Briefly, you need to know how good the ethyl acetate has to be. That means you have to know how pure the ethyl acetate needs to be, and what impurities, at what level, are detrimental. That means a gas chromatography run, to test for other solvents and water, or Karl Fisher analysis, to test for water, as DrCMS: mentioned above. Maybe a pH titration, if you think acetic acid and water are impurities. And multiple tests on your part to determine what levels are acceptable for your application or not.
You might get away with doing this once time, to determine what will and won't work, setting a level that's acceptable, and telling the vendor something like -- 98% ethyl acetate, no more than 100 ppm water (I'm guessing here), no detectable acid. Warning: they will charge you extra for a standard of purity, even if 9 times out of 10, their stock will pass anyway. Double warning: they may send you a certificate, but not bother to test at all, then it may fail, and then you will have to prove it, so you may want to get a contact with an analytical lab to test your raw material often, or every time, or you may want to purchase a GC, KF, autotitrator. It really depends on the rigidness of your application, how your vendors treat you, and your bottom line.
ETA: Credit DrCMS: for a correct first answer