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  • Toward a microfabricated preconcentrator-focuser for a wearable micro-scale gas chromatograph.

Toward a microfabricated preconcentrator-focuser for a wearable micro-scale gas chromatograph.

Journal of chromatography. A (2015-11-05)
Jonathan Bryant-Genevier, Edward T Zellers
ABSTRACT

This article describes work leading to a microfabricated preconcentrator-focuser (μPCF) designed for integration into a wearable microfabricated gas chromatograph (μGC) for monitoring workplace exposures to volatile organic compounds (VOCs) ranging in vapor pressure from ∼0.03 to 13kPa at concentrations near their respective Threshold Limit Values. Testing was performed on both single- and dual-cavity, etched-Si μPCF devices with Pyrex caps and integrated resistive heaters, packed with the graphitized carbons Carbopack X (C-X) and/or Carbopack B (C-B). Performance was assessed by measuring the 10% breakthrough volumes and injection bandwidths of a series of VOCs, individually and in mixtures, as a function of the VOC air concentrations, mixture complexity, sampling and desorption flow rates, adsorbent masses, temperature, and the injection split ratio. A dual-cavity device containing 1.4mg of C-X and 2.0mg of C-B was capable of selectively and quantitatively capturing a mixture of 14 VOCs at low-ppm concentrations in a few minutes from sample volumes sufficiently large to permit detection at relevant concentrations for workplace applications with the μGC detector that we ultimately plan to use. Thermal desorption at 225°C for 40s yielded ≥99% desorption of all analytes, and injected bandwidths as narrow as 0.6s facilitated efficient separation on a downstream 6-m GC column in <3min. A preconcentration factor of 620 was achieved for benzene from a sample of just 31mL. Increasing the mass of C-X to 2.3mg would be required for exhaustive capture of the more volatile target VOCs at high-ppm concentrations.

MATERIALS
Product Number
Brand
Product Description

Supelco
Carbopack X, glass TD tube, fritted, O.D. × L 1/4 in. × 3 1/2 in., preconditioned, pkg of 10 ea
Supelco
Carbopack Adsorbent, matrix Carbopack B, 60-80 mesh, bottle of 10 g
Supelco
Carbopack B, glass TD tube, fritted, O.D. × L 1/4 in. × 3 1/2 in., preconditioned, pkg of 10 ea
Supelco
Carbopack Adsorbent, matrix Carbopack X, 60-80 mesh, bottle of 10 g
Supelco
Carbopack Adsorbent, matrix Carbopack X, 40-60 mesh, bottle of 10 g
Supelco
Carbopack Adsorbent, matrix Carbopack X, 120-400 mesh, bottle of 50 g
Supelco
Carbopack Adsorbent, matrix Carbopack C, 60-80 mesh, bottle of 10 g
Supelco
Carbopack Adsorbent, matrix Carbopack C, 80-100 mesh, bottle of 10 g
Supelco
Carbopack B, glass TD tube, fritted, O.D. × L 1/4 in. × 3 1/2 in., unconditioned, pkg of 10 ea, matrix Carbopack
Supelco
Supel-Inert Multi-Layer Foil, maximum volume 10 L, Push/Pull Lock Valve (PLV), pkg of 10 bags
Supelco
Carbopack B, stainless steel TD tube, O.D. × L 1/4 × 3 1/2, unconditioned, pkg of 10 ea
Supelco
FLM Carbopack X Deactivated Stainless Steel TD Tube, preconditioned, pkg of 10 tubes, O.D. × L 1/4 in. (6.35 mm) × 3 1/2 in. (89 mm)
Supelco
Carbopack B, O.D. × L 1/4 in. × 3 1/2 in., glass TD tube, fritted, Sealed with Brass Endcaps, preconditioned, pkg of 10 ea