Headspace preconcentrator

Entech Instruments has released the 7150 Headspace Preconcentrator, designed to recover thermally labile compounds for GC and GCMS applications, such as those containing sulfur, phosphorus and nitrogen compounds.

The 7150 is able to recover C2 to C25 compounds at ppm to sub-ppb levels, including labile compounds unable to survive strong adsorbents or a hot GC injector.

A first stage implements ‘active SPME’ allowing compounds from C12 to C25 to be trapped and desorbed quantitatively. The initial SPME stage eliminates the exposure of heavy VOCs and SVOCs to strong adsorbents, allowing their effective recovery and transmission to the GC.

Lighter, unretained compounds that are typically missed using classical, diffusion-based SPME are recovered utilising a CO₂ cooled Tenax trap. Cold trapping allows recovery of sulfur compounds, amines and other thermally labile compounds.

Active SPME utilises a PDMS (polydimethysiloxane) coating that is similar to most SPME filaments, but places this coating into a precise, actively swept flow path allowing a known volume to be collected for quantitative measurements (up to 1000 cc).

Active SPME also features a much thinner PDMS film, reducing siloxane bleed and ensuring carryover elimination before any subsequent sample analysis. Lighter analytes not retained within the Active SPME trap are collected on cold Tenax, allowing for true quantitation of both the light and heavy headspace compounds.

Dean Switching rather than rotary valves is used to control flows, eliminating absorptive surfaces and dead volume associated with the carryover of heavier and more polar compounds. Moisture is removed prior to GCMS sample injection using direct vapour to solid phase cold trap dehydration that does not cause the loss of other headspace compounds.

The combination of quantitative volume measurements and recovery of the widest range of GC compatible headspace compounds enables the true determination of aroma-significant compounds during food and flavour testing. The 7150 system is compatible with the Entech 7405 and 7500A robotic autosamplers for R&D and production laboratory applications.

Other applications for the instrument include environmental testing (air, water and soil), industrial hygiene, breath analysis, forensics, product testing, homeland security, package testing, and residual solvent testing in pharmaceuticals.