Determination of azoxystrobin residues in grapes, musts and wines with a multicommuted flow-through optosensor implemented with photochemically induced fluorescence

In this paper, the conversion of azoxystrobin in a strongly fluorescent degradation product by UV irradiation with quantitative purposes and its fluorimetric determination are reported for the first time. A multicommuted flow injection-solid phase spectroscopy (FI-SPS) system combined with photochemically-induced fluorescence (PIF) is developed for the determination of azoxystrobin in grapes, must and wine. Grape samples were homogenized and extracted with methanol and further cleaned-up by solid-phase extraction on C₁₈ silica gel. Wine samples were solid-phase extracted on C₁₈ sorbent using dichloromethane as eluent. Recoveries of azoxystrobin from spiked grapes (0.5-2.0 mg Kg⁻¹), must (0.5-2.0 μg mL⁻¹) and wine (0.5-2.0 μg mL⁻¹) were 84.0-87.6%, 95.5-105.9% and 88.5-111.2%, respectively. The quantification limit for grapes was 0.021 mg Kg⁻¹, being within European Union regulations, and 18 μg L⁻¹ and 8 μg L⁻¹ for must and wine, respectively.     

Potentialities of two solventless extraction approaches—Stir bar sorptive extraction and headspace solid-phase microextraction for determination of higher alcohol acetates, isoamyl esters and ethyl esters in wines

A stir bar sorptive extraction with liquid desorption followed by large volume injection coupled to gas chromatography-quadrupole mass spectrometry (SBSE-LD/LVI-GC-qMS) was evaluated for the simultaneous determination of higher alcohol acetates (HAA), isoamyl esters (IsoE) and ethyl esters (EE) of fatty acids. The method performance was assessed and compared with other solventless technique, the solid-phase microextraction (SPME) in headspace mode (HS). For both techniques, influential experimental parameters were optimised to provide sensitive and robust methods. The SBSE-LD/LVI methodology was previously optimised in terms of extraction time, influence of ethanol in the matrix, liquid desorption (LD) conditions and instrumental settings. Higher extraction efficiency was obtained using 60 min of extraction time, 10% ethanol content, n-pentane as desorption solvent, 15 min for the back-extraction period, 10 mL min⁻¹ for the solvent vent flow rate and 10 °C for the inlet temperature. For HS-SPME, the fibre coated with 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) afforded highest extraction efficiency, providing the best sensitivity for the target volatiles, particularly when the samples were extracted at 25 °C for 60 min under continuous stirring in the presence of sodium chloride (10% (w/v)). Both methodologies showed good linearity over the concentration range tested, with correlation coefficients higher than 0.984 for HS-SPME and 0.982 for SBES-LD approach, for all analytes. A good reproducibility was attained and low detection limits were achieved using both SBSE-LD (0.03-28.96 μg L⁻¹) and HS-SPME (0.02-20.29 μg L⁻¹) methodologies. The quantification limits for SBSE-LD approach ranging from 0.11 to 96.56 μg L⁻and from 0.06 to 67.63 μg L⁻¹ for HS-SPME. Using the HS-SPME approach an average recovery of about 70% was obtained whilst by using SBSE-LD obtained average recovery were close to 80%. The analytical and procedural advantages and disadvantages of these two methods have been compared.Both analytical methods were used to determine the HAA, IsoE and EE fatty acids content in “Terras Madeirenses” table wines. A total of 16 esters were identified and quantified from the wine extracts by HS-SPME whereas by SBSE-LD technique were found 25 esters which include 2 higher alcohol acetates, 4 isoamyl esters and 19 ethyl esters of fatty acids. Generally SBSE-LD provided higher sensitivity with decreased analysis time.     

A comparison of solid-phase microextraction and stir bar sorptive extraction coupled to liquid chromatography for the rapid analysis of resveratrol isomers in wines, musts and fruit juices

A comparison of direct immersion solid-phase microextraction (DI-SPME) and stir bar sorptive extraction (SBSE) coupled to liquid chromatography (HPLC) with fluorimetric detection for the rapid analysis of resveratrol isomers is described. For DI-SPME, a polar Carbowax-template resin (CW/TPR) 50 μm fiber was the most efficient and optimum extraction conditions were 40 °C and an extraction time of 30 min, stirring in the presence of 5% (m/v) sodium chloride and 0.07 M acetate/acetic acid buffer (pH 6). Desorption was carried out using the static mode for 10 min. Linearity was obtained in the 5-150 and 2-150 ng mL⁻¹ ranges for trans- and cis-resveratrol, with detection limits of 2 and 0.5 ng mL⁻¹, respectively. When using SBSE, a polydimethylsiloxane (PDMS) twister provided best extraction by means of a derivatization reaction in the presence of acetic anhydride and potassium carbonate. The same time and temperature were used for the extraction step in the presence of 2.5% (m/v) sodium chloride, and liquid desorption was performed with 150 μL of a 50/50 (v/v) acetonitrile/1% (v/v) acetic acid solution in a desorption time of 15 min. Linearity was now between 0.5 and 50 ng mL⁻¹ for trans-resveratrol with a detection limit of 0.1 ng mL⁻¹, while cis-resveratrol could not be extracted. The proposed methods were successfully applied to determining the resveratrol isomer content of wine, must and fruit juices.     

Development of different temoporfin-loaded invasomes—novel nanocarriers of temoporfin: Characterization, stability and in vitro skin penetration studies

A previous study revealed that the invasome dispersion containing 3.3% (w/v) ethanol and 1% (w/v) of the terpene mixture (cineole:citral:d-limonene = 45:45:10, v/v = standard mixture) could significantly enhance skin penetration of the highly hydrophobic photosensitizer temoporfin (mTHPC). Invasomes enhanced mTHPC-deposition in stratum corneum (SC) compared to liposomes without terpenes and conventional liposomes, and they were efficient in delivering mTHPC to deeper skin layers [J. Control. Release 127 (2008) 271–280]. The aim of this study was to develop new mTHPC-loaded invasomes in order to further enhance the drug penetration. The ratio between d-limonene, citral and cineole was varied in the standard terpene mixture and also single terpenes were used. As a result new mTHPC-loaded invasome dispersions were prepared, characterized and investigated for stability and in vitro penetration of mTHPC into abdominal human skin using Franz diffusion cells.Invasomes were of a small particle size (<150 nm), high homogeneity (<0.3), mostly unilamellar and spherical, but also deformed vesicles were detected. Invasomes containing 1% (w/v) cineole provided the highest skin penetration enhancement of mTHPC, i.e. they provided high amounts of mTHPC in the SC and deeper skin layers, indicating that also incorporation of a single terpene into invasomes could provide efficient nanocarriers of mTHPC. These invasomes could be considered as a promising tool for delivering the photosensitizer mTHPC to the skin.However, in contrast to most invasomes, being effective nanocarriers of mTHPC, there were also formulations less effective than liposomes containing 3.3% (w/v) ethanol and one formulation was less efficient than conventional liposomes.     

Magnetic solid‐phase extraction and ultrafast liquid chromatographic detection of Sudan dyes in red wines,juices, and mature vinegars

A nanocomposite of polystyrene‐coated magnetic nanoparticles was successfully synthesized and employed as adsorbent for magnetic solid‐phase extraction of four Sudan dyes (I, II III, and IV) in red wines, juices, and mature vinegars. The prepared magnetic nanoparticles with highly hydrophobic properties have excellent adsorption capacity for these lipophilic Sudan dyes. Extraction conditions were optimized. Experimental results showed that the recoveries of the four Sudan dyes were very satisfactory when 70 mg of polystyrene‐coated magnetic nanoparticles were used and the extraction could be completed within 20 min. It was proved that these magnetic nanoparticles can be reused after an easy washing process. By coupling the magnetic solid‐phase extraction with ultrafast liquid chromatography‐ultraviolet spectrometry, a rapid, green, effective, and sensitive method for the determination of Sudan dyes was developed. The LOD for Sudan I, Sudan II, Sudan III, and Sudan IV were 0.0039, 0.0063, 0.0057, and 0.017 ng/mL, respectively. Recoveries obtained by analyzing spiked water samples at three concentration levels (0.1, 1.0, and 10.0 ng/mL) were between 76.3 and 96.6%. The intra‐ and interday RSDs for the analytes were lower than 9.6%.     

Isolation of volatiles from Nigella sativa seeds using microwave‐assisted extraction: effect of whole extracts on canine and murine CYP1A

The volatile components of Nigella sativa seeds were isolated using microwave‐assisted extraction (MAE) and identified using gas chromatography. Further investigations were carried out to demonstrate the effects of whole extracts on canine (dog) and murine (rat) cytochrome P450 1A (CYP1A). The optimal extraction conditions of MAE were as follows: 25 mL of water, medium level of microwave oven power and 10 min of extraction time. A total of 32 compounds were identified under the conditions using GC‐FID and GC‐MS. Thymoquinone (38.23%), p‐cymene (28.61%), 4‐isopropyl‐9‐methoxy‐1‐methyl‐1‐cyclohexene (5.74%), longifolene (5.33%), α‐thujene (3.88) and carvacol (2.31%) were the main compounds emitted from N. sativa seeds. Various extracts including pure compounds, essential oil, nonpolar partition, relatively high‐polar/nonpolar partition, and polar partition extracts effectively inhibited the reaction of ethoxyresorufin O‐de‐ethylation, which is specified for CYP1A activity both in dog and rat. This in vitro data should be heeded as a signal of possible in vivo interactions. The use of human liver preparations would considerably strengthen the practical impact of the data generated from this study. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of needle trap micro‐extraction and solid‐phase micro‐extraction: Obtaining comprehensive information on volatile emissions from in vitro cultures

Volatile organic compounds (VOCs) emitted from in vitro cultures may reveal information on species and metabolism. Owing to low nmol L⁻¹ concentration ranges, pre‐concentration techniques are required for gas chromatography–mass spectrometry (GC–MS) based analyses. This study was intended to compare the efficiency of established micro‐extraction techniques – solid‐phase micro‐extraction (SPME) and needle‐trap micro‐extraction (NTME) – for the analysis of complex VOC patterns. For SPME, a 75 μm Carboxen®/polydimethylsiloxane fiber was used. The NTME needle was packed with divinylbenzene, Carbopack X and Carboxen 1000. The headspace was sampled bi‐directionally. Seventy‐two VOCs were calibrated by reference standard mixtures in the range of 0.041–62.24 nmol L⁻¹ by means of GC–MS. Both pre‐concentration methods were applied to profile VOCs from cultures of Mycobacterium avium ssp. paratuberculosis. Limits of detection ranged from 0.004 to 3.93 nmol L⁻¹ (median = 0.030 nmol L⁻¹) for NTME and from 0.001 to 5.684 nmol L⁻¹ (median = 0.043 nmol L⁻¹) for SPME. NTME showed advantages in assessing polar compounds such as alcohols. SPME showed advantages in reproducibility but disadvantages in sensitivity for N‐containing compounds. Micro‐extraction techniques such as SPME and NTME are well suited for trace VOC profiling over cultures if the limitations of each technique is taken into account.     

Acid extraction treatment of sediment samples for organotin speciation; occurrence of butyltin and phenyltin compounds on the cadiz coast,south-west spain

A method is described for leaching of nanogram amounts of mono-, di and tri-butyltin compounds and mono-, di- and tri-phenyltin compounds from sediments. The procedure is based on soaking the sediments in a water–hydrogen bromide mixture (2:3) with magnetic stirring for 1 h followed by extraction with 0.02% (w/v) tropolone solution in pentane for 2 h. Organotins are determined by GF FPD after clean-up through a Florisil column and derivatization by Grignard pentylation. The method has been applied to the study of water and sediments in different areas of south-west Spain. Predominant species are butyltins, especially tributyltin (TBT), which has high values in waters and sediments of Puerto de Santa Maria and Cadiz Bay, as well as in sediments of the Sancti Petri Channel, which suggests a harmful action on biota. A direct relation has been found beween organotin levels and distance of potential focus determined by boating activities. In addition, the relative occurrence of dibutyltin (DBT) and monobutyltin (MBT) together with TBT has been noted, possibly as a result of a degractation process, and the influence of grain size of sediment and presence of organic matter on organotin accumulation has been studied.     

Application of an efficient strategy based on liquid–liquid extraction,high‐speed counter‐current chromatography,and preparative HPLC for the rapid enrichment,separation, and purification of four anthraquinones from Rheum tanguticum

This study presents an efficient strategy based on liquid–liquid extraction, high‐speed counter‐current chromatography, and preparative HPLC for the rapid enrichment, separation, and purification of four anthraquinones from Rheum tanguticum. A new solvent system composed of petroleum ether/ethyl acetate/water (4:2:1, v/v/v) was developed for the liquid–liquid extraction of the crude extract from R. tanguticum. As a result, emodin, aloe‐emodin, physcion, and chrysophanol were greatly enriched in the organic layer. In addition, an efficient method was successfully established to separate and purify the above anthraquinones by high‐speed counter‐current chromatography and preparative HPLC. This study supplies a new alternative method for the rapid enrichment, separation, and purification of emodin, aloe‐emodin, physcione, and chrysophanol.     

Simultaneous sonication-assisted extraction, and determination by gas chromatography-mass spectrometry, of di-(2-ethylhexyl)phthalate, nonylphenol, nonylphenol ethoxylates and polychlorinated biphenyls in sludge from wastewater treatment plants

Di-(2-ethyl-hexyl)phthalate (DEHP), nonylphenol, nonylphenol mono- and diethoxylates (NPEs) and polychlorinated biphenyls (PCBs) are organic pollutants in sewage sludge which have to be monitored in the European Union according to a future Sludge Directive. In the present work, an analytical method for the simultaneous extraction and determination of DEHP, NPEs and PCBs is proposed for the routine analysis of these compounds in sludge from wastewater treatment plants. All the compounds were simultaneously extracted by sonication with hexane and analysed by gas chromatography-mass spectrometry (GC-MS) in electronic impact mode. Recoveries achieved were 105% for DEHP, 61.4-88.6% for NPEs and 55.8-108.3% for PCBs with relative standard deviation bellow 10%. Limits of quantification were 65 μg kg⁻¹ for DEHP, from 630 to 2504 μg kg⁻¹ for NPEs and from 5.4 to 10.6 μg kg⁻¹ for PCBs in dried sludge. The applicability of the proposed method was evaluated by the determination of these compounds in sludge from wastewater treatment plants in Seville (South Spain).     

An efficient strategy based on liquid‐liquid extraction and pH‐zone‐refining counter‐current chromatography for selective enrichment,separation, and purification of alkaloids and organic Acids from natural products

This study presents an efficient strategy based on liquid‐liquid extraction and pH‐zone‐refining counter‐current chromatography for selective enrichment, separation, and purification of alkaloids and organic acids from natural products. First, an acid or base modified two‐phase solvent system with maximum or minimum partition coefficient was developed for the liquid‐liquid extraction of the crude extract. As a result, alkaloids or organic acids could be selectively enriched in the upper or lower phase. Then pH‐zone‐refining counter‐current chromatography was employed to separate and purify the selectively enriched alkaloids or organic acids efficiently. The selective enrichment and separation of five bufadienolide from toad venom of Bufo marinus was used as an example to show the advantage of this strategy. As a result, 759 mg of selectively enriched bufadienolide was obtained from 2 g of crude extract and the total content of five targets was increased from 14.64 to 83%. A total of 31 mg of marinobufagin‐3‐adipoyl‐l ‐arginine, 42 mg of telocinobufagin‐3‐pimeloyl‐l ‐arginine, 51 mg of telocinobufagin‐3‐suberoyl‐l ‐arginine, 132 mg of marinobufagin‐3‐suberoyl‐l ‐arginine, and 57 mg of bufalin‐3‐suberoyl‐l ‐arginine were all simultaneously separated from 500 mg of selectively enriched sample, with the purity of 92.4, 97.5, 90.3, 92.1, and 92.8%, respectively.     

Application of an efficient strategy based on MAE,HPLC‐DAD‐MS/MS and HSCCC for the rapid extraction,identification, separation and purification of flavonoids from Fructus Aurantii Immaturus

This study presents an efficient strategy based on microwave‐assisted extraction (MAE), HPLC‐DAD‐MS/MS and high‐speed counter‐current chromatography (HSCCC) for the rapid extraction, identification, separation and purification of active components from the traditional Chinese medicine Fructus Aurantii Immaturus. An LC‐DAD‐MS/MS method was applied for the screening and structural identification of main components in crude extract, and five components were preliminarily identified as neoeriocitrin, narirutin, naringin, hesperidin and neohesperidin according to their UV and mass spectra. An efficient MAE method for the extraction of the three most abundant components (narirutin, naringin and neohesperidin) was optimized by the combination of univariate and multivariate approaches. The crude extract was then separated and purified by HSCCC and a total of 61.6 mg of narirutin, 207.3 mg of naringin and 159.5 mg of neohesperidin at high purities of 98.1, 97.2 and 99.5%, respectively, were obtained from 1.42 g of crude extract. The recoveries of these compounds were 86, 93 and 89%, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of PCL,PEG and PLGA polymers on curcumin release from calcium phosphate matrix for in vitro and in vivo bone regeneration

Calcium phosphate materials are widely used as bone-like scaffolds or coating for metallic hip and knee implants due to their excellent biocompatibility, compositional similarity to natural bone and controllable bioresorbability. Local delivery of drugs or osteogenic factors from scaffolds and implants are required over a desired period of time for an effectual treatment of various musculoskeletal disorders. Curcumin, an antioxidant and anti-inflammatory molecule, enhances osteoblastic activity in addition to its anti-osteoclastic activity. However, due to its poor solubility and high intestinal liver metabolism, it showed limited oral efficacy in various preclinical and clinical studies. To enhance its bioavailability and to provide higher release, we have used poly (ε-caprolactone) (PCL), poly ethylene glycol (PEG) and poly lactide co glycolide (PLGA) as the polymeric system to enable continuous release of curcumin from the hydroxyapatite matrix for 22 days. Additionally, curcumin was incorporated in plasma sprayed hydroxyapatite coated Ti6Al4V substrate to study in vitro cell material interaction using human fetal osteoblast (hFOB) cells for load bearing implants. MTT cell viability assay and morphological characterization by FESEM showed highest cell viability with samples coated with curcumin-PCL-PEG. Finally, 3D printed interconnected macro porous β-TCP scaffolds were prepared and curcumin-PCL-PEG was loaded to assess the effects of curcumin on in vivo bone regeneration. The presence of curcumin in TCP results in enhanced bone formation after 6 weeks. Complete mineralized bone formation increased from 29.6% to 44.9% in curcumin-coated scaffolds compared to pure TCP. Results show that local release of curcumin can be designed for both load bearing or non-load bearing implants with the aid of polymers, which can be considered an excellent candidate for wound healing and tissue regeneration applications in bone tissue engineering.     

Purification,Structural Characterization and Immunomodulatory Effects of Polysaccharides from Amomum villosum Lour. on RAW 264.7 Macrophages

Amomum Villosum Lour. (A. villosum) is a folk medicine that has been used for more than 1300 years. However, study of the polysaccharides of A. villosum is seriously neglected. The objectives of this study are to explore the structural characteristics of polysaccharides from A. villosum (AVPs) and their effects on immune cells. In this study, the acidic polysaccharides (AVPG-1 and AVPG-2) were isolated from AVPs and purified via anion exchange and gel filtration chromatography. The structural characteristics of the polysaccharides were characterized by methylation, HPSEC-MALLS-RID, HPLC, FT-IR, SEM, GC-MS and NMR techniques. AVPG-1 with a molecular weight of 514 kDa had the backbone of → 4)-α-d-Glcp-(1 → 3,4)-β-d-Glcp-(1 → 4)-α-d-Glcp-(1 →. AVPG-2 with a higher molecular weight (14800 kDa) comprised a backbone of → 4)-α-d-Glcp-(1 → 3,6)-β-d-Galp-(1 → 4)-α-d-Glcp-(1 →. RAW 264.7 cells were used to investigate the potential effect of AVPG-1 and AVPG-2 on macrophages, and lipopolysaccharide (LPS) was used as a positive control. The results from bioassays showed that AVPG-2 exhibited stronger immunomodulatory activity than AVPG-1. AVPG-2 significantly induced nitric oxide (NO) production as well as the release of interleukin (IL)-6 and tumor necrosis factor alpha (TNF-α), and upregulated phagocytic capacities of RAW 264.7 cells. Real-time PCR analysis revealed that AVPG-2 was able to turn the polarization of macrophages to the M1 direction. These results suggested that AVPs could be explored as potential immunomodulatory agents of the functional foods or complementary medicine.     

Ligand‐Modification Effects on the Reactivity,Solubility, and Stability of Organometallic Tantalum Complexes in Water

Tantalum complexes [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NMe₂)?CH)py}] ( 4 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NH₂)?CH)py}] ( 5 ), which contain modified alkoxide pincer ligands, were synthesized from the reactions of [TaCp*Me{κ³‐N,O,O‐(OCH₂)(OCH)py}] (Cp*=η⁵‐C₅Me₅) with HC?CCH₂NMe₂ and HC?CCH₂NH₂, respectively. The reactions of [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(Ph)?CH)py}] ( 2 ) and [TaCp*Me{κ⁴‐C,N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH)py}] ( 3 ) with triflic acid (1:2 molar ratio) rendered the corresponding bis‐triflate derivatives [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(Ph)?CH₂)py}] ( 6 ) and [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(OCHC(SiMe₃)?CH₂)py}] ( 7 ), respectively. Complex 4 reacted with triflic acid in a 1:2 molar ratio to selectively yield the water‐soluble cationic complex [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH)py}]OTf ( 8 ). Compound 8 reacted with water to afford the hydrolyzed complex [TaCp*(OH)(H₂O){κ³‐N,O,O‐(OCH₂)(OCHC(CH₂NHMe₂)?CH₂)py}](OTf)₂ ( 9 ). Protonation of compound 8 with triflic acid gave the new tantalum compound [TaCp*(OTf){κ⁴‐C,N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH)py}](OTf)₂ ( 10 ), which afforded the corresponding protonolysis derivative [TaCp*(OTf)₂{κ³‐N,O,O‐(OCH₂)(HOCHC(CH₂NHMe₂)?CH₂)py}](OTf) ( 11 ) in solution. Complex 8 reacted with CNtBu and potassium 2‐isocyanoacetate to give the corresponding iminoacyl derivatives 12 and 13 , respectively. The molecular structures of complexes 5 , 7 , and 10 were established by single‐crystal X‐ray diffraction studies.     

Comparison of three different dispersive liquid–liquid microextraction modes performed on their most usual configurations for the extraction of phenolic,neutral aromatic,and amino compounds from waters

In this work we seek clues to select the appropriate dispersive liquid–liquid microextraction mode for extracting three categories of compounds. For this purpose, three common dispersive liquid–liquid microextraction modes were compared under optimized conditions. Traditional dispersive liquid–liquid microextraction, in situ ionic liquid dispersive liquid–liquid microextraction, and conventional ionic liquid dispersive liquid–liquid microextraction using chloroform, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, and 1‐hexyl‐3‐methylimidazolium hexafluorophosphate as the extraction solvent, respectively, were considered in this work. Phenolic, neutral aromatic, and amino compounds (each category included six members) were studied as analytes. The analytes in the extracts were determined by high‐performance liquid chromatography with UV detection. For the analytes with polar functionalities, the in situ ionic liquid dispersive liquid–liquid microextraction mode mostly led to better results. In contrast, for neutral hydrocarbons without polar functionalities, traditional dispersive liquid–liquid microextraction using chloroform produced better results. In this case, where dispersion forces were the dominant interactions in the extraction, the refractive index of solvent and analyte predicted the extraction performance better than the octanol/water partition coefficient. It was also revealed that none of the methods were successful in extracting hydrophilic analytes (compounds with the log octanol/water partition coefficient <2). The results of this study could be helpful in selecting a dispersive liquid–liquid microextraction mode for the extraction of various groups of compounds.     

Concentration‐Dependent Hydrogen‐Bonding Effects on the Dimethyl Sulfoxide Vibrational Structure in the Presence of Water,Methanol, and Ethanol

The effects of hydrogen bonding between dimethyl sulfoxide (DMSO) and the co‐solvents water, methanol, and ethanol on the symmetric and antisymmetric CSC stretching vibrations of DMSO are investigated by means of Raman spectroscopy. The Raman spectra are recorded as a function of co‐solvent concentration and reflect changes in structure and polarizability as well as hydrogen‐bond donor and acceptor ability. In all cases studied a nonideal mixing behavior is observed. The spectra of the DMSO/water system show blue‐shifted CSC stretching modes. The antisymmetric frequencies are always further blue‐shifted than the symmetric stretching ones. The DMSO/methanol system also features blue‐shifted CSC stretching frequencies but at high mole fractions a pronounced red shifting is observed. In the binary DMSO/ethanol system, the co‐solvent also gives rise to blue shifts of the CSC stretching frequencies but restricted to mole fractions between x=0.38 and 0.45. The different magnitudes and occurrences of both blue‐ and red‐shifted spectral lines are comprehensively and critically discussed with respect to the existing literature concerning wavenumbers and Raman intensities in both absolute and normalized values. In particular, the normalized Raman intensities show a higher sensitivity for the nonideal mixing behavior because they are independent of the mole fraction.     

Use of fullerene‐, octadecyl‐, and triaconthyl silica for solid phase extraction of tryptic peptides obtained from unmodified and in vitro glycated human serum albumin and fibrinogen

SPE plays a crucial role in bioanalytical research. In the present work a novel fullerene(C60)‐derivatised silica material is compared with octadecyl(C18) – and triaconthyl(C30)‐silicas regarding recoveries of peptides and sequence coverage of HSA and fibrinogen digests. C30‐ and C60(30 nm)‐SPE materials were found to be the two most prominent SPE materials. At low peptide concentrations C60‐material prepared from a silica gel with a pore size of 30 nm has proven to be the best material with regards to recoveries. By increasing the amount of loaded peptides recoveries decrease due to its relative low binding capacity in contrast to C30‐silica particles, showing no changes. The best sequence coverages of Aα‐ and Bβ‐chains of 20 pmol fibrinogen digest can also be achieved using these two SPE materials, C60 (30 nm) demonstrates an outstanding value of sequence coverage (62.15%) achieved for the γ‐chain. After nonenzymatic glycation the digests of fibrinogen and HSA were also separated. This makes the detection of a considerably higher number of glycated peptides possible compared to the unfractionated digests and the use of boronate affinity chromatography in the case of fibrinogen. For HSA, ten new sites of glycation at lysine and arginine residues have been explored. Using the detailed SPE/off‐line MALDI method the glycation sites on fibrinogen are first described in this paper.     

Online hyphenation of extraction,Sephadex LH‐20 column chromatography,and high‐speed countercurrent chromatography: A highly efficient strategy for the preparative separation of andrographolide from Andrographis paniculata in a single step

A novel isolation strategy, online hyphenation of ultrasonic extraction, Sephadex LH‐20 column chromatography combined with high‐speed countercurrent chromatography, was developed for pure compounds extraction and purification. Andrographolide from Andrographis paniculata was achieved only in a single step purification protocol via the present strategy. The crude powder was ultrasonic extracted and extraction was pumped into Sephadex LH‐20 column directly to cut the nontarget fractions followed by the second‐dimensional high‐speed countercurrent chromatography, hyphenated by a six‐port valve equipped at the post‐end of Sephadex LH‐20 column, for the final purification. The results yielded andrographolide with the amount of 1.02 mg and a purity of 98.5% in a single step, indicating that the present method is effective to harvest target compound from medicinal plant.     

Simultaneous assay of glucose,lactate, <Emphasis Type="SmallCaps">L</Emphasis>-glutamate and hypoxanthine levels in a rat striatum using enzyme electrodes based on neutral red-doped silica nanoparticles

An electrochemical method suitable for the simultaneous measurement of cerebral glucose, lactate, L-glutamate and hypoxanthine concentrations from in vivo microdialysis sampling has been successfully performed for the first time using a neutral red-doped silica (NRDS) nanoparticle-derived enzyme sensor system. These uniform NRDS nanoparticles (about 50±3 nm) were prepared by a water-in-oil (W/O) microemulsion method, and characterized by a TEM technique. The neutral red-doped interior maintained its high electron-activity, while the exterior nano-silica surface prevented the mediator from leaching out into the aqueous solution, and showed high biocompability. These nanoparticles were then mixing with the glucose oxidase (GOD), lactate oxidase (LOD), L-glutamate oxidase (L-GLOD) or xanthine oxidase (XOD), and immobilized on four glassy carbon electrodes, respectively. A thin Nafion film was coated on the enzyme layer to prevent interference from molecules such as ascorbic acid and uric acid in the dialysate. The high sensitivity of the NRDS modified enzyme electrode system enables the simultaneous monitoring of trace levels of glucose, L-glutamate, lactate and hypoxanthine in diluted dialysate samples from a rat striatum.