Other limitations / “issues”
In practice the HaySep-D is needed for CO2 separation from methane but is somewhat limited for higher MW VOCs by column bleed and/or flow sensitivity drift of the TCD during temp programming to propane(?) EtOH, MEK for example at 180C max unless you use ultra pure He and/or Oxytraps
The HS-D can be replaced with capillary column for more detailed resolution of high MW or polar components but CO2CH4 may be then sacrificed !
Calibration of these is assisted by the on-column liquid injection port fitted standard on the MG#5 ( expande to 2 ports ( heated if necessary and with a Splitter option
The set up is somewhat convoluted and users need to understand the logic and peculiarities of the GC set-up re “Timed Events” of PeakSimple and sorting occasional duplicated & multiple-peaks etc !
Definitely NOT a “DO-All . . . Do everything” ! concept & NOT For GC BEGINNERS !
- For H2 an extended design of the MG#5 may become too complex mechanically / re GC internal space etc adds to the overall price
> a separate GC(s) using Argon carrier gas is recommended if throgh pur a problem
For high concentrations of H2 a simplified GC / is suggested using a CCD Detector ( 500ppM LOD) with 1 cc sample size for H2, CO, methane and C2 ( & combustibles ) > so NOT CO2 or Air ( Ar/ O2/ N2 )
> much lower cost
- columns to be decided on MolSieve for CO from Air) and CCD Not suitable for capillary columns CO2 > non-responsive in CCD and no need to separate CO2 on HS-D; backflushing of the CCD may still be required and can suffer from over 5A
On-Lne auto analysis of gases AND complex VOCs is fraught with difficulties particularly related to
“Headspace Gases Analysis” ( re sample size available from the process AND re LODs and the need for more sophisticated GC Detectors ( HID with adequate Gas Purification or VICI-Valco PPD to improve trace gas analysis ! ) see above
NO Equivocation here ! . . . Just stark reality !
- Yes there are some answers here ! > but . . . more complex, more expensive > ASK ! > RFQ !
Justification maybe > NEW MG#6 ( in future ? OR to Order ! )
- Gas Purification > SS diapbram regulators ( NO EPCs ) > & essential !
- HID ( SRI or Vici-Valco miniPDD ) ONLY
- 1cc Auto Gas Sample Injector; Silcosteel Loop
- Gas Splitter Manual Injection System ( for high sample concentrations,>~0.1%)
- ShinCarbon HT 2 to3m 0.75mm Silcosteel Column
- Vacuum Pump Interface ( for added ease of sampling)
- Quantitative H2, compromised O2/N2 ~1% O2?) but on TIS/PPD
- Improved trace gases > <1ppM on HID low ppB on PDD
- Shincarbon limited to approx C2 HCs, or for CO2 programmed MS5A >200degC)
ALL HIDs are limited to ~1%Max (1CC) inc NEW BID ( Shimadzu ) &
LDETEK ; ASDevices requiring a Gas splitter and/or a TCD ( > ~100ppM permanent gases) or FID-Methaniser ( for CO/CO2 LOD ~1ppM)
Plenty of compromisess ! > ASK CT for recommendations !
HID & Methaniser > DON’T assume linearity at high(er) concentrations ( >1000ppM?)
CO2 Calibration - Do NOT rely on ambient Air for any sample dilutions
- Ambient can be 400ppM but up to 1000ppM > Indoors
Humid Air samples can be up to 7% water even if NOT measured and correction of results are required or Sample Drying
- a NAFION Drier (SRI /+MS5A) needs equilibration time and at best 1-2% water is residual still ! )
STANDARD GCs Can NOT be assumed to be “Gas-Tight” All tend to diffuse ambient Air into the GC system ( through O-rings, regulator, diaphhrams, flow meters, septa even against +ve gas pressure
Process control GC and Trace Gas Analysers ALL are custom designed specifically
- ANY “marketing” chromatograms ARE DONE ON OEM STANDARD GCs without due consideration
- Gas SUPPLIES ( He ) High Purity are bulk-tested ONLY Can be UNRELIABLE
- Always use an Oxytrap preferably a GETTER” Purifier mounted closed to the GC as possible
- ANY Manifold Purifiers are NEXT TO USELESS without an Indicating OXY-Trap verification next to GC & after the “Getter” Trap