Chromatography Forum

hi
i´m working for a school project with a shimadzu but no one can explain me what to do and i'm having troubles with the calibration curve. When i try to make the curve and get the equation for the adjust the R coefficient is diferent from the excel with the same values and i don't understand why because both equations are equal. Another problem that i have is the peaks sometimes i can get nice peaks but when i do again the same sample they get worst. I hope someone can help me with this because i'm going crazzy.

thanks

sorry for the english but i'm portuguse

The square of the corelation coefficient is a statistical calulation, the values might differ. I would concern myself more with the software, especially since your equations are the same. Just look at the value as a guide in that if r2 > .99 the calibration curve is good.

The second issue could stem from several different things.
Are you manually injecting? Do you see a great amount of tailing (post pr pre)? The R.T consistant?
A little more details on the problem would be helpful.

Good luck,

Will

hi will thank you so much for your help , only today i was able to check your message!

the problems i told you are gonne but now i have another problem, when i try to analyse samples of wine (with dilution) appears a message detector satured and i don´t understand why or what should i do to stopp that. i' m working with a 6% of alcool solution.

thanks

catia

Hi Catituxa

We are using the same shimadzu system. The detector saturated basicly means you just overloaded your MS detector (which is bad)

but no worries the shimadzu system has a safety feature that protects itself from overloading caused by new users like us.

Are you doing liquid injection? if you are then you better checked your solvent cut off time in your method file. you probably need to set the solvent cut-time to be longer.

Solvent cut time is important since your sample is mostly solvent and you dont want that to reach the detector.


Tarapan

hi tarapan

yes i'm doing liquid injection, i thought that solvent cut time was the problem first i put 2.1 min and then i raise to 3 min but the detector still satured. What range of values are you using?

thanks

catituxa

Its best you find out the retention time of your solvent first.

what we did before was inject as little solvent as we can with a very very high split ratio (around 1000 or higher)

dont forget to set the solvent cut time and MS scan start close to zero minute

Once you got your solvent's retention time set the solvent cut time 1 to 2 minute after the solvent's retention time (the longer the better) This way you can be sure that all solvent has been expelled from the system.