Why don't you just ask the people who make it. McDonald's use 100% pure beef patties and uses fresh ingredients which are shipped weekly so that all our ingredients are fresh. If you would like to know what is in McDonald's food just go to

http://www.mcdonalds.com/

There already is such a thing. It's called a mass spectrometer. But it's not going to tell you that a hamburger is made out of beef, fat, crap, whatever - it's going to break it all the way down to the elements (carbon, potassium, etc).

Yes - that's how the nutrition information gets on the McD flyers.

It's not hard to do.

is impossible.. several test must be used to test for all ingredients... maybe in the future yes

It can already be done, with a combination of mass spectrometry (as eri mentioned), but also a good deal of chromatographic columns with a wide variety of chemistries/separation schemes. You'd also have to compare your result with how various components (e.g. tomato puree) would look after a chromatographic separation... because chromatography with MS will give you the overall composition of your sample. It will say that there is this type of fat, this type of protein, etc., but it won't say which component contributed that thing, i.e. it won't say that the fat came from the beef, or from the special sauce on the burger, only that it's there. Now, if you took a burger and separated the pieces (like scraped off the sauce), it would greatly simplify the determination of origin of the fats, carbohydrates, etc..

This sort of reverse engineering has already been done by competitors in the restaurant business and elsewhere.