Further development of the application for calculating the measurement uncertainty of measurement methods for particulate, gaseous and vaporous hazardous substances ("MUST") with regard to extraction methods

Status:

projected 04/2024

Aims:

This project follows on from the preceding project, 2102 – Development of a tool for calculating the measurement uncertainty. The application enables specific mathematical models to be used to calculate the expanded measurement uncertainty for three different analysis methods that are used to determine the concentration of hazardous substances in workplace atmospheres. These three methods are thermal desorption, metals analysis by means of mass spectrometry with inductively coupled plasma, and extraction. Before now, the models included only the respective standard analysis methods, which for some hazardous chemicals are not sufficient. The next step in progressive extension of the tool was to extend the extraction process to include further, Institute for Occupational Safety and Health (IFA) extraction methods.

Activities/Methods:

The first step involved identifying the additional methods used for extraction in the IFA’s "Chemical and Biological Hazards" department. The necessary modifications/extensions to the existing mathematical model for calculating the measurement uncertainty were then specified, implemented and reviewed. This involved direct changes to the established model functions, and also new uncertainty parameters that either had to be taken into account or could be omitted. During modification of the model, modifications were also made to the application’s user interface to permit selection of different extraction methods. Following validation of the extensions to the method (with the use of other tools to check the analysis, such as QMSys, GUM Professional/Excel), the changes to the method were documented in the English and German versions of the user manual. In addition, users at the institute tested the new extensions’ usability and functionality and the user-friendliness of the application’s modified graphical user interface, and provided feedback to the developers. The test phase will be followed by internal training.

The application and manual were made available on the IFA’s website in the fourth quarter of 2023. Once the extensions to the extraction methods had been implemented in the application, MUST was also updated on the IFA website (the German version in Q4 2023, the English version in Q1 2024).

Results:

Some analytical methods for determining hazardous substances in workplace atmospheres include an extraction step during sample preparation. In this project, MUST was extended with the inclusion of different extraction volumes. In the latest version of MUST, different extraction volumes are stored together with their associated systematic and random deviations. These can be taken into account in the mathematical model for calculating the expanded measurement uncertainty. In addition, a function was created for calculating the measurement uncertainty for methods where the measured value represents the mean of two different measurements (e.g. two separate columns in the form of polar and non-polar stationary phases), for which two different calibrations were performed for the analysis. Furthermore, selection is possible of whether the sampling head is included in calculation of the measurement uncertainty, depending on whether the method is a gas/vapour or particle/vapour mixture method. These extensions to the method were tested for their functionality and ease of use, and published on the IFA’s website (MUST version 1.2). The changes are also available on the website in the English and German user manuals. Internal training in MUST was begun.

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