Chromatography Forum

Hi all,

On a recent HP GC-FID run, I noticed that the detector temperature is exceeding its set-point of 260C during the run. I've noticed a maximum temperature of 279C, which is obviously damaging for the columns stationary phase.

Also, at the end of the run, it is taking almost three times as long to cool the detector back to 260C.

Any ideas on what might be going wrong here?

Many Thanks,

James.

What temperature does the column temperature go to during the run?

Are you sure that 279C will damage the stationary phase?

Are the oven flaps on the rear of the 5890 fully closed during a run?

Hi there,

The column starts at 50C, and follows a variable gradient to 250C over approx 15mins.

The detector is fixed at 260C on our method.

Yesterday's run finished overnight, but it wouldn't complete our "Shutdown" injection. This sets the front inlet, oven and detectors at 50C as the last injection of the sequence. Upon checking today, everything had a 50C readback except the detector which was around 250C!

Not sure about the oven flaps being closed at the rear of the GC, but we had that problem fixed about 3 years ago where the oven wouldn't cool down to our starting point of 50C as the flaps would not open.

Does the detector setpoint get changed to 50C when the method calls for that?

Does the detector respond normally if you manually change the temperature set point? If it's a 250 and you set it to 40, how long does that take?

I'd also check that the detector temperature is being read accurately. If the temperature sensor wire has a break or a short, it can be completely off. I've seen a 5890 display 400C for the detector when it was cool enough to touch. If I wiggled the sensor wire going into the detector, the temp would jump all over the place, sometimes down to minus 200.

If the temperature is being read correctly, I'd try plugging the heater and sensor wires into the other detector's spot on the circuit board. (I.E. swap the front and back position).

Hi all,

Turns out it was a burnt-out temperature sensor.

Replaced with detector B sensor, and all good.

Thanks for the update.