GERSTEL Cooled Injection System (CIS)

The most widely sold PTV inlet in the world

Since Martin and Synge invented gas chromatography (GC) in 1940, a steady stream of innovations has improved performance and reliability of GC instrumentation. The GC technique is one of the most widely used for the determination of volatile and semi-volatile organic compounds (VOCs and SVOCs). Among the significant developments along the way were the temperature programmed GC oven, capillary columns, selective detectors and modern sample inlets, such as the Programmed Temperature Vaporizer (PTV). The PTV improved performance by ensuring discrimination free analyte transfer to the GC column and enabling analyte concentration. The GERSTEL Cooled Injection System (CIS) with the patented septum-less head (SLH) was first introduced 25 years ago. Today, the 4th generation CIS is the most widely sold and installed PTV-type inlet in the world.

With the introduction of the 5890 GC in the 1980s, Hewlett Packard set itself firmly on the path to becoming the leader in GC instrumentation. The 5890 GC was designed for capillary columns, it had a powerful autosampler and it was equipped with Electronic Pressure Control (EPC) for the carrier gas, enabling optimized GC separation for analytes over a wide boiling point range. These advances clearly exposed the limitations of the sample inlets available at the time. In hot inlets, solvents and volatile analytes would evaporate extremely quickly in an uncontrolled manner giving rise to discrimination and reduced recovery, especially for high-boiling compounds that would condense in unheated areas around the GC inlet. In addition, thermally labile analytes were also prone to decomposition when exposed to temperatures needed to quickly vaporize a sample.

In 1984, GERSTEL introduced the Cooled Injection System (CIS). The patented CIS is a Programmed Temperature Vaporizer (PTV), often referred to as a “Universal GC Inlet”. In contrast to permanently heated GC inlets, the CIS enables introduction of liquid sample a low temperature followed by programmed heating with controlled evaporation and transfer of analytes to the GC column. The result is better separation, improved recovery, lower detection limits, and more accurate quantitative results.
The description “Universal GC Inlet” refers to the unique flexibility of the CIS. It can be used for either hot or cold injection combined with split, splitless, or direct on-column analyte transfer. The CIS can be cooled to temperatures as low as – 180 °C making it uniquely suitable as cryo-trap for VOC analyte concentration in combination, for example, with Thermal Desorption. Additionally, the CIS can be used to concentrate analytes through Large Volume Injection (LVI) with solvent venting. This provides to substantially lower limits of detection. PTV and LVI injections are typically performed using GERSTEL exclusive cryogen-free peltier or cryostaic cooling.

Depending on the required starting temperature, cryogenic cooling may also be used. At the other end of the temperature scale, the CIS 4 operates up to 450 °C for determination of SVOC, PAHs and some waxes. The high temperature version (CIS 6) scales the heights up to 650 °C, enabling pyrolysis of polymers in suspension following initial evaporation of the solvent. Whichever version the analyst is using, all CIS inlets are based on patented heating and cooling systems and optimized inlet liner dimensions that provide uniform temperature profiles throughout the entire – 180 °C to 650 °C temperature range for controlled evaporation and best possible results.

CIS benefits

  • Improved quantitation due to controlled evaporation and discrimination free analyte transfer.
  • Improved limits of detection, improved identification and improved quantitation through sharper peaks.
  • Lower background signal, no septum bleed, improved detection limits thanks to patented Septum-Less Head (SLH).
  • Best possible transfer and recovery of thermally labile analytes due to patented heating system and freely programmable heating rates.
  • Reliable analysis of samples with high matrix load using Automated Liner EXchange (GERSTEL ALEX).