Gas and Residual Gas Analysis with a Quadrupole Mass Spectrometer
Mass spectrometry is a widely used analytical method that looks at the chemical composition of substances. Our devices for (residual) gas analysis all have the same core: a quadrupole mass spectrometer (QMS).
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- 48 variants available
- 48 variants available
- 108 variants available
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.
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)
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.
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:
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Areas of application
If I am already in the area of low pressure and thus molecular flow, the pressure may not need to be reduced any further - depending on the accuracy required. This is called residual gas analysis in the vacuum system. For example, if the gas to be examined is at atmospheric pressure, components are required to reduce the pressure. This is called gas analysis at atmospheric pressure.
Construction
For the residual gas analysis in the vacuum system, no additional pumps are usually required, which reduce the pressure to < 5 ∙ 10−4 mbar. Accordingly, so-called standalone components are used, basically just the mass spectrometer itself.
Complete systems are used when the existing gas pressure required for the analysis still needs to be reduced by pumping via a gas inlet system.
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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.
a. Masses to be detected
b. Resolution
c. Limit of detection
d. Measuring speed
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.
Masses to be detected
Which masses must be found for the area of application? The smallest suitable mass range should be chosen. Smaller mass range ensures better sensitivity (signal).
Resolution
The resolution can be adjusted depending on the area of application, mainly via the software. It affects separation and signal height. A so-called standard resolution is common.
Measuring speed
The measurement speed can also be adjusted depending on the analysis task, for example with the PrismaPro from a minimum of 1 ms up to 16s. The measurement speed influences the amount of noise (both the signal and the background).
Detection limit
The detection limit is influenced by the sensitivity and peak overlap. Sensitivity also varies depending on the detector used (Faraday vs. Faraday/SEM).
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.
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Configurable RGA systems
Every test task is different. In addition to the standard OmniStar / ThermoStar solutions, our team of experts accesses the full range of Pfeiffer Vacuum products and uses them to configure the system that best suits your requirements. One example is our RGA cleanliness verification system called OmniGrade. Not only are the individual components such as quadrupole mass spectrometers, vacuum pumps, chambers and other individual components selected, but the total operating costs and delivery times of the tailor-made, turnkey solution are also taken into account. With our expertise, we can help you achieve test results with the precision you need while minimizing unnecessary effort.
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Software and interfaces (Ethernet)
PV Mass Spec software is easy to use and is provided when you purchase the device, and updates are also available online. Our mass spectrometers also offer certain interfaces to communicate directly with a PLC.
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Video for a quick start after receiving the device. You can find this, as well as other interesting videos, on our YouTube channel.
Hardware connection
The following hardware connections are available for integrating our devices: The Prisma Pro is equipped with a DN 40 CF flange, the HiQuad Neo with DN 63 CF, and OmniStar and ThermoStar each with capillary hose or a suitable adapter 1/4" / DN 16 ISO-KF to meet the requirements of various applications.
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Support & Service
We have experts working for different areas of application. They are available to advise you on choosing the right equipment, to help you with any questions you may have about the measuring recipe, or to help you with other questions. In addition to support, we also offer services for the devices.
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