Chromatography Forum

Hi to all can any one explain me actually what is the concept of Attenuation and FID Range in PERKIN ELMER GC. We know how it works but yet i not got full knowledge of this any one explain to me. Thank you

Well
Attenuation - reduces the analog signal to X times, at 2, 4, 8 ... 1024
The larger division, the smaller the signal, the lower peak on the recorder.
Range - sets the signal range. In the range of equal napryazhniyu detector in the range of 1 x10 x100
Important - to work correctly - radiobutton. Calling 2 overrides 4-1024h, and the like.
Important. In the old amps need for changing the range to adjust the baseline under the zero trimmer potentiometers, which rotates. Just as in the old radio volume and radio station.
Google translate

kalidassa,

Range is generally a function of the resistor across the amplifier in the electronic circuit. A range of 12 might use a 10 mega ohm resistor while 11 might use a 1 mega ohm resistor (just as an example). It describes the amount of current that can be processed by the amplifier before it becomes saturated. Attenuation is what you do to the reported signal, divide the analog output by 1 over 2 to the n. It is entirely possible to attenuate an output signal where you can keep it on the strip chart but still have a clipped peak because you have exceeded the range of the electronics (with too much analyte injected.)

Best regards,

AICMM

I am pretty sure it is not related to the FID signal as it is very specific for compounds I know to be active. I've seen similar effects on the GC/MS when I have a bad liner. When I run capsaicin an amide it will literally disappear at low levels with a bad liner.

In this case I am pretty sure the inlet path is good so I am wondering if it is plausible the jet is oxidized or something and causing analyte adsorption.

Yes indeed the calibration range is quadratic for the active compounds (or entirely absent at the bottom) and fine for most of the less active compounds.

Edit I just tried another new liner with more or less the same result. I am seeing a the analtes badly tailed where they were not tailed on the GC/MS.

I would say that AICMM is right. In fact, you do find the same control on all older analog detectors for GC (ECD, NPD) but also on older lab equipements (UVs, etc)