Lifetime on parts for CG 6890 / 7890

Discussions about GC and other "gas phase" separation techniques.

5 posts Page 1 of 1
Hello.

Was wondering if there is any experts that can respond on these questions?

Using the chromatograph for gas monitoring.

Question 1

How many runs is the expected life span on these parts?

10port valve
6port valve
Jet's
Glowplugs

A retailer said jets should be changed every 50k runs.

Question 2

Anyways, the chromatograph i've got now - Came in with the error "Pneumatics Board, PCB failure"
Changed the PC Board Assy, EPC, HP 6890 PN : 67690-018
And everything was working as it should.

But when I started to test the linarity of the gas I couldnt to more then -7 %

Testing with Methan gas, with 3 calibration points.
Zero air
1%
10%
Question 1 Liftime: Don't have quite the time answers but:
10port valve - Don't know
6port valve - Don't know
We run our headspace GCs (residual solvents in Pharmaceuticals) almost 24/7, using 6890/7890. On the 6 port valve in headspace we change rotor seal on yearly basis or if problem arise.
Jet's - If there is high noise on only one FID, loss of sensitivity or poor peak shape and I have excluded everything. I would take it apart and clean collector and jet in hot ultrasonic water bath. Clean jet with wire (I use violin string that coworker provide on regular basis), visually check inside if it is OK and flush it with methanol. I would say that there is no need to change it on regular basis, I have jet's that are probably decades old, but if there is rust change it the price is not huge.
Glowplugs - If that failed in old times I could use lighter, but now days they are prohibited in my lab in connection with GC :) . I still have original igniter in 6890A instrument so I would say change it per case not as preventive maintenance. If you are unable to see glow from it then it is time to change.

Question 2

6890 with EPC has calibration option, check manual for it. If I remember correctly you have to calibrate it at zero flow and at 100 if you use 100 EPC, I can check it tomorrow.
Got a linarity down to -0,47%

Cleaned 6 & 8port rotor with deonized water
And cleaned the collectors with deoinized water, think this was the main thing

With the setting before I cleaned, it was with 23ml flow
Resulted in 47500pA

With the cleaning of collectors and rotors resulted in 41700pA

Significant improvement with only cleaning :mrgreen:
mrGasMan wrote:
With the cleaning of collectors and rotors resulted in 41700pA


41700pA that is awful, I wouldn't start analysis with signal higher than 50pA, normally I have it below 10pA. Did you clean entire collector with insulator? Are they rusty? If there is no observable contamination on it I would say that electrometer (the spring that goes into collector) could be damaged or someone with sweaty hand touched it
Zero Air (0%) = 62 pA
1% Metan gas = 41700pA
10% Metan gas = 420000pA

So its a good result :)

I could adjust the restrictor to get the pA lvl down, but then the linairty would be shit : )
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