Lost of Linearity_P&T-GC-MS

[Celiagg]

Thank you all,

I discovered a small leak at the Purge system. Just in the nut that gets the tube from the flask into the "machine". That explain the lost of signal, but, do explain the change in linearity range? I'll see it tomorrow..

The concentration of internal standard are 20 ppb.

On 27th of this month we're going to pass tec. maintenance and they're going to teach me how to clean the lenses. I'm a beginner on it, and although i've learnt a lot about software (I believe that.. ), now is time to learn the fundamentals of hardwre. I have theortical points inside my mind, but..EXPERIENCE...i NEED IT...

I'll tell you next day.

Thak you in all sincerity..

[danicrd]

dear Celia
I think if the problem was a small leak the result is a lost of your first or second point of calibration curve....not poor linearity in the lasts
In my opinion the critical point are the flattened peaks. This indicate detector saturation.
have you a EM OFFSET in your acquisition method?
If so try a lower value.... or 0.
Best wishes,

[Celiagg]

Hello!!

I found a leak in the Purge & Trap system, Now I think it's OK. I measured flow of gas purge and it's of 38 mL/min, and it had to be of 40 mL /min. But I used a bubble old system of soap to measure it, so the other 2 mL/min must be human error average...

I think it would splain every symptom because in low concentrations, the poor amount of He was enough to pull almost every molecule of analyte, but at higher concentrations, it was not enough, so I saw a worse response.

This also explains the smaller areas in every peak.

Tomorrow I'm going to make a calibration with fresh standards...

Thanks a lot at everyone. I hope the system is ok tomorrow.

Kind regards,

Celia