Autosampling system for gas chromatography

Content

• Features and advantages
• Principle and flow chart
• Conventional technique vs. "in vial purging"
• Micro-packed trap
• Cryo focussing with LN2, CO2 or Peltier
• Available water traps
• Analytical performance
• Methode configuration
• Technical data

Features and advantages

• ultra trace analysis of volatile organic compounds (VOCs) with detection limits in the ppt range
• "in vial purging" with 20 ml headspace vials - no purge vessle - no blank runs
• one micro-packed trap for all polar and non polar analytes - no multiple beds of various sorbent materials
• multi matrix sytem for liquid, solid and mixed samples (drinking water, wastewater, foil, paper, soil, sludges, flavor, food, spices,...)
• micro-packed 1/16" trap for excellent peaks and detection limits down to the lower ppt-range
• cryo-trap with liquid nitrogen, liquid carbon dioxide or Peltier-cooling system
• reliable water trap technology for polar and non polar analytes with separating rates up to 99.9%
• best performance for the European water standard EN ISO 15680
• for all capillary columns with an inside diameter of 0.15 to 0.53 mm
• system pollution avoided by an optical foam sensor
• dead volume free construction with short and inert lines
• optimized flash heating guarantees perfect desorption of the analytes from the trap to the GC column
• direct (e.g. HP6890, Shimadzu 17A, Fisons Mega/Vega) GC adaption or via transferline
• small dimensions 41 x 33 x 39 cm (w x h x d)
• high sample throughput with low personal costs guarantees a fast amortization of investments
• compact and reliable purge and trap system - "made in Germany"

Principle and flow chart

The new device concept allows for the first time a direct purging of volatile substances from 20 ml vials, which can be filled with solid or liquid samples. Each vial is moved into a heated sample unit, where a long and a short needle penetrates the sealing septum. All volatile substances are purged and enriched in the micro-packed trap. Here the substances are froozen out with liquid nitrogen or CO2 or a Peltier cooler and finally transferred by fast thermal desorption to the gas chromatograph. As the purged water is seperated from the sample in a chemical, membrane or peltier water-trap, very sensitive detectors like a flame ionization detector, a mass spectrometer or an atomic emission detector can be used. Via a sample loop additionally internal standards or regents can be added into the sample. After processing a sample, the needles and the watertrap are backrinsed with carrier gas, impurities and water are removed securely from the system. 

Conventional technique vs. "in vial purging"

The following figures show the gas flow of the conventional technique and the "in vial purging" of the PTA3000. The advantages during the purging process can be seen:

Micro-packed trap

The system performance and low detection limits attainable with the PTA3000 are particularly due to the very small adsorbent volume in the micro-packed trap. In the stable trap with an outside diameter of 1/16" different adsorbents (Cromosorb G HP, Tenax TA...) can be micro-packed. The minimum thermal mass of the trap allows a fast desorption with approx. 900°C/min , whereby excellent peak forms are obtained.

Cryo-focussing with LN2, CO2 or Peltier

During the purging process the purged substances are concentrated by freezing out in the mikro-packed trap. The cooling of the trap can be reached by different techniques:

• liquid nitrogen LN2: -160°C, 10 l Dewar
  
• iquid carbon dioxide CO2: -65°C, CO2-bottle 
• Peltier elements: -35°C, water cooling system with integrated sensor control

Available water traps

With the analysis of water samples it is important to separte the purged water. According to the substances the separation can be done with differnet water trap techniques:

• PWT Peltier water trap: polar substances
  
• CWT chemical water trap: for non-polar substances 
• MWT membrane water trap: non-polar substances
  
• none: for all substances, only for absolute dry samples
  

The water traps hold back up to 99.98% of the purged water and allows perfect chromatography. Since the water traps are installed on the top side of the PTA3000, a simple exchange is possible.

Analytical performance

The micro-packed trap, kryo focussing, inert lines and the "in-vial-purging"guarantee best performance and low detection limits. In the following some chromatograms and the list of measured substances are shown:

• Chromatogram 1: substances from US EPA524.2, 2ppb in water, FID
  
• Chromatogram 2: validation of vinyl chloride, 100ppt, 0.1ppt
• List of measured substances
• List of measured substances in olive oil
• Analysis with internal sample loop

If you have any questions or problems with your purge-and-trap system do not hesitate to contact us. We can send you different chromatograms in the range of food, liquids, soils, spices, cardboard, paper, oils...

Method configuration

The editing of the methods can be done dialog-guided and directly via the PTA3000 keyboard or with the method editor PTAWIN at the PC. Up to 30 different methods can be stored in the PTA3000. The possible method parameters and the appropriate input limits become obvious from the following PTAWIN mask: 

Technical data

Vials:	number: 20; volume: 20ml; dimensions: D=23mm; H=79mm; septa: silikon-PTFE (ultra low bleed)
Trap:	diameter: 1/16" glas lined tube; Chromosorb or Tenax or customer specific
Signals and interfaces:	RS232; GC-Ready; GC-Start; PTA-Ready
Electrical control:	16bit processor; 512k RAM; 128k ROM; graphic display 240x128 pixel
Installation conditions:	power supply: 230V; 50 Hz; power consumption: 450VA; weight: 20 kg; ambient temperature: 15-25°C
GC-connection:	via transfer line or direct
Gases:	carrier gas: He 5.0; cryogenic gases: LN2 or CO2; dry N2

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