Hello @Kaur I’ve discussed this with a few of our support teams on recommendations and advice for you. To guide you further, it would be helpful to understand the instrumentation you are working with. If you would like a representative to contact you about specific technical questions, then you can request support using the Contact Us | Thermo Fisher Scientific - US.
If you have a question on the best methodology, you might consider submitting this question to the EPA directly. We found this link - ECSS Get Help - ECSS (servicenowservices.com). It seems to be a way to ask a question online.
In addition, I did come across a few resources on using GCMS and EPA method 8270D.
Resource 1, Application note: The Optimized Analysis of the U.S. EPA Method 8270... - AnalyteGuru
Resource 2, Poster Note: Optimizing the Analysis of Semi-volatiles by EPA Method 8270
Resource 3, Analyzer kit information: EPA 8270D Analyzer Kit – Update Your Lab and Overcome the Challenges of Semi-Volatile (SVOC) Analysi...
Please let me know if I can help in any other way.