In providing chemical and physical analytical services for industry and the public sector, the identification and characterization of
has become indispensable. A particularly efficient as well as convenient technique is represented by an advanced method of mass spectrometry by means of chemical ionization.
In mass spectrometry, it is essential to ionize the molecules of the analyte. The most common method for the generation is electron shock ionization (EI). This form of "hard" ionization leads to a high fragmentation of the molecules, which leads to complex spectra and an increasing chemical background.
A “soft” method for ionization of the sample is represented by chemical ionization (CI) with reactive gases. The advanced method presented here is a modified mass spectrometer, which makes water vapor usable for chemical ionization by protonation with hydronium ions. This allows the low-fractioning ionization of numerous compounds in the mass range of 25 to 650 g/mol. This special GC-MS process is coupled with an upstream solid-phase microextraction (SPME), providing an extremely high degree of selectivity and detection sensitivity for volatile organic substances.
Sampling can be carried out easily and quickly using vials:
Air samples were collected from a clean room and from a lab. More than 400 organic substances were detected and summarized in groups. The detected signals are presented in the diagram as intensities.
The organic load on the cleanroom air is lower by several orders of magnitude than on the laboratory room.
Regular repeat measurements of cleanroom air can be used for detecting deviations and their causes. Furthermore, specifications for cleanroom air quality can also be determined.
In the semiconductor industry, so-called FOUPs (Front Opening Unified Pod) are used for the transport of wafers. They are made of plastic and must not release any substances onto the wafers by outgassing or sublimation.
During an inspection, a strange smell was detected in a FOUP which was due to a possible incident. The root cause had to be evaluated.
After evaluating several 100 individual substances, three odor-intensive VOC candidates were shortlisted for comparison with the ambient air: Acetaldehyde was identified as the key substance for the odor in question.
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