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Hartmut Henneken (promotion date: 25 October 2006)

Sampling Strategies for the Analysis of Reactive Low-Molecular Weight Compounds in Air

Promotion Date: 25 October 2006

Hartmut Henneken

I developed a badge for workers to wear on their clothing. The badge is collecting certain chemicals to assess the workers exposure to those hazardous compounds.
The staff of the radiology departments of hospitals wear similar badges.
But there is no discoloration in the badge I developed, it needs to be sent in for analysis.
There are two stages during the development.
At first you must collect the sample somehow and trap the compound that you want to analyse and secondly there is the analysis itself.
I worked mostly on the detection of isocyanates, very toxic components, even in low concentrations.

What was your thesis about?

I developed a badge for workers to wear on their clothing. The badge is collecting certain chemicals to assess the workers exposure to those hazardous compounds. The staff of the radiology departments of hospitals wear similar badges. But there is no discoloration in the badge I developed, it needs to be sent in for analysis.

It sounds very useful.

It is. There are two stages during the development. At first you must collect the sample somehow and trap the compound that you want to analyse and secondly there is the analysis itself. I worked mostly on the detection of isocyanates, very toxic components, even in low concentrations. The badge has a filter that is impregnated with a chemical (NBDPZ) and by diffusion the isocyanates reach the filter tape and are reacting. This reaction product is stable and can later be analysed in a laboratory. We are detecting concentrations down to parts per trillion in the air.

But since you are detecting isocyanates only, the badge is limited to certain working environments only?

It is no limitation, because it is made for those environments. The isocyanate hazard occurs in working environments where a variety of chemical substances are used. And of course you only want to measure a specific substance, you don’t want your badge to give false positive signals due to reaction with different chemicals.

If for instance, polyurethane is heated to a temperature of 2500 C or above, isocyanates are set free. And also in all welding and metal cutting processes, in which certain coatings are present. By the way, methyl isocyanate was the chemical that killed and injured the people in India in the Bopal accident.

Now something about phase two.

The method we developed is very sensitive. You can have 15 minutes of sampling and then remove the filter tape from the badge, go to the lab and analyse it. The advantage of the badge is that you can also do the measuring in a full work shift, as it is very easy to use and not interfering with the work process. However, the analysing method in the lab must be sensitive enough to also detect the short exposures. We used mass spectrometry to detect the substances in the filter. Mass spectrometry is expensive and modern technology, so in real life the badge filters have to be sent away to specialized certified labs and cannot be analysed at the workplace.

Will industry adopt your method?

They might. Taking air samples using sampling pumps is more complicated and the badges are cheaper. In the future safety officials may decide that this method is reliable, enhances safety and incorporate it in their set of rules and regulations.

Is your system patented?

The badge is probably patented, as it is commercially available with different coatings for other chemicals; the analysis method is patented to Uwe Karst and Martin Vogel.

Did you experience any setbacks in your research?

Like in every PhD research there were a few puzzles to solve. At first the device did not work at high humidity, whereas it did with a different reagent. We found that the filter material was accumulating humidity and the hydrophobic reagent was displaced from the filter surface. We could solve those problems by using different filter types.

What did you specifically like about your research?

The fact that is so close to real life.

What didn’t you like?

The fact that I did not have my own mass spectrometer. I am only kidding of course, but the fact is that I did about 150 experiments, each of which needed far more than 24 hours measuring time and obviously encountered waiting times to do my measurements.

What are you going to do next?

In August I have already started my new job at Collano AG (polymer industry) in Switzerland as Head of Analytics.

For the summary of the thesis, click here.

Voor de samenvatting van het proefschrift, click hier.