Analytical approach to the metallomic of Nile tilapia (Oreochromis niloticus) liver tissue by SRXRF and FAAS after 2D-PAGE separation: Preliminary results

An investigation was made into calcium, iron and zinc in protein spots in samples of Nile tilapia (Oreochromis niloticus) liver tissue obtained after protein separation by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and subsequent qualitative and quantitative evaluation by synchrotron radiation X-ray fluorescence (SRXRF) and Flame Atomic Absorption Spectrometry (FAAS). An analysis of the fluorescence spectra indicated the presence of calcium, iron and zinc in 12, 6 and 8 liver protein spots, respectively. The metal ions found were distributed mainly in proteins with a molar mass of less than 40.00 kDa and more than 12.00 kDa, with pI in the range of 4.70-9.40. The only exception was a spot presenting protein with a molar mass of 10.10 kDa. In addition to calcium, iron and zinc, sulfur and phosphorus - which are non-metals that may be part of the protein structure, were also detected. After microwave-assisted acid mineralization of the proteins spots, a FAAS estimation of the concentration of calcium, iron and zinc ions bound to these proteins indicated a range of 1.08-5.80 mg g⁻¹, 2.02-8.03 mg g⁻¹ and 1.60-8.55 mg g⁻¹, respectively.     

Determination of rare earth elements in geological samples by inductively-coupled plasma atomic emission spectrometry after oxalate coprecipitation and cation-exchange column separation

A method for separation and determination of traces of 14 rare earth elements (REEs) in geological samples is described. Determination by inductively-coupled plasma atomic emission spectrometry follows oxalate coprecipitation of the REEs with calcium as carrier and cation- exchange column separation in nitric acid. The combination of the two separation techniques improved the low recoveries found for Sm, Eu, and Gd when only ion-exchange was used, especially for iron- and aluminum-rich samples. The method was applied to the analysis of geological standard materials NBS SRM 688 (basalt), NBS SRM 278 (obsidian), GSJ JB-1 (basalt), GSJ JA- 2 (andesite), and CCRMP SY-3 (syenite). The results were evaluated on the basis of chondrite- normalized rare earth element distribution patterns.     

Mass spectrometric characterization of the zein protein composition in maize flour extracts upon protein separation by SDS‐PAGE and 2D gel electrophoresis

Highly homogenous α zein protein was isolated from maize kernels in an environment‐friendly process using 95% ethanol as solvent. Due to the polyploidy and genetic polymorphism of the plant source, the application of high resolution separation methods in conjunction with precise analytical methods, such as MALDI‐TOF‐MS, is required to accurately estimate homogeneity of products that contain natural zein protein. The α zein protein product revealed two main bands in SDS‐PAGE analysis, one at 25 kDa and other at 20 kDa apparent molecular mass. Yet, high resolution 2DE revealed approximately five protein spot groups in each row, the first at ca. 25 kDa and the second at ca. 20 kDa. Peptide mass fingerprinting data of the proteins in the two dominant SDS‐PAGE bands matched to 30 amino acid sequence entries out of 102 non‐redundant data base entries. MALDI‐TOF‐MS peptide mapping of the proteins from all spots indicated the presence of only α zein proteins. The most prominent ion signals in the MALDI mass spectra of the protein mixture of the 25 kDa SDS gel band after in‐gel digestion were found at m/z 1272.6 and m/z 2009.1, and the most prominent ion signals of the protein mixture of the 20 kDa band after in‐gel digestion were recorded at m/z 1083.5 and m/z 1691.8. These ion signals have been found typical for α zein proteins and may serve as marker ion signals which upon chymotryptic digestion reliably indicate the presence of α zein protein in two hybrid corn products.     

Critical investigation of the separation of noradrenaline and adrenaline from urine samples using Al2O3 as adsorbant

A critical investigation of the separation of free noradrenaline and adrenaline from urine samples revealed serious errors during sample pretreatment using Al₂O₃ as adsorbant. An exact and rapid pH adjustment of the sample, using thymol-blue as indicator, proved to be the chief prerequisite for precise and accurate results. Increasing temperature and pH favour the oxidative decomposition of the catecholamines during routine analysis. This was examined, using the radiotracer method and liquid scintillation counting.     

2D silver nanocrystal ordering modulated by various substrates and revealed using oxygen plasma treatment

Here, 5 nm Ag nanocrystals are deposited, using the same procedure, on various substrates differing by their rms roughness, wetting properties and nanoparticle-substrate interactions leading, consequently, to different nanocrystal orderings. Theoretical calculations are carried out to understand how these parameters influence the size of the nanocrystal organizations on the substrate surface. When these nanocrystal arrays are subjected to an oxygen plasma treatment, the nanocrystals perfectly assembled in hexagonal networks remain intact, while the nanocrystals that are not well-packed coalesce to form larger particles independently on the used substrate. This phenomenon is observed on the entire substrate surface. This procedure gives an innovative way of using oxygen plasma generated by the reactive ion etching technique, as a new method to reveal defects in 2D Ag nanocrystal self-assemblies.     

Extraction of hydrocarbons from seaweed samples using sonication and microwave-assisted extraction: a comparative study

A sonication method is compared with a microwave-assisted extraction method for recovering polycyclic aromatic hydrocarbons and aliphatic hydrocarbons from seaweed and acid humic samples. Different extracting solvents and adsorbents for the purification step are tested. For the sonication extraction, 10 g of the sample are extracted in an ultrasonic bath (60 degrees C for 15 min with 20 mL of hexane). For the microwave-assisted extraction two steps are carried out, each step at 90 degrees C under pressure in closed vessels with 20 mL of hexane for 10 min at 950 W. A clean-up step is performed for both extraction techniques. The results indicate that the recovery of hydrocarbons is dependent on both the extraction technique and the type of matrix. The most suitable technique appears to be sonication employing hexane as the extraction solvent. The recoveries obtained for aliphatic hydrocarbons are higher than those achieved for the polycyclic aromatic hydrocarbons, with values ranging within 81-109% and 40-76%, respectively.     

Determination of platinum and palladium in environmental samples by graphite furnace atomic absorption spectrometry after separation on dithizone sorbent

A graphite furnace atomic absorption method of platinum and palladium determination after their separation from environmental samples has been presented. The samples were digested by aqua regia and the analyte elements were separated on the dithizone sorbent. The procedure of sorbent preparation was described and their properties were established. Two various procedures of elution by thiourea and concentrated nitric acid were described and discussed. The low limit of detection was established as 1 ng g⁻¹ for platinum and 0.2 ng g⁻¹ for palladium.There was also investigated the behaviour of platinum and palladium introduced into the soil in various chemical forms.     

Speciation analysis of vanadium in natural water samples by electrothermal vaporization inductively coupled plasma optical emission spectrometry after separation/preconcentration with thenoyltrifluoroacetone immobilized on microcrystalline naphthalene

A sensitive and simple method for low temperature electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) determination of V(IV) and V(V) after separation/preconcentration by a micro-column packed with immobilized thenoyltrifluoroacetone (TTA) on microcrystalline naphthalene has been developed. Thenoyltrifluoroacetone was used as both a chelating agent for micro-column separation/preconcentration and a chemical modifier for ETV-ICP-OES determination of vanadium. Both vanadium species could be trapped by micro-column at pH 4.0, and the vanadate (VO₂⁺) ion could be collected selectively at pH 2.4. Solid material loaded with analyte in the micro-column was dissolved with 100 μL of acetone containing 2.0 mmol L⁻¹ TTA and the vanadium was determined subsequently by ETV-ICP-OES. The concentration of vanadyl (VO²⁺) ion was calculated by subtracting the vanadate concentration from the total concentration of vanadium. Under the optimized experimental conditions, the detection limit (3σ) for the preconcentration of 5 mL of aqueous solution is 0.068 μg L⁻¹ for both species and the relative standard deviations were 4.3% for vanadium(V) and 4.8% for vanadium(IV) (c=10 μg L⁻¹, n=7), respectively. The method was applied successfully to the determination of vanadium(IV) and vanadium(V) in natural water samples.     

Speciation of inorganic selenium in environmental water samples by inductively coupled plasma optical emission spectrometry after preconcentration by using a mesoporous zirconia coating on coal cinder

A simple, novel, and selective flow‐injection solid‐phase extraction with inductively coupled plasma optical emission spectrometry method was developed for the speciation of inorganic selenium in environmental water samples. A mesoporous zirconia film was simply introduced to coat coal cinder by means of the sol–gel technique, and the adsorptive performance of the coated material for Se(IV)/Se(VI) was investigated in different media. Both Se(IV) and Se(VI) can be retained quantitatively by the material in HCl/NaOH (pH 1.0–9.0) media, while only Se(IV) was adsorbed quantitatively in sodium acetate buffer (pH 3.5–6.0). Thus, the assay of Se(VI) is based on subtracting Se(IV) from total selenium by controlling different adsorptive media without employing any redox procedure. Under the optimum conditions, the detection limit of Se(IV) is 9.0 ng/L with an enrichment factor of 100, and the relative standard deviation is 3.6% (n = 9, C = 5.0 ng/mL). The developed method was successfully applied to the speciation of inorganic selenium in environmental water samples with satisfactory results. In order to further verify the accuracy of the developed method, it was applied to analysis of total selenium in GSBZ 50031–94 certified reference environmental water, and the determined values coincided with the certified values very well.     

Nonlinear calibrations on the assay of dilitiazem and two of its metabolites from plasma samples by means of liquid chromatography and ESI/MS(2) detection: application to a bioequivalence study

The assay of diltiazem (DLTZ) and its active metabolites desacetyldiltiazem (DAcD) and desmethyldiltiazem (DMeD) in plasma samples was achieved by means of an HPLC/(ESI)MS(2) method. The diastereoisomer of diltiazem, namely {(2R,3S)-5-[2-(dimethylamino)ethyl]-2-(4-methoxyphenyl)-4-oxo-2,3,4,5-tetrahydro-1,5-benzothiazepin-3-yl acetate} was used as internal standard (IS). Sample preparation was based on protein precipitation by means of organic solvent addition (acetonitrile). The isocratic elution based on a reversed-phase mechanism allows good separation of the analytes within 15 min. Atmospheric pressure electrospray ionization was used. All analytes were monitored in the MS(2)-MRM mode. A fragmentation schema is proposed for the target compounds. As the method was designed for bioequivalence purposes, a full validation procedure was considered. On validation, nonlinear calibrations were observed. Consequently, concentration intervals requiring nonlinear calibrations are discussed. Low limits of quantification in the 0.6-1 ng/mL concentration range were obtained. The analytical method was successfully applied to a single dose (120 mg), open-label, randomized, two-period, two-sequence, crossover bioequivalence study of two commercially available solid oral dosage pharmaceutical formulations (tablets).     

Metal Al produced by H2 plasma reduction of AlCl3: a thermodynamic and kinetic study on the plasma chemistry

In this paper we reported that low temperature plasma may reverse the direction of a chemical reaction. The thermodynamically forbidden reaction between H 2 and AlCl 3 was able to take place with the assistance of low temperature plasma, yielding metal Al. The plasma chemistry of the reaction was investigated by optical emission spectroscopy, which suggested that the dissociation of H 2 and AlCl 3 molecules by plasma led the reaction to a thermodynamically favorable one by creating reaction channels with low Gibbs free energy change. The addition of Ar promoted the reaction kinetics dramatically, which was attributed to the enhanced dissociation of AlCl 3 molecules by excited Ar species.     

Capture and separation of CO2 on BC3 nanosheets: A DFT study

In order to reduce the greenhouse effect caused by the rapid increase of CO₂ concentration in the atmosphere, it is necessary to develop more efficient, controllable, and highly sensitive adsorbing materials. In this study, the adsorption behavior of CO₂ on BC₃ nanosheets under an external electric field was explored based on density functional theory (DFT). It was found that CO₂ experienced a transition from physisorption to chemisorption in the electric field range of 0.0060-0.0065 a.u.. In addition, the adsorption/desorption of CO₂ is reversible and can be precisely controlled by switching on/off at the electric field of 0.0065 a.u.. The selective adsorption of CO₂/H₂/CH₄ by BC₃ can also be used to realize gas separation and purification under different electric fields. This study highlighted the potential application of BC₃ nanosheets as a high-performance, controllable material for CO₂ capture, regeneration, and separation in an electric field.     

Determination of chromatographic separation parameters of tryptophan enantiomers on a Chirosil-SCA chiral stationary phase by using the inverse method based on the initial guesses estimated from elution by characteristic point method

An effective chiral stationary phase (CSP) for enantioseparation of amino acids was established previously by bonding (18-crown-6)-2, 3, 11, 12-tetracarboxylic acid to silica gel. This CSP has recently been commercialized under the name of Chirosil-SCA. As a first step for developing a Chirosil-SCA simulated moving bed chromatographic process for separation of tryptophan enantiomers, the adsorption isotherm and mass-transfer parameters of each tryptophan enantiomer on the Chirosil-SCA CSP were determined in this study while using only water as a mobile phase. For this task, inverse method (IM) was applied on the basis of the initial guesses estimated from elution by characteristic point (ECP) method, which was found to be more advantageous in the aspects of both accuracy and computational efficiency than the case of utilizing individually only IM or ECP method. The results revealed that the adsorption behavior of each tryptophan enantiomer on the Chirosil-SCA could be well described by the Langmuir-Freundlich isotherm. The model predictions based on the determined parameter values were in close agreement with the experimental chromatograms from a series of single-component or mixture pulse tests that were performed under various feed concentrations and flow rates. It was also found that the Langmuir-Freundlich isotherm parameters of each enantiomer were largely affected by temperature. Such a marked dependence of the parameters on temperature was investigated quantitatively. The results of such an investigation indicated that as the temperature decreases, the adsorption affinities of both enantiomers become higher and the heterogeneity of the Chirosil-SCA becomes more pronounced.     

Sorption separation of Eu and As from single-component systems by Fe-modified biochar: kinetic and equilibrium study

The utilization of carbonaceous materials in separation processes of radionuclides, heavy metals and metalloids represents a burning issue in environmental and waste management. The main objective of this study was to characterize the effect of chemical modification of corncob-derived biochar by Fe-impregnations on sorption efficiency of Eu and As as a model compounds of cationic lanthanides and anionic metalloids. The biochar sample produced in slow pyrolysis process at 500 °C before (BC) and after (IBC) impregnation process was characterized by elemental, FTIR, SEM-EDX analysis to confirm the effectiveness of Fe-impregnation process. The basic physico-chemical properties showed differences in surface area and pH values of BC- and IBC-derived sorbents. Sorption processes of Eu and As by BC and IBC were characterized as a time- and initial concentration of sorbate-dependent processes. The sorption equilibrium was reached for both sorbates in 24 h of contact time. Batch equilibrium experiments revealed the increased maximum sorption capacities (Q _max) of IBC for As about more than 20 times (Q _max BC 0.11 and Q _max IBC 2.26 mg g^?1). Our study confirmed negligible effect of Fe-impregnation on sorption capacity of biochar for Eu (Q _max BC 0.89 and Q _max IBC 0.98 mg g^?1). The iron-impregnation of biochar-derived sorbents can be utilized as a valuable treatment method to produce stable and more effective sorption materials for various xenobiotics separation from liquid wastes and aqueous solutions.     

High-performance liquid chromatography of fat-soluble vitamins: separation and identification of vitamins D2 and D3 and their isomers in food samples in the presence of vitamin A, vitamin E and carotene

Vitamins D2 and D3 and their corresponding previtamins and provitamins were resolved by reversed-phase high-performance liquid chromatography using a ternary solvent system (acetonitrile-methanol-water) pumped according to a gradient elution programme. The D vitamins were also resolved in the presence of other lipid-soluble vitamins (A, E and K1) and carotene. The peaks were monitored with a UV-visible variable-wavelength detector and were detected at their maximum absorbance, resulting in maximum sensitivity. Lipid-soluble vitamins and carotene were resolved in extracts obtained from oils and butter, thus permitting their identification in a single chromatographic run.     

Recovery of atrazine, bromacil, chlorpyrifos, and metolachlor from water samples after concentration on solid-phase extraction disks: interlaboratory study

An interlaboratory comparison was conducted in 1997 and 1998 to examine the feasibility of using C18 solid-phase extraction disks (Empore) to simultaneously determine the herbicides atrazine, bromacil, and metolachlor and the insecticide chlorpyrifos in water samples. A common fortification source and sample processing procedure were used to minimize variation in initial concentrations and operator inconsistencies. The protocol consisted of paired laboratories in different locations coordinating their activities and shipping fortified water samples (deionized or local surface water) or Empore disks on which the pesticides had been retained and then quantitating the analytes by a variety of gas chromatographic methods. Average recoveries from all laboratories were >80% for atrazine, bromacil, and metolachlor, and >70% for chlorpyrifos. Detection of bromacil was unachievable at some locations because of chromatographic problems. Shipping samples between cooperating laboratories did not affect the recovery of atrazine, chlorpyrifos, or metolachlor in either matrix. Recoveries tended to be higher from disks shipped to cooperating laboratories compared with those from fortified water. Shipping disks eliminated many problems associated with the shipment of water samples, such as bottle breakage, higher shipping cost, and possible pesticide degradation. Recoveries of bromacil and metolachlor were lower from fortified surface water samples than from fortified deionized water samples. This collaborative research demonstrated that pesticides in water samples can be concentrated on solid-phase extraction disks at one location and quantitated under diverse analytical conditions at another location. The extraction efficiencies of the disks were comparable with or better than the recoveries obtained from the shipped water samples, and the problems associated with shipping water samples were eliminated by using the disks.     

Determination of trace molybdenum in biological and water samples by graphite furnace atomic absorption spectrometry after separation and preconcentration on immobilized titanium dioxide nanoparticles

A new method has been developed for the determination of trace molybdenum based on separation and preconcentration with TiO₂ nanoparticles immobilized on silica gel (immobilized TiO₂ nanoparticles) prior to its determination by graphite furnace atomic absorption spectrometry (GFAAS). The optimum experimental parameters for preconcentration of molybdenum, such as pH of the sample, sample flow rate and volume, eluent and interfering ions, have been investigated. Molybdenum can be quantitatively retained by immobilized TiO₂ nanoparticles at pH 1.0 and separated from the metal cations in the solution, then eluted completely with 0.5 mol L^?1 NaOH. The detection limit of this method for Mo was 0.6 ng L^?1 with an enrichment factor of 100, and the relative standard deviation (RSD) was 3.4% at the 10 ng mL^?1 Mo level. The method has been applied to the determination of trace amounts of Mo in biological and water samples with satisfactory results.     

Simultaneous separation and preconcentration of trace elements in water samples by coprecipitation on manganese dioxide using D-glucose as reductant for KMnO(4)

A field oriented and economical method of coprecipitation of trace elements like Al, Au, Bi, Cd, Co, Cu, Fe, Mo, Ni, Pb, Pd, Ti, V, W, Zn and REE has been developed. A novel reductant D-glucose, reduces KMnO₄ in solution to form a precipitate of MnO_2. Two liters of clear natural water sample is adjusted to pH 3.5–4.0, and is treated with 10 ml of 1% KMnO₄ and 20 ml of 0.1% D-glucose. The sample is heated at a temperature of 75–80 °C, MnO₂ is formed which coprecipitates the above trace elements. The precipitate is separated by filtration, dissolved in 2 ml of 50% HCl and 2 ml of 30% H₂O₂ and diluted to 25 ml for analysis using AAS and ICP-AES. The recoveries were found to be 96–105%. The preconcentration factor is 80. Limits of determination by the proposed method in natural waters are 1 μg l⁻¹ for Al, Cd, Mo, V, W, Ti and Zn, 5 μg l⁻¹ for Au, Bi, Co, Cu, Fe, Ni, Pb and Pd and 8 μg l⁻¹ for REE. The RSD of the present procedure (n=5) is 8% at 5 μg l⁻¹ level. Twenty water samples can be analyzed by an analyst in an 8-h day.     

Application of novel copper organic material for facile microextraction of sodium valproate from human plasma samples: Experimental design optimization and isotherm study

Well‐designed metal organic materials (MOMs) were synthesized and applied for pre‐concentration and determination of sodium valproate (Na‐VP) from biological samples, bound to the copper complex of 1,4‐phenylenedioxydiacetic acid under mild conditions. The channels of this sorbent provide high efficiency and also selectivity. The MOMs were structurally characterized using Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning electron microscopy and X‐ray diffraction, and they were found to have suitable features for quantification of Na‐VP using HPLC coupled with UV detection at λ = 215 nm. Moreover, the rate of adsorption is improved by ultrasonic power and the experimental data are best fitted according to Freundlich adsorption isotherm. According to the central composite design, the best experimental conditions are 280.0 μl, 3.0 min and 17.0 mg for volume of eluent, sonication time and sorbent mass respectively. Calibration plots show linear responses towards Na‐VP concentrations (0.4–18.0 μg ml^?1), satisfactory limit of detection (0.06 μg ml^?1, S/N = 3) and reasonable enrichment factor (70.58). The coefficient of variation values of both inter‐ and intra‐day analyses were less than 4.0%, indicating a candidate method for the determination of Na‐VP in human plasma with reasonable recovery and efficiency.