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Good Separation (good + separation)
Selected AbstractsSeparation and aquatic toxicity of enantiomers of the pyrethroid insecticide lambda-cyhalothrin,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2008Chao Xu Abstract Chiral pollutants are receiving growing environmental concern due to differential biological activities of their enantio-mers. In the present study, enantiomeric separation of the pyrethroid insecticide lambda-cyhalothrin (LCT) was investigated by high-performance liquid chromatography (HPLC) using the columns of Chiralpak AD (amylase tris[3,5-dimethyl-phenylcarbamate]), Chiralpak AS (amylase tris[(S)-1-phenyl carbamate]), Chiralcel OD (cellulose tris[3,5-dimethylphenyl carbamate]), and Chiralcel OJ (cellulose tris[4-methyl benzoate]) with different chiral stationary phases. The differential toxicities of the enantiomers in aquatic systems were evaluated using the acute zebrafish (Danio rerio) toxicity test and the zebrafish embryo test. The enantiomers of LCT were separated completely on all the columns tested and detected by circular dichroism at 236 nm. Better separations were achieved at lower temperatures (e.g., 20°C) and lower levels of polar modifiers (,5%) in mobile phase. Ethanol was found to be a good modifier of the mobile phase for all the columns, although isopropanol acted better for the Chiralcel OD column. The (,)-enantiomer was >162 times more toxic than its antipode to zebrafish in the acute test. The embryo test indicated that the exposure to LCT enantioselectively induced crooked body, yolk sac edema, and pericardial edema and that the (,)-enantiomer was 7.2 times stronger than the (+)-enantiomer in 96-h mortality. The malformations were induced by the racemate and its (,)-enantiomer at lower concentrations tested (e.g., 50 ,g L,1), whereas the (+)-enantiomer induced malformations at relatively higher concentrations (,100 ,g L,1). These results suggest that the toxicological effects of chiral pesticides must be evaluated using their individual enantiomers. [source] Multilayer poly(vinyl alcohol)-adsorbed coating on poly(dimethylsiloxane) microfluidic chips for biopolymer separationELECTROPHORESIS, Issue 1 2005Dapeng Wu Abstract A poly(dimethylsiloxane) (PDMS) microfluidic chip surface was modified by multilayer-adsorbed and heat-immobilized poly(vinyl alcohol) (PVA) after oxygen plasma treatment. The reflection absorption infrared spectrum (RAIRS) showed that 88% hydrolyzed PVA adsorbed more strongly than 100% hydrolyzed one on the oxygen plasma-pretreated PDMS surface, and they all had little adsorption on original PDMS surface. Repeating the coating procedure three times was found to produce the most robust and effective coating. PVA coating converted the original PDMS surface from a hydrophobic one into a hydrophilic surface, and suppressed electroosmotic flow (EOF) in the range of pH 3,11. More than 1 000,000 plates/m and baseline resolution were obtained for separation of fluorescently labeled basic proteins (lysozyme, ribonuclease B). Fluorescently labeled acidic proteins (bovine serum albumin, ,-lactoglobulin) and fragments of dsDNA ,X174 RF/HaeIII were also separated satisfactorily in the three-layer 88% PVA-coated PDMS microchip. Good separation of basic proteins was obtained for about 70 consecutive runs. [source] Fat-water separation in dynamic objects using an UNFOLD-like temporal processingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2010Riad Ababneh PhD Abstract Purpose To separate fat and water signals in dynamic imaging. Because important features may be embedded in fat, and because fat may take part in disease processes, separating fat and water signals may be of great importance in a number of clinical applications. This work aims to achieve such separation at nearly no loss in temporal resolution compared to usual, nonseparated acquisitions. In contrast, the well-known 3-point Dixon method may cause as much as a 3-fold reduction in temporal resolution. Materials and Methods The proposed approach involves modulating the echo time TE from frame to frame, to force fat signals to behave in a conspicuous manner through time, so they can be readily identified and separated from water signals. The strategy is inspired from the "unaliasing by Fourier encoding the overlaps in the temporal direction" (UNFOLD) method, although UNFOLD involves changes in the sampling function rather than TE, and aims at suppressing aliased material rather than fat. Results The method was implemented at 1.5 T and 3 T, on cardiac cine and multiframe steady-state free precession sequences. In addition to phantom results, in vivo results from volunteers are presented. Conclusion Good separation of fat and water signals was achieved in all cases. J. Magn. Reson. Imaging 2010;32:962,970. © 2010 Wiley-Liss, Inc. [source] RP-HPTLC densitometric determination and validation of vanillin and related phenolic compounds in accelerated solvent extract of Vanilla planifolia,*JOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2007Upendra Kumar Sharma Abstract A simple, fast and sensitive RP-HPTLC method is developed for simultaneous quantitative determination of vanillin and related phenolic compounds in ethanolic extracts of Vanilla planifolia pods. In addition to this, the applicability of accelerated solvent extraction (ASE) as an alternative to microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and Soxhlet extraction was also explored for the rapid extraction of phenolic compounds in vanilla pods. Good separation was achieved on aluminium plates precoated with silica gel RP-18 F254S in the mobile phase of methanol/water/isopropanol/acetic acid (30:65:2:3, by volume). The method showed good linearity, high precision and good recovery of compounds of interest. ASE showed good extraction efficiency in less time as compared to other techniques for all the phenolic compounds. The present method would be useful for analytical research and for routine analysis of vanilla extracts for their quality control. [source] Glycoform characterization of erythropoietin combining glycan and intact protein analysis by capillary electrophoresis , electrospray , time-of-flight mass spectrometryELECTROPHORESIS, Issue 13 2006Elvira Balaguer Abstract Glycosylation of recombinant human erythropoietin (rHuEPO) is a post-translational process that alters biological activity, solubility and lifetime of the glycoprotein in blood, and strongly depends on the type of cell and the cell culture conditions. A fast and simple method providing extensive carbohydrate information about the glycans present in rHuEPO and other glycoproteins is needed in order to improve current methods in drug development or product quality control. Here, an improved method for intact rHuEPO glycoform characterization by CZE-ESI-TOF MS has been developed using a novel capillary coating and compared to a previous study. Both methods allow a fast separation in combination with accurate mass characterization of the single protein isoforms. The novel dynamic coating provides a separation at an EOF close to zero, enabling better separation. This results in an improved mass spectrometric resolution and the detection of minor isoforms. In order to assign an unequivocal carbohydrate composition to every intact glycoform, a CZE-ESI-MS separation method for enzymatically released underivatized N -glycans has been developed. The TOF,MS allows the correct identification of the glycans due to its high mass accuracy and resolution. Therefore, glycan modifications such as acetylation, oxidation, sulfation and even the exchange of OH by NH2 are successfully characterized. Information of the protein-backbone molecular mass has been combined with results from peptide analysis (revealing information about O -glycosylation) and from the glycan analysis, including the detection of as yet undescribed glycans containing four antennae and five sialic acids. This allows an unequivocal assignment of an overall glycosylation composition to the molecular masses obtained for the intact rHuEPO glycoforms. [source] Analytical potential of 6-oxy-(N -succinimidyl acetate)-9-(2'-methoxycarbonyl) fluorescein for the determination of amino compounds by capillary electrophoresis with laser-induced fluorescence detectionELECTROPHORESIS, Issue 10 2005Liwei Cao Abstract The analytical potential of a fluorescein analogue, 6-oxy-(N -succinimidyl acetate)-9-(2'-methoxycarbonyl) fluorescein (SAMF), for the first time synthesized in our laboratory, as a labeling reagent for the labeling and determination of amino compounds by capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was investigated. Biogenic monoamines and amino acids were chosen as model analytes to evaluate the analytical possibilities of this approach. The derivatization conditions and separation parameters for the biogenic amines were optimized in detail. The derivatization was performed at 30°C for 6 min in boric acid buffer (pH 8.0). The derivatives were baseline-separated in 15 min with 25 mM boric acid running buffer (pH 9.0), containing 24 mM SDS and 12.5% v/v acetonitrile. The concentration detection limit for biogenic amines reaches 8×10,11 mol·L,1 (signal-to-noise ratio = 3). The application of CE in the analysis of the SAMF-derivatized amino acids was also exploited. The optimal running buffer for amino acids suggested that weak acidic background electrolyte offered better separation than the basic one. The proposed method was applied to the determination of biogenic amines in three different beer samples with satisfying recoveries varying from 92.8% to 104.8%. Finally, comparison of several fluorescein-based probes for amino compounds was discussed. With good labeling reaction, excellent photostability, pH-independent fluorescence (pH 4,9), and the resultant widely suited running buffer pH, SAMF has a great prospect in the determination of amino compounds in CE. [source] Application of dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium in wall modification for capillary electrophoresis separation of proteinsELECTROPHORESIS, Issue 3 2005Wei Wei Abstract A zwitterionic surfactant, dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium (C12H25N+(CH3)2CH2CHOHCH2SO3,), named dodecyl sulfobetaine (DSB), was used as a novel modifier to coat dynamically capillary walls for capillary electrophoresis separation of basic proteins. The DSB coating suppressed the electroosmotic flow (EOF) in the pH range of 3,12. At high DSB concentration, the EOF was suppressed by more than 8.8,times. The DSB coating also prevented successfully the adsorption of cationic proteins on the capillary wall. Anions, such as Cl,, Br,, I,, SO42,, CO32,, and ClO4,, could be used as running buffer modifiers to adjust the EOF for better separation of analytes. Using this dynamically coated capillary, a mixture of eight inorganic anions achieved complete separation within 4.2,min with the efficiencies from 24,000 to 1,310,000,plates/m. In the presence of ClO4, as EOF adjustor, the separation of a mixture containing four basic proteins (lysozyme, cytochrome c, ,-chymotrypsinogen,A, and myoglobin) yielded efficiencies of 204,000,896,000,plates/m and recoveries of 88%,98%. Migration time reproducibility of these proteins was less than 0.5% relative standard deviation (RSD) from run to run and less than 3.1% RSD from day to day, showing promising application of this novel modifier in protein separation. [source] Upper mantle stratification by P and S receiver functionsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2000Véronique Farra Summary Seismic stratification of the upper mantle is investigated by applying two complementary techniques to the records of the Graefenberg array in southern Germany. The anisotropic P receiver function technique (Kosarev et al. 1984; Vinnik & Montagner 1996) is modified by using summary seismic events instead of individual events and different weighting functions instead of the same function for the harmonic angular analysis of the SV and T components of the Pds phases. The summary events provide better separation of the second azimuthal harmonic than the individual events. The parameters of the second harmonics of SV and T thus evaluated should be similar if they reflect the effects of azimuthal anisotropy. This can be used as a criterion to identify the anisotropy. To detect the Sdp phases and their azimuthal variations caused by azimuthal anisotropy we have developed a stacking technique, which can be termed the S receiver function technique It includes axis rotation to separate interfering P and S arrivals, determination of the principal (M) component of the S -wave motion, deconvolution of the P components of many recordings by their respective M components and stacking of the deconvolved P components with weights depending on the level of noise and the angle between the M direction and the backazimuth of the event. Both techniques yield consistent results for the Graefenberg array. As indicated by the P receiver functions, the upper layer of the mantle between the Moho and 80 km depth is anisotropic with dVs/Vs around 0.03 and the fast direction close to 20° clockwise from north. The fast direction of anisotropy below this layer is around 110°, The boundary between the upper and the lower anisotropic layers is manifested by the detectable Pds and Sdp converted phases. Shear wave splitting in SKS is strongly dominated by azimuthal anisotropy in the lower layer (asthenosphere). [source] Laser desorption/ionization techniques in the characterization of high molecular weight oil fractions.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2006Part 1: asphaltenes Abstract The molecular weight distribution of the asphaltene fractions of two types of crude oils from two different Italian fields (samples 1 and 2) was investigated. The analytical tools used to perform these analyses were matrix assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) mass spectrometry. After observing that the use of the matrix (as well as the addition of Ag+) did not improve the quality of the data compared to that obtained in LDI conditions, all further measurements were performed with the latter technique. Operating under usual conditions of laser power and delay time, a very low resolution was observed, showing only macroscopic differences between the two samples in the molecular weight distribution of the different components. An accurate study on the possible reasons of this undesirable behavior indicates that it can originate from space charge phenomena occurring either in the ion source region or during the flight. A valid parameterization of the delay time and the laser power allowed higher quality spectra to be obtained. Surface-enhanced laser desorption ionization (SELDI) measurements were also performed using normal phase (silica) as the sample holder surface. Under these conditions, better results are obtained, proving that the sample,surface interaction is important to achieve, by means of laser irradiation, a homogeneous set of product ions. Both asphaltene samples were fractionated in five subfractions by gel-permeation chromatography (GPC) to obtain a better separation of the molecular weight distributions; the related spectra confirmed these findings. By using different approaches, relevant and reproducible differences between the asphaltene fractions of the two oil samples were observed. Copyright © 2006 John Wiley & Sons, Ltd. [source] Protein separations using polyelectrolyte multilayer coatings with molecular micelles in open tubular capillary electrochromatographyELECTROPHORESIS, Issue 4 2008Candace A. Luces Abstract Novel polyelectrolyte multilayer (PEM) coatings for enhanced protein separations in open tubular CEC (OT-CEC) are reported. Use of four cationic polymers (poly- L -lysine, poly- L -ornithine, poly- L -lysine-serine, and poly- L -glutamic acid-lysine), and three anionic molecular micelles, sodium poly(N -undecanoyl- L -leucyl-alaninate) (poly- L -SULA), sodium poly(N -undecanoyl- L -leucyl-valinate) (poly- L -SULV), and sodium poly(undecylenic sulfate) (poly-SUS) were investigated in PEM coatings for protein separations. The simultaneous effects of cationic polymer concentration, number of bilayers, temperature, applied voltage, and pH of the BGE on the separation of four basic proteins (,-chymotrypsinogen A, lysozyme, ribonuclease A, and cytochrome c) were analyzed using a Box Behnken experimental design. The influence of NaCl on the run-to-run reproducibility was investigated for PEM coatings containing each cationic polymer. All coatings exhibited excellent reproducibilities with a %RSD of the EOF less than 1% in the presence of NaCl. Optimal conditions were dependent on both the cationic and anionic polymers used in the PEM coatings. Poly- L -glutamic acid-lysine produced the highest resolution and longest migration time. The use of molecular micelles to form PEM coatings resulted in better separations than single cationic coatings. Chiral poly- L -SULA and poly- L -SULV resulted in higher protein resolutions as compared to the achiral, poly-SUS. Furthermore, the use of poly- L -SULV reversed the elution order of lysozyme and cytochrome c when compared to poly- L -SULA and poly-SUS. [source] Analysis of hepatic vitamins A1, A2, their fatty acyl esters, and vitamin E for biomonitoring mammals feeding on freshwater fishENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2002Anne Käkelä Abstract In tissues of freshwater fish,feeding mammals, 3,4-didehydroretinol (A2) is a major form of vitamin A. In mink liver, with organochlorine exposure, this analog has been found to decrease more than retinol (A1) and thus has potential as a sensitive freshwater biomarker. The presence of the analogs A1 and A2 as alcohol and different fatty acyl esters, which react to polychlorinated biphenyls differently, necessitates detailed analyses achieved by using direct extraction of tissue homogenate. In direct hexane extraction, compared to total levels of the vitamins obtained in the saponification procedure, a large proportion of the vitamins was released only after repeated and long-time vortex mixing with the extraction solvent. Thus, in tissue extraction, the use of internal standardization alone can lead to a rough underestimation of the levels of these fat-soluble vitamins. For analyses of vitamins A1 and A2 in liver, we applied the argentation high-performance liquid chromatography, which provided good separation of individual A1 and A2 fatty acyl esters. We report retention times for numerous esters of A1 and A2 and, to aid identification, the change in their retention properties after adding AgNO3 to the mobile phase. The argentation did not affect the recoveries of any forms of the retinoids studied but destroyed half the vitamin E. Despite selective acylation of fatty acids into the vitamin A esters, the fatty acids of the esters were the same as those found to be the major fatty acids in the gas,liquid chromatography of total lipids. The goal of this work was to create a methodology that is suitable for biomonitoring alcoholic and esterified vitamins A1 and A2 in tissues of freshwater fish,feeding mammals. [source] Examination of membrane protein expression in Paracoccus denitrificans by two-dimensional gel electrophoresisJOURNAL OF BASIC MICROBIOLOGY, Issue 1 2004Pavel Bouchal The well-known metabolic versatility of the soil bacterium Paracoccus denitrificans poses a challenge for modern proteomic approaches. We describe here improved preparation conditions that allow good separation and quantitative analyses of hundreds of membrane or periplasmic proteins. To illustrate this optimized procedure, the results of a screening for membrane proteins associated predominantly with aerobic or anaerobic (denitrifying) modes of growth are presented. [source] Enantioselective HPLC resolution of synthetic intermediates of armodafinil and related substancesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2008Ramisetti Nageswara Rao Abstract Armodafinil is a unique psychostimulant recently approved by the US Food and Drug Administration for the treatment of narcolepsy. The chromatographic resolution of its chiral intermediates including related substances in the total synthesis of armodafinil was studied on polysaccharide-based stationary phases, viz. cellulose tris-(3,5-dimethylphenylcarbamate) (Chiralcel OD-H) and amylose tris-(3,5-dimethylphenylcarbamate) (Chiralpak AD-H) by HPLC. The effects of 1-propanol, 2-propanol, ethanol, and trifluoroacetic acid added to the mobile phase and of column temperature on resolution were studied. A good separation was achieved on cellulose-based Chiralcel OD-H column compared to amylose-based Chiralpak AD-H. The effects of structural features of the solutes and solvents on discrimination between the enantiomers were examined. Baseline separation with Rs >1.38 was obtained using a mobile phase containing n -hexane,ethanol,TFA (75:25:0.15 v/v/v). Detection was carried out at 225 nm with photodiode array detector while identification of enantiomers was accomplished by a polarimetric detector connected in series. The method was found to be suitable not only for process development of armodafinil but also for determination of the enantiomeric purity of bulk drugs and pharmaceuticals. [source] Simultaneous determination of digoxin and digitoxin by micellar electrokinetic chromatography and application to drug formulationsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2003Hsiu-Hui Tseng Abstract A simple micellar electrokinetic chromatographic method is described for simultaneous determination of digoxin and digitoxin. The simultaneous analysis of digoxin and digitoxin was performed in Tris buffer (10 mM; pH 9) with 90 mM sodium dodecyl sulfate and 10% isopropyl alcohol as an anionic surfactant and organic modifier. Under these conditions, good separation with high efficiency is achieved in short analysis times. Several parameters affecting the separation of the drugs were studied, including the pH and concentrations of the Tris buffer and sodium dodecyl sulfate. The linear range of the method for the determination of digoxin and digitoxin was over 0.01,0.3 mg/mL; the detection limit (signal to noise ratio = 3; injection 3.5 kPa 3 s) was 4 and 6 ,g/mL, respectively. Application of the proposed method to the determination of digoxin in commercial tablets and in injections proved to be feasible. [source] Investigation of the separability of thaumatin by capillary electrophoresisJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2003Milena Vespalcová Abstract The electrophoretic behaviour of the highly basic protein thaumatin was explored in strongly acid (pH 2) and mildly acid (pH 4.5) separation systems using both bare and coated fused silica capillaries. The separation selectivity for thaumatin I, thaumatin II, and for other sample constituents was insufficient for their baseline separation at pH 2 in an uncoated capillary because the separation efficiency was markedly lower than is common in the electrophoretic separations of proteins. A separation selectivity higher by up to one order of magnitude has been reached at pH 4.5. A pronounced asymmetry of zones, which impaired resolution at this pH, was effectively suppressed by coating of the capillary wall with a polymer. In fact, adsorption on the capillary coating always plays a contributory role whenever a good separation of thaumatin constituents is attained. This indicates that electrochromatographic separation systems based on capillaries coated with the layer of either cationic or hydrophilic uncharged polymer hold promise for the development of methods for thaumatin analysis. [source] rpoB -PCR amplified gene and temporal temperature gradient gel electrophoresis: a rapid tool to analyse bacterial strains representative of cold-smoked salmon microfloraLETTERS IN APPLIED MICROBIOLOGY, Issue 2 2004S. Giacomazzi Abstract Aim:, To evaluate rpoB gene as a biomarker of microbial biodiversity associated to cold-smoked salmon by a novel nested-polymerase chain reaction/temporal temperature gradient gel electrophoresis (PCR/TTGE) technique applied on pure cultures of reference strains. Methods and Results:, DNA obtained from pure cultures of reference strains was used in a succession of a first PCR amplification of rpoB fragment with degenerated nonclamped primers and a nested-PCR with nondegenerated clamped primers. PCR products were then applied on a TTGE gel in order to analyse strains profile. High quantity of nested-PCR products were obtained for each tested strain and TTGE profiles showed a good separation between the different reference bacteria and an easy way to associate one band to one species. Conclusion:, The nested-PCR/TTGE technique used in this study is a promising way of investigating bacterial community structure of cold-smoked salmon or other food matrix. Significance and Impact of the Study:, Because of its single copy state leading to single band profiles in TTGE, rpoB constitute a good potential molecular marker for further development of cold-smoked salmon biodiversity analysis. [source] GC,MS characterization of oligomers in polyadipates used as plasticizers for PVC in food contactPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2006Maurus Biedermann Abstract Fourteen commercial polyadipates and a polysebacate were analysed for their components of a molecular mass below 1000,Da, primarily with the aim of generating the background data for measuring the migration of this type of polymeric additives from plasticized PVC (e.g. cling films and gaskets of lids) into foods or food simulants. Since the composition of the material <1000,Da varies between the polyadipates, the main components must be identified to enable a correct quantification. Polyadipates differ in the diol used as linker, their termination (acid or alcohol) and in the end-capping (free alcohols, acetylation, acylation with fatty acids, esterification with octanol/decanol). Gas chromatography (GC) provides good separation, but the material remaining in the column up to high temperatures decomposes and forms a hump in the rear part of the chromatogram. Examples of mass spectra are shown, the most indicative fragments pointed out and spectra of 159 components listed. The polyadipates and the sebacate are characterized by their structure, the main components <1000,Da and the fraction of material <1000,Da. Copyright © 2006 John Wiley & Sons, Ltd. [source] Determination of ,-caprolactam migration from polyamide plastics: a new approachPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2001Z. Pogorzelska Abstract A new gas chromatography method for determination of ,-caprolactam (CPR) migration from packaging materials such as: polyamide (PA) films, PA granulates, PA/PE (polyethylene) laminates, PA casings, etc., to food simulants has been developed. Water, 3% w/v acetic acid, 15% and 95% v/v ethanol and olive oil have been used as a food simulants. Using the 1,4-butanediol (BUG) as an internal standard (instead of aza-2-cyclononanone), calibration curves were constructed. Very good separation of CPR from BUG was achieved by using a Nukol fused silica capillary column (Supelco), 25 m,×,0.32,mm. The time of analysis is shorter than 12 min: 7.69,min for BUG and 11.60,min for CPR. The regression line equation for CPR migration to water is: y,=,0.080x,+,0.14; to olive oil: y,=,0.010x. The sensitivity of the developed method is appropriate for the quantitative determination of CPR in an analyte concentration of approximately 0.2,mg/kg, when the specific migration limit (SML) for this compound, according to Directive 90/128/EEC, is 15,mg/kg food simulant. Copyright © 2001 John Wiley & Sons, Ltd. [source] A versatile method for stable carbon isotope analysis of carbohydrates by high-performance liquid chromatography/isotope ratio mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2008H. T. S. Boschker We have developed a method to analyze stable carbon isotope (13C/12C) ratios in a variety of carbohydrates using high-performance liquid chromatography/isotope ratio mass spectrometry (HPLC/IRMS). The chromatography is based on strong anion-exchange columns with low strength NaOH eluents. An eluent concentration of 1,mM resulted in low background signals and good separation of most of the typical plant neutral carbohydrates. We also show that more strongly bound carbohydrates such as acidic carbohydrates can be separated by inclusion of NO as an inorganic pusher ion in the eluent. Analyses of neutral carbohydrate concentrations and their stable carbon isotope ratios are shown for plant materials and marine sediment samples both at natural abundance and for 13C-enriched samples. The main advantage of HPLC/IRMS analysis over traditional gas chromatography based methods is that no derivatization is needed resulting in simple sample treatment and improved accuracy and reproducibility. Copyright © 2008 John Wiley & Sons, Ltd. [source] A simple and sensitive HPLC-fluorescence method for quantification of MDMA and MDA in blood with 4-(4,5-diphenyl-1H -imidazol-2-yl)benzoyl chloride (DIB-Cl) as a labelBIOMEDICAL CHROMATOGRAPHY, Issue 12 2006Mamoru Tomita Abstract A sensitive high-performance liquid chromatographic method with fluorescence detection to determine 3,4-methylenedioxymethamphethamine (MDMA) and 3,4-methylenedioxyamphethamine (MDA) in human and rat whole blood or plasma samples was developed by using 4-(4,5-diphenyl-1H -imidazol-2-yl)benzoyl chloride (DIB-Cl) as a label. MDMA and MDA in a small amount of blood sample (ca 100 µL) were extracted by liquid,liquid extraction with ethyl acetate, and were derivatized with DIB-Cl under mild conditions (10 min at room temperature). A good separation of DIB-derivatives could be achieved within 45 min using a commercially available ODS column with an isocratic eluent of 10 mm citric acid,20 mm Na2HPO4 aqueous buffer (pH 4.0),CH3CN,CH3OH (50:45:5, v/v/v %). The calibration curves prepared with 1-methyl-3-phenylpropylamine (MPPA) as an internal standard showed good linearity (r = 0.999) with 0.36,0.83 ng/mL detection limit at a signal-to-noise ratio of 3. MDMA and MDA in rat whole blood could be monitored for 6 h after a single administration of MDMA (2.2 mg/kg, i.p.). The pharmacokinetic parameters for MDMA and MDA obtained by triplicate measurements were 426 ± 23 and 39 ± 6 ng/mL (Cmax), 20 ± 5 and 100 ± 10 min (Tmax), respectively. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||