In our lab we are searching for a new gaschromatograph equipped with head space sampler.
The budget allow the possibility to obtain a configuration with three detectors and so the choice is for ECD, PID and FID based on our activity in environmental analysis.
The question is on the optimal coupling of one of non-destructive detectors (ECD and PID) with FID.
There are problems with PID-FID coupling in series? Is preferable a PID-ECD coupling?
Have anyone experience in this coupling matter?
Any input is greatly appreciated.
Thanks in advance.
By Ron on Tuesday, July 1, 2003 - 05:34 am:
PID-FID coupling is a standard configuration, and there are commercially available tandem detctors. I have not seen an ECD coupled to a PID, and I would not recommend this configuration as bleed from the sealing O-rings and other potential contamination from the PID could affect the performance of the ECD.
By Anonymous on Tuesday, July 1, 2003 - 05:52 am:
By Anonymous on Tuesday, July 1, 2003 - 06:12 am:
Actually I think have seen coupling of an ECD to a PID detector, in that order. I believe this is the better config since there is inherently more dead volume in the PID, so to keep the sharpest peaks I think the column to ECD to PID is optimal when stacing detectors.
By Ron on Wednesday, July 2, 2003 - 05:25 am:
The only other issue I see with doing it with the ECD first is that now the PID will also have to have a wipe test performed as it is downstream from the ECD, so any radioactive leakage will contaminate the PID. I am not sure if radiation safety requirements even allow the mounting of another detector downstream of the ECD.
By Anonymous on Wednesday, July 2, 2003 - 06:42 am:
I suppose a wipe test would be needed every 6 or 12 months but my experience with the Ni-63 foils is they never had any measurable release. I don't know of any regs that specifically prohibit mounting these detectors in series, but I have been wrong many times before. It might do to contact specific vendors such as Varian, HP, etc., and see what configs they offer.
By Anonymous on Friday, July 4, 2003 - 12:02 am:
Thanks to Ron and Mark for your useful hints!