Chromatography Forum

HP 5890 w/ 5972
Tekmar 2000 and 2016 ALS

Purge parameters:

Supelco K fresh install
12min purge @30C
Desorb preheat to 245
Desorb at 250 for 2min
Bake at 260 for 8min
Purge flow measured at 39ml/min
Purge pressure 20psi through all stages
Desorb flow: not sure how to measure
Moisture control not installed & no dry purge

GC/MS parameters:

1ml/min column
Split flow measured at 25ml/min & split throughout run
35C for 4 min
Ramp 18 to 220C

This is an older instrument that we want to....resurrect if possible. The MS is a recent refurb and the Tekmar 2000 is 'low mileage,' looking probably how it did in 1990 =)

2-CEVE is totally broken down in the ALS. Acrolein is absent at any concentration 50ug/L on up to 2000ug/L when purged; direct inject isn't much better. The standard is as new as they get.

SPCC all easily pass RF and peak shape of gases are pretty sharp. Bromomethane and chloroethane are squashed into oblivion, however. The methanol solvent peak does elute with bromomethane and chloroethane with this column--RTX VMS. Compounds after benzene are substantially higher in response compared to early eluters. Dry purge further depresses response of first 20ish compounds and murders chloroethane.

Standards are fresh. K trap is new. The ALS is currently disconnected and replumbed to purge from 2000 sample concentrator.

Any suggestions?

I'd start by changing the split to 50 to 1 (or more) and looking for an relative improvement in the chloroethane and bromomethane. It may be too much methanol and / or water in the GC. Especially if it's a .25mm column.