Versatile sampling system
for gas chromatography

VSP4000 purge and trap

IMT is specialized in sample preparation of  Volatile Organic Compounds (VOC) and offer a well proven and reliable solution for ultra low trace GC-MS analysis. The "purge-and-trap" system VSP4000 is characterized by carry-over free long therm results based on the unique "in-vial" purging without a purge vessel. The system has certain advantages in the analysis of water.

Content


Features and advantages

  • ultra trace analysis of volatile organic compounds (VOCs) with detection limits in the lower ppt-range (ng/kg)
  • best performance for the European water standard EN ISO 15680
  • unique "in vial purging" - no glass sparkler - no blank runs - no hot water rinse

 purge and trap in vial purging VSP4000

  • 80 vials, 20ml; multi matrix system for liquid, solid and mixed samples (drinking water, surface water, ground water, wastewater, foil, paper, soil, flavor, cosmetics, food, spices, ...)
  • one type of micro packed trap for all polar and non polar substances - no multiple beds of various sorbent materials
  • integrated Peltier cryo-trap at - 35C, holds even dichlorodifluoromethane
  • automatic dosing of gaseous or liquid Internal Standard via sample loop
  • temperature of all components in the purge-and-trap mode up to 200C
  • split-flow up to 50 ml/min by a massflow controller
  • for all capillary columns with an inside diameter of 0.15 to 0.53 mm
  • control of the system parameters by: optical foam sensor, EPC, MFC
  • high sample throughput with low personal costs guarantees a fast amortization of investments
  • compact and reliable purge and trap system  - 100% "Made in Germany"


Principle and flow chart

The sophisticated concept allows for the first time - without any purge vessel - a direct purging of volatile substances from 20 ml vials, which can be filled with solid or liquid samples and optional from thermal desorption tubes. In the purge-and-trap mode, 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. The purged water is seperated from the sample in a Peltier or membrane water trap.  The purged substances are froozen out by a Peltier cooler at -35C and finally transferred by fast thermal desorption to the gas chromatograph. The cooling temperature at -35C  is necessary to hold all analyts on the trap during purging process. By use of a sample loop, additionally internal standards or regents can be added to the sample vial. After processing a sample, the needles and the watertrap are backrinsed with carrier gas, impurities and water are removed securely from the system.

The inert sample pathway and the absence of a glass sparkler guarantees very low detection limits and nearly no carryover.

VSP4000 gasflow chart


Conventional techniques vs. "in vial purging"

The following figure shows the gas flow of the conventional technique and the "in vial purging" of the VSP4000. The analytical advantages during the purging process are evident.

VSP4000 in vial purge advantages

Due to the "in vial purging" of the VSP4000 system combined with  inert analytical tubing material and without using a glass sparkler,  the system archives an excellent performance  in the lower ppt range  with very low carryover and typical standard deviations less than 5% - even years later.


Peltier cryo focussing of the micro-packed trap at - 35C

The system performance and low detection limits attainable with the VSP4000 are particularly based also on  the very small adsorbent volume in the micro-packed trap. In the stable trap with an outside diameter of 1/16" different adsorbents (Tenax TA, Chromosorb G HP...) can be micro-packed. All substances from US EPA 524.2 can be measured with one trap material. With one trap material more than 100 different analyts can be measured and about 2000-3000 runs can be done. The minimum thermal mass of the trap allows a fast desorption with approx. 900C/min, whereby excellent peak forms are obtained.


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 and non polar substances, working at -15C....-20C 
  • MWT  membrane water trap: non-polar substances, working at -45C
  • none: for all substances, only for absolute dry samples, working up to 280C
Since 2000 the water trap of our purge-and-trap systems are positioned directly after the sample. The water removal is not before/during  the desorbing process . This unique VSP4000 advantage is necessary for the excellent system performance in the lower ppt-range.


Analytical performance in the mode purge-and-trap

The performance of the system is mainly based on the mikro packed trap, the cryo focussing and the
"in vial purging".


Option: Thermal desorption up to 280C

The system can be converted from purge and trap mode to thermal desorption mode by a simple modification. This will allow the analysis of stainless steel sample tubes filled e.g. with Tenax TA, paper or by the use of 20 ml standard glass vials filled with the sample material.

VSP4000

The stainless steel sample tube is placed in the axis of a special stainless steel vial with the shape of a 20 ml headspace vial. During the purge process of the sample tube the carrier gas passes the sample tube upwards which is filled with Tenax at a volume of 1ml at maximum. All adsorbed substances of the Tenax are transported to the micropacked cryo-trap. The sample, all tubes and fittings are heated at a temperature of 280C. Also substances with a higher boiling point of 280C can be analysed with a high recovery.

The stainless steel sample tubes can be packed with leather, foil, plastics granules or any sample material. Also the sample tubes can be externally loaded.

VSP4000 sampling methods  

Possible adsorbent material for filling the TD sample tubes:

NAME ADSORBENT MATERIAL Size / Mesh Desorb.- Temp. Surface m2 / g
Carboxen 1000 Carbon molecular sieve 60/80 330C 1200
Carbopack C Graphitisized carbon 60/80 330C 10
Tenax TA Polymer 60/80 300C 35
Chromosorb 106 Polymer 60/80 180C 795
Coconut Charcoal Carbon 20/40 180C 1070


Analytical performance in the mode thermal desorption


Option:  Tedlar Bag sampling

For the sensitive measurement of VOC's in gases or air samples up to 14 pcs Tedlar bags are automatically analyzed. For this purpose, a 1.2 m high aluminum panel is mounted on the left side of the VSP4000. The bags with a volume of 5 liter are connected  on  both sides of the panel.  No additional laboratory space is necessary for the Tedlar bags.  Needles and FEP tubes are connected to a multi-port valve of the VSP4000, to select the appropriate method in the software.

The following picture shows the adaption of Tedlar bags to the VSP4000:

vsp4000_voc_tedlar_bag_sampling

Technical data

Vials (P&T): number: 80; volume: 20ml; dimensions: D=23mm; H=79mm; screw-caps; septa: silikone-PTFE
Desorption tubes (TD): number: 80; material: stainless steel; inner diameter: 5 mm; outer diameter: 6 mm; length: 70 mm; max. volume: 1 ml
Trap: diameter: 1/16" GLT-tube; different adsorbents availabel ( e.g. Tenax  for more than 100 analyts,  Chromosorb, ,...)
Signals and interfaces: USB; GC-Ready; GC-Start; VSP-Ready
Electrical control: 16bit processor;  graphics display
Installation conditions : power supply: 230V; 50 Hz; power consumption: 1100VA; weight: 35 kg; dimensions: 67x 70x 57cm (wxhxd); ambient temperature: 15-25C
GC connection: transfer line, length: 1.5m
Gases: carrier gas: He 5.0, dry N2

Contact IMT for further informations or your local distributor.

Download VSP4000

The VSP4000 system can be installed on every GC type  !

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