UMLS:C0085631 - FACTA Search

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Query: UMLS:C0085631 (agitation)
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Rapid extraction of eight different peptides using electromembrane extraction (EME) was demonstrated for the first time. During an extraction time of 5 min, the model peptides migrated from a 500 microL aqueous acidic sample solution, through a thin supported liquid membrane (SLM) of an organic liquid sustained in the pores in the wall of a porous hollow fiber, and into a 25 microL aqueous acidic acceptor solution present inside the lumen of the hollow fiber. The driving force of the extraction was a 50 V potential sustained across the SLM, with the positive electrode in the sample and the negative electrode in the acceptor solution. The nature and the composition of the SLM were highly important for the EME process, and a mixture of 1-octanol and 15% di(2-ethylhexyl) phosphate was found to work properly. Using 1mM HCl as background electrolyte in the sample and 100 mM HCl in the acceptor solution, and agitation at 1050 rpm, enrichment up to 11 times was achieved. Recoveries were found to be dependent on the structure of the peptide, indicating that the polarity and the number of ionized groups were important parameters affecting the extraction efficiency. The experimental findings suggested that electromembrane extraction of peptides is possible and may be a valuable tool for future extraction of peptides.
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PMID:Electromembrane extraction of peptides. 1847 91

Quality assurance is one of the major issues in forensic analytical laboratories, where the need for a reference material (RM) has rapidly increased. RMs are very useful for method development and validation, internal quality control or proficiency tests. In the present study, we prepared a RM using drug-free hair for the determination of methamphetamine (MA) and its main metabolite, amphetamine (AP) according to the recommendations of ISO Guide 35. The concentrations of MA and AP were determined using two extraction methods, agitation with 1% HCl in methanol at 38 degrees C and ultrasonication with methanol/5M HCl (20:1), followed by gas chromatography/mass spectrometry (GC/MS) after derivatization with trifluoroacetic anhydride (TFAA). The assignment of values was conducted through the homogeneity study and characterization of the material. Furthermore, an internal proficiency test was performed with the prepared RM, of which the results were compared with those of the authentic hair RM prepared in our previous study. As a result, a hair RM containing MA and AP was prepared at the level of 4.86+/-0.69 ng/mg and 4.63+/-0.44 ng/mg, respectively. Most participants showed satisfactory performances in the internal proficiency test with the both RMs. The hair RM prepared in this study demonstrated its suitability for quality assurance in forensic laboratories.
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PMID:Preparation and application of a fortified hair reference material for the determination of methamphetamine and amphetamine. 1850 69

Impregnated resins prepared by the immobilization of an ionic liquid (IL, Cyphos IL-101, tetradecyl(trihexyl)phosphonium chloride) into a composite biopolymer matrix (made of gelatin and alginate) have been tested for recovery of Bi(III) from acidic solutions. The concentration of HCl slightly influenced Bi(III) sorption capacity. Bismuth(III) sorption capacity increased with IL content in the resin but non-linearly. Maximum sorption capacity reached 110-130mgBig(-1) in 1M HCl solutions. The mechanism involved in Bi recovery was probably an ion exchange mechanism, though it was not possible to establish the stoichiometric exchange ratio between BiCl(4)(-) and IL. Sorption kinetics were investigated through the evaluation of a series of parameters: metal concentration, sorbent dosage, type and size of sorbent particles and agitation speed. In order to reinforce the stability of the resin particles, the IL-encapsulated gels were dried; this may cause a reduction in the porosity of the resin particle and then diffusion limitations. The intraparticle diffusion coefficients were evaluated using the Crank's equation. Additionally, the pseudo-first-order and pseudo-second-order equations were systematically tested on sorption kinetics. Metal can be desorbed from loaded resins using either citric acid or KI/HCl solutions. The sorbent could be recycled for at least three sorption/desorption cycles.
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PMID:Bismuth recovery from acidic solutions using Cyphos IL-101 immobilized in a composite biopolymer matrix. 1870 Nov 26

An integrated method of dynamic extraction of perchloroethylene (PCE) with polydimethylsiloxane (PDMS) helical solid sorbent followed by injection into a gas chromatograph was developed for the determination of the real concentration of PCE in groundwater before and after its degradation by oxidation with KMnO(4). The main parameters (agitation, temperature, salts, pH) that affect the extraction efficiency have been evaluated and optimized. The increase of the extracted amount of PCE due to the presence of the salts could be partially compensated by the opposite effect of the insoluble MnO(2), and of the presence of HCl and the global effect of the matrix would be less important for the reproducibility of the PCE extraction. The quantitative analysis of PCE was carried out with the external standard method using the calibration-curve technique. The limit of detection for PCE was found of 0.05 mg L(-1) using flame ionization detector. The solubility of PCE in water was studied by extraction of PCE with PDMS helical solid sorbent from standard solution with different amounts of PCE added into the same volume of water and was found to decrease with settling time, because the fine droplets created during the agitation of the mixture were slowly merged in drops on the bottle walls and were not transferred into the extraction vial for GC analysis. The limit of solubility was evaluated using a graphical method and was estimated at 224.2+/-15.7 mg L(-1) of PCE in water at 25 degrees C.
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PMID:Quantitative evaluation of perchlorethylene in groundwater before and after its oxidation by helical solid sorbent extraction and gas chromatography. 1928 37

Bagasse pith (BP) has been utilized for activated carbon preparation using H(3)PO(4) (BPH) or KOH (BPK) as a chemical activating agent followed by carbonization at 500 degrees C. The physicochemical properties of activated carbon were carried out. The effectiveness of carbon prepared in adsorption of Rhodamine B (RhB) has been studied as a function of adsorbent type, pH, particle size, agitation time, temperature, initial dye concentration, and desorption. The results obtained showed that the adsorb ability of (RhB) to the BPH is higher than that of the BPK carbon by approximately 10 folds (198.6 and 21.5 mg g(-1), respectively). Kinetic studies show that the adsorption of RhB proceeds according to the pseudo-second-order. The intra-particle diffusion was identified to be the rate-limiting step in addition to the film diffusion. The adsorption was analyzed using 5 isotherm models (Langmuir, Freundlich, Temkin, Harkins-Jura, and Halsey isotherm equations). The highest values of r(2) were obtained with Langmuir (0.997). The adsorption capacity, q(m,) was 263.85 (mgg(-1)) at initial pH 5.7 for the particle size 0.25 nm and equilibrium time of 240 min at a temperature of 20 degrees C and initial dye concentration range of 100-600 (mg l(-1)). Temperature effect proves that the adsorption is endothermic with DeltaH=4.151 (kJ mol(-1)), DeltaS=65.786 (J mol(-1)K(-1)) and a decrease in Gibbs energy (DeltaG=-7.939 to -26.729 kJ mol(-1)). Desorption studies were carried out using water medium, HCl and NaOH with desorption of 2.7, 5.4 and 7.8%, respectively of adsorbed RhB confirming the chemical adsorption mechanism of the dye. This adsorbent was found to be both effective and economically viable.
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PMID:Activated carbon from agricultural by-products for the removal of Rhodamine-B from aqueous solution. 1936 14

The capabilities of chitosan and chitosan-EGDE (ethylene glycol diglycidyl ether) beads for removing Acid Red 37 (AR 37) and Acid Blue 25 (AB 25) from aqueous solution were examined. Chitosan beads were cross-linked with EGDE to enhance its chemical resistance and mechanical strength. Experiments were performed as a function of pH, agitation period and concentration of AR 37 and AB 25. It was shown that the adsorption capacities of chitosan for both acid dyes were comparatively higher than those of chitosan-EGDE. This is mainly because cross-linking using EGDE reduces the major adsorption sites -NH3+ on chitosan. Langmuir isotherm model showed the best conformity compared to Freundlich and BET. The kinetic experimental data agreed very well to the pseudo second-order kinetic model. The desorption study revealed that after three cycles of adsorption and desorption by NaOH and HCl, both adsorbents retained their promising adsorption abilities. FT-IR analysis proved that the adsorption of acid dyes onto chitosan-based adsorbents was a physical adsorption. Results also showed that chitosan and chitosan-EGDE beads were favourable adsorbers and could be employed as low-cost alternatives for the removal of acid dyes in wastewater treatment.
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PMID:Chitosan and chemically modified chitosan beads for acid dyes sorption. 1963 39

Alpha-tocopherol (alpha-Toc) targeted membrane adsorbents were prepared by mixing alpha-Toc imprinted particles in polysulfone (PSf) scaffold. The alpha-Toc imprinted particles were prepared with high-shear dispersion copolymerization of alpha-Toc methacrylate (alpha-TMA) and divinylbenzene (DVB) in toluene and water in the agitation range of 300-13,500 rpm. The alpha-Toc groups in resultant imprinted particles were hydrolyzed with 2 M HCl and then the polymers were embedded in PSf membranes by phase inversion technique. The membrane exhibited good selective binding of alpha-Toc with high separation factors to its analogs.
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PMID:Hybrid molecularly imprinted membranes for targeted tocopherol: uses of cross-linked copolymer particles prepared by surfactant-free dispersion technique. 1972 77

This work proposes a new process of recovering Co from spent Li-ion batteries (LIBs) by a combination of crushing, ultrasonic washing, acid leaching and precipitation, in which ultrasonic washing was used for the first time as an alternative process to improve the recovery efficiency of Co and reduce energy consumption and pollution. Spent LIBs were crushed with a 12 mm aperture screen, and the undersize products were put into an ultrasonic washing container to separate electrode materials from their support substrate. The washed materials were filtered through a 2mm aperture screen to get underflow products, namely recovered electrodes. Ninety two percent of the Co was transferred to the recovered electrodes where Co accounted for 28% of the mass and impurities, including Al, Fe, and Cu, accounted for 2%. The valuable materials left in 2-12 mm products, including Cu, Al, and Fe, were presented as thin sheets, and could be easily separated. The recovered electrodes were leached with 4.0M HCl for 2.0 h, at 80 degrees C, along with concurrent agitation. Ninety seven percent of the Li and 99% of the Co in recovered electrodes could be dissolved. The impurities could be removed at pH 4.5-6.0 with little loss of Co by chemical precipitation. This process is feasible for recycling spent LIBs in scale-up.
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PMID:A combined recovery process of metals in spent lithium-ion batteries. 1977 24

Analytical methods which are accurate to about 1 per cent have been developed for the determination of small amounts (ca. 500 gamma) of bis(beta-chloroethyl)-sulfide (H), ethyl-bis(beta-chloroethyl)amine (EBA), tris(beta-chloroethyl)amine (TBA), beta-chloroethyl-benzylsulfide (benzyl-H), and beta-chloroethyl-ethylsulfide (ethyl-H). The determinations are made by micro titration of the HCl liberated upon complete hydrolysis of the vesicants. A description is given of an apparatus suitable for applying vapors of vesicants to unit areas of skin. A very precise and reproducible micropipetting technique is described for the introduction of the vesicants into the penetration apparatus. By means of this penetration apparatus studies have been made of several factors which may influence the rate at which vesicant vapors penetrate into skin. Model experiments have been performed in which H was allowed to vaporize and the vapor was absorbed on a surface such as that of diethylene glycol or vaseline. It has been found that if the surface of liquid H is increased by spreading the agent on filter paper, the rate of evaporation is markedly increased. Furthermore, if the vapor is agitated by means of a magnetically driven fan, the rate of absorption by diethylene glycol is greatly accelerated. With vaseline as the absorbing surface it has been found that the area of the absorbing surface has an effect on the rate of absorption of H vapor. More H is absorbed by vaseline spread on filter paper to give a rough surface than is absorbed by a smooth film of vaseline. Measurements of the rate of penetration into human skin of H, EBA, TBA, benzyl-H, and ethyl-H vapors have been performed at 21-23 degrees C. and 30-31 degrees C. by means of the penetration apparatus described in this paper. The measurements were carred out on human volunteers under conditions of controlled temperature and humidity. When human skin is exposed to air saturated with H vapor, the H penetrates the skin of the forearm at a rate of about 1.4 gamma per cm.(2) per minute (temperature 21-23 degrees C.; relative humidity 46 per cent). This value was found to hold in experiments in which H vapor was applied for 3 to 30 minute intervals, thus indicating that the permeability of the skin to H vapor is not altered during a 30 minute exposure. Agitation of the H vapor by fanning did not result in any measurable increase in the rate of penetration. Two of the volunteers were Negroes; the permeability of their skin to H vapor did not differ appreciably from that found for the other subjects. When human skin is exposed to air saturated with EBA vapor, the vesicant penetrates at the rate of 2.8 gamma per cm.(2) per minute (temperature 22 degrees C., relative humidity 50 to 52 per cent). The amount of EBA penetrated is linear with exposure time for exposure periods of 5 to 20 minutes. Under similar conditions, it was found that TBA penetrates at a rate of about 0.18 gamma per cm.(2) per minute (temperature 22-23 degrees C.; relative humidity 45 to 48 per cent). This value was found to hold in experiments in which TBA vapor was applied for 30 to 60 minute intervals. The amount of TBA penetrated is linear with exposure time. In the case of benzyl-H, a linear relationship between the amount lost from the penetration cup and exposure time was also observed but the plot did not pass through the origin. It is suggested that this anomaly is due to retention on the skin surface of an appreciable quantity of benzyl-H as a result of rapid physical adsorption or chemical combination with a constituent of the skin. The rate of penetration of benzyl-H may be calculated from the slope of the plot and is found to be 0.35 gamma per cm.(2) per minute (temperature 22 degrees C., relative humidity 55 to 60 per cent). The results with ethyl-H showed great variation among individual subjects and no satisfactory value for the rate of penetration can be given as yet. Measurements were also made of the rate of penetration of H, EBA, and TBA vapors at 30-31 degrees C. (relative humidity 47 to 49 per cent). At this temperature, a linear relationship was observed between the amount penetrated and the time of exposure. H vapor penetrated at a rate of 2.7 gamma per cm.(2) per minute, EBA vapor at 5.1 gamma per cm.(2) per minute, and TBA vapor at 0.29 gamma per cm.(2) per minute. Three of the subjects in the EBA measurements were Negroes. The permeability of their skin to EBA vapor did not differ from that found for the white subjects. Despite this fact, their skin failed to vesicate after an exposure period twice that which caused 50 per cent vesication in the white subjects. Calculation of the precision of the data showed that the average deviation, standard deviation, and standard error were not appreciably different for the data obtained with human subjects as compared with data for control experiments in which human skin was not involved. Consequently, no significant differences in the rate of penetration into the skin of individual subjects can be discerned from the data presented in this communication. The increase in the rate of penetration of H, EBA, and TBA vapors from 21-23 degrees C. to 30-31 degrees C. is approximately proportional to the increase in volatility of each agent. These results indicate that at the same gas concentration in milligrams per liter, H, EBA, and TBA vapors would all penetrate at about the same rate. The data presented above permit a determination of the approximate amount of each vesicant which must penetrate to cause vesication in about 50 per cent of the exposed sites. This amount has been designated by the symbol V(50). The V(50) for H and TBA at 21-23 degrees C. is the same, being about 6gamma; at 30-31 degrees C., the V(50) is 4 to 5 gamma. On the other hand, the V(50) for EBA at 22 degrees C. and 30-31 degrees C. is about 26 to 28 gamma. Thus, per gamma penetrated, H and TBA vapors are about equally effective in producing vesication while EBA vapor is only (1/5) to (1/8) as effective.
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PMID:THE PENETRATION OF VESICANT VAPORS INTO HUMAN SKIN. 1987 72

Under the optimal experimental conditions of three-phase hollow fiber liquid-phase microextraction (3p-HFLPME), the behaviors of hydroxybenzoic acids (HBAs) were investigated. The correlation between the enrichment factor (EF) of HBAs and their n-heptanol/water conditional distribution coefficients (log P(n-heptanol/5 mmol/L) HCl), pK(a) mmol/L HCI ), and the number of -OH (N); the extraction mechanism that polyvinylidene difluoride hollow fiber contributed to promote the extraction efficiency by forming charge transfer compound with HBAs and the organic solvents showed notable selectivity for HBAs were elucidated. The optimal 3p-HFLPME conditions were: MOF 503 polyvinylidene difluoride hollow fiber as organic solvent supporter, n-heptanol as organic phase, 5 mmol/L HCl in the donor phase and 80 mmol/L NH3 x H2O as the acceptor phase, the HBAs were extracted for 35 min under an agitation of 1 200 r/min. It was found that the relative standard deviations were lower than 3%, the detection limits were 0.09-30.00 microg/L, the average recoveries of HBAs in Calyx Kaki were 93.3%-107.1% and the EF of HBAs at 5 mg/L was up to 107.6 fold.
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PMID:[Application of three-phase hollow fiber liquid-phase microextraction for analysis of hydroxybenzoic acids]. 2035 29

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