Cryogenic colling for Agilent 6890 GC

[ap01]

Hello,

I am using an Agilent 6890 GC (with MSD) to analyse for BTEX and other volatile hydrocarbons in groundwater using SPME extraction. To attain an initial oven temperature of 30 degC we are using liquid CO2 for cooling. The ambient temperature setting (in ChemStation software) is set to 25 degC, Quick Cooling is set OFF, Timeout Detection is ON and Fault Detection is ON. Ambient room temperature in the lab is about 25-28 degC, but sometimes reaches 30 degC. The system has worked well but we go through a standard size cylinder of LCO2 (50 lb of CO2) in about 20 analyses. Is this to be expected? I had hoped that the cylinder would last longer. Any comments and suggestions most welcome.

Thanks.

Andrew

[Ron]

Sounds about right based on use of cryocooling several years back. Maybe you can use a thicker phase column, or one of the micro-cryo traps like SIS sells?

[xxx]

Your CO2 consumption seems ok ,we use here cryocooling for a ptv,wich needs less co2,and the cylinder last 250/300 analyse,for your oven where the volume is higher,this would not last longer as 20/30 analysis.

A thicker film,would let you start with 40°C,where you don't need cryocoolling .

See you

[chhubert]

You may use other columns (e.g. DB-VRX) specifically designed for VOC analysis. They provide good retention at above ambient temperature.