A sustainable process for adsorptive removal of methylene blue onto a food grade mucilage: kinetics,thermodynamics, and equilibrium evaluation

Abstract

Adsorption of dyes onto natural materials like polysaccharides is considered a green chemistry approach for remediation of wastewater. In this work, the polysaccharide isolated from the corm of Colocasia esculenta (L.) Schott or taro tuber (CEM) was utilized for removing methylene blue (MB) from aqueous solution by batch adsorption method. The CEM adsorbent was characterized by FTIR spectroscopy, Brunauer–Emmett–Teller (BET), and scanning electron microscopy (SEM). The solution pH and adsorbent dose have been found to have a significant positive correlation with the adsorptive removal efficiency of CEM for MB dye. The removal efficiency of CEM was found to be 72.35% under the optimum conditions; 20?mg/L initial concentration of dye, 120?mg of adsorbent dose, solution pH 8.5, 311.2?K temperature and 80?min contact time. The adsorption of MB onto CEM followed best the Freundlich isotherm and pseudo-second-order kinetics. The adsorption was thermodynamically favorable and was endothermic in nature. The desorption/adsorption data justifiably indicated the reuse capability of CEM adsorbent for MB adsorption. Hence, CEM may be regarded as an eco-friendly and cost-effective natural adsorbent for MB dye removal from aqueous solution.     

Complexing of heparin with phosphatidylcholine. A possible supramolecular assembly of plasma heparin.

In a series of attempts to reveal plasma heparin, we found that high ionic strength and modification of protein amino groups were not effective in extracting endogenous heparin (or, indeed, a large percentage of exogenous labelled heparin), whereas delipidation in the presence of 4M-guanidinium chloride gave high yields, indicating that plasma heparin may be assembled with compounds other than proteins, in a form making it inaccessible to water and ions. During the extraction of lipids, a paradoxical entry of heparin into the organic phase was observed. Detergents, including sodium dodecyl sulphate, did not shift heparin into the aqueous phase, whereas repeated chloroform/methanol extraction did so. Using purified compounds we were able to reproduce in vitro both the scavenging of heparin from water as well as the formation of heparin-phosphatidylcholine complexes soluble in organic solvents. Evidence for complexing of heparin with phosphatidylcholine was also obtained by electrophoretic and ultracentrifugation assays. The quaternary-ammonium-containing phosphatidylcholine was the more effective phospholipid in binding heparin; anionic phospholipids did not bind. Only heparin-like glycosaminoglycans bound phosphatidylcholine, but less-sulphated compounds (heparan sulphate and dermatan sulphate) were weaker ligands. Gel-filtration experiments showed that heparin was not bound to liposome vesicles, but that a measurable percentage of the phospholipids was stripped off from vesicles and was found in the form of a complex separable from liposomes by gel filtration. The molecular basis as well as the biological role of the interaction of heparin with major membrane phospholipids are discussed.     

Polyacrylamide films as a tool for investigating qualitative and quantitative aspects of the staining of glycosaminoglycans with basic dyes

Synopsis With the introduction of model films of polyacrylamide gel into which purified glycosaminoglycans (GAGs) have been incorporated, the direct recording of metachromatic spectra with virtually no interference of the corresponding orthochromatic peaks has become possible. Because this model system yields situations comparable to those of stained sections under the microscope, it is well suited for investigating qualitative and quantitative aspects of histochemical staining procedures. Previous model experiments have shown that under aqueous conditions only minor differences can be observed between the metachromatic peaks of different GAGs complexed with a suitable dye (e.g. Toluidine Blue O, Thionin, Safranin O, Cresyl Violet, Crystal Violet). In non-aqueous media, such as glycerol and ethylene glycol, the complexes with Toluidine Blue O revealed a special pattern for heparin, having a metachromatic peak (517 nm) about 30 nm lower than that of all other GAGs. This observation has formed the basis of a method for the qualitative microspectro-photometric detection of heparinin situ which was worked out by combining model film experiments with microspectrophotometric data obtained from rat mast cells. Since only a limited number of cells is necessary for obtaining reliable data with this method, the presence of heparin in the cytoplasmic granules of normal human mast cells and basophilic granulocytes could thus be proved directly.Alcian Blue 8GX, another basic dye frequently used in GAG histochemistry, has also been investigated with polyacrylamide films. In contrast to the metachromatic dyes, the rate of staining with Alcian Blue depends to a large extent on the rate of penetration of the dye into the model films. The rate of penetration is also a phenomenon of great importance for dye bindingin situ, where complex basic protein molecules may form a barrier for the Alcian Blue molecules. The model film studies performed so far have yielded conditions that provide maximal staining (up to an optimal level) and a linear relationship between the concentration of GAG and the AB binding. The presence of basic protein, electrostatically bound to the GAG, was not found to influence either the rate of staining or the maximal amount of dye binding.Paper presented at a symposium The Changing directions of carbohydrate histochemistry, at the fifth International Congress of Cytochemistry and Histochemistry in Bucharest, Romania on 1 September 1976.     

Utilizing a nano‐sorbent for the selective solid‐phase extraction of vanillic acid prior to its determination by photoluminescence spectroscopy

Vanillic acid (VA) is a phenolic acid, and acts as a natural antioxidant in fruits, vegetables and plants. The extraction and determination of trace levels of VA in plants is important, because stimulation of protein synthesis and activation of antioxidant enzymes occur in the presence of phenolic acids at trace levels. In this research, a photoluminescence spectroscopic method was developed for the quantification of VA in plant samples after separation and pre‐concentration. Selective extraction of VA from aqueous solution was performed using a solid‐phase extraction column packed with nickel–aluminum layered double hydroxide as a nano‐sorbent. After elution of extracted analyte from the column using 3 mL of a 3 mol/L NaOH solution, its concentration was determined spectrofluorometrically at λ_em = 357 nm with excitation at λ_ex = 280 nm. The spectrofluorometry method gave a linear response for VA within the range 20.0–900.0 µg/L, with a correlation coefficient of 0.9982. The limit of detection and sorption capacity were 7.6 µg/L and 66.2 mg/g, respectively. The method was validated by comparing the obtained results with gas chromatographic data. This method was used to determine VA in Chenopodium album and Prangos asperula plants. Copyright © 2014 John Wiley & Sons, Ltd.     

Spectroscopic and thermodynamic investigations on the binding of azure B to chondroitin sulfate and the structure of the metachromatic dye complex

The binding of azur B to chondroitin sulfate (CHS) was investigated using absorption spectroscopy. In aqueous solutions it is possible to distinguish three different dye species with absorption bands at 646, 597, and 555 nm. They are assigned to monomers, dimers, and higher aggregates of azure B, which become bound to CHS as the dye concentration (CD) increases. The short-wavelength band (555 nm) causes metachromasia in stained histological materials. When saturation occurs, the metachromatic azure B-CHS complex has a 1:1 composition, i.e., each anionic SO-4 and COO(-)-binding site of CHS binds one dye cation. The composition of the saturated metachromatic complex was determined by spectrophotometric and conductometric titration of CHS with azure B, while the SO-4 and COO- content of CHS was determined by conductometric titration of CHS-acid with NaOH. The binding isotherm of azure B to CHS was determined using gelpermeation chromatography. The isotherm can be described by the model of cooperative binding of ligands to linear biopolymers. We found good agreement between theoretical predictions and experimental findings in the range of 0 less than r less than 0.8 (r = the fraction of occupied binding sites). Using a Schwarz plot, we determined the binding constants of nucleation (Kn = 2.5 X 10(3) M-1) and aggregation (Kq = 1.2 X 10(5) M-1), as well as the cooperativity parameter (q = 50), T = 295 K. With increasing CD, the strong cooperativity of the dye binding favors the formation of metachromatic aggregates rather than monomers and dimers. From the temperature dependence of Kq we evaluated the standard binding enthalpy (delta Hoq = -20.0 kJ mol-1) and entropy (delta Soq = 29.7 JK-1 mol-1) of the cooperative dye binding. The binding was found to be strongly exothermic and accompanied by a thermodynamically favorable entropy increase, this being typical of hydrophobic interactions. Solid azure B-CHS complexes were prepared according to a special dialytic technique and were studied using a microspectrophotometer equipped with a polarizer and an analyzer. The metachromatic 1:1 complex has a broad, intense absorption band whose main peak occurs at 560 nm. This corresponds with the maximum of the metachromatic dye complex in aqueous solution, i.e. 555 nm. The CHS chains of the azure B-CHS complex can be mechanically aligned in a preferred direction (k). We were able to prepare excellently orientated and very fine dye-CHS films which were birefringent and dichroic - the more birefringent, the better the mechanical orientation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Removal of Chromium (VI) from Aqueous Solution Using Mycelial Pellets of Penicillium simplicissimum Impregnated with Powdered Biochar

The mycelia pellets of Penicillium simplicissimum impregnated with powdered biochar (MPPSIPB) were synthesized and applied to remove chromium (VI) from aqueous solution. The effects of pH, MPPSIPB dosage, initial Cr(VI) concentration, and contact time were investigated via batch experiments. Results indicated that the percentage removal of Cr(VI) was significantly dependent on the pH of the solution. Ten grams mycelial pellets and 0.2 g powdered biochar could form the most stable pellets. The maximum value of biosorption of Cr(VI) was 28.0 mg/g. Scanning electron microscopy (SEM) analysis showed that the mycelia pellets of Penicillium simplicissimum had abundant filamentous network, which entrapped powdered biochar firmly. Fourier transform infrared (FTIR) analysis suggested that O?H, N?H, C?H, C?O, and C?OH groups from MPPSIPB were involved in chromium binding and the subsequent reduction. Kinetic studies indicated that the pseudo-second-order equation fit best for Cr(VI) removal from aqueous solution. Freundlich isotherm was found to apply better for the adsorption equilibrium data with respect to the Langmuir isotherm. Furthermore, MPPSIPB can be separated from aqueous solution completely by filtration. Both experimental study and modeling results indicated that MPPSIPB exhibited remarkable affinity for chromate and had a potential application in Cr(VI) removal from water.     

Bench-scale and packed bed sorption of methylene blue using treated olive pomace and charcoal

A combination of olive pomace after solvent extraction and charcoal produced from the solid waste of olive oil press industry was used as an adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Batch tests showed that up to 80% of dye was removed when the dye concentration was 10 mg/ml and the sorbent concentration was 45 mg/ml. An increase in the olive pomace concentration resulted in greater dye removal from aqueous solution, and an increase in MB dye concentration at constant adsorbent concentration increased the dye loading per unit weigh of adsorbent. In the kinetic of the adsorbent process, the adsorption data followed the second-order kinetic model better than first order kinetic model. Charcoal showed higher sorption capacity (uptake) than that of olive pomace. In the fixed bed adsorption experiment, the breakthrough curves showed constant pattern behavior, typical of favorable isotherms. The breakthrough time increased with increasing bed height, decreasing flow rate and decreasing influent concentration and methylene blue dye uptake. The uptake of MB dye was significantly increased when a mixture of olive pomace and charcoal was packed in the column in a multi-layer fashion. Different models were used to describe the behavior of this packed-sorption process.     

Histochemical conditions influencing metachromatic staining. A comparative study by means of a model system of polyacrylamide films

Synopsis The influence of different histochemical conditions on some metachromatic staining reactions has been studied using polyacrylamide films containing pure glycosaminoglycans. The films were incubated in fixatives without staining, and in glycerol, diethylene glycol and other glycols, formamide,N,N-dimethylformamide, dimethyl sulphoxide and ethanol (of several concentrations) after staining and their absorption (metachromatic) spectra recorded. In the case of heparin and heparan sulphate the metachromasy was disturbed when the films were immersed before staining in some fixative solutions containing formaldehyde and acid. After equilibration of stained films in organic solvents, changes in the absorption peaks were found to depend on the type and concentration of solvent, the type of glycosaminoglycan and the type of dye.Films containing glycosaminoglycan plus protein were used to investigate the blocking of the metachromatic reaction as the result of ionic interactions with proteins. The parameters that influence this phenomenon (e.g type of protein, glycosaminoglycan and dye, pH of staining) are discussed and a three-dimensional picture is introduced which can explain some of the results obtained in these experiments.     

High-performance liquid chromatographic determination of hippuric acid in human urine

A method is described for the determination of urinary hippuric acid by high-performance liquid chromatography. The method used ethyl acetate extraction for partial clean-up of the urine. The separation was carried out on a reversed-phase column using 20% methanol in 0.01 M aqueous potassium phosphate containing 0.5% acetic acid as a mobile phase. The column effluent was monitored with a UV detector at 254 nm. Hippuric acid was separated from other normal urine constituents in less than 10 min. Metabolites of xylene and styrene did not interfere with the assay. Analytical recoveries from urine were excellent and peak height and concentration were linearly related.     

Quantitative dehydrogenase histochemistry with exogenous electron carriers (PMS,MPMS, MB)

Summary The relative efficiencies of phenazine methosulfate (PMS), 1-methoxy-phenazine methosulfate (MPMS) and Meldola Blue (MB) as electron carriers were determined biochemically (non-enzymic NADH-tetrazolium salt-test) and by quantitative histochemistry (heart and kidney slices; succinate dehydrogenase, SDH; lactate dehydrogenase, LDH). MPMS developed the highest electron transfer velocity in biochemical assays. The reaction was independent of the pH value between 7.0–8.5. PMS and MB always showed a lower transfer ability in biochemical tests which was higher with iodonitrotetrazolium chloride (INT) than with nitro blue tetrazolium chloride (NBT). A distinct pH dependence was demonstrable with MB in this respect, preferentially using INT as tetrazolium salt.Quantitative histochemical results with electron carriers are often at variance with biochemical ones. MPMS leads to somewhat higher demonstrable activities only in the determination of the NAD-dependent LDH, whereas MB results in somewhat higher LDH activity than PMS (reaction medium with agarose). MB and PMS yielded almost equally high activities in the demonstration of the flavoprotein-dependent SDH using a reaction medium with agarose. With an aqueous reaction medium, PMS resulted in higer SDH activities than MB. MPMS always had the lowest efficiency in electron transfer ability using an aqueous or agarose containing reaction medium (SDH). With PVA in the reaction medium (SDH determination) PMS was clearly superior to MPMS. MB showed only a small transfer activity under these conditions because PVA seems to bind MB almost completely. It is concluded that in histochemistry an appropriate electron carrier and electron carrier concentration must be determined for different incubation conditions, tissues, tissue preparations and dehydrogenases studied. General statements about the efficiency or inefficiency of an electron carrier as a result of only one incubation condition does not seem to be justified.Supported by the Deutsche Forschungsgemeinschaft (SFB 105)     

Binding of methylene blue to alginate: Effect of acid treatment on metachromasy

The spectral properties of methylene blue (MB) in solutions of Na alginate depend on the severity of prior acid treatment of the polysaccharide. The spectral properties affected are the fraction of MB in monomeric form, the relative amounts of metachromatic dye absorbing near 570 and near 595 nm, and the intensity and sign of circular dichroism (CD) activity associated with the 570 nm bands, at various ratios of polymer equivalents to dye (P/D) from 1300 to 4. Acid treatment consisted of reaction of dry, alcohol-precipitated and presumably native alginate with 0·3m HCl at room temperature for 5 min to 8 h. Acid-induced changes showed immediate (5 min) and slow (4–8 h) stages. In both stages the fractions of MB in monomeric form and in the 595 nm metachromatic form increased. CD activity was little affected by brief acid treatment (except in range P/D=165 to 55), but diminished at all P/D values on prolonged acid treatment. Minor changes were observed in the infrared spectra of alginate films. Fresh alcohol-precipitated alginate, untreated with acid, did not precipitate when dye was in excess, nor did it form gel beads in CaCl₂ solution. It is concluded that dilute acid treatment alters the stereospecific properties of native alginate, perhaps by inducing conformational changes in the constituent copolymer segments.     

The Reactions of Isolated Mucopolysaccharides to Several Histochemical Tests

The reaction to three histochemical tests of preparations of hyaluronic acid, chondroitin sulfate, heparin, the acidic mucopolysaccharides from cornea, gastric mucin, and dentine, and also of the neutral mucopolysaccharide from gastric mucin was studied. To 1% aqueous solutions of the acid mucopolysaccharides, equal volumes of 1% casein solution were added; drops of the resulting solutions were placed on slides and dried at 37 °C. The films were then fixed in acetic-alcohol (1:9). The technics employed were the periodic acid-Schiff (PAS) test, the metachromatic reaction and the Hale test. The relative acidity of the preparations was demonstrated by staining in dilute aqueous methylene blue at pH 3-6. With the exception of the preparation from dentine, the acid mucopolysaccharides stained only weakly with PAS; the neutral mucopolysaccharide stained strongly. It is concluded, therefore, that the use of the PAS technic for the histochemical demonstration of acid mucopolysaccharides is misleading, for many important members of this class of tissue component do not react appreciably. On the other hand, metachromasia was shown by all the acidic compounds studied, and the intensity of staining was approximately correlated with the acidity of the preparations. The Hale method was found to be nonspecific.     

Biosorption of reactive and basic dyes using fermentation waste <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis>: the effects of pH and salt concentration and characterization of the binding sites

A low cost biosorbent, Corynebacterium glutamicum, was studied for the sorption of Reactive Red 4 (RR 4) and Methylene Blue (MB). The equilibrium isotherm data were well described by the Langmuir model. pH edge experiments showed that pH of the solution was an important controlling parameter in the sorption process. In the case of RR 4, with increases in the pH from 2 to 10, the uptake decreased from 52 to 1 mg/g; conversely, the uptake of MB increased and the maximum MB uptake was obtained at pH ≥ 9. An increase in the salt concentration strongly influenced the uptake of MB, but had no effect on that of RR 4. In order to identify the binding sites for the dye molecules, the biosorbent was potentiometrically titrated, the results of which showed the presents of four major functional group types on the biomass surface, which were confirmed by FTIR analysis. It was found that positively charged amine groups (Biomass-NH₃ ⁺) were the likely binding sites for anionic RR 4, and negatively charged carboxyl (Biomass-COO⁻) and phosphate groups (Biomass-HPO₄ ⁻) played a role in the electrostatic attraction of cationic MB.     

Optimization of ultrasonic-assisted extraction process of Poria cocos polysaccharides by response surface methodology

Polysaccharides production from Poria cocos was carried out using aqueous NaOH with the assistance of ultrasonic. Experimental design was used to investigate the effect of three parameters (extraction time, extraction concentration of NaOH, and ratio of aqueous NaOH to raw material) on polysaccharides yields. The ranges of the factors investigated were 1–3 min for extraction time (X₁), 0.5–1.0 mol/L for extraction concentration of NaOH (X₂), and 30–50 for ratio of aqueous NaOH to raw material (X₃). The statistical analysis of the experiment indicated that extraction concentration of NaOH had significant effect on P. cocos polysaccharides yields. The central composite design showed that polynomial regression models were in good agreement with the experimental results with the coefficients of determination of 0.9935 for P. cocos polysaccharides yield. The optimal condition for P. cocos polysaccharides yield within the experimental range of the variables studied was at 2.44 min, 0.789 mol/L, and 53.0. At this condition, the predicted yield of polysaccharides extracted was 82.3%.     

Simultaneous filtration and immobilization of cells from a flowing suspension using a bioreactor containing polyethylenimine coated cotton threads: Application in the continuous inversion of concentrated sucrose syrups

Polyethylenimine(PEI)-coated cotton threads were shown to have potential for reducing microbial load from a flowing suspension. Turbid cell suspensions perfused through the PEI column appeared as totally clear in the effluent. The adhesion efficiency of the matrix was found to depend on the concentration of PEI used to treat the threads. Threads coated with 2.5% PEI were found to show optimal retention of cells. A considerable amount of binding was seen over a broad range of ionic concentration (0–0.3 M) and pH (3.6–10.3). Under similar conditions control threads did not show any filtration capacity. Saccharomyces cerevisiae, Saccharomyces fragilis, Escherichia coli and an Acetobacter species could be effectively filtered using PEI-coated threads. This technique can find potential for the simultaneous filtration and immobilization of cells in a bioreactor to be used in continuous bioprocessing as exemplified for the inversion of sucrose syrups using baker's yeast. The bioreactor could continuously hydrolyse 60% (w/v) sucrose syrups with a productivity of 2.25 kg/day for over a month without loss in efficiency.     

93 Spectroscopic investigation of methylene blue binding to DNA

The interaction of methylene blue (MB) with DNA has been investigated by UV absorption spectra, Fluorescence spectra and UV-melting method. Analysis of the results of the melting experiments shows that melting temperature (T _m) of the complexes increases with the [total ligand]: DNA ratio (r) at two concentrations of Na⁺ (2?mM Na⁺ and 20?mM Na⁺) providing support for conclusion that MB is a stabilizer of DNA helix structure. By contrast, the shapes of dependences of width of transition (ΔT) on r at low and high [Na⁺] are different which points to the existence of different types of binding modes of MB with DNA. UV-spectroscopy experiments and fluorescence spectra indicated that the binding modes of MB with DNA depended on r. At high r (r?>?0.25), remarkable hypochromic effect with no shift of λ _max in the absorption spectra of MB was observed. The fluorescence of MB was quenched which indicated that MB was bound to phosphate groups of DNA by electrostatic interaction. At low r ratios (r?<?0.2), the absorption spectra of MB upon increasing the concentration of DNA showed gradually decrease in the peak intensities with a red shift. This phenomenon is usually associated with molecular intercalation into the base stack of the ds-DNA. Using the Scatchard’s model, the complex formation constants for MB with DNA were determined: the binding constant K?≈?6.5?×?10⁵ and binding site size n?≈?4. Obtained data are not typical for intercalation model of ligands to DNA. Moreover, comparison between these data and our early experimental results of interaction of ethidium bromide with DNA made it possible to suggest that this binding type of MB is, more probably, semi-intercalation mode (Vardevanyan et al., 2003). This conclusion is in accordance with the analysis of the model structures of MB–DNA complexes which clearly shows the importance of solvent contributions in suggested structural form (Tong et al., 2010).     

Design of a new cartridge for selective solid phase extraction using molecularly imprinted polymers: Selective extraction of theophylline from human serum samples

This paper describes design of a new cartridge for selective solid phase extraction (SPE) using molecularly imprinted polymers (MIPs). The apparatus which is termed solvent extraction-MISPE (SE-MISPE) cartridge, consisted of a modified conventional micro test tube and has been developed to perform simultaneous forward-extraction of analyte from aqueous sample solution to an organic phase and back-extraction to MIP solid phase. In order to evaluate the performance of the proposed method, extraction of theophylline (THP) from human serum sample was investigated. An appropriate amount of THP-imprinted polymer was placed in the bottom of the micro tube and an organic solvent pipetted onto it and left to swell the polymer completely. A polyethylene frit to secure MIP particles was positioned by two Teflon rings such that it was fixed below the level of the organic layer. Then, aqueous sample solution containing THP was layered over the organic phase and the lid was closed. After completion of extraction, the organic and aqueous phases were removed and the adsorbed analyte was desorbed using a polar organic solvent. In order to reach the highest recovery, the experimental parameters such as the type of organic solvent, pH and ionic strength of aqueous phase, organic to aqueous volume ratio, time of extraction, type and amount of desorbent solvent were optimized. Under the experimental conditions, a plot of HPLC peak areas vs. initial concentrations of THP in the concentration interval of 0.5–30 μg ml⁻¹ showed a good linearity (r = 0.9974). The limit of detection (LOD) and limit of quantification (LOQ) based on three and ten times of the noise of HPLC profile were 0.09 and 0.3 μg ml⁻¹, respectively. The relative standard deviation (RSD) of the proposed method for the extraction and determination of 5 μg THP from 200 μl standard sample solution for 3 replicate measurements was 3.5%. The results showed that by means of the proposed cartridge, THP could significantly separate from the other structurally related compounds such as theobromine (THB) and caffeine (CAF). The added THP could be quantitatively recovered (79–83%) from the serum samples by the proposed procedure, being thus a guarantee of the accuracy of the SE-MISPE procedure. In addition, the loss of capability of the SE-MISPE cartridge was not considerably observed after 10 times loading and elution cycles.     

PEG／（NH4）2SO4双水相体系在加杨叶总黄酮萃取分离中的应用

目的：寻找加杨叶粗提液中的总黄酮的有效方法。方法：利用双水相体系萃取分离、紫外分光光度法直接测定。结果：萃取分离加杨叶总黄酮的最佳双水相体系是25％PEG400与12％（NH4）2SO4,最佳萃取条件为：pH=9,NaCl的添加量为3％,粗提液3mL,温度25℃。结论：该方法的相对标准偏差（RSD）≤0．28％（n=5）,具有良好的精密度和选择性,为黄酮类化合物萃取分离的一种有效方法。     

Electrically Assisted Liquid‐Phase Microextraction Combined With Capillary Electrophoresis for Quantification of Propranolol Enantiomers in Human Body Fluids

In this study, electromembrane extraction (EME) combined with cyclodextrin (CD)‐modified capillary electrophoresis (CE) was applied for the extraction, separation, and quantification of propranolol (PRO) enantiomers from biological samples. The PRO enantiomers were extracted from aqueous donor solutions, through a supported liquid membrane (SLM) consisting of 2‐nitrophenyl octyl ether (NPOE) impregnated on the wall of the hollow fiber, and into a 20‐μL acidic aqueous acceptor solution into the lumen of hollow fiber. Important parameters affecting EME efficiency such as extraction voltage, extraction time, pH of the donor and acceptor solutions were optimized using a Box‐Behnken design (BBD). Then, under these optimized conditions, the acceptor solution was analyzed using an optimized CD‐modified CE. Several types of CD were evaluated and best results were obtained using a fused‐silica capillary with ammonium acetate (80 mM, pH 2.5) containing 8 mM hydroxypropyl‐β‐CD as a chiral selector, applied voltage of 18 kV, and temperature of 20°C. The relative recoveries were obtained in the range of 78–95%. Finally, the performance of the present method was evaluated for the extraction and determination of PRO enantiomers in real biological samples. Chirality 26:260–267, 2014. © 2014 Wiley Periodicals, Inc.     

Micell-mediated extraction for the spectrophotometric determination of nitrite in water and biological samples based on its reaction with p-nitroaniline in the presence of diphenylamine

A cloud point extraction process using the nonionic surfactant Triton X-100 to extract nitrite from aqueous solution was investigated. The method is based on the color reaction of nitrite with p-nitroaniline in the presence of diphenylamine in acid media and micell-mediated extraction of an azo product. The optimal extraction and reaction conditions (e.g., acid concentration, reagent concentration, effect of time) were studied, and the analytical characteristics of the method (e.g., limit of detection, linear range, molar absorptivity, preconcentration, and improvement factors) were obtained. Linearity was obeyed in the range of 2-40 ng ml(-1) of nitrite ion. The detection limit of the method is 0.87 ng ml(-1) of nitrite ion. The interference effect of some anions and cations was also tested. The method was applied to the determination of nitrite in tap water, waste water, and human urine samples.