticles on cellulose nanofibers

The in-situ growth of gold nanoparticles (AuNPs) on cellulose nanofibers (CNFs) is a promising novel method to functionalize the CNFs. This work aims to study the synthesis mechanisms of the AuNP/CNF composites and develop the methods to control the particle size and surface coverage of AuNPs grown on CNFs. The growth process was monitored by the spectral analysis in real time, and the morphology of the AuNP/CNF composites was observed by using the electron microscopic techniques. The crystallography of AuNPs grown on CNFs was investigated by using a transmission electron microscopy (TEM). It has been found that the CNFs contribute to reducing the gold (Au) precursors, albeit at a much lower reduction rate than the citrate ions. The Au monomers have been found to strongly attach onto the CNFs to form the nucleation sites for the subsequent growth of AuNPs. The mechanisms underlying the formation of the AuNP/CNF composites have been proposed, with the emphasis on the effects of the CNFs on the growth of Au nanocrystals: the citrate ions play the dominant role in the reduction of Au precursors; the CNFs are able to offer the reduction sites for Au precursors and provide the nucleation sites for the formation of Au nanocrystals, and at the same time, having a prevention effect on the fusion of AuNPs formed on CNFs. Based on the proposed mechanisms, the methods of controlling the growth of AuNPs on CNFs have been developed: the size of AuNPs can be controlled by manipulating either the concentration of citrate ions or the initial pH value of the reaction suspension; the surface coverage of AuNPs on CNFs can be controlled by adjusting either the solid content of the CNFs or the initial pH value of the reaction suspension.

СИНТЕЗ И ИССЛЕДОВАНИЕ СВОЙСТВ БИОМИМЕТИЧЕСКОГО ГИДРОКСИАПАТИТА, ДОПИРОВАННОГО СИЛИКАТ- И КАРБОНАТ-АНИОНАМИ В ПРИСУТСТВИИ ЦИТРАТ-ИОНОВ

In the present work, biomimetic hydroxyapatite (BHAP) doped with silicate and carbonate anions in the presence of citrate ions are synthesized by chemical precipitation from aqueous solutions. According to the results of X-ray phase analysis (XRD), all the obtained materials are single-phase. Scanning electron microscopy (SEM) demonstrates that BHAP powders are a collection of agglomerated particles with similar morphology. Dynamic light scattering confirms that the synthesized BHAPs consist of agglomerates 1–4μm in size. For all samples, with an increase in the number of introduced citrate ions, decreases in the average crystallite size and degree of crystallinity are observed. With an increase in the concentration of citrate ions, the content of agglomerate fractions of 1–2μm in size increases from 70.16 to 75.43%. The solubility of hydroxyapatite samples in physiological saline (ω(NaCl) = 0.9%) at temperatures of 22°C and 37°C is studied. It is revealed that for all synthesized BHAPs, the amount of released Ca2+ ions into the liquid phase increases. The maximum yield of Ca2+ ions in physiological saline is recorded in BHAP with the highest content of citrate ions. The obtained results allow to consider the synthesized BHAP as a promising medical biomaterial for the regeneration of bone tissue.

Decolorization of methylene blue using Fe(III)-citrate complex in a solar photo-Fenton process: impact of solar variability on process optimization.

This study investigates the solar photo-Fenton based decolorization of a cationic dye methylene blue (MB) at circumneutral pH conditions. Water-soluble Fe(III)-citrate complex was used as a source of Fe(II) during the reaction by ligand-to-metal charge transfer under solar irradiation, and consequently, for the production of hydroxyl radicals. Solar decolorization of methylene blue was studied in sunny as well as cloudy weather, and further optimized using response surface methodology and Box-Behnken statistical experimental design. In this model, Fe(III) dose, citrate ion dose, and initial pH of the solution were used as independent parameters, and percentage decolorization of MB was used as a response. Better decolorization of MB was observed in sunny weather as compared to cloudy weather. A particular combination of parameters, i.e. pH of 7, Fe(III) of 0.5 mM, and citrate ion concentration of 10 mM, was found to achieve 89.19% and 51.22% decolorization in sunny and in cloudy weather respectively, which were the optimum/near-optimum performances for these weather conditions. Hence the process initiated with these parameters may potentially achieve better performance than any other parameter combination in all weathers, although the absolute removal would still depend on incident solar irradiation.

Determination of citrat ions in drugs on molecular luminescence of rutine in complex with yttrium (III)

The development of methods for qualitative and quantitative analysis of drugs can guarantee their identity and quality. Drugs used in the form of salts of organic bases are often determined by the anionic part of these salts. Citrate ions are a part of many drugs in the form of citric acid, salts of alkaline and alkaline earth metals.
 The purpose of this study was to develop a method for the luminescent determination of citrate ions in dosage forms using a complex of yttrium (III) with rutine (Rut) as a luminescent probe. It has been experimentally established that citrate ions increase the luminescence intensity of the Y(III)–Rut complex. The spectral and luminescence characteristics of the complex was studied. The luminescence spectrum of the Y(III)–Rut complex has a maximum at λlum = 570 nm. The luminescence intensity of the Y(III)–Rut complex increases and the luminescence peak shifts to the short-wave region of the spectrum (λlum = 522 nm) in the presence of sodium citrate. The maximum effect is observed at a pH of 6.5–7.5. The dependencies of the luminescence intensity on the concentration of Y(III) and Rut for the Y(III)–Rut–Cit complex at the constant concentration of citrate ions (1·10-3 mol/l) were studied. It was established that the maximum luminescence intensity was observed at concentrations of Y(III) – 2·10-3 mol/l and Rut – 5·10-4 mol/l. The linear region of the dependence of the luminescence intensity of the complex on the concentrations of Y(III) and Rut is observed in the range of yttrium concentrations 0.3–2.0·10-3 mol/l and rutine 0.5–5.0·10-4 mol/l.
 The method of luminescent determination of citrate ions in dosage forms has been developed. The method is based on the use of rutine molecular luminescence in the multi-ligand complex Y(III)–Rut–Cit.
 The method of determination of citrate ions in dosage forms differs favorably from the existing absence of toxic reagents, expensive equipment, short-term analysis time, allows rapid screening of samples of drugs.

Controlled electrodeposited cobalt phases for efficient OER catalysis, RRDE and eQCM studies

Different cobalt phases are deposited on graphite discs from CoSO4 baths in absence and presence of equimolar concentration of citrate ions, Co/G and Co(cit)/G, respectively. The prepared electrodes are subjected to different electrochemical studies. Benchmark recommends the use of the overpotential required to achieve current density of 10 mA.cm−2(ηt=0) in linear sweep voltammetry, LSV, at 10 mV.s−1 as an activity parameter for oxygen evolution reaction, OER. The values of ηt=0 equal 0.443 and 0.440 for Co/G and Co(cit)/G, respectively. This work suggests an activation routine based on the observed sequential enhancing of ηt=0 values through successive cyclic voltammetry in 1 M NaOH. Satisfactory ηt=0 values of 0.437 and 0.394 V are obtained for the activated electrodes prepared in absence and presence of citrate anions, respectively. All the prepared electrodes show noteworthy stability over 2hrs. The values of overpotential after 2 hrs ηt=2h in 1 M NaOH reveals higher efficiency for the electrodes prepared from citrate-containing bath rather than citrate free bath. The morphology and the structure of the optimum electrodes are characterized. RRDE and eQCM studies clarify the role of the citrate anion in controlling the deposited cobalt phases. The OER catalytic activities are correlated with the deposited cobalt phase structure for the prepared electrodes.

Effect of citrate ions on the electrochemical migration of tin in thin electrolyte layer containing chloride ions

The effect of tri-sodium citrate dehydrate on the electrochemical migration of tin in thin electrolyte layers containing chloride ions was investigated through potentiodynamic polarization, cyclic voltammetry, scanning electron microscopy, X-ray photoelectron spectroscopy, and optical techniques. The effects of applied bias voltage and concentration of citrate ions were also studied. Results showed that tri-sodium citrate dehydrate acts as an inhibitor by suppressing anodic dissolution and metallic ion transfer through the formation of tin citrate complexes. The mechanisms involved were proposed to explain the inhibition effect.

Preparation, corrosion, and wear resistance of Ni‐Mo/Al composite coating reinforced with Al particles

In this research, Ni‐Mo/Al composite coatings were deposited from a citrate bath containing Al metallic particles. The impact of Al particle content in the bath on the microstructure, texture, thickness, current efficiency, wear and corrosion behaviors of Ni–Mo/Al coatings was surveyed. The [200] preferred orientation developed slowly to the [111] orientation with increasing Al loadings in the bath. The results showed that electroplating at 40°C and citrate ion concentration of 0.15M had the highest current efficiency and produced a dense coating free of cracks. Because of the presence of Mo, the morphology of the matrix changed from a regular pyramidal structure for Ni‐Al composite coatings to cauliflower for Ni‐Mo/Al composite coatings. The wear resistance of coatings decreased due to the increase of Al content in the coating. The polarization tests indicated that the corrosion resistance of the Ni‐Mo/Al composite coating was enhanced by adding Al metal particles. This was due to the increase of Al content and decrease of the grain size of the coatings.

Bio-inspired citrate functionalized apatite coating on rapid prototyped titanium scaffold

Abstract Scaffold functionalized with appropriate osteogenic coatings can significantly improve implant-bone response. In this study, with designed model and optimized manufacture parameters, reproducible and precise titanium scaffolds were produced. Reconstructed three-dimensional image and sectional structure of the scaffold were examined by micro-computed tomography and relative software. Alkali treatment was carried out on these manufactured porous scaffolds to produce nanoporous hydrophilic film. After 6 days deposition in simulated body fluid (SBF) containing sodium citrate (SC-SBF), plate-like amorphous calcium phosphate (ACP) coating was deposited on scaffold surface. Ultrasonication tests qualitatively indicated an enhanced adhesion force of apatite coatings deposited in SC-SBF compared to that deposited in SBF. And the effect of citrate ions on the CO 3 2− incorporation rate in apatite coating was quantitatively examined by bending vibration of CO 3 2− at ∼874 cm −1 . Results indicated the highest carbonate content was obtained at the citrate ion concentration of 6 × 10 −5 mol/L in SC-SBF. These three-dimensional porous titanium-apatite hybrid scaffolds are expected to find application in bone tissue regeneration.

Size control in the formation of magnetite nanoparticles in the presence of citrate ions

A one-pot synthesis method for the controllable growth of magnetite nanoparticles directly during the process of co-precipitation using citrate ions was developed. The effects of the concentration of citrate ions and the solution pH on the characteristics of magnetite particles with sizes in the range of 4–10 nm synthesized by the method of co-precipitation were studied. The results showed that the specified concentration of citrate ions allowed the preparation of magnetite particles with a definite size that exhibited superparamagnetic behaviour in a particular temperature range. As the concentration ratio of citrate to iron ions was increased from 0 to 0.11, the average size of the prepared magnetite particles decreased from 10.5 to 4.4 nm. As a result, the superparamagnetic blocking temperature decreased from 300 to 20 K, the saturation magnetisation decreased from 50 to 20 emu g−1, and the average magnetic moment decreased from 8000 μB to 340 μB (at T = 300 K).The obtained experimental data proved that the size effects of the magnetite nanoparticles can be attributed to the capping of the magnetite surface by adsorbed citrate ions. Thus, the suggested approach allows magnetite nanoparticles to be prepared with an optimum particle size around superparamagnetic threshold that prevents their irreversible agglomeration and simultaneously allows them to be removed from a solution at an acceptable rate.

Magnetic-based silver composite microspheres with nanosheet-assembled shell for effective SERS substrate

Well-dispersed magnetic-based silver composite microspheres (Fe3O4@SiO2@Ag) with a nanosheet-assembled shell structure were synthesized at room temperature, where sonicating and mechanical stirring techniques were both employed and played important roles during the silver shell growth process. The results show that the nanosheet-assembled silver shell could be obtained and controlled by adjusting the concentration of citrate ions as a morphology directing-reagent. The gaps in or between cross-linked nanosheets in the shell of the composite microspheres were proposed to provide sufficient “hot spots” when they were used as a SERS substrate. The SERS measurements exhibit clear enhancement signals by using R6G as a probe molecule, and even at concentrations as low as 10−14 M, all enhancement peaks could be observed clearly. The film assembled from the composite microspheres exhibited good reproducibility across the entire area. Additionally, the magnetic Fe3O4@SiO2@Ag microspheres can be separated from solution rapidly, which shortened the detection time. Considering their excellent SERS performance, this kind of composite microsphere, which has both a SERS active shell and a magnetically separable core, would be very useful as an effective SERS substrate for detecting organic pollutants in solution.

Influence of oxygen on the process of formation of silver nanoparticles during citrate/borohydride synthesis of silver sols

In this work, we investigate the influence of oxygen on the process of formation of silver nanoparticles during reduction of silver nitrate with sodium borohydride in the presence of sodium citrate (Na3Cit) at room temperature. When small amount of borohydrides (0.02μmol of NaBH4 per 1μmol of AgNO3) is added to the solution of AgNO3 and Na3Cit, silver nanoparticles created “under air” are about 5 times larger than Ag nanoparticles created in the deaerated conditions. Further addition of borohydrides to the reaction mixtures leads to decrease in the average size of “large” nanoparticles formed “under air” and to increase in the size of nanoparticles formed in the deaerated solution. Explanation of the observed phenomenon is proposed (involving oxidation back by the oxygen of small silver clusters formed at a very early stage of Ag+ reduction and possible fragmentation of large particles in the presence of borohydrides ions). When Ag+ cations are reduced by borohydrides at room temperature, stable silver sols may be only formed when a stabilizer of silver clusters is present in the reaction mixture. We show that, for citrates used in this contribution as stabilizers, the most stable silver sols are formed during reduction of Ag+ with BH4− at room temperature, when the concentration of citrate ions is in a range of ca. 0.5–5mM.

Optical properties of citrate-stabilized CdS nanoparticles

Citrate-stabilized CdS nanoparticles of size ∼4 nm are obtained by varying the sulfide:citrate ion concentration in a simple aqueous synthesis method. The optical absorption and photoluminescence properties of the nanoparticles are studied. The size of the crystallites is found to be less affected by sulfide:citrate ratio. At lower concentrations of S 2−, trap state emission is favoured and at higher concentrations excitonic transition is predominant as shown by optical absorption and photoluminescence spectra. Effective surface capping and optimum concentration of S 2− leads to the quenching of surface-defect-related emission. Increase in citrate ion concentration is found to increase the intensity of photoluminescence band arising from trap state emission revealing the role of sulfide:citrate ratio on surface modification of CdS nanocrystals. The nanoparticles are hexagonal as shown by the X-ray diffraction and selected area electron diffraction pattern.

Template-Free Synthesis of Porous Platinum Networks of Different Morphologies

A simple one-pot template-free synthesis was used to form porous Pt networks from the CO-induced self-organization of monodisperse primary Pt nanoparticles. Spherical, rod-shaped, knot-like, multibranched, and hyperbranched porous networks could be obtained under different conditions through changes in the reaction temperature and citrate ion concentration. The formation of these porous platinum networks could be rationalized by a mechanism where citrate ions and Chini-like platinum carbonyl clusters formed upon CO exposure are the most important contributors.

Biodistribution of colloidal gold nanoparticles after intravenous administration: Effect of particle size

Purpose of the present research work was to evaluate the biological distribution of differently size gold nanoparticles (NP) up on intravenous administration in mice. Another objective was to study effect of particle size on biological distribution of gold NP to enable their diverse applications in nanotechnology. Gold NP of different particle sizes, mainly 15, 50, 100 and 200 nm, were synthesized by modifying citrate ion concentration. Synthesized gold nanoparticles were characterized by SEM and their size distribution was studied by particle size analyzer. Gold NP was suspended in sodium alginate solution (0.5%, w/v) and administered to mice (1 g/kg, intravenously) [ n = 3]. After 24 h of administration of gold NP, blood was collected under light ether anesthesia, mice were sacrificed by cervical dislocation and various tissues/organs were removed. The tissues were then washed with saline, homogenized and lysed with aqua regia. The determination of gold in samples was carried out quantitatively by inductively coupled plasma mass spectrometry (ICP-MS). SEM study revealed spherical morphology of gold NP with narrow particle size distribution. Biodistribution study revealed gold NPs of all sizes were mainly accumulated in organs like liver, lung and spleen. The accumulation of gold NP in various tissues was found to be depending on particle size. 15 nm gold NP revealed higher amount of gold and number of particles in all the tissues including blood, liver, lung, spleen, kidney, brain, heart, stomach. Interestingly, 15 and 50 nm gold NP were able to pass blood–brain barrier as evident from gold concentration in brain. Two-hundred nanometers gold NP showed very minute presence in organs including blood, brain, stomach and pancreas. The results revealed that tissue distribution of gold nanoparticles is size-dependent with the smallest 15 nm nanoparticles showing the most widespread organ distribution.

Development of an alkali-metal-free bath for electroless deposition of Co-W-P capping layers for copper interconnections

A bath containing alkali-metal-free chemicals was developed for electroless deposition of Co-W-P thin films on a copper substrate and an optimisation of bath compositions was made. Ammonium cobalt sulphate, ammonium tungstate and ammonium hypophosphite were used as the precursors of cobalt, tungsten and phosphorus, respectively. Dimethylamine borane and ammonium citrate were used as reducing and complexing agents, respectively. It was found that the cobalt content, film thickness and grain size increased with increase in cobalt ion concentration in the bath. Tungsten in the films increased from 1 to 6 at.% when its concentration in the bath was increased from 0.001 to 0.009 M. A variation of phosphorus content from 2 to 12 at.% was made by increasing its concentration from 0.01 to 0.05 M. It was found that the deposition rate decreased with increasing citrate ion concentration. Amorphous films were obtained when the combined amount of phosphorus and tungsten exceeded 12 at.% in the films. The crystalline film had small spherical crystallites with diameter less than 40 nm.

Modulation of tetracycline–phospholipid interactions by tuning of pH at the water–air interface

This paper is part of a systematic study of the interactions of tetracycline antibiotics with phospholipid monolayers at the water–air interface. Tetracyclines are widespread antibiotics that undergo a series of protonation equilibria in solution, depending on the pH. The surface activity of tetracyclines was determined by means of surface tension measurements for three different systems, i.e. water, TRIS and McIlvaine-EDTA buffer. Surface pressure–molecular area and surface potential–molecular area isotherms were acquired for dipalmitoylphosphatidic acid monolayers on TRIS buffer (pH=7.0) and McIlvaine-EDTA buffer (pH=4.0) solution as a function of tetracycline concentration in the subphase. Comparative analysis of surface potential data, with the molecular dipole moment of tetracycline obtained from semiempirical calculations, provided information on the orientation of tetracycline at the interface. Surface pressure measurements as a function of monolayer compression were described, applying either a continuous partition model or Langmuir adsorption isotherms. The results obtained in the case of buffer solutions were compared to those obtained for tetracycline in water subphases. The analysis of the results indicated that electrostatic interactions dictate the migration of tetracycline to the monolayer interface. Penetration of the molecule to the lipophilic portion of the monolayer was unlikely, especially at high surface pressures. The results showed that stronger interactions are established between the zwitterionic tetracycline and the deprotonated phosphatidic group in TRIS buffer solution; in this case, tetracycline binds at the monolayer interface following a Langmuir type adsorption. In the case of water, where the monodeprotonated acid and the tetracycline zwitterions are the only species involved, the data can be described by continuous partition of tetracycline between interfacial and bulk phases. The same holds for McIlvaine-EDTA buffer subphases, although the high concentrations of citrate ions in this buffer competitively interfere with tetracycline association at the monolayer interface.

Interaction of Citric or Hydrochloric Acid with Calcium Fluorapatite: Precipitation of Calcium Fluoride

The interaction of citric acid (H3Ci) with calcium fluorapatite(Ca10 F2(PO4)6) was explored for two reasons: (i) to determine the role of the acid in the dissolution process and hence in the mechanism of tooth fluoridation and (ii) to determine whether there is any formation of calcium citrate. It was found that the concentration of calcium or fluoride ions is not stoichiometric with respect to that of phosphate ions in the solution and the stoichiometric deficiency of the amount of fluoride ions in the solution is twice that of the calcium ions and this demonstrates that some calcium fluoride is precipitated. The interaction may be represented by the following chemical equation (pH ≈ 2.5):where x (presently < 1) is related to the amount of CaF2 that has precipitated and may be calculated from the experimental ratio of Ca to P in the solution. In order to establish that the interaction occurs generally with all acids, the reaction of hydrochloric acid with fluoroapatite was studied, and exactly analogous behavior was observed. These facts are also in accord with the solubility of fluorapatite and calcium fluoride. When the amounts of Ca and P in solution are corrected for the precipitated CaF2, the ratio of Ca to P becomes stoichiometric (= 1.67). Preliminary X-ray analysis of the reacted fluorapatite showed that it contained calcium fluoride. The precipitated CaF2 may act as a reservoir for the subsequent fluoridation of the mineral and may inhibit bacterial action in the mouth. The concentration of citrate ions does not change in solution, and no formation of calcium citrate is observed.

Interaction of some alkali metal citrates with hydroxyapatite: Ion-exchange adsorption and role of charge balance

Proper balancing of the concentration of citrate ions in soft drinks is important in order to regulate the cariogenic potential of these ions. The uptake, or ion-exchange adsorption, of sodium or potassium citrates from their aqueous solutions onto synthetic hydroxyapatite at 22°C was investigated in the present study as a means to elucidate the role of citrate ions in the cariogenic process. For each salt, the amount of uptake, or removal of citrate ions from its aqueous solutions by the apatite, bears a simple ratio to the amount of calcium or phosphate ions released into the solution by the substrate. The uptake isotherms may be represented by their Langmuir plots. The interaction is purely ion-exchange adsorption; there is no indication of the presence of any foreign phase. Plausible equations for ion-exchange equilibria show that the surface is electrically charged upon the adsorption of salts, but remains neutral upon the adsorption of the citric acid, and this may have a bearing on the effective area occupied by the absorbate species.