We maintain that knowing the producer is the best safeguard against adulteration. While we also analyze our essential oils by GC/MS, we do know that analysis alone has not kept adulterated oils out of aromatherapy. To the contrary, analysis hype is often used to sell cleverly adulterated oils. 

-Kurt Schnaubelt, Ph.D. (Author of several aromatherapy books, Educator, Chemist, Founder of Pacific Institute of Aromatherapy)