Hi, guys. I'm beginning to fit XPS peaks from a environmental measurement but, as I'm unfamiliar with the exact process I have a lot of doubts. I have solved some of them using the info in http://xpssimplified.com/periodictable.php and in the XPS manual from Moulder and Stickle but I'm not sure if I'm making it right. The question is: how do I know if in the sample is present an element? I mean, I know I should check for the difference between 2p1/2 and 2p3/2, por example, but this is the accurate way to make it? If the difference is approximately the same that is presented in the literature but the ratio is not, is still the element there? What else should I look for? Thank you very much for your help.