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Chapter 22: QAE (page 598)
Measure the width at half-height of the peak at m/z53and calculate the resolving power of the spectrometer from the expression . Would you expect to be able to resolve two peaks at 100and 101Da?
The width which is present at half-height is 0.60 m/z .
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Bone consists of the protein collagen and the mineral hydroxyapatite,. The content of archaeological humanskeletons measured by graphite furnace atomic absorption shedslight on customs and economic status of individuals in historicaltimes. 37Explain why La3+ is added to bone samples to suppressmatrix interference in Pbanalysis.
30: (a)The mean free pathis the average distance a molecule travels before colliding with another molecule. The mean free path, l, is given by l 5 kT/(12sP), where kis Boltzmann鈥檚 constant, Tis temperature (K), Pis pressure (Pa), and s is the collision cross section. For a molecule with a diameter d, the collision cross section is pd2. The collision cross section is the area swept out by the molecule within which it will strike any other molecule it encounters. The magnetic sector mass spectrometer is maintained at a pressure of |1025 Pa so that ions do not collide with (and deflect) one another as they travel through the mass
analyzer. What is the mean free path of a molecule with a diameter of 1 nm at 300 K in the mass analyzer?
(b)The vacuum in an orbital mass separator is 1028 Pa. Find the mean free path in the orbital for the same conditions as (a).
Explain what is meant by spectral, chemical, ionization, andisobaric interference.
Protein molecular mass from electrospray. The enzyme lysozyme 59exhibits peaks at m/z = 1789.1, 1590.4, 1301.5 and 1 193.1. Follow the procedure of Table 22-3 to find the mean molecular mass and its standard deviation.
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 and . In fact, the probability of finding a molecule with only and 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.
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