Measurement of isomeric nitrotoluenes by means of silica gel tubes and GC/ECD

Status:

completed 04/2009

Aims:

The measurement method of the BGIA Institute for Occupational Safety and Health of the German Social Accident Insurance for quantitative assessment of nitrotoluenes was to be revised, since the method parameters and validation previously available were incomplete. The revised method will be employed as a standard measurement method in the BGMG hazardous substances measurement system of the accident insurance institutions, and published in the BGIA Folder.

Activities/Methods:

Silica gel is employed as the sampling medium. Gas chromatography and electron capture detection (ECD) were to be used for measurement of the nitrotoluenes. A range of calibrations and sampling tests were performed in accordance with DIN EN 482, "Workplace atmospheres – General requirements for the performance of procedures for the measurement of chemical agents", and the new prDIN EN 1076, "Workplace exposure – Procedures for measuring gases and vapours using pumped samplers – Requirements and test methods". The objectives included determining of the statistical data (standard deviation of the procedure) and the recovery rates for various concentrations, the amenability of the coated sampling media to storage, and the limits of measurement. Once all necessary data had been obtained, standard work instructions were formulated.

Results:

A method for measurement of the nitrotoluenes in the room air was developed further and validated in the course of the project. Silica gel tubes are employed as the sampling medium for the measurement of nitrotoluenes. Five ml diethylether is used for desorption. The sampling time is two hours at a volumetric flow rate of 20 l/h, or a maximum of eight hours at a volumetric flow rate of five l/h. Analysis is performed by means of gas chromatography and electron capture detection (GC/ECD) with the use of a non-polar column. The limit of detection of the method is 0.05 mg/m³ for all isomers, and its variation coefficients range from 2% to 3%. The method satisfies the requirements for measurement methods to DIN EN 482. It is being prepared for publication in the BGIA Folder.

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