When evaluating herbicide quality, you must focus on the Active Ingredient (AI) concentration, which determines efficacy. Common formulations include SL (Soluble Liquid), EC (Emulsifiable Concentrate), and WDG (Water Dispersible Granules). Ensure the factory provides a Certificate of Analysis (COA) for every batch to verify that the purity levels meet your local agricultural standards. Additionally, check the surfactant quality, as it affects the rain-fastness and absorption rate of the weed killer.