Again, Mahsa Lotfi Marchoubeh please do not overload the detector, column or injector. Choose injection volumes and concentrations that do not result in "column effects", resulting in column fouling or poor reproducibility. Please contact an experienced chromatographer to assist you using the GC-MS system. Continuing to ask such basic questions on RG and not having the needed training to implement the suggestions continues to lead to failure. Please have someone with the formal training and skills needed to use this instrument and develop new methods analyze the samples. If this is not possible and your work place or school classroom has no one trained in GC-MS, then send the samples out to a professional laboratory for analysis. No one like you would be expected to have this knowledge out-of-school or even after a few years of full-time industrial laboratory training just on GC-MS. "Figuring it out on your own", as you are trying to do, when you do not yet have the basics will only lead to frustration and poor quality methods. Continuing to ignore these facts will not change things. A web forum like this is not the place to try and learn five to ten years of needed full-time, hands-on knowledge to use the GC-MS and run samples.

Mahsa Lotfi Marchoubeh: My responses on RG are always 100% relevant to the posted query. You can ignore the facts, but that does not make the advice offered false or irrelevant. You can not learn GC-MS "on your own". You still do not know what you do not know. As a professional scientific consultant and instructor with three decades of experience, I have witnessed many fail attempted to learn a technique like this one in a week, month or years with no professional guidance. These failures can be prevented by educating students like yourself with some basic facts, early on, and advising them to find local professional help with their project. Failure to do so will result in lost time, money and opportunity to learn.

If you are interested in developing valid analytical methods you may want to limit your irrational criticism towards others and instead listen to the more experienced advice and suggestions made. *GET LOCAL professional "hands-on" HELP! **This advice is directed to lead to your success and allow YOU to increase your basic knowledge on the topic. It may also permit you to learn a useful scientific skill too (when you do not know what you are doing, find and work with someone who does). A web forum such as RG is no place to learn this complex technique.

BEST ANSWER: Please work with someone local who has the formal training and skills needed to use this instrument and develop new methods analyze the samples for you. If this is not possible and your work place (or school) has no one trained in GC-MS, then send the samples out to a professional laboratory for analysis.