Chromatography Forum

Hello
I have an issues with TraceFinder software which controls Thermo GC/MS Instrument (TSQ 8000 EVO). The problem lies in red flags assigned to acquired files: ISTD and examined samples. One of these informs that ISTD area (recovery) is out of bounds. The second is Ion raitio failure. What kind of factor could cause that data failure? Could it be loss of sensitivity?
I'm counting on Your help

Hello,

Are the "samples" in this case solvent blanks? It's obvious that they will have no iSTD and an ion ratio of 0 (= no peaks).

If you're looking at samples there are many possibilities:

For internal standard recovery:

- No internal standard, or the wrong amount of internal standard added (check calculations)
- Loss of internal standard during sample prep
- Sensitivity of the instrument changes during the batch
- Higher/lower signal in samples compared to calibration curve (matrix effect in GC, very common and very dependant on the analyte).
-....

For ion ratio:

- There is no analyte present in the sample
- The ion ratio is not set at the right value (define it on a calibration standard)
- The peak is not the analyte peak
- Interference
- For low amounts of analyte: the qualifier ion (typically lower in signal compared to the quantifier) can be below the LOD/LOQ, which can significantly inflate the quantifier/qualifier ratio.
-...

The "samples" 1 & 2 contain unknown concentrations of target analite and 10ug/mL internal st (deuterated). Examined matrix is blood, whereas the cal curve was made with serum, so maybe there is the answer to failed recovery calculation.

Thanks for quick reply