Tetraborate Solution Research Articles

Stacking, derivatization, and separation by capillary electrophoresis of amino acids from cerebrospinal fluids

This paper describes the in-column derivatization, stacking, and separation of amino acids by CE in conjunction with light-emitting diode-induced fluorescence using naphthalene-2,3-dicarboxaldehyde (NDA). According to the relative electrophoretic mobilities and the migration direction in tetraborate solution (pH 9.3), the injection order is cyanide, then amino acids, then NDA. Once poly(ethylene oxide) (PEO) migrates through the capillary under EOF, the amino acid.NDA derivatives, amino acids, and CN- ions migrating against the EOF enter the PEO zone. As a result of increases in viscosity and possible interactions with PEO molecules, the reagents/analytes slow down such that they become stacked at the boundary. In comparison with the off-column approach to the analysis of amino acids, our proposed method provides a lower degree of interference from polymeric NDA compounds and other side products. As a result, the plot of the peak height as a function of gamma-aminobutyric acid (GABA) concentration is linear over the range from 10(-5) to 10(-8) M, with the LOD being 4 nM. We demonstrate the diagnostic potential of this approach for the determination of amino acids, including GABA and glutamine, in biological samples through the analysis of large volumes of cerebral spinal fluids without the need for sample pretreatment.

Ultrastructural findings in feline corneal sequestra

(1) To describe the ultrastructural features of corneal sequestra in cats; and (2) to enhance our understanding regarding the pathogenesis of feline corneal sequestration. Nine corneal sequestra were harvested via keratectomy from globes of nine cats. The sequestra were routinely fixed then postfixed for high resolution light and transmission electron microscopy (HR-LM and TEM, respectively). The tissues were embedded in Epon/Araldite. Sections of 0.5-microm thickness were cut and stained with 1% toluidine blue in 1% sodium tetraborate solution for HR-LM. Ultrathin sections were collected on copper grids and stained with uranyl acetate and Sato's lead stain for TEM. Ultrathin sections were examined and the images were captured on an Advantage HR CCD camera using a Hitachi 7500 electron microscope operated at 80 kV. Two healthy corneas from two cats were harvested immediately following euthanasia. These corneal tissues (control samples) were processed in the same manner as the corneal sequestra for HR-LM and TEM. A portion of each sequestrum was also submitted for polymerase chain reaction (PCR) testing for infectious agents including feline herpesvirus-1 (FHV-1), Toxoplasma gondii, Chlamydophila felis and Mycoplasma spp. Ultrastructure of healthy corneal tissues revealed basal corneal epithelial cells aligned adjacent to a thin acellular layer similar to Bowman's layer with underlying tightly packed, regularly arranged, collagen fibrils oriented in different planes. Keratocytes were elongated and had long and irregularly shaped nuclei, and cytoplasm contained rough endoplasmic reticulum and abundant membrane-bound vesicles. In contrast, corneal sequestra contained varying amounts of an amorphous, electron-dense substance, continuous with intact basal epithelial basement membranes peripherally, and overlying corneal ulceration and loosely packed collagen fibrils. Remnants of necrotic keratocytes were seen in spaces between disarranged collagen layers. In all samples, occasional keratocytes exhibited morphology indicative of apoptosis including clumping and margination of chromatin, and shrunken cytoplasm. Varying degrees of inflammation were noted on HR-LM and TEM of affected corneas including peri- and intralesional neutrophils, lymphocytes, plasma cells, and macrophages. Corneal sequestra were FHV-1-positive (n = 3), FHV-1- and T. gondii-positive (n = 1), T. gondii-positive (n = 3), or negative for DNA of these infectious agents (n = 2) using PCR. All corneal sequestra were negative for DNA of Chlamydophila felis and Mycoplasma spp. using PCR. Apoptosis may play a role in the pathogenesis of feline corneal sequestration independent of the presence of DNA of these infectious organisms. Prospective clinical studies are warranted to further understand the significance of T. gondii in relation to feline corneal sequestration.

Assay of the synthetic estrogen fosfestrol in pharmaceutical formulations using capillary electrophoresis

This study reports – for the first time – a capillary electrophoretic method for the determination of fosfestrol, a synthetic estrogen used in the treatment of metastatic prostate cancer. The effects of the carrier ion concentration, injected volume and applied voltage were studied and optimized. A 10 mM sodium tetraborate solution was selected as the carrier electrolyte solution, while the sample was injected hydrodynamically by applying a 20 mmHg vacuum for 1 s. The driving voltage was 30 kV and the absorbance of the analyte (peak height) was monitored at 240 nm. Under the above-mentioned conditions, the migration time of fosfestrol was 6.6 min. Linearity was achieved in the analyte range 3–150 mg L −1 with the detection limit being 1 mg L −1. The proposed method is adequately precise ( s r = 2.8% at 100 mg L −1 fosfestrol, n = 10) without the use of an internal standard and was applied to the determination of fosfestrol in a pharmaceutical formulation. The results obtained by the proposed method were in good agreement with those derived from the USP reference method.

Characterisation of the anodic layers formed on 2024 aluminium alloy, in tetraborate electrolyte containing molybdate ions

Anodic layer growth on 2024 aluminium alloy at 70 °C, under 40 V, during 60 min, in 50 g L −1 di-sodium tetraborate solution containing di-sodium molybdate from 0.1 to 0.5 M (pH 10) is examined. Anodising behaviours strongly depend on additive concentration. Development of anodic films is favoured with weak molybdate additions (<0.3–0.4 M). The film thicknesses increase and the porosity of anodic layers decreases. Molybdenum (+VI), detected by X-ray photoelectron spectroscopy (XPS) analysis, is present in the anodic films and the Mo incorporation, studied by energy dispersive spectroscopy (EDS) analysis, increases with molybdate concentration. However, for high molybdate concentrations (>0.4 M), anodising behaviour becomes complex with the formation of a blue molybdenum oxide at the cathode. The growth of aluminium oxide is hindered. As the anodic layers are thinner, the Mo(+VI) incorporation significantly decreases. These two configurations implicate different corrosion performances in 5% sodium chloride solution at 35 °C. As the alkaline anodic layer formed with 0.3 M molybdate species is the thickest and the Mo incorporation is the more pronounced, its corrosion resistance is the highest. The effect of morphology and composition of anodic films on pitting corrosion is also discussed.

The role of electrolyte concentration in the decomposition of water and generation of electrons under conditions of anodic microdischarges

The dependence of the yield of water decomposition (from the measured yield of formation of hydrogen peroxide and yield of scavenging of OH radicals by isopropanol), as well as the yield of electron scavenging by a solute (nitrobenzene), on the concentration of aqueous electrolyte (sodium tetraborate and ammonium tetraborate) solutions under the action of anodic microdischarges was determined. Nonmonotonic functions were found, which exhibited maximums at 0.03 and 0.1 M concentrations for water decomposition and electrons, respectively. The results were explained by an increase in the fraction of anionic current through the discharge plasma-liquid cathode interface as the electrolyte concentration was increased.

The influence of chloride ions and benzotriazole on the corrosion behavior of Cu37Zn brass in alkaline medium

This paper describes an investigation of the corrosion behavior of Cu37Zn brass in a solution of sodium tetraborate, at pH 10.0, with the addition of chloride ions and benzotriazole (BTA) inhibitor. The application of cyclic voltammetry has led to the conclusion that the anodic current densities increase with increase in immersion time in sodium tetraborate solution as well as in solutions of sodium tetraborate containing chloride ions of various concentrations. The values of anodic current density are considerably smaller in sodium tetraborate solutions with the addition of BTA compared with those in the inhibitor-free solution. The study also analyses the electrochemical behavior of Cu37Zn brass after various times of alloy exposure to BTA solution, as well as its behavior in BTA solutions of various concentrations. Also, the study describes the electrochemical behavior of Cu37Zn brass after the effect of Cl − ions, but subsequent to the formation of a polymeric protective film on the electrode surface.

Plasma-electrolytic formation, composition and catalytic activity of manganese oxide containing structures on titanium

In the present work, we report the data about formation of TiO 2-rutile or TiO 2 and Mn 2O 3, Mn 3O 4 containing oxide structures on titanium in aqueous electrolytes by means of plasma-electrolytic deposition. The layers formed are characterized by X-ray diffraction, electron probe microanalysis and scanning electron microscopy methods. The PEO coatings on titanium formed in sodium tetraborate solution contain the TiO 2 stabile rutile modification that is important when utilizing such a structure as a catalyst carrier. Manganese acetate adding into the electrolyte leads to formation of layers that contain Mn 2O 3, Mn 3O 4 and TiO 2-rutile in outer region. The manganese content in the surface layer depends on the formation conditions as well as on manganese acetate concentration in the electrolyte. Catalytic activity of the layers in CO → CO 2 reaction is studied in the static and flow conditions. The manganese-containing layers obtained possess the catalytic activity in CO → CO 2 oxidation reaction at the temperature range of 250–350 °C. The catalytic activity depends on the concentration and surface distribution of manganese as well as on the layers morphology.

Simultaneous determination of ingredients in a cold medicine by cyclodextrin-modified microemulsion electrokinetic chromatography

Cyclodextrin-modified microemulsion electrokinetic chromatography (CD-MEEKC) was used to simultaneously determine 14 active ingredients (thiamine nitrate, anhydrous caffeine, acetaminophen, riboflavin, guaifenesin, pseudoephedrine hydrochloride, ascorbic acid, ethenzamide, DL-methylephedrine hydrochloride, dihydrocodeine phosphate, ibuprofen, noscapine, carbinoxamine maleate, and bromhexine hydrochloride) in a cold medicine. Separation of the ingredients was optimized by changing the SDS concentration and oil type and the addition of 2-propanol and cyclodextrin (CD) to the separation solution. The separation selectivity was improved dramatically by changing CD type. All of the active ingredients and formulation excipients were successfully separated with the use of a separation solution consisting of 0.81% (w/w) pentane, 6.61% (w/w) 1-butanol, 2% (w/w) 2-propanol, 4.47% (w/w) SDS, and 86.11% (w/w) 10 mM sodium tetraborate solution with 3 mM 2,6-di- O-methyl-β-CD. The established method was then validated and demonstrated to be applicable to the determination of the active ingredients in a model cold medicine. No interference from the formulation excipients was observed. Good linearities were obtained with correlation coefficients above 0.999. Recovery and precision ranged from 99.1 to 100.7% and from 0.5 to 2.8% R.S.D., respectively. The detection limit for ingredients ranged from 0.6 to 4.2 μg ml −1. Good agreement was obtained between the established method and the traditional HPLC method. These results suggest that CD-MEEKC can be used for the determination of multiple ingredients in cold medicine.

Quantitative determination of rutin, quercetin, and adenosine in Flos Carthami by capillary electrophoresis

AbstractA capillary electrophoresis method was developed for the separation and determination of adenosine, rutin, and quercetin in Flos Carthami. The CE separation was achieved using 50 mmol L–1 sodium tetraborate solution (pH 9.7) containing 18% methanol as the running buffer, with an applied voltage of 24 kV and detection at 210 nm. The contents of these constituents in an ethanol‐water extract of Flos Carthami could be easily determined within 45 min. The RSDs of the contents of these constituents were within 5.2% (n = 5). The contents of adenosine, rutin, and quercetin were determined in Flos Carthami from ten sources. Differences in contents were observed between various sources, which may be attributed to the growth environment of the plant, the time of harvesting, the storage conditions, and the drying process. The current method may serve as a valuable tool for the quality control of Flos Carthami.

Simultaneous determination of ingredients in a vitamin-enriched drink by micellar electrokinetic chromatography

Micellar electrokinetic chromatography was used to simultaneously determine six active ingredients (2-aminoethanesulfonic acid, nicotinamide, pyridoxine hydrochloride, anhydrous caffeine, riboflavin sodium phosphate and thiamine nitrate) in a vitamin-enriched drink. All the active ingredients and the formulation excipients were successfully separated by micellar electrokinetic chromatography with 135 mM sodium dodecyl sulfate, and were subsequently detected using a diode-array detector operating at 210 nm. The peak shape of pyridoxine hydrochloride was improved by use of sodium tetraborate solution as sample solvent. Sample and standard solutions were stable for at least 24 h in a light-resistant container at room temperature. The established method was validated and demonstrated to be applicable to the determination of the active ingredients in a vitamin-enriched drink. Good linearities were obtained, with correlation coefficients above 0.999. Recoveries and precisions ranged from 99.0 to 101.2%, and from 0.4 to 2.5% RSD, respectively. The detection limit for ingredients ranged from 0.3 to 125 μg ml −1. These results suggest that micellar electrokinetic chromatography can be used for the determination of ingredients in vitamin-enriched drinks.

Conduction Mechanism of the Passive Film on Iron Based on Contact Electric Impedance and Resistance Measurements

The application of a mixed conduction model and a new contact electric impedance (CEI) technique to predict quantitatively the electronic and ionic transport properties of oxide films on iron in a nearly neutral tetraborate solution is discussed. The mixed-conduction model emphasizes the coupling between the ionic defect structure and the electronic conductivity in an anodic film. Conventional electrochemical techniques have not been sufficient to characterize properly the electronic and ionic properties of anodic films on metals. The CEI technique makes it possible to distinguish between processes taking place at different rates within oxide films. Using this technique together with the contact electric resistance technique, we have found that the diffusion coefficient for the electronic conduction in the anodic film on iron is several orders of magnitude higher than that for the ionic transport. This shows that the passive film on iron is predominantly an electronic conductor. The fitting of the experimental results to the mixed conduction model gives a good agreement and thus supports the validity of this model in the present case. © 2001 The Electrochemical Society. All rights reserved.

Indirect photometric ion chromatographic analysis of anions in Haematococcus pluvialis culture media

An indirect photometric ion chromatographic method for the simultaneous determination of chloride, nitrate and sulfate ions was developed and applied to the determination of anions, mainly nitrate, in the alga Haematococcus pluvialis culture media. Using phthalic acid/sodium tetraborate aqueous solution as the mobile phase, anions can be detected indirectly by a UV detector. The calibration curves for these anions gave good linearity from 1 to 1000 μg ml−1.

Separation of sympathomimetic amines of abuse and related compounds by micellar electrokinetic chromatography.

Separation of twelve sympathomimetic amines and related compounds by micellar electrokinetic chromatography (MEKC) with UV absorbance detection is described. These amines were well separated within 25 min using 50 mM sodium tetraborate solution containing 15 mM sodium dodecylsulfate (SDS) of pH 9.3 as a running solution and detected at 210 nm. MEKC was performed with an applied voltage of 13 kV at 25 degrees C using a fused-silica capillary (50 cm x 75 mm i.d.) with effective length of 37.5 cm. The detection limits of these compounds were in the range from 4 to 97 fmol/injection at a signal-to-noise ratio (S/N) of 3. The reproducibility of the method expressed as relative standard deviation (RSD) for within-day (n=6) and between-day (n=5) assays was less than 4.8 and 8.8%, respectively. The proposed method could be applied to the determination of an anorectic drug, phentermine, in Chinese tea with a detection limit of 99 microg/g (105 fmol/injection, S/N=3).

Pharmacokinetics and effects after intravenous administration of high-dose boron to rat.

Boron (B) compounds have been widely used in the chemical industry, agriculture, and environmental science. The kinetics and toxicity of B were studied by analyzing several serum and urine parameters after a single intravenous injection of sodium tetraborate solution (B: 85.7 mg/kg) in Wistar male rats. Blood samples were removed at 0, 1, 2, 4, and 6 h after injection. The serum parameters studied included: B, Na, Ca, K, P, Mg, gamma-GTP, AST, ALT, BUN, Cr, CK, LDH and ALD. Plasma concentration-time profiles of B were evaluated by a nonlinear least-squares method for fitting data to polyexponential equations and calculation of relevant pharmacokinetic parameters. Urine samples were collected from the bladder following infusion. The urinary parameters that were studied included urine volume and excretion of B, Cr and NAG. Results indicated that a two-compartment model could describe the elimination of B from plasma after intravenous administration. Urine volume significantly increased. A diuretic effect of B was noted.

Capillary Electrophoresis Method for the Determination of Amino Acids in Pharmaceutical Samples Based on Precolumn Derivatization Using 1,2-Naphthoquinone-4-Sulfonate

A new method for the determination of amino acids by capillary electrophoresis based on derivatization with 1,2-naphthoquinone4-sulfonate is developed. The separation of amino acid derivatives can be performed in a fused-silica capillary with a 40mM aqueous sodium tetraborate solution‐isopropanol background electrolyte solution (3:1, v/v) under an applied potential of 30 kV. Glutamic and aspartic acids and cysteine can be separated faster in a 20mM sodium tetraborate solution at 15 kV. Amino acid derivatives are spectrophotometrically detected at 480 nm. The precapillary derivatization is developed for 5 min at 65°C and pH 10. The linear range for lysine is up to 1.25  10 —3 M, the repeatability is 3.0%, and the detection limit is 0.67 pmol when injecting 22.5 nL. The method is applied to the determination of amino acids in pharmaceutical samples. Good agreement is found between the method proposed and the standard method.

Preparation of boron nitride fibers with the use of hydrated cellulose. II. Nitriding hydrated cellulose fibers impregnated with ammonium borate

The effect of preliminary heat treatment (PHT) of hydrated cellulose fibers impregnated with an ammonium tetraborate solution on the composition and structure of nitrided products was studied. The PHT conditions which upon subsequent nitriding led to the formation of C—BN fibers with a coating of BN, and also hollow and solid BN fibers, were determined

Thermal and viscoelastic properties of alginate/poly(vinyl alcohol) blends cross-linked with calcium tetraborate

Binary blends of alginate (Alg) with poly(vinyl alcohol) (PVA) were cast in film form from mixed aqueous polymer solutions by solvent evaporation. The thermal transition and viscoelastic behavior of the Alg/PVA blends were investigated by differential scanning calorimetry and dynamic mechanical analysis. Irrespective of composition, blend samples gave a single glass transition temperature ( T g) situated between the T gs of PVA and alginate per se. The melting point of the PVA component was depressed systematically with increasing alginate content in the blends. These observations indicate that the polymer blend of Alg/PVA is capable of forming a thermodynamically miscible phase in the amorphous state. An additional treatment of as-cast samples with calcium tetraborate solution gave rise to a marked elevation of their T gs. This may be ascribed to the possible, simultaneous occurrence of a chelate complexation of alginates with Ca 2+ cation and a borate ion-aided cross-links between PVA chains, resulting in the formation of an ‘IPN’ structure.

Serum and urinary boron levels in rats after single administration of sodium tetraborate.

The pharmacokinetics of boron was studied in rats by administering a 1 ml oral dose of sodium tetraborate solution to several groups of rats (n=20) at eleven different dose levels ranging from 0 to 0.4 mg/100 g body weight as boron. Twenty-four-hour urine samples were collected after boron administration. After 24 h the average urinary recovery rate for this element was 99.6+/-7.9. The relationship between boron dose and excretion was linear (r=0.999) with a regression coefficient of 0.954. This result suggests that the oral bioavailability (F) of boron was complete. Another group of rats (n=10) was given a single oral injection of 2 ml of sodium tetraborate solution containing 0.4 mg of boron/100 g body wt. The serum decay of boron was followed and found to be monophasic. The data were interpreted according to a one-compartment open model. The appropriate pharmacokinetic parameters were estimated as follows: absorption half-life, t1/2a=0.608+/-0.432 h; elimination half-life, t1/2=4.64+/-1.19 h; volume of distribution, Vd = 142.0+/-30.2 ml/100 g body wt.; total clearance, Ctot=0.359+/-0.0285 ml/min per 100 g body wt. The maximum boron concentration in serum after administration (Cmax) was 2.13+/-0.270 mg/l, and the time needed to reach this maximum concentration (Tmax) was 1.76+/-0.887 h. Our results suggest that orally administered boric acid is rapidly and completely absorbed from the gastrointestinal tract into the blood stream. Boric acid in the intravascular space does not have a strong affinity to serum proteins, and rapidly diffuses to the extravascular space in proportion to blood flow without massive accumulation or binding in tissues. The main route of boron excretion from the body is via glomerular filtration. It may be inferred that there is partial tubular resorption at low plasma levels. The animal model is proposed as a useful tool to approach the problem of environmental or industrial exposure to boron or in cases of accidental acute boron intoxication.

The Use of Additional Redox Couples in the Investigation of the Electronic Conductivity of Passive Layers

Passive layers developed at the alloy surface may be undesirable in some industrial applications. In lead-acid batteries, the passivation of lead alloy electrodes has been a problem to resolve. The addition of tin to lead alloys has overcome the passivation phenomenon. To follow in situ the electrical properties of the passive layer, the ferro-ferricyanide couple was added to the electrolyte (tetraborate solution, pH 9.1) and polarization currents were measured in the passive potential range. The modification of the electronic conductivity of the passive layer by alloying lead with tin altered the exchange current density of the redox reaction. No electron transfer was observed on passive lead alloyed with less than 0.8wt% tin. The electronic conductivity of the passive layer increased sharply when the alloying tin level increased from 0.8 to 1.5 wt% and reached a plateau at higher tin levels. Ferrous-ferric and cerous-ceric couples were used in sulfuric solutions, to follow the conductivity of various passive layers formed at various potentials for various times. Potentiodynamic studies showed that, for lead alloys containing more than 1wt% tin, the passive layer formed by polarization from -400 to 1000mV/Hg-Hg 2 SO 4 was non-conducting. But, after an incursion into high potential, i.e 1550 mV, the passive layer became electron conducting, even at low potentials, in the range 1000 to -400 mV. The change with time of the conductivity of the passive layer was followed by the oxidation rate of ferrous ions dissolved in sulfuric solutions. It was shown that the level of the conductivity was closely related to the proportion of tin in the lead-tin alloys.

Formation and Breakdown of Anodic Oxide Films on Aluminum in Boric Acid/Borate Solutions

Highly pure aluminum was anodized at a constant current density of at 293 Kin 0.5 M boric acid/0, 0.005, or 0.05 M sodium tetraborate solutions, to examine the effect of sodium tetraborate concentration on the formation and breakdown characteristics of barrier oxide films by using inductively coupled plasma atomic emission spectrometry, electroluminescence/photoluminescence measurements, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy. In boric acid/borate solutions, a crystalline alumina formed locally in the middle of the amorphous oxide film. Above the crystalline alumina, a void is formed and may lead to a breakdown of the oxide film at 420 to 540 V. In boric acid solution, an amorphous oxide film grew until 1180 V with the formation and development of imperfections and with enhancement of electroluminescence and gas evolution. At imperfections, the oxide/solution interface was convex and the oxide/metal interface curved in the opposite direction. This deformation is attributed to high‐pressure evolved in the pores of imperfections and to the local formation and dissolution of oxide. The breakdown of the oxide film started when the evolution and oxide dissolution at imperfections become predominant. The mechanism of formation and breakdown of the anodic film in the boric acid/borate solutions is discussed in terms of pH buffering of the anodizing solution, and the electronic structure of anodic oxide films is correlated with electroluminescence and photoluminescence spectrum results.