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Quadrupole rods

Ion that is unsuccessful

at reaching detector

Detector

RF supply

DC supply

+

+

Ions

Fig. 9.5Quadrupole analyser. The fixed (DC) and oscillating (RF) fields cause the ions to undergo complicated

trajectories through the quadrupole filter. For a given set of fields, only certain trajectories are stable, which

only allows ions of specificm/zto travel through to the detector. The efficiency of the quadrupole is

impaired after a build-up of ions that do not reach the detector. Therefore a set of pre-filters is added to the

quadrupole to remove the ions that would otherwise affect the main quadrupole.

100

Relative ion intensity (%)

900

0

1000 1100

m/z

1200 1300 1400 1500

%

A100

1027.6

A106

988.0

A106

969.4

A97

1059.4A94

1093.1

A86

1154.6

A86

1194.6

A80

1284.0

A78

1317.3

A76

1352.1

M= 102658.3 ±7.0

Fig. 9.6Large intact protein mass accurately measured in electrospray MS. The species of ions are

annotated by the charge state, e.g. with 99, 100, 101 charges, etc., and the associatedm/zvalue. The inset

shows the ‘deconvoluted spectrum’.

361 9.3 Mass analysers