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Capillary Column (capillary + column)
Kinds of Capillary Column Selected AbstractsCapillary columns in liquid chromatography: between conventional columns and microchipsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2004Yoshihiro Saito Abstract Liquid chromatography on columns with small internal diameters has been reviewed as the intermediate technique between conventional liquid chromatography and microchip separations. The development of micro column separations in the early years has been described, starting with the papers of Horváth and co-workers and Ishii and co-workers, continuing into the first part of the eighties, then making a leap in time to recent innovations with small-bore columns. Based on internal diameters a classification of the different analytical HPLC columns has been suggested. The advantages of small-bore columns have been discussed, with particular emphasis on the advantage of coupling to concentration sensitive detectors when the sample amount is limited. Open tubular columns are treated as a part of the historic background. The recent developments include a brief look into the current status of monolithic columns, the use of packed nano columns and micro columns with electrospray mass spectrometry, and the potential of two-dimensional comprehensive liquid chromatography. Finally, the coupling of sample preparation to analytical columns and the future applications of the novel technological improvements to the microchip separation methods have been discussed. [source] Novel negatively charged tentacle-type polymer coating for on-line preconcentration of proteins in CEELECTROPHORESIS, Issue 4 2009Liang Xu Abstract A novel negatively charged tentacle-type polymer-coated capillary column was fabricated and applied for on-line extraction and preconcentration of proteins. The polymer coating was prepared by glycidyl-methacrylate graft polymerization in a silanized capillary column and the following sulfonic acid group functionalization. It had high surface area and offered high phase ratio for protein adsorption. In addition, the polymer-coated capillary column provided more stable EOF than a bare uncoated capillary. These features of the polymer coating facilitated the extraction of proteins through electrostatic interactions. This was used to extract proteins. The extracted analytes were then desorbed and focused by EOF in the direction opposite to the sample injection flow for subsequent CE. With this procedure, over 1500-fold sensitivity enhancement was realized for myoglobin (MB) as compared with a normal capillary zone electrophoresis. By comparison of the peak areas of the enriched protein, it was found that the polymer-coated column could capture proteins about 30 times more than the uncoated column. In addition, the separation of a protein mixture containing 0.4,,g/mL of MB and 0.4,,g/mL of insulin was demonstrated by the on-line preconcentration and electrophoretic separation with the polymer-coated column. [source] Open-tubular capillary electrochromatography using a capillary coated with octadecylamine-capped gold nanoparticlesELECTROPHORESIS, Issue 4 2008Qishu Qu Dr. Abstract Octadecylamine-capped gold nanoparticles (ODA-Au-NPs) were prepared and characterized by using UV,Vis adsorption spectrum, transmission electron chromatography (TEM), SEM, and FT-IR. A simple but robust hydrophobic coating was easily developed by flushing a capillary with a solution of ODA-Au-NPs, because the positive charges were carried by the nanoparticles which strongly adsorb to the negatively charged inner surface of a fused-silica capillary via electrostatic and hydrophobic interactions. The chromatographic characteristics of the coated capillary was investigated by varying the experimental parameters such as buffer pH, buffer concentration, and percentage of organic modifier in the mobile phase. The results show that (i) resolution between thiourea and naphthalene is almost the same when comparing the electrochromatograms obtained using pH,7 buffer as mobile phase after and before the capillary column was operated using pH,11 and 3 mobile phase; (ii) no significant changes in retention time and deterioration in peak efficiency were found after 60,runs of test aromatic mixtures; and (iii) column efficiency up to 189,000 theoretical plates/meter for testosterone was obtained. All of the results indicated that the coating could act as a stable stationary phase for open tubular CEC as well as for bioanalysis. [source] Capillary electrochromatography with zwitterionic stationary phase on the lysine-bonded poly(glycidyl methacrylate- co -ethylene dimethacrylate) monolithic capillary columnELECTROPHORESIS, Issue 12 2006Xiaoli Dong Abstract A polymer-based neutral monolithic capillary column was prepared by radical polymerization of glycidyl methacrylate and ethylene dimethacrylate in a 100,,m id fused-silica capillary, and the prepared monolithic column was subsequently modified based on a ring opening reaction of epoxide groups with 1,M,lysine in solution (pH,8.0) at 75°C for 10,h to produce a lysine chemically bonded stationary phases in capillary column. The ring opening reaction conditions were optimized so that the column could generate substantial EOF. Due to the zwitterionic functional groups of the lysine covalently bonded on the polymer monolithic rod, the prepared column can generate cathodic and anodic EOF by varying the pH values of running buffer during CEC separation. EOF reached the maximum of ,2.0×10,8,m2v,1s,1 and 2.6×10,8,m2v,1s,1 with pH of the running buffer of 2.25 and 10, respectively. As a consequence, neutral compounds, ionic solutes such as phenols, aromatic acids, anilines, and basic pharmaceuticals were all successfully separated on the column by CEC. Hydrophobic interaction is responsible for separation of neutral analytes. In addition, the electrostatic and hydrophobic interaction and the electrophoretic migration play a significant role in separation of the ionic or ionizable analytes. [source] Poly(methacrylic acid-ethylene glycol dimethacrylate) monolith in-tube solid-phase microextraction applied to simultaneous analysis of some amphetamine derivatives in urine by capillary zone electrophoresisELECTROPHORESIS, Issue 16 2005Fang Wei Abstract A method based on in-tube solid-phase microextraction and capillary zone electrophoresis (CZE) was proposed for simultaneously determining four amphetamines (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine) in urine. A poly(methacrylic acid-ethylene glycol dimethacrylate) monolithic capillary column, which can provide sufficient extraction efficiency, was introduced for the extraction of amphetamines from urine samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the samples were analyzed by CZE. The best separation was achieved using a buffer composed of 0.1,M disodium hydrogen phosphate (adjusted to pH,4.5 with 1,M hydrochloric acid) and 20% methanol v/v, with a temperature and voltage of 25°C and 20,kV, respectively. By applying electrokinetic injection with field-amplified sample stacking, detection limits of 25,34,µg/L were achieved. Excellent method of reproducibility was found over a linear range of 0.1,5,mg/L. Determination of these analytes from abusers' urine sample was also demonstrated. [source] Rapid determination of aliphatic amines in water samples by pressure-assisted monolithic octadecylsilica capillary electrochromatography-mass spectrometryELECTROPHORESIS, Issue 18-19 2004Bricio Santos Abstract A pressure-assisted capillary chromatography-mass spectrometry method based on the use of a monolithic octadecylsilica (ODS) capillary is proposed for the determination of aliphatic amines. A 25 mM citric acid buffer containing 10% methanol is used as running electrolyte. Separation is achieved by simultaneously applying a capillary electrophoresis (CE) voltage of 13 kV and an overimposed pressure of 8 bar. The use of pressure is required to ensure stable electrospray conditions. Analysis times are reduced by using a capillary column consisting of a 30 cm long monolithic silica capillary column bound with ODS and a fused-silica capillary column also 30 cm long. The proposed method was successfully applied to the determination of low-molecular-weight aliphatic amines in tap and river water. The analysis of real samples requires cleanup and preconcentration, which can be performed automatically by inserting a minicolumn in the replenishment system of the commercial instrument. [source] High-efficiency peptide analysis on monolithic multimode capillary columns: Pressure-assisted capillary electrochromatography/capillary electrophoresis coupled to UV and electrospray ionization-mass spectrometryELECTROPHORESIS, Issue 21 2003Alexander R. Ivanov Abstract High-efficiency peptide analysis using multimode pressure-assisted capillary electrochromatography/capillary electrophoresis (pCEC/pCE) monolithic polymeric columns and the separation of model peptide mixtures and protein digests by isocratic and gradient elution under an applied electric field with UV and electrospray ionization-mass spectrometry (ESI-MS) detection is demonstrated. Capillary multipurpose columns were prepared in silanized fused-silica capillaries of 50, 75, and 100 ,m inner diameters by thermally induced in situ copolymerization of methacrylic monomers in the presence of n -propanol and formamide as porogens and azobisisobutyronitrile as initiator. N -Ethylbutylamine was used to modify the chromatographic surface of the monolith from neutral to cationic. Monolithic columns were termed as multipurpose or multimode columns because they showed mixed modes of separation mechanisms under different conditions. Anion-exchange separation ability in the liquid chromatography (LC) mode can be determined by the cationic chromatographic surface of the monolith. At acidic pH and high voltage across the column, the monolithic stationary phase provided conditions for predominantly capillary electrophoretic migration of peptides. At basic pH and electric field across the column, enhanced chromatographic retention of peptides on monolithic capillary column made CEC mechanisms of migration responsible for separation. The role of pressure, ionic strength, pH, and organic content of the mobile phase on chromatographic performance was investigated. High efficiencies (exceeding 300,000 plates/m) of the monolithic columns for peptide separations are shown using volatile and nonvolatile, acidic and basic buffers. Good reproducibility and robustness of isocratic and gradient elution pressure-assisted CEC/CE separations were achieved for both UV and ESI-MS detection. Manipulation of the electric field and gradient conditions allowed high-throughput analysis of complex peptide mixtures. A simple design of sheathless electrospray emitter provided effective and robust low dead volume interfacing of monolithic multimode columns with ESI-MS. Gradient elution pressure-assisted mixed-mode separation CE/CEC-ESI-MS mass fingerprinting and data-dependent pCE/pCEC-ESI-MS/MS analysis of a bovine serum albumin (BSA) tryptic digest in less than 5 min yielding high sequence coverage (73%) demonstrated the potential of the method. [source] A method for the determination of polyunsaturated fatty acid methyl esters in biodiesel: Results of an interlaboratory studyEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 8 2009Sigurd Schober Abstract A gas chromatographic method for the determination of fatty acid methyl esters with four or more double bonds in biodiesel was developed and tested. The method is based on gas chromatographic separation on a wax capillary column using methyl tricosanoate as internal standard. The performance of the method was proved with the participation of 11,European laboratories by a Round Robin test on six different biodiesel samples containing different amounts of polyunsaturated fatty acid methyl esters. The results showed that the precision is sufficient around the EN,14214 limit of 1,% (m/m). At lower concentrations the variation is too high. The scope of the application can be given between as 0.6 and 1.5%. [source] Micro-reactor for transesterification of plant seed oilsEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 5 2009Phattaraporn Kaewkool Abstract The fatty acid compositions of vegetable or other plant seed oils are generally determined by gas chromatography (GC). Methyl esters (the most volatile derivatives) are the preferred derivatives for GC analysis. Esters of higher alcohols are good for the separation of volatile and positional isomers. All the esters of the C1,C8 alcohols of vegetable oils were silmilarly prepared by passing the reaction mixture containing the desired alcohol, oil and tetrahydrofuran through the micro-reactor (a 3-mL dispossible syringe packed with 0.5,g of NaOH powder). The reaction products were acidified with acetic acid and the mixture was analyzed by high-performance size exclusion chromatography and GC. Transesterification was quantitative for primary alcohols, but an appreciable amount of free fatty acids was formed for secondary alcohols. Coriander seed oil was quantitatively esterified with 2-ethyl 1-hexanol with the micro-reactor in less than 1,min. Oleic and petroselinic acid 2-ethyl 1-hexyl esters are baseline separated on an Rtx-2330 capillary column (30,m×0.25,mm, 0.25,µm film thickness). [source] Distribution of piperitone oxide stereoisomers in Mentha and Micromeria species and their chemical synthesesFLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2007Olga Larkov Abstract Chiral GC,MS analyses of natural and synthetic trans- and cis- piperitone oxide were performed on an Rt- ,DEX-sm capillary column in order to clarify the stereochemistry of their enantiomeric forms. Only enantiomerically pure laevo-rotatory piperitone oxides, (1S,2S,4S)- trans- piperitone oxide and (1S,2S,4R)- cis- piperitone oxide, were detected by chiral analyses of Micromeria fruticosa (L.) Druce and Mentha longifolia L. The occurrence of the cis - and trans -piperitone oxides was dependent on the population of the species. In all cases (1S,2S,4S)- trans- piperitone oxide was detected together with (4S)-piperitone, while (1S,2S,4R)- cis- piperitone oxide was detected together with (4R)-piperitone in the plants analysed. The four stereoisomers of trans - and cis -piperitone oxide were obtained by alkaline epoxidation of both (4R)- and (4S)-piperitone. The formation of the 1,2-epoxide can take place on either side of the 1,4-substituted six-membered ring. Racemization at C4 was observed under alkaline epoxidation reaction conditions due to keto-enol tautomerism. Copyright © 2007 John Wiley & Sons, Ltd. [source] GC separation of amino acid enantiomers via derivatization with heptafluorobutyl chloroformate and Chirasil- L -Val columnJOURNAL OF SEPARATION SCIENCE, JSS, Issue 22 2009Helena Zahradní Abstract Heptafluorobutyl chloroformate (HFBCF), a recently introduced derivatization reagent, was examined in enantioseparation of amino acids (AAs) by GC. Twenty proteinogenic AAs, plus ornithine, cystine and 4-fluorophenylalanine (internal standard) were treated with the reagent and separation properties of the derivatives were assessed on a Chirasil-Val capillary column. Nineteen AA enantiomers were efficiently separated in 43,min except proline, arginine and cystine. The HFBCF derivatives of the studied DL -AAs show improved separation over other chloroformate-based derivatives hitherto reported. A combination of the improved and faster separation with a simple derivatization protocol, involving an immediate one-step reaction,extraction in two-phase aqueous-organic medium, and low elution temperatures extend application of HFBCF to chiral AA analysis. [source] Performance of wide-pore monolithic silica column in protein separationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009Hironobu Morisaka Abstract A monolithic wide-pore silica column was newly prepared for protein separation. The wide distribution of the pore sizes of monolithic columns was evaluated by mercury porosimetry. This column, as well as the conventional monolithic column, shows high permeability in the chromatographic separation of low-molecular-sized substances. In higher-molecular-sized protein separation, the wide-pore monolithic silica column shows better performance than that of the conventional monolithic column. Under optimized conditions, five different proteins , ribonuclease A, albumin, aldolase, catalase, and ferritin , were baseline-separated within 3 min, which is faster than that using the particle-packed columns. In addition, the monolithic wide-pore silica column could also be prepared in fused silica capillary (600 mm long, 0.2 mm i.d.) for highly efficient protein separation. The peak capacity of the wide-pore monolithic silica capillary column is estimated to be approximately 300 in the case of protein separation, which is a characteristic performance. [source] Capillary gas-chromatographic determination of spermidine in hair lotionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006Veniero Gambaro Abstract Biogenic polyamines, such as spermidine (SPD, NH2,(CH2)4,NH,(CH2)3,NH2), are ubiquitous polycationic molecules which play a definitive role in many biological processes such as nucleic acid metabolism, protein synthesis, and cell growth. SPD is commonly used as an ingredient in hair lotions, because it seems to promote hair growth. This work describes a capillary GC method for quantitative determination of SPD in hair lotions using 1,6-diaminohexane as internal standard, a methyl silicone capillary column, and a flame ionisation detector. Aliquots of hair lotion were treated with an alkaline aqueous solution and internal standard was added. The emulsion was extracted with diethyl ether containing ethyl chloroformate. Ether extracts, evaporated to dryness and reconstituted in ethyl acetate, were analysed by capillary GC with flame ionisation detection. Validation took into account the specificity, linearity, precision, and accuracy of the analytical method: these parameters were valid for the quantitative determination of SPD in hair lotion. [source] Enantiomeric separation of mirtazapine and its metabolites by nano-liquid chromatography with UV-absorption and mass spectrometric detectionJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2005Salvatore Fanali Abstract Mirtazapine (MIR) and two of its main metabolites, namely, 8-hydroxymirtazapine and N -desmethylmirtazapine, were separated in totheir enantiomers by nanoLC in a laboratory-made fused-silica capillary column (75 ,m ID) packed with a vancomycin-modified silica stationary phase. The simultaneous separation of the three couples of the studied enantiomers was achieved in less than 33 min, using an experimentally optimized mobile phase delivered in the isocratic mode. Optimization of the mobile-phase composition was achieved by testing the influence of the buffer pH and concentration, the water concentration, the organic modifier type and concentration, and on the retention and resolution of the analytes. The optimum mobile-phase composition contained 500 mM ammonium acetate pH 4.5/water/MeOH/MeCN, 1 : 14 : 40 : 45 v/v/v/v. Using a UV detector at 205 nm, the method was validated studying several experimental parameters such as LOD and LOQ, intraday and interday repeatability, and linearity. Good results were achieved: LOD and LOQ were in the range 5,15 and 10,40 ,g/mL, respectively (the highest value was obtained for the DEMIR enantiomers); correlation coefficients, 0.9993,0.9999; the intraday and interday precision was acceptable (RSD < 2%) using an internal standard. The method was tested for the separation of the studied enantiomers in an extracted (solid-phase) serum sample spiked with standard racemic mixture of MIR and its two metabolites. Finally, the nanoLC system was connected to a mass spectrometer through a nanoelectrospray interface and the MS, MS2, and MS3 spectra were acquired showing the potential of the system used for characterization and identification of the separated analytes. [source] Packing capillary electrochromatography columns using vacuum , A preliminary studyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2004Qishu Qu Abstract This paper introduces a novel method for packing Capillary Electrochromatography Columns (CEC). Using vacuum packing methodology, silica particles as small as 1 ,m were successfully packed into the capillary columns with 75 ,m inner diameter. The columns are very stable and show no noticeable loss in efficiency after 200 sample injections. The performance of these vacuum packed capillary columns was evaluated with a mixture of aromatic and non-aromatic compounds. A 24 cm long capillary column can produce peak efficiencies of around 45 000 plates for benzene. [source] Rapid and sensitive determination of morphine in street opium samples by thermal desorption gas chromatography using a microfurnace pyrolyzerJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2004Minemasa Hida Abstract Thermal desorption of the alkaloids in opium samples at 300°C using a vertical microfurnace pyrolyzer was followed by their on-line gas chromatographic (GC) analysis on a large-bore glass capillary column. This method permitted rapid and sensitive determination of the content of the main alkaloid, morphine, in the small (ca. 100 ,g) opium samples with a relative standard deviation within 4% for 5 runs. The observed morphine contents of about 12 to 15 w/w% in the given opium samples were in fairly good agreement with those estimated by a conventional GC-MS method. [source] Simple 2D-HPLC using a monolithic silica column for peptide separationJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10-11 2004Hiroshi Kimura Abstract Separation of peptides by fast and simple two-dimensional (2D)-HPLC was studied using a monolithic silica column as a second-dimension (2nd-D) column. Every fraction from the first column, 5 cm long (2.1 mm ID) packed with polymer-based cation exchange beads, was subjected to separation in the 2nd-D using an octadecylsilylated (C18) monolithic silica column (4.6 mm ID, 2.5 cm). A capillary-type monolithic silica C18 column (0.1 mm ID, 10 cm) was also employed as a 2nd-D column with split flow/injection. Effluent of the first dimension (1st-D) was directly loaded into an injector loop of 2nd-D HPLC. UV and MS detection were successfully carried out at high linear velocity of mobile phase at 2nd-D using flow splitting for the 4.6 mm ID 2nd-D column, or with direct connection of the capillary column to the MS interface. Two-minute fractionation in the 1st-D, 118-second loading, and 2-second injection by the 2nd-D injector, allowed one minute for gradient separation in the 2nd-D, resulting in a maximum peak capacity of about 700 within 40 min. The use of a capillary column in the 2nd-D led to less solvent consumption and better MS detectability compared to a larger-sized column. This kind of fast and simple 2D-HPLC utilizing monolithic silica columns will be useful for the separation of complex mixtures in a short time. [source] Prediction of gas chromatographic retention times of capillary columns of different inside diametersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 18 2003Kornkanok Aryusuk Abstract The retention times (t R) of n -alkanes (C16,C22) eluted from capillary columns of different diameters are accurately predicted by using the equation proposed by Krisnangkura et al. (J. Chromatogr. Sci.1997, 35, 329,332). The numerical values of four thermodynamically related constants (a, b, c, and d) of the BP-1 (100% dimethylpolysiloxane) capillary column (0.32 mm ID×25 m, film thickness, 0.25 ,m) are ,6.169, ,0.512, 226.98, and 410.30, respectively. For columns of the same stationary phase but of different inside diameters and film thickness, accurate tR values can be predicted by using the same numerical values of the last three constants but the first constant (a) is changed by the difference in the natural logarithm of the column phase ratios (,). All the derived numerical values of each column were tested with FAMEs and with n -alkanes in temperature-programmed GC (TPGC). All the predicted tR values agree well with the experimental values. About 77% of the TPGC data have errors lower than 0.5% and the largest value is ,1.04%. [source] New method for bonding an adsorbent film to the walls of capillary columnsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2003Wawrzyniak Abstract A new method for immobilisation of an adsorbent on the wall of a capillary column ensures high thermal and mechanical stability of the resulting coating. The method can be applied to a variety of adsorbents of natural or synthetic origin. Its effectiveness is illustrated by results obtained for coating with modified silica or molecular sieve 13X. [source] Study of electroosmotic flow profile by processing of virtual digital Shah function mask and Fourier transformJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12-13 2003Shinya Kitagawa Abstract The electroosmotic flow in a packed capillary column (CEC) and in a rectangular capillary (CE) was observed by using a microscope-CCD-camera system. The observed image was captured to PC, and virtual digital Shah function mask processing was applied. The flow velocity was calculated by Fourier transform methods. The flow profile was analyzed by multiple measurements of the flow velocity in adjoining regions. The velocity of the electroosmotic flow in a packed capillary column (ID 150 ,m, length 18 mm, packed with cation exchanger) was 4.49 ,m/s at any point of the column, and the flow profile was flat. The effect of gravity on electroosmotic flow was also studied. The profile of the electroosmotic flow was almost flat under both 1-G and microgravity, and the electroosmotic flow velocity under microgravity was found to be significantly faster than that under 1-G. [source] Investigation of factors influencing the performance of open-tubular stationary phases in capillary electrochromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2003Ruth Freitag Abstract Silica-based, open-tubular capillary columns bearing C8-moieties were produced by the sol gel approach. The influence of experimental conditions adjusted during the preparation of the stationary phase on the performance of the resulting capillary column were investigated in terms of the plate height, the resolution, and the capacity factors, taking the separation of three non-charged polyaromatic hydrocarbons (naphthalene, phenanthrene, pyrene) as example. Acetone served as EOF marker. The optimal synthesis protocol was then used to prepare columns for an analogous investigation of the chromatographic parameters, namely the mobile phase composition, the applied voltage and temperature, as well as the column length, thickness, and inner diameter on the performance of the capillary columns. [source] Development of cryogenic chromatography using thermoelectric modules for the separation of methyltin compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2003Liu Jiemin Abstract A nonliquid cryogenic gas chromatograph using thermoelectric modules for the cryogenic separation of low boiling-point compounds was developed. The new system included four thermoelectric modules, a U shape heat exchanger, a cold block, a temperature controller, and three aluminum sheets. The minimum operating temperature of the assembly was ,10°C. This thermoelectric system was used to directly cool the capillary column, without any need for a traditional cryogen and had a small volume. The system was cost-effective and convenient to operate. It was successfully applied to the separation of methyltin species. [source] Analysis and characterization of aroma-active compounds of Schizandra chinensis (omija) leavesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2005Cheng Hao Zheng Abstract Volatile components from leaves of Schizandra chinensis (omija), a native plant of Korea, were extracted by simultaneous distillation,extraction (SDE) and analyzed by gas chromatography,mass spectrometry (GC-MS) using two types of capillary column with different polarities (DB-5MS and DB-Wax). The GC-MS analysis of volatile compounds obtained by SDE revealed that germacrene D is the most abundant compound (22.6%) in omija leaves, followed by ,-elemene (17.4%), (E)-2-hexenal (8.7%), and (E)-,-ocimene (7.2%). Aroma-active compounds were determined by gas chromatography,olfactometry (GC-O) using the aroma-extract-dilution analysis method. (E,Z)-2,6-Nonadienal (cucumber) was the most intense aroma-active compound due to its higher flavor-dilution factor (243,729) than any other compound. (Z)-3-Hexenal (green/apple), (E)-2-hexenal (green/fruity), and (E)-,-ocimene (wither green/grass) were also identified as important aroma-active compounds by GC-O. In addition, the volatile compounds were extracted by solid-phase microextraction (SPME), and the quantitative analysis of the SPME samples gave slightly different results, depending on the type of SPME fiber, compared with those from SDE, However, the aroma-active compounds identified in SPME were similar to those in SDE. Copyright © 2004 Society of Chemical Industry [source] A comparison of capillary-scale LC,NMR with alternative techniques: spectroscopic and practical considerations,MAGNETIC RESONANCE IN CHEMISTRY, Issue 9 2005Richard J. Lewis Abstract Experimental and practical details for the use of capillary LC (CapLC),NMR are reported. The capillary NMR probe has high sensitivity and excellent flow characteristics and we found CapLC,NMR to be best suited to samples that are truly mass limited. CapLC,NMR relies on good capillary-scale chromatography where highly concentrated peaks with a volume closely matched to the NMR flow cell are achievable. Provided that the loading capacity of the capillary column is not limiting, the combination of high sensitivity and high solvent suppression quality makes CapLC,NMR an excellent choice. For many real samples, however, the loading is limiting and we found the combination of LC,SPE,MS,NMR with a cryoprobe enables more material to be purified for NMR analysis, while retaining sensitivity. Copyright © 2005 John Wiley & Sons, Ltd. [source] A systematic study on the stability of UV ink photoinitiators in food simulants using GCPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2009Zhi-Wei Wang Abstract Several studies have been published on the stability of plastic monomers and additives in food simulants. However, there are practically no published results about the stability of ink components in food simulants. In this work, the stability of two ultraviolet (UV) ink photoinitiators (PIs) in one aqueous and in two substitute fat food simulants was studied under various time,temperature conditions. Furthermore, the addition of the stabilizing agent hydroquinone monomethyl ester (HQMME) in the same conditions was considered as a comparative experiment. The PIs tested were 1-hydroxycyclohexyl-1-phenyl ketone (Irgacure-184) and benzyldimethyl ketal (Irgacure-651). The various test conditions included exposure of 10 days to temperatures of 20, 40 and 60°C for 10% ethanol and 95% ethanol simulants, and exposure of 2 days to temperatures of 20, 40 and 60°C for isooctane. Following exposure to these conditions, the additive samples were analysed. The extracts of samples exposed to various temperature conditions as well as unexposed spiked controls and blanks were analysed by gas chromatography (GC) on a non-polar (5%-phenyl)-methylpolysiloxane capillary column. The results showed that the protective effect of HQMME was not obvious in all test conditions under dark conditions. The Irgacure-184 was quite stable under all test conditions whether the stabilizing agent was added or not. Irgacure-651 was stable almost under all test conditions, except in 10% ethanol at 60°C. The mass spectrum of decomposed product of Irgacure-651 was detected by GC-MS (Mass Spectrum), and the structure of the decomposed product was obtained by mass spectrographic analysis. The method of detection and disposal is also applicable for UV ink PI migration testing from several different paper or paperboard-plastic coating layer materials into the food simulants used in the study. Copyright © 2008 John Wiley & Sons, Ltd. 2008 [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] Fe3+ immobilized metal affinity chromatography with silica monolithic capillary column for phosphoproteome analysisPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 3 2007Shun Feng Abstract Immobilized metal affinity chromatography (IMAC) is a commonly used technique for phosphoproteome analysis due to its high affinity for adsorption of phosphopeptides. Miniaturization of IMAC column is essential for the analysis of a small amount of sample. Nanoscale IMAC column was prepared by chemical modification of silica monolith with iminodiacetic acid (IDA) followed by the immobilization of Fe3+ ion inside the capillary. It was demonstrated that Fe3+ -IDA silica monolithic IMAC capillary column could specifically capture the phosphopeptides from tryptic digest of ,-casein with analysis by MALDI-TOF MS. The silica monolithic IMAC capillary column was manually coupled with nanoflow RPLC/nanospray ESI mass spectrometer (,RPLC,nanoESI MS) for phosphoproteome analysis. The system was validated by analysis of standard phosphoproteins and then it was applied to the analysis of protein phosphorylation in mouse liver lysate. Besides MS/MS spectra, MS/MS/MS spectra were also collected for neutral loss peak. After database search and manual validation with conservative criteria, 29 singly phosphorylated peptides were identified by analyzing a tryptic digest of only 12,,g mouse liver lysate. The results demonstrated that the silica monolithic IMAC capillary column coupled with ,RPLC-nanoESI MS was very suitable for the phosphoproteome analysis of minute sample. [source] Semi-online nanoflow liquid chromatography/matrix-assisted laser desorption ionization mass spectrometry of synthetic polymers using an octadecylsilyl-modified monolithic silica capillary columnRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2010Takehiro Watanabe We have designed a semi-online liquid chromatography/matrix-assisted laser desorption/ionization mass spectrometry (LC/MALDI-MS) system to introduce eluent from a octadecylsilyl (ODS) group modified monolithic silica capillary chromatographic column directly onto a sample plate for MALDI-MS analysis. Our novel semi-online system is useful for rapidly and sensitively examining the performance of a monolithic capillary column. An additional advantage is the small elution volume of a monolithic capillary column, which allows delicate eluents, such as 1,1,1,3,3,3,-hexafluoroisopropyl alcohol (HFIP), to be used to achieve cost-effective analysis. Using the semi-online LC/MALDI-MS system, chromatographic separation of polymers by the monolithic column with different eluents was studied. Separation of poly(methyl methacrylate) and Nylon 6/6 showed that the column functioned via size-exclusion separation when tetrahydrofuran or HFIP eluent was used. On the other hand, the separation behavior of Nylon 11 indicated a reversed-phase mode owing to the interaction of the polymer with the modified ODS group in the column. Using tetrahydrofuran/methanol (1:1, v/v) as the eluent, the LC/MALDI-MS spectra of poly(lactic acid), which contains both linear and cyclic polymer structures, showed that the column could separate the hydrophobic cyclic polymer and elute it out relatively slowly. The monolithic column functions basically via size-exclusion separation; the reversed-phase separation by interaction with the ODS functions may have less influence on column separation. The semi-online monolithic capillary LC/MALDI-MS method we have developed should provide a means of effectively analyzing synthetic polymers. Copyright © 2010 John Wiley & Sons, Ltd. [source] A continuous flow mass spectrometry technique of argon isotope measurement for K/Ar geochronology,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2009Alexander V. Ignatiev A new method for the measurement of argon isotope composition in a continuous flow of helium for potassium/argon geochronology is described. Extraction of argon from geological samples in multiple-sample holders was carried out in a chamber by heating with a continuous Nd-YAG laser. The extracted and pre-concentrated argon is passed through a chromatographic capillary column in a flow of helium. Argon is separated from possible contaminants in the column and is injected through an open split into the ion source of an isotope ratio mass spectrometer. Measurement of the 36Ar, 38Ar and 40Ar isotopes was carried out in dynamic mode, using a triple-collector ion detector. These experiments have shown that continuous flow mass spectrometry can be used for the analysis of radiogenic argon in picogram quantities with an accuracy that is satisfactory for the solution of many geochronological problems. The method of argon isotope measurement in a continuous flow of helium is an alternative to the measurement of argon isotopes in the static mode. The sensitivity and accuracy of argon measurement by this method are comparable with those provided by the classical static method. The measurement of argon isotopes in a continuous flow of helium is simpler and more reliable than measurement in the static mode. Copyright © 2009 John Wiley & Sons, Ltd. [source] Speciation of volatile antimony compounds in culture headspace gases of Cryptococcus humicolus using solid phase microextraction and gas chromatography,mass spectrometryAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2002L. M. Smith Abstract Direct analysis of the volatile antimony compounds stibine (SbH3), monomethylantimony, dimethylantimony (Me2Sb) and trimethylantimony (Me3Sb) using solid phase microextraction (SPME) with polydimethylsiloxane fibres and gas chromatography,mass spectrometry (GC,MS) is described. The best analyte to background signal ratio was achieved using a 20,min extraction time. Antimony species were separated using a 3% phenylmethylsilicone capillary column operated at a column pressure of 70,kPa, a flow rate of 1.4,ml min,1 and temperature ramping from 30 to 36,°C at 0.1,°C min,1. Cryogenic focusing of desorbed species was required to achieve resolution of antimony species. The optimized SPME,GC,MS method was applied to the analysis of headspace gases from cultures of Cryptococcus humicolus incubated with inorganic antimony(III) and (V) substrates. The headspace gases from biphasic (aerobic,anaerobic) biomass-concentrated culture incubations revealed the presence of SbH3, Me2Sb and Me3Sb. Stibine was the major antimony species detected in cultures amended with inorganic antimony(V). Me3Sb was the sole volatile antimony species detected when cultures were amended with antimony(III). Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||