The ability of the gelatin (or BSA)-trehalose film to convert normally fragile dry immobilized acetylcholinesterase enzyme (AchE) into a stable reagent is shown. The remarkable properties of the dry immobilized AchE enzyme preparation are its stability to prolonged exposure to temperature as high as +50 degrees C and its tolerance to damages due to acidic pH. The proposed method offers a rapid simple, and inexpensive means for mass screening of AchE inhibitor residues such as pesticides and drugs in water, vegetables, and human blood serum.