Chromatography Forum

Dear Colleagues:

I intend to install a 6-port sampling valve (Valco Instruments) over the inyection port of a GC/ MS. Its a 2 positions valve with 1 / 16 " fittings and 0.75 mm ports. Anyone know what is the minimum inlet pressure that must have the sample flow to enter the valve?.

The sample is a gas flow coming from TGA/DSC (around 60 mL/min and slightly higher than atmospheric pressure).

Thanks a lot

Cris.

A 6 port valve is usually installed in the carrier gas in line, so the pressure required to load the loop must be high enough to fill the loop in the time you analyzes of interest are coming out the exhaust of the TGA/DSC. The pressure required depends on the id of the sampling loop, a 500 uL loop of 1/16" tubing requires more pressure than a 500 uL mado of 1/8" tubing. Depending on loop size and restriction of the 6 port, I would estimate around 5 psi above atmospheric pressure should be a good starting point.

Of course more pressure is better, but we routinely run samples through a GSV with pressures less than 10 psig.

Ok, thanks a lot for your answers.
kind regards

Cris.