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Digitale Medien

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)

Noy, Th. ; Curvers, J. ; Cramers, C. A.

Weinheim : Wiley-Blackwell

Journal of High Resolution Chromatography 9 (1986), S. 752-759

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ISSN: 0935-6304

Schlagwort(e): Capillary gas chromatography ; Detection limits ; Trace analysis ; Narrow bore columns ; Wide bore columns ; Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 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.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jhrc.1240091208

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Digitale Medien

Detection limits of thermal conductivity and photoionization detectors in high speed narrow bore CGC (1989)

van Es, A. ; Cramers, C. ; Rijks, J.

Weinheim : Wiley-Blackwell

Journal of High Resolution Chromatography 12 (1989), S. 303-307

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ISSN: 0935-6304

Schlagwort(e): Capillary gas chromatography ; Narrow bore columns ; Photoionization detection ; Thermal conductivity detection ; Detection limits ; Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 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.

Zusätzliches Material: 6 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jhrc.1240120513

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GC/MS and the chromatographic challenge (1988)

Leclercq, P. A. ; Cramers, C. A.

Weinheim : Wiley-Blackwell

Journal of High Resolution Chromatography 11 (1988), S. 845-848

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ISSN: 0935-6304

Schlagwort(e): Capillary gas chromatography ; GC/MS ; Theory ; Ceparation speed ; Detection limits ; Identification limits ; Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jhrc.1240111121

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