355 agilent SCD noise baseline

[engineer24098]

HI,

the problem from the begining apears by low response for all peaks which is H2S, COS ,DI ETHYLSULFIDE AND DI METHYLSULFIDE .i tried to remove the detector and open the reaction cell, i found alot of dirt inside it after cleaning every thing back to normal.but after inject one run by standard gas high noise apear in baseline.

detector sitting:-
mv attenuation at 1
signal display: continous change from 0.3 to 15 mv
pressure:10 TORR

NOTE:WHILE SWITCH THE OZONE GENERATOR OFF THE BASE LINE BECOME OKAY

your assistant is highly apreciated

regards,

[muGC]

Does the baseline change look wavy or spiky?

Sounds like your PMT is possibly bad. Did you protect it from light when cleaning the reaction cell?

[engineer24098]

Thanks muGC

Base line spiky

and regading the cleaning i have protect it well from the light but unfortntly i forget to cap the union fitting for vacum pumb.

Regards,

[muGC]

The significant spiky baseline means you need to order and install a new photomultiplier tube detector. It must have been exposed to light during the cleaning procedure.

[AICMM]

engineer24098,

Seems to me that if your PM was bad your baseline would be noisy whether your ozone was on or off. With ozone off, you get a smooth baseline? I would then suspect either more contamination somewhere especially considering low response (either sulfur stuck somewhere or other components bleeding off somewhere.) The other thing I would ask is what you sample matrix is because 'enes will react with ozone and lead to signal (although I am rusty on wavelengths and filters......)

Best regards,

AICMM