Impurities can arise from various sources in pharmaceutical preparations including raw materials, equipment, reagents, solvents, and the manufacturing process itself. Raw materials may introduce impurities like heavy metals, chemicals used to eliminate other impurities can become impurities themselves if not removed properly. The equipment, intermediates generated during synthesis, chemical reactions used, and defects in manufacturing can all contribute to impurities being introduced. Proper specifications and analytical procedures are needed to identify, quantify, and limit both known and unknown impurities.