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32:Why is direct electron ionization in Figure 22-14 permissible for gas chromatography, but only for capillary columns in liquidchromatography in Figure 22-29?

Short Answer

Expert verified

A technique for coupling liquid chromatography and mass spectrometry

Step by step solution

01

 Direct electron ionization chromatography:

A direct electron ionization liquid chromatography–mass spectrometry interface (Direct-EI LC-MS interface ) based on the direct introduction of the liquid effluent into an electron ionization (EI) source.

02

 Answering the above mentioned question

A direct electron ionization liquid chromatography–mass spectrometry interface (Direct-EI LC-MS interface ) is a technique for coupling liquid chromatography and mass spectrometry (LC-MS) based on the direct introduction of the liquid effluent into an electron ionization (EI) source.

Library searchable mass spectra are generated. Gas-phase EI has many applications for the detection of HPLC amenable compounds showing minimal adverse matrix effects. The direct-EI LC-MS interface provides access to well-characterized electron ionization data for a variety of LC applications and readily interpretable spectra from electronic libraries for environmental, food safety, pharmaceutical, biomedical, and other applications.

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Most popular questions from this chapter

Measure the width at half-height of the peak at m/z53and calculate the resolving power of the spectrometer from the expression m/m1/2. Would you expect to be able to resolve two peaks at 100and 101Da?

The molecular ion region in the mass spectrum of a large molecule, such as a protein, consists of a cluster of peaks differing by 1 Da. This pattern occurs because a molecule with many atoms has a high probability of containing one or several atoms of C1315N,18O,2Hand 32S. In fact, the probability of finding a molecule with only C1214N,16O,1Hand 32S may be so small that the nominal molecular ion is not observed. The electrospray mass spectrum of the rat protein interleukin-8 consists of a series of clusters of peaks arising from intact molecular ions with different charge. One cluster has peaks at m/z 1 961.12, 1 961.35, 1 961.63, 1 961.88, 1 962.12 (tallest peak), 1 962.36, 1 962.60, 1 962.87, 1 963.10, 1 963.34, 1 963.59, 1 963.85, and 1 964.09. These peaks correspond to isotopic ions differing by 1 Da. From the observed peak separation, fi nd the charge of the ions in this cluster. From m/z of the tallest peak, estimate the molecular mass of the protein.

34: What is collisionally activated dissociation? At what points in a mass spectrometer does it occur?

(a) Spectra A and B belong to isomers of C6H12O. Explain how you can tell which isomer goes with each spectrum.

(b) The intensity of theM + 1peak at m/z,101mustbe incorrect in both spectra. It is entirely missing in spectrum A and too intense (15.6% of intensity of M+* ) in spectrum B. What should be the intensity of M + 1 relative to M+* for the compositionC6H12O?

33:Why does vacuum ultraviolet photoionization with |120-nmwavelength radiation produce less molecular fragmentation than

does 70 eV electron ionization?

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