TABLE OF CONTENTS Computers now play a central role in all mass spectrometry experiments. Computers are used for instrument control, data acquisition, data processing and storage. Once the sample is introduced into the mass spectrometer, all remaining functions are performed under computer-control. This includes mass calibration and tuning of the instrument to optimise the ion signal at the detector.
Both personal computers and UNIX-based workstations are used to control mass spectrometers. Mass spectrometry experiments are preprogrammed using the computer software where method files control instrument parameters including source temperatures, gas pressures, lens and detector voltages. The same computer is typically also used to control peripheral devices such as gas and high pressure liquid chromatographs when these are coupled to the mass spectrometer. Computers allow the chromatographic conditions to be pre-programmed and the user to monitor the results at a second detector (such as a UV detector) in addition to the mass spectral data within a common interface.
Computers also allow a multitude of different scan experiments to be performed during a single acquisition. Tandem mass spectra (see Chapter 4) can be recorded where sufficient ion current for a nominated m/z is detected in a preliminary MS scan. This enables both molecular weight and structural information to be derived in an automated manner.
Since the mass spectrometer acquires data in an analog format, an analog-to-digital converter (ADC) is used to convert the detector response into a digital...
