Rapid test for chemical weapons detection

TNO has designed a new test to identify the use of chemical warfare agents directly in the field. The chemical industry and forensic researchers also see potential applications. 'Such a simple design and it works extremely well.'Also read the article: Looking for evidence of chemical attackThe technique in question, near-infrared spectroscopy, is already used for other applications such as identifying narcotics. 'With this technique we can measure through a bag of powder, which is kind of safe,' says Jelle de Koning, researcher at TNO's Chemical, Biological, Radiological and Nuclear Protection Department and PhD student at the University of Amsterdam. 'But a method to measure hazardous liquids, such as chemical warfare agents, with this technique was not yet available.'The advantages are clear: this form of spectroscopy is lightning-fast, reproducible, relatively cheap and can measure through materials such as plastic and glass. Ideal for analysing hazardous liquids.TNO researcher Jelle Koning conducting tests in the laboratory. The screen displays the near-infrared spectrum of the liquid being measured. Photo: TNO Liquid samplesFor a measurement, a sample container is placed on a detector. Near-infrared light shines through it and the light reflecting off the contents goes back into the detector which records the signal. 'With a solid, a lot of light is reflected back and measuring a signal is not a problem, but with clear liquids, which are chemical warfare agents, this is not the case,' says De Koning.In the food industry, among others, liquid samples are measured through with this technique, but those systems are expensive, complex and also open. 'The substances we work with are highly toxic and reactive,' says De Koning. 'You don't want to touch those at any time.'For field measurements, a small box containing the sensor and a display for the results will suffice. The near-infrared light shines upward through the glass vial and the liquid, is reflected by the reflective material, passes back through the liquid, and then returns to the detector, which registers the signal. Image: TNO Mini measurement systemTo solve all these practical problems at once, De Koning started designing himself. This started with a simple cobbled-together system of a glass jar into which a stick fitted with reflective material fits, held together by tape. This design turned out to work with test liquids, such as transparent organic solvents. 'The result is best when the liquid is trapped without air between the glass and the reflective material. A layer thickness of half a millimetre proved best for a range of liquids. Only a hundred microlitres are then needed to measure. That's fine is because these are extremely toxic substances.'In the end, De Koning tested a number of different classes of chemical warfare agents, such as blister agents and some nerve gases. 'This kind of measurement is very sensitive to variation in the thickness of the glass bottom and the layer of liquid. That determines the strength of the measurement signal,' says De Koning. 'To make reproducible measurements, each jar has to be exactly the same.3D glass printingAccording to De Koning, the best method to produce jars with as little variation as possible is 3D glass printing. For this, he worked with a glassblower from the University of Amsterdam who also specialises in glass processing. 'He made jars for us in different ways. First by "hand", then with the printer.'This goes as follows: a kind of resin contains the material to be printed. For 3D glass printing, these are silica particles with a number of other additives. By shining focused light on the resin, it turns into a hard, glass-like material at that spot. This still has to harden in the oven into real glass, a type of quartz glass that has very good light transmission for near-infrared spectroscopy and gives a nice signal. 'With a 3D printer, we can make all the shapes and sizes we want, including threads that fit exactly into a standard cap.'The solution for reflective material that traps the liquid layer in the jar was a kind of PTFE 'cork' that fits into a standard cap for laboratory equipment. 'That makes the system relatively cheap. PTFE is a Teflon-like material that is chemically very inert so the chemical pesticide does not react with it. Otherwise, you measure something completely different from what you put in.'After the glass sample jar is produced using the 3D glass printer (left), it must be cured in the oven (center). It is then ready for use (right). Photos: TNO Stably locked upThe current design is a completely sealed system, from which nothing can escape. 'We also conducted stability tests to see if the substance in the jar changed over time. There too, we found no effect.' After being measured in the field, these jars can be safely taken to the lab for confirmatory testing, and then destroyed.Using near-infrared has more advantages. The small sensor, the size of an average flat eraser, fits into a variety of enclosures. For example, one fitted with a display that shows immediately what kind of dust is involved and what measures need to be taken. 'You can also put the sensor on a circuit board, allowing you to link the system to a database with profiles of known hazardous chemicals and measures.' For this, De Koning worked with the developer of the near-infrared detector TIPb and the University of Amsterdam.ResilienceDe Koning received enthusiastic reactions to the scientific publication with accompanying drawings of how such jars can be made: 'Such a simple design and it works really well,' was the response. There was also interest from the chemical industry and from forensic investigators who sometimes have few samples available or are at an illegal lab or storage site.'Apparently more people were running into the problem of being able to test liquids quickly, safely and properly.' And because this technique is reasonably affordable, more people can be equipped with such a detector. That in turn contributes to resilience, De Koning believes. 'The faster you can measure in all kinds of locations, the earlier you can take measures to prevent spread or casualties.'Opening photo: TNO

Rapid test for chemical weapons detection

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