Gas Analysis by Process Mass Spectrometry

How does mass spectrometry work?

A mass spectrometer works by ionizing the molecules in a sample, separating the ions according to mass-to-charge ratio and measuring the current of each ion group. The sample is taken under vacuum into an ion source and ionized by electron bombardment. Within a magnetic sector analyzer, ions are separated into different trajectories according to their mass-to-charge ratios.

A Faraday detector measures the ion current for each mass. The concentration of each component in the sample is calculated from the mass spectrum. In process applications, the instrument combines a vacuum pump, temperature-controlled ion source, embedded processor and multi-stream sample selector in one housing.

What process mass spectrometry measures and where it is used

The method can measure many gas components simultaneously and analyzes different sample streams in turn. Main areas of use:

• Process gas composition monitoring in petrochemical and chemical plants
• Loop gas control in ammonia, methanol and similar synthesis processes
• Fertilizer and hydrogen production plants
• Refinery gas streams and quality control
• Impurity monitoring in CO₂ production

Where process mass spectrometry works well and where it struggles

Because a mass spectrometer can measure many gases and many sample points with one instrument, it can replace a large number of individual analyzers. Response time is short, and it covers a wide concentration range. Simultaneous measurement allows faster process control.

Limitations: spectrum resolution calculations are needed to separate components with the same mass-to-charge ratio. The instrument needs continuous vacuum and regular calibration. The sampling and conditioning system directly affects measurement quality. Installation requires planning for hazardous area classification and suitable cabinet design.

Choosing an instrument for process mass spectrometry

When selecting, the component list, number of sample streams, measurement cycle time and hazardous area requirements are determined. The vacuum system, calibration gases and sample line design are planned together at the installation stage.

Tetra and mass spectrometers

Tetra supplies, installs, commissions and services process mass spectrometers in Türkiye. The product range includes the Thermo Scientific Prima PRO Ex process mass spectrometer, offered with a magnetic sector analyzer, Faraday detector and ATEX/IECEx Zone 1 purge option. Tetra also delivers this instrument with sample preparation and cabinet integration, as process gas systems such as CO₂ purity monitoring.