Chemical Performance Evaluation on 6890

[cdcl3]

I tried the Chemical Performance Evaluation test from Agilent to requalify a 6890A. I have injected 1ul of the flame ionization detector sample (a mix from Agilent of n-tetradecane, n-pentadecane and n-hexadecane in hexane).The area of each peak must be higher than 4000. Last year we were bordeline and today I got areas between 2800 and 3350. The detector and inlet (purge-pack) has been cleaned.

Any idea to resolve this problem?

[CIL-BAHA]

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[cdcl3]

2003 C14 area=4287 plate=200000; C15 a=4190 p=218000; C16 area=4044 p=250000

2005 C14 area=3000 plate=205000; C15 a=2787 p=323817; C16 a=2498 plate=282567

[cdcl3]

I have checked the data of a method for BHT assay and the area has decreased of 30-40% in 9 months.

In nov-2004 the std area was 585, in may-2005 the area was 480 and in july 2005 it was 394. The concentration was about 0.025 mg/ml.

[CIL-BAHA]

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[cdcl3]

The peak area control is from Agilent OQ protocol.
The mixture was receive 3 years ago but the sample was not open.
The problem seem to happen to different methods with different columns on this instrument.
Septum and liner are changed every day.
Gas flow are mesured with two digital flow meters calibrated every 18 month. The make-up gas is Helium.

Is there a test who will help to determine if the problem come from the inlet or the detector?

[CIL-BAHA]

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[cdcl3]

The inlet is a purged packed. I have done a leak test after the cleaning yesterday and it lose 0.0 psi.

I try a new syringe and I got area of 3845, 3675 and 3502.

I will check again the gas flow with the second flow meter and will increase a little bit the make-up gas.

[CIL-BAHA]

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[cdcl3]

Thanks for the info but I have verified the noise today with the test from my OQ protocol (same as Agilent).
The noise is very low:
Initial signal (<25pA): 3.5pA
ASTM noise (<0.10pA): 0.02813pA
ASTM Wander (<0.20pA): 0.02068pA
ASTM Drift (<2.5pA/hr): 0.07427pA

[cdcl3]

Do you thing if I change the jet it will be higher. The jet was changed one year ago.

[cdcl3]

Thaks for the help.

It's now ok after change of the jet, ignitor castle and collector insulator.

I got area between 4350 and 4050.

[CIL-BAHA]

You are welcome