Performance Abstract on the EST-4200 Ultimate Vapor Tracer Page 2

Chemical Profiling with High Speed Gas Chromatography

 

A portable chemical profiling system (Figure 1) incorporating an ultra-high speed chromatography column, a solid-state sensor, a programmable gate array microprocessor, and an integrated vapor preconcentrator is able to speciate and quantify the vapor chemistry within a cargo container in 10 seconds.  Vapors within the container are sampled by inserting a sampling tube attached to the inlet of the instrument through a small opening in the container door (Figure 2).

 

          The EST-4200 Ultimate Vapor Tracer

 

 

 

 

 

 

 

 

 

 

      Figure 2- Portable chemical profiling system

         incorporating an ultra-high speed  gas

 

 

 

 

 

 

 

 

 

 

The chromatograph system (Figure 4) contains a minimum number of parts and temperature programming a directly heated capillary column at rates as high as 18 degrees C/second produces 10 second chromatograms. A small capillary trap filled with tenax preconcetrates sampled vapors and injects them into the capillary column. A key component of the system is a solid-state sur­face-acoustic-wave (SAW) detector which has zero dead volume and can detect quantities as small as one picogram.   The sensitivity of the de­tector chip (0.100 x 0.100 inch) is de­pendent upon tempera­ture which is electroni­cally controlled by means of a Peltier ther­moelectric element.

 

      

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

            Figure 4- Diagram of high speed GC and details of SAW detector.

 

 

Olfactory Images and Virtual Chemical Sensors

 

The SAW sensor is non-ionic and non-specific.  It directly measures the total mass of each chemical compound as it exits the GC column and condenses on the crystal surface, causing a change in the fundamental acoustic frequency of the crystal.   Odor concentration is directly measured with this integrating type of detector.  Column flux (conventional chromatogram) is obtained from a microprocessor which continuously calculates the derivative of the SAW frequency.

 

Plotting sensor frequency change (radial) vs elution time (angle) produces a high- resolution 2-dimensional olfactory image called a VaporPrint™ as shown in Figure 5.  These images display the entire odor chemistry and enable the chemical profiling system to recognize complex odors and fragrances based upon their full chemical signature.

 

Different chemicals have different retention times and this allows for the creation of hundreds of specific virtual chemical sensors and sensor arrays for performing trace detection.  Virtual chemical sensors (Figure 6) combined with odor profiles are effective methods for recognizing the signature of known hazardous materials.

 

Retention time indices (Kovats) of known chemicals relative to n-alkanes al­lows the use of a chemical library and electronic odor profiles that can be shared by many users.  Users can quickly distribute and share odor profiles of cargo, new threats, or contraband of any kind.    Next Page>>>

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

          Figure 5- VaporPrint™ olfactory images                                       Figure 6- Virtual Chemical Sensor Arrays

                                                                                                     

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Figure 3- Vapors are sampled by inserting a probe attached to the inlet of the instrument into a small re-sealable hole in the container.