Dear all,
At this moment I am using a GC-MS system for DEHP trace measurements. I use an internal standard method to analyse a range of 5 to 40 ppm DEHP in solution (DCM). This range has been limited by the fact that above (and below) these amounts, there seems to be an exponential increase of the area response of DEHP. The linear curve also shows a high negative intercept compared to the slope of the curve. This is both the case with the TIC and m/z = 149 signal.
Can someone tell me which settings of the GC-MS system might have influence on this phenomenon and improve the linearity of my calibration curve on a broader range?
With kind regards,
Rick Raaijmakers
Your actual method and sample concentrations used are responsible for the response. MS is poor at quant (esp TIC), better for qualitative.
As William elaborated,
Using SIM mode with atleast 2 major m/z values might be a better option for quantification
The range of 5 to 40 ppm DEHP in solution (DCM) is far above trace measurements! Use GC-FID for ppm DEHP level analysis. For GC-MS measurements, calibrate the instrument in the ppb range and use the vial septa of good quality to avoid the peak 149 from the septa.
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