Chemical assays determine the quality of raw materials using quantitative analysis techniques. Many raw materials used in manufacturing processes are tested using classical methods, such as titrations and gravimetric analysis. Organic chemicals and solvents can be assayed using gas chromatography and infrared spectroscopy. Chemical purity is typically determined from the amount of impurities present in a material. The methods used to determine impurities range from classical “wet chemical” tests to trace element analysis using ICP-OES, ICP-MS, WDXRF and C/S/O/N/H elemental analyzers.