Aqueous Solution Of Citric Acid Research Articles

Synthesis and electrochemical properties of layered Li[Li (1/3− x/3) Cr xMn (2/3−2 x/3) ]O 2 prepared by sol–gel method

The Li[Li (1/3− x/3) Cr x Mn (2/3−2 x/3) ]O 2 (0.15 ≤ x ≤ 0.3) cathode materials were synthesized by sol–gel process using aqueous solutions of metal acetates and citric acid as the chelating agent. The precipitate of metal citrate was dried in a vacuum oven for 10 h at 100 °C. After drying, the gel precursor was calcined at 300 °C for about 10 h. The resulted powder was ground and heated at 900 °C. The structural characterization was carried out by fitting the XRD data with Rietveld program. The samples exhibited a well defined layered structure and the unit cell parameters linearly increased with increasing chromium contents in Li[Li (1/3− x/3) Cr x Mn (2/3−2 x/3) ]O 2 Surface morphology was determined by SEM and HRTEM and it is found that the cathode material consisted of highly ordered single crystalline particles with layered-hexagonal structure. Test cells were assembled and cycled in the voltage range of 2.0–4.9 V with a current density of 7.947 mA/g. Electrode with ( x = 0.2) delivered a high reversible capacity of around 280 mA h/g in cycling.

On the preparation of single-crystalline gold microplates

Heating a concentrated HAuCl 4–citric acid aqueous solution results in the formation of single-crystalline gold microplates. It suggests that both the concentration of reactants and medium pH value are key to producing microplates.

Influence of citrate-to-nitrate ratio on the thermal behavior and chemical environment of alumina gel

Thermal behavior and chemical environment of the product obtained by gelling an aqueous solution of nitrate and citric acid with different ratio (citrate-to-nitrate ratio γ) were investigated. The TG–DSC analysis indicates that a higher amount of nitrate in the gel (G1, γ = 0.1) should be effective in the redox system in completing the combustion of citrates and that decomposition occurs in a single step. When a higher amount of citric acid (0.33 > γ > 0.1) is used, decomposition occurs in two steps through an unstable intermediate. When an even higher amount of citric acid ( γ > 0.33) is used, decomposition occurs in three steps. Phase transformation temperature increases with the increase of γ in the fuel-lean condition and decreases with the increase of γ in the fuel-rich condition. An attempt was made to understand the status of anions in the chemical environments of the gels by infrared spectroscopy, the gels differing in their thermal behavior. Differences in FTIR spectra of ashes are mainly caused by the thermal reactivity.

Synthesis and Characterization of (La<sub>1-x</sub>Sr<sub>x</sub>)(Ga<sub>1-y</sub>Mg<sub>y</sub>)O<sub>3</sub> Particles by Spray Pyrolysis

Spherical La0.8Sr0.2Ga0.8Mg0.2O2.8 precursor powders were synthesized by ultrasonic spray pyrolysis using aqueous solution of citric acid and of metal nitrate. As-prepared powders obtained by this method have a spherical morphology with a submicron size. The calcination behavior of the precursor powders of the above phases were examined in the temperature range of 1073 –1773 K in an air atmosphere. XRD, SEM, DTA-TG and BET analysis were used for determination of the composition, morphology, particle size and surface area. XRD revealed that as-prepared powders were crystallized to perovskite structure after the sintering at 1573 K for 10 h.

The use of citric acid to prolong the in vivo gastro-retention of a floating dosage form in the fasted state

Gastro-retentive dosage forms have the potential to improve local therapy and decrease the variation in bioavailability that is observed with a number of commercially available immediate and modified release preparations. In this study, a dosage form has been developed, utilising freeze-dried calcium alginate beads, designed to float on the surface of the stomach contents thus prolonging the retention time. The aim of the study was to also assess the in vivo behaviour of the radio-labelled calcium alginate beads when they were administered under fasting conditions with either water or an aqueous solution of citric acid, a potential gut transit delaying substance. The study was performed in healthy male volunteers who swallowed the radio-labelled calcium alginate beads after a 10 h overnight fast. Gamma scintigraphy was selected as the method to monitor the movement of the calcium alginate beads. The volunteers consumed no further food or drink until gastric emptying of the calcium alginate beads was complete. The results indicated that prolonged gastric retention was achieved when the dosage form was administered with the citric acid solution when compared to retention in the absence of citric acid. Citric acid, therefore, has the potential to delay the gastric emptying of the calcium alginate beads when administered to fasted volunteers.

Intracellular recovery of gold by microbial reduction of AuCl 4− ions using the anaerobic bacterium Shewanella algae

Microbial reduction and intracellular precipitation of gold was achieved at 25 °C and pH 7 by using the mesophilic anaerobic bacterium Shewanella algae with H 2 as the electron donor. The reductive precipitation of gold by S. algae was a fast process: 0.1–1 mol/m 3 AuCl 4 − ions were completely reduced to insoluble gold within 30 min. The biogenic precipitates were crystalline gold nanoparticles of 10–20 nm present in the periplasmic space. The reducing power of S. algae at 3.2 × 10 15 cells/m 3 and 25 °C was comparable to that of aqueous citric acid solution (chemical reductant) at 20 mol/m 3 and 50 °C. The intracellular recovery of gold is potentially attractive as an environmentally friendly alternative to conventional methods.

Reaction of Urea with Citric Acid

Reaction of urea with citric acid in aqueous solutions at molar ratios of 1 : 1, 1 : 2, and 2 : 1 and the solubility of urea citrate were studied. The data obtained can serve to optimize use of citric acid as a physiologically active substance or nitrification inhibitor and in production of liquid fertilizers containing urea.

Development of calcium phosphate cement

Calcium phosphate cements were prepared by mixing α-type calcium phosphate, aqueous solutions of polyvinyl alcohol and citric acid, and silicate sand. Higher concentration of polyvinyl alcohol and citric acid gave a cured body having higher mechanical strength and 50% aqueous solutions of polyvinyl alcohol and citric acid were the highest concentration to be available in this hardening process. Polyvinyl alcohol gave better mechanical strength to a hard body than citric acid. Smaller particle size of silicate sand gave stronger mechanical strength to a cured body. The highest mechanical strength of a cured body was obtained when the mixing weight ratio of α-type calcium phosphate to silicate sand was1–0.5. The calcium phosphate cement showed very good adhesion strength for cement plates with an analogous component.

Preparation of ultrafine LiTaO3 powders by citrate gel method

A gel was formed when a aqueous solution of Li(NO3), TaF5 and citric acid in stoichiometric ratio was heated in a water bath. This gel on decomposition at 700°C produced fine crystallites of ternary oxide, LiTaO3 (LT). The phase contents and lattice parameters were studied by powder X-ray diffraction (XRD). Particle size and morphology were studied by transmission electron spectroscopy (TEM).

WITHDRAWN: Synthesis of Sr0.5Ba0.5Nb2O6 by citrate gel method

Abstract A gel was formed when an aqueous solution of BaCl2, SrCl2, NbF5 and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 700 °C yielded the nanocrystallites of ternary oxide, Sr0.5Ba0.5Nb2O6 (SBN) as confirmed by X-ray diffraction study (XRD). Particle size and morphology was studied by transmission electron spectroscopy (TEM). The room temperature dielectric constant at 1 kHz is 1000. The ferroelectric hysteresis loop parameters of these samples were also studied by a home built Sawyer–Tower circuit.

Preparation of nanocrystalline LiNbO3 by citrate gel method

A gel was formed when an aqueous solution of Li(NO3), NbF5 and citric acid in stoichiometric ratio is heated in a water bath at 100 °C. This gel on decomposition at 700 °C produced the fine crystallites of ternary oxide, LiNbO3 (LN). The phase contents and lattice parameters were studied by the powder X-ray diffraction (XRD). Particle size and morphology was studied by transmission electron spectroscopy (TEM).

Preparation of nanocrystalline ferroelectric BaNb2O6 by citrate gel method

A gel was formed when a aqueous solution of BaCl2, NbF5 and citric acid in stoichiometric ratio is heated on a water bath. This gel on decomposition at 600°C yielded the nano crystallites of BaNb2O6, as confirmed by X-ray diffraction study (XRD). This is a much lower temperature as compared to that prepared by traditional solid state method (1000°C) as reported for the formation of BaNb2O6. Transmission electron microscopic (TEM) investigations revealed that the average particle size is 50 nm for the calcined powders. The room temperature dielectric constant at 1 kHz is found to be 1000. The ferroelectric hysteresis loop parameters of these samples were also studied.

Structural Study of Very Thin Anodic Alumina Films on Silicon by Anodization in Citric Acid Aqueous Solution

The formation of thin alumina films on a silicon substrate by anodization in a mild acid, specifically in 1% wt citric acid aqueous solution, is investigated by transmission electron microscopy (TEM). We present a comparative study between two cases of starting material: pure aluminum and an alloy of aluminum with 1% silicon. In both cases the thickness of the Al layer was less than 50 nm. It was observed that under exactly the same conditions, in the first case the anodization was stopping before anodizing the whole film and a remaining non-anodized Al layer was always present, while in the second case, the Al layer was fully anodized, resulting in an alumina matrix with a very high density of silicon nanocrystals of uniform sizes embedded in it. In both cases the alumina film was compact and amorphous.

Preparation of La 0.5Sr 0.5CoO 3 powders and thin film from a new aqueous solution–gel precursor

This paper reports on the spin deposition of LSCO thin films on a SiO 2/Si substrate by a new aqueous solution–gel route. Stable and monometallic precursor solutions are prepared from common and inexpensive oxides or hydroxides. The aqueous La 3+ precursor is synthesized by reaction of La 2O 3 with citric acid. In order to prepare an aqueous Sr 2+ precursor Sr(OH) 2 is complexed by EDTA. The new peroxo citrato Co 2+ precursor is synthesized by reaction of Co(OH) 2 with hydrogen peroxide in an aqueous solution of citric acid. Mixing the individual precursors in stoichiometric quantities results in a clear and stable aqueous LSCO precursor solution. Evaporation of water transforms this solution in an amorphous gel that is homogeneous down to nanometer scale. In situ high temperature X-ray diffraction analysis of the gel reveals that phase pure LSCO powder is formed at 550 °C without detection of any intermediate crystalline phase. Spin deposition and crystallization at 625 °C in pure O 2 of this aqueous precursor solution resulted in a phase pure conductive LSCO thin film. The sheet resistance of this thin film amounted to 235 Ω/sq. Since the thickness of the film is 120 nm, the specific resistivity was calculated to be 2.8 mΩ cm at room temperature.

Spectrophotometric determination of oxiconazole in topical lotion using methyl orange

A spectrophotometric method is described for the determination of oxiconazole in raw material and in topical lotion. This method is based on the reaction of the oxiconazole with methyl orange in buffered aqueous solution of citric acid at pH 2.3. The chromogen, being extractable with dichloromethane, could be measured quantitatively with maximum absorption at 427 nm. The Lambert-Beer law was obeyed in the concentration range of 4.0–14.0 μg ml −1. A prospective validation of the method showed that the method was linear ( r = 0.9995), precise (intra-day: CV = 1.57% and inter-day: CV = 1.50%) and accurate (mean recoveries: 99.69%). The results compared favourably with those of the HPLC method.

Coordination compounds of chromium(III) with different complexones and citric acid in aqueous solutions

Coordination compounds of chromium(III) with different complexones and citric acid in aqueous solutions

Gas chromatographic evaluation of pesticide residue contents in nectarines after non-toxic washing treatments☆

Washing with aqueous solutions of citric acid, ethanol, glycerol, hydrogen peroxide, potassium permanganate, sodium metabisulfite, sodium laurylsulfate (SLS), sodium hypochlorite, and urea is evaluated for pesticide residue reduction in nectarines and compared with simple tap water washing. Residues of pesticides commonly utilized in nectarines (chlorpyrifos, fenarimol, iprodione, malathion, methidathion, myclobutanil, parathion and pirimicarb) are extracted with ethyl acetate and anhydrous sodium sulfate, extract is concentred and analyzed by GC with nitrogen-phosphorus detection. The formation of possible toxic by-products (chlorpyrifos oxon, malaoxon, methidaoxon and paraoxon methyl) is studied by GC-MS. No toxic by-products are identified in the extracts of the washed samples for the washing-time and concentrations studied, but high levels of sodium hypochlorite, hydrogen peroxide and potassium permanganate form oxons from the organophosphorus pesticides. Ethanol, glycerol and SLS solutions removed near the 50% of the pesticide residues. The other solutions were not more effective than tap water washing. The amount of pesticide removed by washings is related to its water solubility and octanol-water partition coefficient.

Gas chromatographic evaluation of pesticide residue contents in nectarines after non-toxic washing treatments

Washing with aqueous solutions of citric acid, ethanol, glycerol, hydrogen peroxide, potassium permanganate, sodium metabisulfite, sodium laurylsulfate (SLS), sodium hypochlorite, and urea is evaluated for pesticide residue reduction in nectarines and compared with simple tap water washing. Residues of pesticides commonly utilized in nectarines (chlorpyrifos, fenarimol, iprodione, malathion, methidathion, myclobutanil, parathion and pirimicarb) are extracted with ethyl acetate and anhydrous sodium sulfate, extract is concentred and analyzed by GC with nitrogen–phosphorus detection. The formation of possible toxic by-products (chlorpyrifos oxon, malaoxon, methidaoxon and paraoxon methyl) is studied by GC–MS. No toxic by-products are identified in the extracts of the washed samples for the washing-time and concentrations studied, but high levels of sodium hypochlorite, hydrogen peroxide and potassium permanganate form oxons from the organophosphorus pesticides. Ethanol, glycerol and SLS solutions removed near the 50% of the pesticide residues. The other solutions were not more effective than tap water washing. The amount of pesticide removed by washings is related to its water solubility and octanol–water partition coefficient.

Studies on rancidity inhibition in frozen horse mackerel (Trachurus trachurus) by citric and ascorbic acids

AbstractThis study is aimed to investigate the effect of aqueous solutions of citric acid (CA) and ascorbic acid (AA) on the lipid stability of horse mackerel (Trachurus trachurus) fillets and whole fish during frozen storage (up to 6 and 9 months, respectively) by means of a soaking pretreatment. Best oxidation inhibition results on fish fillets were obtained when employing a 0.5% CA solution. Lower (p<0.05) peroxide (month 3), thiobarbituric acid‐reactive substance (months 1 and 3) and fluorescent compound formation (month 6) values were obtained from CA‐treated fish fillets than from the untreated (blank control) and water‐treated (water control) fish fillets. In the case of whole fish, soaking pretreatment with a mixture consisting of 0.5% CA and 0.5% AA showed the best results in inhibiting oxidation, as lower (p<0.05) peroxide formation was observed at 6 and 9 months of frozen storage compared to the untreated or water‐soaked counterparts. Advantages of both acids (CA and AA) are discussed, and further studies based on the positive role of a CA‐AA mixture will be carried out to extend the shelf life of medium‐ and high‐fat content fish species during frozen storage.

A New Series of Highly Potent Non-Peptide Bradykinin B2 Receptor Antagonists Incorporating the 4-Heteroarylquinoline Framework. Improvement of Aqueous Solubility and New Insights into Species Difference

Introduction of nitrogen-containing heteroaromatic groups at the 4-position of the quinoline moiety of our non-peptide B(2) receptor antagonists resulted in enhancing binding affinities for the human B(2) receptor and reducing binding affinities for the guinea pig one, providing new structural insights into species difference. A CoMFA study focused on the diversity of the quinoline moiety afforded correlative and predictive QSAR models of binding for the human B(2) receptor but not for the guinea pig one. A series of 4-(1-imidazolyl)quinoline derivatives could be dissolved in a 5% aqueous solution of citric acid up to a concentration of 10 mg/mL. A representative compound 48a inhibited the specific binding of [(3)H]BK to the cloned human B(2) receptor expressed in Chinese hamster ovary cells with an IC(50) value of 0.26 nM and significantly inhibited BK-induced bronchoconstriction in guinea pigs even at 1 microg/kg by intravenous administration.