bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on cryogenic trapping of solutes during chromatographic elution in capillary gas chromatography
Authors: Marriott Philip J. , Kinghorn Russell M. 
Published: May 2005

AbstractCryogenic trapping of solutes leads to narrowing of the chromatographic band. By placing the trap at the end of a capillary column, it is possible to study the effectiveness of the trap in terms of producing a sharpened elution profile. The trap may be heated by supplementary heating, but here convective heating from the GC oven is employed simply by turning off the cryogenic coolant. It is estimated that it takes about 50 s for the trap to heat up sufficiently to allow trapped solute to be remobilized, although this depends upon the oven temperature and thermal mass of the trap. It can also be shown that the more volatile solutes mobilize faster from the trap in this particular mode of operation. The recovery of trapped components shows that there is essentially quantitative trapping, and the solutes are trapped just at the leading edge of the trap.
Screening of four beta‐blockers and codeine in urine by on‐line coupled RPLC‐GC with on‐line derivatization
Authors: Hyötyläinen Tuulia , Pilviö Riitta , Riekkola Marja‐Liisa 
Published: May 2005

AbstractOn‐line coupled reversed phase liquid chromatography‐capillary gas chromatography (RPLC‐GC) was used in the separation of four derivatized beta‐blockers and codeine in urine. Sample clean‐up was accomplished in the LC part and compounds were separated in the GC part. After the LC column the aqueous phase was switched to organic solvent by on‐line liquid‐liquid extraction and the two phases were separated in a sandwich‐type phase separator. The organic extract was then transferred to a loop‐type LC‐GC interface. Beta‐blockers were derivatized on‐line in the interface before GC analysis. Concurrent eluent evaporation was used during the introduction of the sample fraction, and excess of solvent vapors was removed via an early vapor exit. The sample pretreatment was minimal; the only manual pretreatment step was the filtration of the urine sample.
Pressure drop effects on selectivity and resolution in packed column supercritical fluid chromatography
Authors: Lou Xianwen , Janssen Hans‐Gerd , Snijders Henri , Cramers Carel A. 
Published: May 2005

AbstractThe influence of pressure drop on retention, selectivity, plate height and resolution was investigated systematically in packed supercritical fluid chromatography (SFC) using pure carbon dioxide as the mobile phase. Numerical methods developed previously which enabled the prediction of pressure gradients, diffusivities, capacity factors, plate heights and resolutions along the length of the column were used for the model calculations. The effects of inlet pressure and supercritical fluid flow rate on selectivity and resolution are studied. In packed column SFC with pure carbon dioxide as the mobile phase, the pressure drop can have a significant effect on resolution. The flow rate is shown to have a larger effect than generally realized. The calculated data are shown to be in good agreement with the experimental results. Finally, the variation of the chromatographic parameters along a 5.5 meter long model SFC column is illustrated. The possibilities and limitations of using long packed columns in SFC are discussed. It is demonstrated that long columns with large plate numbers do not necessarily yield better separations.
On‐line coupling of liquid chromatography and capillary gas chromatography for the determination of a trace pyrethroid insecticide in fruit extracts
Authors: Modeste Fabrice , Caude Marcel , Devaux Philippe 
Published: May 2005

AbstractThe following paper presents a fast, selective, sensitive, and automated procedure for the residue analysis of the pyrethroid insecticide acrinathrin in various fruit samples by on‐line combination of Liquid Chromatography (LC) with capillary Gas Chromatography (GC) and an Electron‐Capture Detector (ECD). The loop‐type interface and Fully Concurrent Solvent Evaporation (FCSE) were chosen due to their ease of use and low volatility of acrinathrin. Commercially available LC diol columns with small internal diameters (2.1 mm) provided the selectivity required for the separation of the solute from matrix components and permitted the transfer of fraction volumes up to 500 μl into the retention gap, located inside the gas chromatograph. Optimization of the operating conditions with standard solutions showed the influence of the GC initial transfer temperature on the response of acrinathrin and the quantitative nature of the transfer was established by liquid scintillation counting. The linearity and precision were studied with the aid of calibration plots, whereas quantitative recoveries of the analyte (at least 95 %) were determined in spiked fruits. Compared to the corresponding off‐line technique, the on‐line approach allows us to reach lower detection limits (ppb level when 20 μl LC injections are performed) with excellent repeatability between 0.6 and 6.6 %. Moreover, the integrated analytical set‐up is robust, less time‐consuming and subsequently brings a marked improvement in the sample preparation step of complex biological matrices. Finally, the versatility of the system renders it highly suitable for the determination of other similar pyrethroids in order to develop a multiresidue method.
Determination of low molecular weight aliphatic amines by HPLC in environmental water samples
Authors: Djozan Dj. , Faraj‐Zadeh M. A. 
Published: May 2005

AbstractA high resolution liquid chromatographic method is described for determination of low molecular weight (LMW) aliphatic amines in environmental waters. The analytes after isolation are derivatized by fluram and separated with isocratic elution on octyl (C8) column, followed by fluorimetric detection in 395/495 nm. Different isolation procedures such as octadecylsilane (ODS) and strong cation exchanger (SCX) solid phase extraction (SPE) cartridges and Amberlite CG‐120 resin were evaluated. The quantitative characteristics such as recovery, linear dynamic range, correlation coefficient, limit of detection (LOD), and relative standard deviation (RSD) are presented. Using this method, aliphatic amines were analyzed in rain and tap water as well as in waste water.
Enantiomeric separation of acidic drugs by capillary electrophoresis using a combination of charged and uncharged β‐cyclodextrins as chiral selectors
Authors: Fillet Marianne , Bechet Isabelle , Schomburg Gerhard , Hubert Philippe , Crommen Jacques 
Published: May 2005

AbstractHigh resolution could be achieved for the enantiomers of acidic drugs, namely, sulindac, fenoprofen, ketoprofen, warfarin, and hexobarbital, in a buffer of pH 3 by the simultaneous addition of uncharged and charged β‐cyclodextrin derivatives. The interaction of the analytes with the anionic sulfobutyl ether β‐cyclodextrin provides the analytes with an adequate electrophoretic mobility whereas the interaction with various neutral β‐cyclodextrins generates high enantioselectivity. Five neutral cyclodextrins, the native β‐cyclodextrin, as well as methyl‐, dimethyl‐, trimethyl‐ and hydroxypropyl‐β‐cyclodextrin, were tested to enhance the enantioselectivity of the electrophoretic system. High resolution values and the shortest analysis times for the five drugs tested were achieved in a buffer made of 100 mM phosphoric acid adjusted to pH 3 with triethanolamine and containing dimethyl‐ or trimethyl‐β‐cyclodextrin in addition to sulfobutyl ether β‐cyclodextrin.
On‐line solid‐phase extraction‐thermal desorption‐gas chromatography with ion trap detection tandem mass spectrometry for the analysis of microcontaminants in water
Authors: Louter Arjan J. H. , Van Doornmalen Jacco , Vreuls Jolan J. , Brinkman Udo A. Th. 
Published: May 2005

AbstractAn improved set‐up for solid‐phase extraction with thermal desorption coupled on‐line to gas chromatography (SPETD‐GC) is presented. It includes a newly designed liner for a programmable temperature vaporizer (PTV) and an improved water elimination system. The SPETD procedure now includes a washing step with HPLC‐grade water to prevent degradation of analytes due to interaction with remaining sample constituents. The system was used to analyze surface and tap water samples over a 4‐month period. No decrease of chromatographic or trace‐enrichment performance was observed, and a liner packed with Tenax GR could be used for at least 150 analyses. The SPETD module was coupled to GC with ion‐trap detection for mass spectrometric (MS) and MS/MS detection. The linearity and repeatability of the procedure for several pesticides which were tested in the 0.5–10 μg/1 range were fully satisfactory (1 μg/1, RSD range 5–11%; n = 5). When using sample volumes of 0.1 ml only, detection limits were as low as 0. 1‐0.2 μg/1. As an example, the confirmation and quantification of a suspected pesticide in a real‐life sample using electron impact and positive chemical ionization in both the MS and MS/MS mode is shown.
Isolation and determination of toxic congeners of polychlorinated biphenyls in environmental samples
Authors: Huang Eleanor B. , Poole Gray , Chiu Chunh 
Published: May 2005

AbstractA Method has been developed for the separation and enrichemen of there non‐ortho, eight mono‐ortho, and di‐ortho substituted polychlorinated biphenyls (PCBs) from Aroclor formulations and environmental samples. The fractionation is accomplished using high performance liquid chromatography (HPLC) with a 2‐(1‐pyrenyl)ethyldimethylsilysily silca column. GC‐MSD with an optimized temperature program was used for quantitation, Hexane, pentane, cyclohexane, iso‐octane, and 2‐propanol were tested as a mobile phase for the isolation of the thirteen target PCBs in a Aroclor 1242, 1254, and 1260 (1:1:1) misture, Pentane at room temperature with a slow rate of 0.7 ml/min is the condition of choice. The average recovery of thirteen target PCBs spiked in the Aroclor mixture is 99.5% with an average relative standard deviation of 4.5%. The average method detection limit is 8pg/μl. Targer PCBs in the reference solis, incinarator ash, and sediment samples were measured.
Initial bandwidth resulting from splitless and solid phase microextraction gas chromatographic injections
Authors: Snow Nicholas H. , Okeyo Pius 
Published: May 2005

AbstractThe initial width of the injected solute bands is a major determinant of the final measured peak width. While the individual processes contributing to this intial width have been observed and described qualitatively by many authors, little attention has been focused on their quantitative relationship. Using solid phase microextraction (SPME) and splitless injections of a hydrocarbon test mixutre the contributions to overall peak variance in SPME and splitless injections can be separated and quantitated. In SPME, it is seen that thermal focusing or rapid desorption must serve to provide focused bands. In splitless, thermal fucusing and solvent effects provide focusing. Variance contributions for each of these are calculated and shown.
Characterization and monitoring of amitraz degradation products in honey
Authors: Jiméanez Juan Joséa , Bernal Joséa Luis , Del Nozal María Jesús , Toribio Laura , Atienza Julián 
Published: May 2005

AbstractCapillary gas chromatography in combination with atomic emission and electron impact‐chemical ionizaion mass spectrometry detectors have been used to detect amitraz degradation products in honey storage, characterize their structure, and evaluate their occurrence over a 100 day peroid. To this end, honey samples were extracted with an 8:2 v/v n‐hexane/acetone mixture. Amitraz was found to be rapidly decomposed into five related compounds, of which N‐(2,4‐dimethylphenyl)formamide was the most abundant and persistent.
Oral malodor, assessed by closed‐loop, gas chromatography, and ion‐trap technology
Authors: Claus Dirk , Geypens Benny , Ghoos Yvo , Rutgeerts Paul , Ghyselen Jenny , Hoshi Keika , Delanghe Geertrui 
Published: May 2005

AbstractA method is described for the analysis of volatile organic compounds in saliva and tongue coating samples. The techniue is based on an off‐line preconcentration step by means of a closed‐loop trapping system followed by gas chromatography‐ion trap detection. With the closed‐loop technique, the volatile organic compounds(VOCs) are released from the matrix and trapped on an adsorbent without interference of water. The VOCs are released from the adsorbent into the gas chromatograph by thermdesorption. After separation, identification of the compounds is performed by ion trap technology.By this technique 82 compounds could be demonstrated in saliva and tongue coating samples. The technique is also used to demonstrate the formation of volatile bacterial fermentation compounds when a protein substrate is added to tongue coating samples. It is considered a very promising tool in further research on oral malodor.
The characterization and quantitation of sulfur‐containing compounds in (heavy) middle distillates by LC‐GC‐FID‐SCD
Authors: Beens Jan , Tijssen Robert 
Published: May 2005

AbstractA modified sulfur chemiluniinescence detector (SCO) has been interfaced to a HPLC‐HRGC hyphenated system. This combination enables the full characterization and quantitation of the sulfur containing compounds in (heavy) middle distillate oil fractions (boiling range 150–450°C). The system is suited to identify and determine the various groups of orgaiio‐sulfur structures such as: thiols + sulfides + thiophencs, benzothiophenes, dibenzothiophenes and benzo‐naphthothiophenes. Within these groups a separation according to boiling point is accomplished. Therefore it allows the separation, identification and quantitation of a number of individual species, especially those which are refractory to hydrodesulfu‐rization (HDS), such as 3‐methyl‐benzothiophene, 4‐methyl‐dibenzothiophene and ‐J,6‐dimethyl‐dibenzothiophene. The analysis of these groups and specific compounds is the key in understanding the kinetics of the chemistry involved in HDS. The complete instrumental set‐up is fully automated by computer control. To suppress possible interferences and quenching of the sulfur response of the SCL from (large amounts of) hydrocarbons, it is aligned above the adapted flame ionization detector (FID) of the GC. This renders a sensitivity of the SCO for sulfur of 2 pg. s−1, which corresponds to a minimum detectable level for individual sulfur species in oil fractions for the complete system of 1 ppm (mg. kg−1) sulfur. Its linear dynamic range exceeds 105, which means that also untreated, high sulfur containing feedstocks can be analyzed directly. The selectivity of sulfur to carbon of the modified SCO exceeds 106. A number of HDS feedstocks and desulfurized products of different desulfurization levels have been analyzed with the system. From the analysis results the behavior of the refractory compounds in HDS can now be followed closely.
Detection of volatile organic sulfur compounds in water by headspace gas chromatography and membrane inlet mass spectrometry
Authors: Ojala Marja , Ketola Raimo , Mansikka Timo , Kotiaho Tapio , Kostiainen Risto 
Published: May 2005

AbstractTwo gas chromatographic methods, GC‐FID (flame ionization detection) and GC‐ELCD (electrolytic conductivity detector) are compared in tlie analysis of volatile organic sulfur compounds (VOSCs) in water samples with a membrane inlet mass spectrometry (MIMS) technique. Carbon disulfide, ethanethiol, dimethyl sulfide, ethyl‐methyl sulfide, thiophene, and dimethyl disulfide were used as test compounds. Linear dynamic ranges were found to be two decades with the GC‐ELCD method and four decades with the GC‐FID and MIMS methods. Detection limits were at low (μg/1 levels with the two gas chromatographic methods and clearly below μg/1 level with the MIMS method. Analysis of one sample takes 40 min with the gas chromatographic methods and five minutes with the MIMS method. The selectivity was good, especially with the GC‐ELCD and the MIMS method. In addition, quantitative results obtained with spiked water samples by the three methods are compared.
Methodological aspects of headspace SPME: Application of the retention index system
Authors: Schäfer Brit , Hennig Peter , Engewald Werner 
Published: May 2005

AbstractThe applicability of the retention index system to hcadspacc solid phase microextraxtion (HS–SPME) was investigated. In headspace SPME, the two equilibria gas phase/matrix and fiber coating/gas phase have to he considered. In this paper the equilibrium fiber coating/gas phase is discussed separately to characterize it more detailed and to investigate several methodical aspects. Therefore, the different distribution constants Kfiber/gas of n‐alkanes, which were used for reference compounds, were related to their Kováts retention indices. The validity of the derived linear relationship log Kfiber/gas versus retention index I is demonstrated for various examples. This relation is helpful for the assessment of distribution constants of substances not available and for the choice of a suitable fiber coating. Furthermore, quantification of analytes in the gas phase can be done without authentic substances.
Supercritical fluid extraction of oxindole alkaloids from Uncaria tormentosa
Authors: Lopez‐Avila Viorica , Benedicto Janet , Robaugh Dave 
Published: May 2005

AbstractSupercritical fluid extraction of oxindole alkaloids from Uncaria Tormentosa is described. The extraction was performed with supercritical carbon dioxide alone and with supercritical carbon dioxide modified with 10% metanol, and the extracts were analyzed by GC/MS and HPLC/MS.
Determination of inosine 5′‐monophosphate and guanosine 5′‐monophosphate in pig feed by capillary zone electrophoresis
Authors: Liu Huwei , Qi Shize , Zhang Yingnan , Huang Aijin , Sun Yiliang 
Published: May 2005

AbstractA capillary zone clectrophoresis method was developed for the determination of IMP and GIMP, commonly used as flavor enhancers in poultry feed, in a real sample of complex composition. A baseline separation of inosine 5′‐monophosphate and guanosine 5′‐monophosphate was achieved within 10 min and the other components in the sample did not interfere with the separation. Quantitative results obtained from pig feed samples are presented. The separation conditions and experimental reproducibility are also discussed.
Effect of temperature, collection mode, and modifier on the supercritical CO2 extraction of dicofol residues from fish samples
Authors: Lanças Fernando M. , Galhiane Mário S. , Rissato Sandra R. , Barbirato Marco A. 
Published: May 2005

AbstractToxicity evaluation of Dicofol to Astyanax bimaculatus schubarti, a characteristic fish species living in tropical rivers and lakes was carried out through LC50 – 96 Hours. These experiments were performed under laboratory controlled conditions with atmospheric air flow and dilution water at 25°C in the static mode, supercritical fluid extraction (SFE) with pure CO2 and CO2 modified with hexane and methanol were used at 50, 70, 80, and 100°C and 300 atm. Several collection modes were studied to extract Dicofol from fish samples. The extraction efficiencies were directly comparedd with those obtained after 8 h of Soxhlet extraction using the same clean‐up with Florisil and analysis by HRGC/ECD and HRGC/MS as a confirmatory analytical technique. The SFE recoveries at temperatures lower than 80°C were typically lower than soxhlet recoveries; however a temperature increase enhanced the efficiency of SFE. The results showed that under certain conditions, supercritical fluid gave higher extractio power (extracted 11 % more pesticide), shorter extraction time, and lower solvent consumption than Soxhlet, thus affording an excellent alternative to the conventional method for extracting Dicofol from fish sample.
A new method for sorptive enrichment of gaseous samples: Application in air analysis and natural gas characterization
Authors: Baltussen Erik , Janssen Hans‐Gred , Sandra Pat , Cramers Carel A. 
Published: May 2005

AbstractA new method for the preconcentration of trace components from gaseous samples is described. The system is based on enrichment of the solutes on a packed bed of 100% polydimethylsiloxane (PDMS) particles followed by thermal desorption and GC analysis. It was demonstrated that breakthrough volumes for packed PDMS traps can be calculated from theoretical equations. The PDMS material exhibits excellent thermal stability even after 200 consecutive runs. Additional advantages of packed sorbent beds over conventional adsorbent materials include high inertness, the absence of displacement effects and a reduced affinity for water. The practicality of the system was demonstrated by the analysis of air and natural gas using the system described here, components in the range of octane to benso[a] pyrene could be quantitatively trapped and thermally desorbed at mild temperatures. With the present set‐up the detection limit is in the order of 0.1 ng/m3 (MSD detector).
Current measurement of nonaqueous solvents: Applicatons to capillry electrophoresis and electrochromatography
Authors: Lister Ashley S. , Dorsey John G. , Burton D. Edward 
Published: May 2005

AbstractThe solvents acetonitrile, methanol, N, N‐dimethylformamide, dimethyl sulfoxide, formamide, and deionized water were investigated for their ability to support current flow without added electrolyte. Using open tubular capillary electrophoresis, currents were measured to be in the nanoampere (10−9 A) range for all solvents but formamide (10−6 A). Comparisons with flow data showed no clear relationship between current and electroosmotic flow. Packed capillary columns (3‐μm ODS) were used for separations using both pure solvent and hydrophobic dyes showed mild retention in pure ACN. A 16 polynuclear aromatic hydrocarbon (PAH) standard soluton was separated in 80/20 ACN/H2O with reduced plate heights (h) between 2.8 and 3.1 for retained species. A separation of nine androstenediones was achieved using a 70/30 MeOH/H2O mobile phase.
Packed column SFC of gas oils part I: Hydrocarbon group separation using pure carbon dioxide
Authors: M'Hamdi Rachid , Thiéabaut Duduer , Caude Marcel 
Published: May 2005

AbstractIn this paper, the critical application of the ASTM method to hydrocarbon group separation in gas oils using conventional packed column SFC coupled to FID is described. Resolution of model compounds is studied using a recent commercial apparatus and the chromatographic conditions such as pressure, temperature, and density of the mobile phase and the nature of the stationary phase after FID detection conditions have been selected to give the best sensitivity. Three gas oils differing in composition (ratio arimatic/non‐aromatic hydrocarbons)have been selected to evaluate the method for separation of the non‐aromatic hydrocarbon group from mono‐, di‐, and polyaromatic hydrocarbons groups (sub‐aromatic groups).The ASTM requiements for this analysis are very easy to obtain in adsorption chromatography. However, in adsorption or normal phase chromatography, SFC results cannot be perfect either for the quantification of aromatic and non‐aromatic hydrocarbon fractions because there is still an overlap between the two groups (the separation is better in adsorption chromatography than in normal phase chromatography) or for sub‐aromatic fractionation (the separation is better in normal phase chromatography than in adsorption chromatography); combination of both separation techniques only improves the sub‐aromatic group fractionation. Thus, further enhancement of resolution for group and sub‐group separation is needed.