A non-invasive and non-destructive apparatus and testing method for analytes in sealed containers are provided, which are especially useful for identifying bottles of wine that are contaminated with 2,4,6-trichloroanisole (TCA) without destroying the value of uncontaminated wine by opening the bottles or marring the containers or labeling. The apparatus and method are applicable to non-destructively testing any “stream-of-commerce” containers such as shampoo bottles, aerosol containers, toothpaste tubes, and soft drink cans, and other such containers for the presence of contaminants, explosives, poisons, drugs, and other dangerous or illegal materials. The method provided is orders of magnitude more sensitive than other methods, and can detect the presence of diffused substances at the nanogram per liter (parts-per-billion) level.