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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 66 (1994), S. 3005-3012 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1612-1112
    Keywords: Open-tubular liquid chromatography ; External peak broadening ; Exponentially modified Gaussian model ; Mass Spectrometry ; Laser-induced fluorescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary To optimize performance in Open-Tubular Liquid Chromatography (OTLC) it is necessary to minimize external peak broadening. To see how to reduce the external broadening an insight into its origins is required. This can be obtained by careful evaluation of experimental results with peak deconvolution methods based on the exponentially modified Gaussian model and comparison with theoretical predictions. It is assumed that the column response is Gaussian and that the responses due to the external effects are exponential. For peak deconvolution the algorithm described by Yau was used. Simulations were carried out to check the performance of the algorithm in calculating the standard deviation and the time constant. The effects of the presence of more than one time constant and of the number of data points and their position were investigated. The limits within which reliable results can be obtained are reported. Experimental results were obtained with laser-induced fluorescence and mass spectrometric detection. It is shown that the Yau algorithm can be used to obtain physically realistic estimates of the contribution to peak distortion in the various system components. By suitable design external effects can be reduced to the order of 1 nl and in some cases even lower limits can be reached.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 21 (1986), S. 342-354 
    ISSN: 1612-1112
    Keywords: Liquid chromatography/mass spectrometry ; Direct liquid introduction ; Chemical ionization ; Applications
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The coupling liquid chromatography and mass spectrometry is still growing in popularity. Direct liquid introduction has become one of the most important interfaces in LC/MS coupling. The various aspects of the interface have been investigated by several groups. This paper is the second part of a review of the developments in direct liquid introduction. Instrumental aspects of direct liquid introduction interfacing were discussed in the first part. This part will deal with the mass spectrometric aspects, i.e. chemical ionization and the influence of the various experimental conditions on the spectra. The applications of direct liquid introduction will also be reviewed briefly.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-739X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1612-1112
    Keywords: Single short-column LC ; On-column sample enrichment ; Atmospheric pressure chemical ionization ; LC-tandem MS ; Environmental analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Single short, i.e. ca 2-cm long, high-pressure-packed columns coupled with mass spectrometric (MS) or tandem MS detection enable rapid trace-level determination and identification of environmental pollutants in water samples. In this study an atmospheric pressure chemical ionization (APCI) interface has been used and the overall set-up was tested with a mixture of seventeen pesticides, including organophosphates, carbamates, phenylureas and triazines. For the majority of the test analytes, the most prominent peaks in the positive-ion APCI-MS spectra resulted from protonated molecules. For fifteen out of the seventeen pesticides short-column liquid chromatography (LC)-APCI-MS of water samples as small as 15 mL resulted in detection limits between 0.03 and 5 μg L−1 in full-scan mode and between 2 and 750 ng L−1 by selected ion monitoring (SIM), both recorded in the positive-ion mode. Production spectra from protonated molecules of the majority of the selected pesticides present at a level of 0.1 μg L−1 in tap water are successfully identified from a search against a pesticide MS-MS library compiled in-house. This short-column LC-APCI-MS(-MS) approach has, on the basis of full-scan positive-ion data and their product-ion spectra, also been used to confirm the identity of target compounds and to identify unknown organic micropollutants in environmental waters.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Atmopheric Pressure Chemical Ionization (APCI) mass ; spectrometry ; Glucuronide-conjugates ; Toxicological compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new chromatographic method for the direct determination of metabolites (glucuronide-conjugates) of molecules of toxicological relevance in biological media with the minimum sample pre-treatment has been developed. A high performance liquid chromatographyatmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) system was used for this purpose. The separation of four glucuronides Aminophenylglucuronide (APhG), Phenylglucuronide (PhG),p-Nitrophenylglucuronide (NPhG) and α-Naphthylglucuronide (NG) was obtained under ion-suppressed reversed-phase chromatography conditions, by using high-speed (3 cm, 3 μm) columns and formic acid (2 mM) as the acid modifier in the mobile phase. Different C-18 stationary phases (partially endcapped and non-endcapped) were evaluated in order to obtain retention for these very polar, water soluble molecules. The ionization of the analytes was obtained in negativeion (NI) mode. Detection limits were in the range 1–5 mg L−1 and calibration curves were linear over two order of magnitude. Intra-day and inter-day precision were in the range 2.9–10.6% for all the compounds. The method was successfully applied for the determination of PhG in a urine sample of a European Quality Assurance Programme for Organic Solvent Metabolites.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Short-Column LC ; Environmental water samples ; MS-MS detection ; Pesticide degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The applicability of solid-phase extraction-LC using two short columns (SPE-LC) and/or single-short-column liquid chromatography (SSC) combined on-line with tandem mass spectrometry (MS) was demonstrated for the rapid study of pesticide degradation. A fast analytical procedure was developed to provide preliminary information concerning experimental conditions, approximate rates of degradation and identity of the degradation products. Surface water samples were spiked at relevant concentration levels with well-known microcontaminants and photolysis was used to transform parent compounds into their degradation products. In general, the strategy was as follows: at 30-min intervals 10-mL samples were on-line enriched, separated by short-column LC and recorded in full-scan MS to obtain information on the disappearance of the parent compound and the appearance of breakdown products. To obtain structural information, product-ion spectra of selected compounds appearing in the full-scan MS chromatogram were recorded; this enabled the identification of several degradation products. Total analysis time of enrichment/separation and detection was about 10–15 min.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 21 (1986), S. 277-287 
    ISSN: 1612-1112
    Keywords: Liquid chromatography/mass spectrometry ; Direct liquid introduction ; Diaphragm ; Liquid jet formation ; Desolvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Considerable progress has been made in the coupling of liquid chromatography and mass spectrometry over the past ten years. Three interfaces tend to dominate the LC/MS market: transport systems, direct liquid introduction, and the thermospray interface. In this paper the developments in direct liquid introduction interfacing for LC/MS will be reviewed. The paper will be published in two parts. Mass spectrometry and applications will be discussed in the second part. This first part of the review concentrates on the various instrumental aspects of direct liquid introduction, such as the design of vacuum systems, the interface probes and the desolvation chambers.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 341-342 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 197-202 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The analysis of intact neutral oligosaccharides by on-line liquid chromatography/thermospray mass spectrometry is described. Molecular-weight information on oligomers up to a degree of polymerization of 10 is obtained using an aqueous mobile phase containing 10-4 mol/L sodium acetate, which was found to be compatible with thermospray interfacing and ionization. Ions due to sodiated and disodiated oligosaccharides are observed under these conditions without fragmentation. The aqueous 10-4 mol/L sodium acetate mobile phase is demonstated to be applicable in the separation of mixtures of oligosaccharides on a reversed-phase octadecyl-modified silica column.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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