Chapter 2 System Information; Theory Of Operation; Data Handling; System Overview - AB Sciex 4500 Series System User's Manual

2
System Information
The 4500 series of instruments are intended for the qualitative and quantitative analysis of
chemical species. The system includes a mass spectrometer, a Turbo V™ ion source, a
®
computer, and the Analyst software.

Theory of Operation

Mass spectrometry measures the mass-to-charge ratio of ions to identify unknown compounds,
to quantify known compounds, and to provide information about the structural and chemical
properties of molecules.
The 4500 series of instruments have a series of quadrupole filters that transmit ions according to
their mass-to-charge (m/z) value. The first quadrupole in this series is the QJet Ion Guide located
between the orifice plate and Q0. The QJet Ion Guide does not filter ions, but focuses them
before they enter Q0. By prefocusing the larger ion flux created by the wider orifice, the QJet Ion
Guide increases instrument sensitivity and improves the signal-to-noise ratio. In Q0 the ions are
again focused before passing into Q1.
Q1 is a filtering quadrupole that sorts the ions before they enter Q2. Q2 is a collision cell in which
an ions internal energy is increased though collisions with gas molecules to the point that
molecular bonds break creating product ions. This technique allows users to design experiments
that measure the m/z of product ions to determine the composition of the parent ions.
After passing through Q2 the ions enter Q3 for additional filtering, and then enter the detector. In
the detector, the ions create a current that is converted into a voltage pulse. The voltage pulses
leaving the detector are directly proportional to the quantity of ions entering the detector. The
instrument monitors these voltage pulses and converts the information into a signal. The signal
represents the ion intensity for a particular m/z value and the instrument displays this formation
as a mass spectrum.

Data Handling

The Analyst software requires a computer running the Windows operating system. The computer
with the associated system software works with the system controller and associated firmware to
control the instrument and data acquisition. When operating the instrument, the acquired data is
sent to the Analyst software where it can be displayed as either full mass spectra, intensity of
single or multiple ions versus time, or total ion current versus time.

System Overview

Figure 2-1 Front View shows a system with a syringe pump, Turbo V ion source, a diverter valve,
®
and the optional NanoSpray ion source monitors.
System User Guide 4500 Series of Instruments
Document Number: D5030863 A 17 of 142