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  • 1
    Electronic Resource
    Electronic Resource
    Temperature programmed retention indices: Calculation from isothermal data. Part 1: Theory (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 607-610 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Temperature programmed retention indices ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Direct conversion of isothermal to temperature programmed indices is not possible. In this work it is shown that linear temperature programmed retention indices can only be calculated from isothermal retention data if the temperature dependence of both the distribution coefficients and the column dead time are taken into account.Procedures are described which allow calculation of retention temperatures and from these, accurate programmed retention indices. Within certain limits the initial oven temperature and programming rate can be chosen freely. The prerequisite for this calculation is the availability of reliable isothermal retention data (retention times, retention factors, relative retention times, or retention indices) at two different temperatures for one column.The use of compiled isothermal retention indices at two different temperatures for the calculation of retention temperatures and thus temperature programmed indices is demonstrated. For the column for which programmed retention indices have to be determined, the isothermal retention times of the n-alkanes and the column dead time as a function of temperature have to be known in addition to the compiled data for a given stationary phase.Once the programmed retention indices have been calculated for a given column the concept allows the calculation of temperature programmed indices for columns with different specifications. The characteristics which can be varied are: column length, column inner diameter, phase-ratio, initial oven temperature, and programming rate.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240080926
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  • 2
    Electronic Resource
    Electronic Resource
    Correlations between HPLC and NMR properties of some selected alkyl bonded phases (1983)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 6 (1983), S. 433-435 
    Details
    ISSN: 0935-6304
    Keywords: Reversed-phase HPLC ; Solid state NMR ; Surface characterization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240060806
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature programmed retention indices: Calculation from isothermal data. Part 2: Results with nonpolar columns (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 611-617 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Temperature programmed retention indices ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The procedure for calculating linear temperature programmed indices as described in part 1 has been evaluated using five different nonpolar columns, with OV-1 as the stationary phase. For fourty-three different solutes covering five different classes of components, including n-alkanes and alkyl-aromatic compounds, both isothermal and temperature programmed indices were determined. The isothermal information was used to calculate temperature programmed indices. For several linear programmed conditions accuracies better than 0.51T-units were usually obtained. The results are compared with published procedures.It is demonstrated that isothermal retention information obtained on one column can be transferred to another column with the same stationary phase but different column dimensions and/or phase ratio. The temperature programmed indices calculated in this way also have an accuracy better than 0.51T-u.The temperature accuracy and precision of the GC-instrumentation used was of the order of 0.1°C. All calculations can be run with a Basic-programmed microcomputer.
    Additional Material: 12 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240080927
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  • 4
    Electronic Resource
    Electronic Resource
    Optimum performance of capillary GC columns as a function of tube diameter and film thickness under various operating conditionsDedicated to Professor Kurt Grob in recognition of his invaluable contributions to capillary gas chromatography, particularly his work on column quality testing.. Computer program for calculation of H-ū curves and minimum analysis times (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 764-771 
    Details
    ISSN: 0935-6304
    Keywords: Open tubular gas chromatography ; Theory ; Vacuum outlet ; BASIC program for calculation of optimum conditions ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Golay-Giddings and Poiseuille equations are used to derive equations for the calculation of the maximum plate number and minimum time conditions for given columns at fixed, but selectable, outlet pressures. In addition, expressions are presented for the determination of minimum analysis times for separation problems requiring given plate numbers. In this instance, the optimum column length can be calculated as a function of outlet pressure. A Basic computer program, incorporating the equations for the various optima, together with the H-ū curves, is described. Input variables are either column length or desired plate number, column diameter, film thickness, capacity ratio of the solute, column outlet pressure, seperation temperature, and carrier gas. The carrier gas viscosity is automatically calculated in the case of hydrogen, helium, or nitrogen. For these gases, and if the solute is a n-alkane, the diffusivity of the solute in the mobile phase is calculated. In this case, the carbon number of the solute is needed in the computation.For high molecular weight polydimethylsilicone phases (e.g. SE-30), the program can approximate the diffusivity of n-alkanes in the stationary phase at the given temperature as a function of the carbon number. Of course, manually entered values of viscosity and diffusion coefficients can be included in the calculations.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240081112
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of column characteristics on the minimum analyte concentration and the minimum detectable amount in capillary gas chromatographyBased on a lecture delivered at the First Latin-American Congress on Chromatography (COLACRO) Rio de Janeiro, Brazil, March 17-19, 1986. (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 752-759 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Detection limits ; Trace analysis ; Narrow bore columns ; Wide bore columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The need for faster and more efficient separations of complex mixtures of organic compounds by gas chromatography has led to the development of small inner diameter open tubular columns. Owing to their decreased plate height, extremely narrow peaks are obtained. When differently sized columns with equal plate numbers are compared, injection of a fixed amount of a solute will give the highest detector signals for the smallest bore columns. When P is defined as the ratio of the column inlet and outlet pressures, it can be seen from theory that under normalized chromatographic conditions the minimum detectable amount (Qº) for a mass flow sensitive detector increases proportionally to the square of the column diameter for P = 1. In the situation of greater interest in the practice of open tubular gas chromatography where P is large, a linear relationship is derived between Qº and the column diameter.It is a widespread misunderstanding, however, that narrow bore capillary columns should be used for this reason in trace analysis. If a fixed relative contribution of the injection band width to the overall peak variance is allowed, a decreased plate height drastically restricts the maximum sample volume to be injected. It is shown that the minimum analyte concentration in the injected sample (Cº) is inversely proportional to the column inner diameter when a mass flow sensitive detector is used. For actual concentrations less than Cº, sample preconcentration is required. The effect of peak resolution and selectivity of the stationary phase in relation to Cº and Qº will be discussed as well. The validity of the given theory is experimentally investigated. Minimum analyte concentrations and minimum detectable amounts are compared using columns with different inner diameter.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240091208
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  • 6
    Electronic Resource
    Electronic Resource
    Estimation of the instrumental band broadening contribution to the column elution profiles in open tubular capillary liquid chromatography (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 176-180 
    Details
    ISSN: 0935-6304
    Keywords: Open tubular liquid chromatography ; Instrument band broadening ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In comparison with conventionally packed HPLC columns, from a theoretical point of view, open capillary liquid chromatography (OTLC) systems offer a number of advantages like high plate numbers and short analysis times. On the other hand, drastic changes have to be made to the instrumentation. In particular, the contribution to band broadening by the chromatographic equipment must be considerably reduced. In the present study an OTLC system was developed and evaluated, which yields satisfactory results for 26 μm i. d. columns. The determination of the contribution of the chromatographic equipment to the total band broadening is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110207
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of column characteristics on the minimum analyte concentration and the minimum detectable amount in capillary gas chromatography. Part IIFor part I, describing the effect of the column diameter, see reference [9].: The stationary phase film thickness (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 264-270 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Detectability ; Thick films ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For a typical narrow bore (50 μm) and wide bore (320 μm) capillary column the effects of increased stationary phase film thickness (df) on the minimum detectable amount, Qo, as well as on the minimum analyte concentration, Co, are described. In treating the effect of an increased film thickness, two approaches can be followed; either the separation temperature is kept constant, resulting in larger values of the capacity ratio, k, or the column temperature is increased such as to keep k constant. For normalized chromatographic conditions the effects of both approaches on the minimum plate height, optimum carrier gas velocity, and required plate number are described, finally yielding expressions for Qo and Co for both mass flow and concentration sensitive detectors. At constant temperature, Co always increases with the film thickness for mass flow sensitive detectors (e.g. FID). Wide bore thin film columns offer the lowest value of Co attainable. For concentration sensitive detectors (e.g. TCD), Co is affected neither by column diameter nor by film thickness. The Qo-df plot for constant temperature shows a minimum, suggesting an optimum film thickness for mass flow sensitive as well as concentration sensitive detectors. The corresponding capacity ratio has a value between 0.5 and 1.5. At elevated temperatures (k constant) in combination with mass flow sensitive detectors, again an optimum film thickness exists, corresponding to a minimum value of Co. For constant capacity ratio Qo always increases with the film thickness for both types of detectors. As indicated above, in some situations the lowest values of Co and Qo are obtained at an increased film thickness, the effect being marginal. As an initial guideline, for the daily practice of capillary gas chromatography with respect to minimum values of Co and Qo, the use of thin film columns is to be preferred.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110309
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  • 8
    Electronic Resource
    Electronic Resource
    Detection limits of thermal conductivity and photoionization detectors in high speed narrow bore CGC (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 303-307 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Narrow bore columns ; Photoionization detection ; Thermal conductivity detection ; Detection limits ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Not only the required input band width and the availability of compatible instrumentation limit the reduction of column diameter but so do the column sample capacity and detector characteristics, such as volume and sensitivity. In this paper the scope and limitations of thermal conductivity and photoionization detection at atmospheric and reduced pressures for capillary gas chromatography are discussed at length.It is shown that the sensitivity of a thermal conductivity detector is inversely proportional to the pressure. Reduction of cell volume and decrease of pressure appear equivalent with respect to minimum detectable amount and peak broadening. This results in femtogram detection limits for column diameters as low as 10 μm.For photoionization detectors the sensitivity did not improve at reduced pressures, so that the effect of reduced pressure and addition of make-up gas on the detection limits is the same. Nevertheless, the applicability of a low volume photoionization detector (40 μl) for capillary columns with a diameter as low as 50 μm will be demonstrated by series coupled PID and FID detectors and illustrated with various applications.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240120513
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  • 9
    Electronic Resource
    Electronic Resource
    Deactivation by polysiloxane and phenyl containing disilazane: A 29SI CP-MAS NMR study after the formation of polysiloxane chains at the surface (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 510-516 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Deactivation ; 29Si-NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A high degree of deactivation of glass and fused-silica capillary column walls is attainable by means of high temperature silylation (HTS) with or without a preceding leaching process. HTS with a phenyl containing disilazane, diphenyltetramethyldisilazane (DPTMDS), and polydimethylsiloxane (PDMS) are studied on Cab-O-Sil, a fumed silica, as a model substrate. Using 29Si CP-MAS NMR, it was shown that no dimethylsiloxane chains were formed upon silylation with DPTMDS under different conditions of humidity and stoichiometry at 377°C. With DPTMDS deactivation it is possible that amino trisiloxy silane groups are formed, these groups add extra activity to the surface. Silylation with a PDMS, OV 101, at various temperatures between 300°-420°C did show that dimethylsiloxane chains were bonded at the surface. Using the 29Si CP-MAS NMR technique with variable contact times to reveal siloxy group mobility, the degradation of dimethylsiloxane chains at the surface was studied. PDMS degradation at an optimal temperature gives a more effective diminuation of the silane activity caused by chemical reaction with the silanol groups and the effective screening of the remaining silanol groups with anchored polydimethylsiloxane chains and small cyclodimethylsiloxane ring structures at the surface.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110703
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  • 10
    Electronic Resource
    Electronic Resource
    GC/MS and the chromatographic challenge (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 845-848 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; GC/MS ; Theory ; Ceparation speed ; Detection limits ; Identification limits ; 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
    URL: http://dx.doi.org/10.1002/jhrc.1240111121
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