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Guiding the way for on-line gas analysis

The pharmaceutical industry needs to monitor hazardous gases and vapours.

Monitoring low levels of hazardous gases in the workplace is not easy, especially if you want real-time, on-line results rather than taking samples away to the laboratory to be tested. An SME, a university and a research institute worked together to develop novel hollow waveguide technology to accurately perform on-line chemical analysis of vapours and gases. As industry is responsible, under legislation, to monitor hazardous gases and vapours, the market potential for the system is significant.


European Directives state that workers must be protected from exposure to carcinogenic agents and the employer is obliged to determine the nature, degree and time that workers are exposed to such agents.

The problem with many health hazards in industry is that it can be a technical challenge to detect and measure them on site. When it comes to toxic gases and vapours, the difficulty is compounded. Often, they are considered to be dangerous even at very low levels - in the range of parts per billion (ppb) or parts per million (ppm).

A recent project, supported by the Measurements and Testing programme, developed novel technology, namely optical waveguides for sensing toxic and hazardous gases using infra-red tunable laser technology, and showed that it could be used for real-time, on-line applications. Techniques like these are preferred to the extractive sampling approach that currently prevails.

Improved sensitivity

The optical waveguides and fibres applied were capable of transmitting infra-red radiation. A further feature concerned the use of hollow waveguide sensors which contained the sample as they directed the laser signal for interaction. Mid Infra-red tunable diode lasers and a CO2 gas laser were used as their absorption by the sample can provide detailed and sensitive analytical data. The team - an Italian SME, a British university and a French research institute - demonstrated that these techniques are sensitive enough to measure several toxic gases at levels in the region of ppm to ppb. In particular, they used examples of aldehydes and nitrosamines.

"Using hollow waveguides, very small sample volumes of gas or vapour can be measured giving good measurement response times," explains Clive Worrell, the project coordinator from the University of Sussex. "Optical fibres enable the remote location of sophisticated instrumentation away from hostile or hazardous environments and different types of waveguides can be applied depending on the system or measurement needs. There is an extensive range of gases and vapours to which this approach is relevant."

Gas mixtures to test the instrument

To test the accuracy of the system, two new calibrated vapour mixtures, containing between 0.6 and 30 ppm of volatile organic compounds - or VOCs, were prepared. The new technology was used to measure the vapour level and the results were validated against those obtained with chromatography, a traditional, off-line analysis technique.

According to Dr Worrell, the development of cost-effective analytical measurement techniques for monitoring hazardous gases has been stimulated by recent requirements and legislation concerning environmental and safe work practices as well as by the need for product testing and more efficient process control. If the product is tested on the production line, the manufacturing processes can be altered quickly in comparison to testing which requires samples to be taken to the laboratory. The potential cost savings of moving process control on-line are great.

Market opportunities

The European market for flammable and toxic gas sensors can be estimated in terms of the number of measuring points in industry, although the number of instruments needed to measure VOCs is difficult to estimate as accurate and sensitive instrumentation is largely absent at the moment. Nevertheless, there is a need for these instruments, driven by the emerging legislation. This will evolve into a significant market for on-line chemical sensing. Relevant industrial sectors include chemicals, petrochemicals and agrochemicals, and particular product areas comprise plastics, rubbers and paints amongst others.

These could provide more significant opportunities than the environmental monitoring applications, particularly with the need for ever more efficient industrial processes.

The project results have been communicated to the academic community through reputable scientific journals and the Italian partner, TRI, is currently developing plans to commercialise the product. As well as demonstrating that this new measurement technique works, the consortium is also involved with a European Standard entitled "Control gas mixtures to be used within the framework of European Standard: stationary source emissions".



Project Title:  Remote Monitoring of Hazardous Gases and Vapours using Mid Infra-red optical fibres

Programmes: Measurements and Testing
Contract Reference: MAT4-CT94-0026

Cordis DatabaseFor more information on this project,
go to the Cordis Database Record