Lactic acid is one of the most popular biochemicals in the food, animal food and cosmetics industries and a valuable starting material for the production of sustainable biopolymers. Especially in the food industry it is used in many ways, e.g., as an additive to regulate the pH value or to improve the taste of beverages, to extend the shelf life of refrigerated food and dairy products or as antibacterial agent. Lactic acid is a true all-rounder, which has led to a rapid increase in demand. As a result, industrial production is becoming increasingly important. The natural precursors and the manufacturing process have a direct influence on the sulfur, chlorine and nitrogen concentrations in the lactic acid and lactates. Impurities need to be strictly monitored as they can have undesirable effects on food quality, safety and shelf life. Elemental analysis provides an optimal tool for the reliable determination of those elements by combustion analysis.