Automated Vapor Sampling -Transfer Line Gas Chromatography (AVS-TLGC)

What is AVS-TLGC?

AVS-TLGC is the powerful combination of a unique pneumatic sampling system, known as Atmospheric (or Automated) Vapor Sampling (AVS), and a high speed capillary gas chromatography approach known as Transfer Line Gas Chromatography (TLGC). The AVS is a gas phase sampling system designed to eliminate the sample loss problems of conventional syringe, sample loop or trap-and-desorb injection systems. The sample handling portions of the AVS system are constructed from the same materials as capillary GC columns. There are no intervening valves, pumps or other analyte adsorption sites in the sample path (see Figure 1.) AVS operation uses pneumatically controlled carrier and analyte gas flows to control the timing of sample introduction. This involves periodically exchanging the carrier gas flow in the second tube for sample flow in the opposite direction, then restoring the carrier gas flow as a diffusion barrier against additional sample flow. This approach allows millisecond resolution of injection pulse widths without additional sample adsorption sites. The GC separation is actually performed in the capillary flow restrictor of a mass spectrometry system, known as a "transfer line". The title "Transfer Line Gas Chromatography" indicates that the GC conditions are optimized (based on both separation and flow rate considerations) using variations in the column length and radius in the context of fixed pressure drops from ambient conditions to the detector.
 The AVS-TLGC approach was conceived for on-line measurement of ambient atmospheres to protect U.S. soldiers against chemical attack. This approach is naturally extended to measuring hazardous industrial chemicals or environmental pollutants. In addition to sampling local atmospheric chemical environments, the technology can be coupled into a number of on-line applications including:

Systems ranging from microscale reactors with 100 µm coal particles to 600 MW power plants have been successfully monitored using AVS-TLGC technology at reactor pressures between 0.5 and 70 atm.

The technology has been implemented into two FemtoScan products: the Enviroprobe Module and the Enviromental Vapor Monitor (EVM) II.

These products were developed to address a number of real-world analytical problems based on a new analytical paradigm. Simply stated: "every sample handling step and every minute waiting for a result cost you money!" Therefore, the most expeditious way to tackle an analytical problem is to provide on-line or in-situ sampling, thereby paving the way for real-time analytical results to be ready for immediate on-site use. In real-world applications, this is easier said than done. Real-world samples involve mixtures. In order to separate and quantitate mixtures of analytes and interferants, the analytical chemist requires either off-line sample preparation or powerful on-line analytical methods capable of separating the target constituents. AVS-TLGC is designed to apply the latter approach to gas phase analytes in a way that is consistent with the on-line, in-situ, real-time, on-site philosophy.

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Additional links:

  FemtoScan - The Company
  Product - Enviroprobe Module
  Product - Enviromental Vapor Monitor (EVM) II
  Product - HYPHEN Software
  Application Note 9701 - Detection of Pesticide Vapors ...
  Application Note 9702 - Examining the Analytical Capabilities...
  Application - University of Utah Roving GC/MS and TG/GC/IR/MS
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Page last updated  on 7/19/99