NPL has successfully tested the miniaturisation of gas chromatography (GC) equipment for environmental testing, in collaboration with the Atmospheric Chemistry Group at the University of York and Dolomite (a UK company specialising in manufacturing micro-structured components).

The MEMS (micro-electro-mechanical- system) device, the size of a CD, is constructed on a glass chip, 300µm thick, fabricated with isotropic channels, which replace the capillary structure that is characteristic of standard GC columns.

This microfluidic miniaturisation enables the production of portable, robust and low power GC systems suitable for environmental applications such as monitoring trace atmospheric components and detecting toxic vapours.

It contains two columns (7.5 m and 1.4 m long) that have been uniformally coated at NPL, allowing the separation of monoaromatic and monoterpene species at the parts per million (ppm) level.

The microfluidic glass GC device with a low power photoionization detector (PID) offers substantial potential as a field portable GC instrument and is a useful alternative to typically square channelled silicon devices of restricted physical size and higher material cost. In common with other planar GC approaches, the ability to directly cool this device using the Peltier effect may offer substantial advantages over typical cryogenic cooling of drawn capillaries in standard GC ovens for the analysis of very volatile species. The low power GC-PID device showed good performance for a small set of VOCs (Volatile Organic Compounds) and sub ng detection sensitivity to monoaromatics.

This research has shown that microfluidics is an enabling technology for the next generation of environmental testing equipment. It provides in-situenvironmental monitoring capabilities with the possibility of a more rapid response to adverse changes in air quality. The results have been published in the Journal of Chromatography A (A Lewis et al, J Chrom A, 1217(20100) 768-774).

Chromatogram showing separation of the 10ppm BTEX standard gas mixture. 0.5mL sample loop in combination with the planar glass 7.5m GC column programmed from 10 to 100 °C at 20 °C/min heated using Peltier and resistive elements. Detection is by low power photoionization detector.

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