n SRI MGA-5 Update

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SRI MGA-5 Update
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MGA#5 is a Unique SRI Configuration
SRI MG5 2016-Update18 ) acrobat (2.3Mb)
* MG5 Update Oct2022 * -proposed upgrade SRI-EPC(s) radioactive license required) !
> MG#6? * maybe?    ;& CT specs >>  MFC for SRI EPCs)
* to minimise air diffusion within the GC.
HighPurity mini Pressure Regulator (SS Diaphram recommended (or on Gas Cylinder)
Getter Gas Purifier ( mounted close to GC essential)
Silcosteel loop, columns & transfer line recommended >> ppB sensitivity 104 range linearity ?

  • TCD for ~100ppM LOD to (mid) percent
  • FID-Methaniser down to low ppM CO/CO2
  • HID for Trace Gas Analysis ( low ppM (SRI >10 ?)
  • S-Cpds requires a FID-FPD (optional)
  • HS-D maybe a limitation ( eg ethanol Max); OR may require other HaySep (Q, N, S etc ) columns for limited polar compounds . . .
    > also try > .
  • Restek MicroPacked HayeSep columns or PLOT Columns as options
    Dual Oven extra possibity 8619D as a MG#5 option ?
    MS in 2nd ( easier bake-out) > 250degC HS-D ( Max 200degC )

    Trace Gas Analysis (low ppB) -  a “custom” far more specialised
    App & specs
    > ASK! ( can use existing electromterer and pulse control box depending
    on SRI detector space available ! )

    - requires 3rd Det SRI-HID ( or VICI Valco miniPDD ?) > better for“trace” permanent gases  & a different format GC eg SRI 8610V
  • SRI HID ???  H2 > ASK SRI ? for specs re sensitivity - but  not necessarily recommended by SRI for “trace gas”
    - CT with Modes ( gas purity and NO EPC; SS Mass Flow Controller ! for . . .  ( MG5 proposed CT-Update ).
  • allows “quant) H2 & O2/N2 (%) HID Matrix & Carrier Gas, High Purity Regulators & Getter Gas Purifier for LODs <10ppM ?
  • “SHINCarbon ST - DOES offer a one-column analysis of O2/N2 CO/CO2
    BUT NOT without it’s own idiosynchrasies / problems
    eg AR / O2 No! / C2 max at >300C ?;
    O2/N2 requires LDV HID and > 4m Packed Column > SRI-TCD > marginal ?


Multi-Gas Analysis - NO Simple Answers ! > many Options > this applies to ALL GCs any brand!
          SRI’s  MGA#5 is far BETTER Than Most designs !
- more innovative . . . for a very difficult still existing  gas analysis problem

  • H2 Quantitation requires use of Ar Carrier NOT He
    ( non quantitaive peak reversl with He ( 1-10%)
  • TCD almost useless requires low Dead-volume VICI HID Detector  for CAPILLARY PEAKs
  • Ar / O2 separation is very difficult and requires PLOT MS5A Column - some other  limitations
  • NEW  ! Methane CO2 elutes on micropacled Shincarbon HT ( 100/120# 0.75mmID 2m but TCS a limitation with deadvolme resolution loss for O2/N2 separation !
  • MS13X recommended for CO@ NOE ewltes ~175-200C but susceptible to legth bakeout occasionaly deoene on sample PPM and ware content
  • MS5A becomes deactivated if repetiitive runs and with excessive water/CO2 in matrix Gas
     > dual Oven 8610D optional (??? ASK!) re GasValves as well ? !
  • S-cpds can deactivate the Methaniser Answer ? ASK!
  • excess water / humid samples ( we suggest>  a Nafion Drier on the sample stream prior to GC )
                          ASK for some (more) ANSWERS !

    ASK for details (CT) / advice ! > but these are NOT necessarily just for SRI GCs TCDs / HIDs etc but ALL OEM brands of GCs
 > Buyer B’where ! some OEMs can deliberately obscure the “technicality > details” > called “marketing !

MGA#5 Options
MGA#5 ConfigB
MGA#5 Config

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
  • Split for > ~100:1
  • 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

New GSV Types 2019+ > PDF

  • COVID19 WW shortage of ‘chips” > “maybe” other improvements ? SRI to advise !
  • maybe for “trace” Gas Analysis > improved Rotors re “wear& tear“
  • & gas purging >essemtial for low ppB
  • 2022 SRI introduces a new range of Gas Valves ( some Helium purged )

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