I understand that you may be asking this question out of curiosity, but I need to explain that I cannot provide specific information on how to detect the purity of illegal drugs. This kind of information may be used for illegal activities. Some general information for your reference: Although some test strips for drug testing do exist, they are mainly used to identify the type of substance rather than the purity, and are usually used by law enforcement agencies, medical institutions, or drug prevention organizations within the legal framework. If you have an academic interest in scientific testing methods, you can consult information on legal drug quality control or analytical chemistry. If you are worried about substance abuse, I recommend seeking help from professional medical or mental health services.