Gas and Residual Gas Analysis with a Quadrupole Mass Spectrometer

Suitable for every application

There are various configurations and different peripheral devices for quadrupole mass spectrometers (QMS), which can be selected specifically to suit the area of application depending on the requirements.

Basically, partial pressures are determined with a mass spectrometer, also known as RGA for short, while vacuum measuring tubes are used to measure total pressure. Only the measurement of gases is possible - which includes the analysis of solid or liquid substances if they have previously been evaporated.

Important decision criteria for device selection are:

• The pressure range and the associated design

• Analytical performance (this includes masses to be detected, resolution, detection limit, measurement speed)

Influence of the pressure range on the construction

The gases in a chamber that has been pumped down to low pressure, are prepared for analysis by ionizing the electrons. The ions generated in this way are separated in a mass filter according to their mass to charge ratio. High vacuum is a mandatory requirement for these processes. Accordingly, the pressure range in which the gas is to be analyzed usually also dictates the design.

Analytical performance

There is no one universal mass spectrometer that covers all possible applications. Regardless of the pressure, the initial conditions and the goal of the analysis vary. Therefore, before selecting the equipment, it makes sense to be clear about which analysis task is to be solved and to define what goal you want to achieve with the equipment. The requirements to be taken into account primarily include the following criteria.

• Measuring speed

• Resolution

• Masses to be detected

• Limit of detection

Let's look at the influence of the individual components on analytical performance. The general rule also applies to mass spectrometry: precision is proportional to price. In some use cases, there are critical factors to consider that require specific actions or special attention.

The criteria in detail

Detectors

Depending on the operating pressure, different detectors are used:

For the Faraday detector (F), the operating pressure does not need to be as low as for the combined Farady /C-SEM detector (M). However, this has a direct impact on the detection limits. The exact numbers depend, among other things, on the residence time and the ion source used, which can be found in our brochures.

FAQ