LC-MS is a technique routinely used in sample analysis that combines liquid chromatography (LC) with mass spectrometry (MS). Extremely sensitive modern MS has helped LC-MS replace several immunoassays. LC-MS has helped improve the efficiency of drug discovery due to its excellent sensitivity and specificity. The technique can be combined with stable isotope dilution for precise and reproducible assays. The LC-MS technique is useful for the detection of steroid drugs in body fluids and in profiling endogenous steroids. Steroid sulfates have been detected with high sensitivity using this method. Plasmaspray has been used to test saliva for steroid hormones in patients suffering from congenital adrenal hyperplasia. Ultra-pure additives and solvents such as acetic acid, acetonitrile, ammonium acetate, ammonium bicarbonate, ammonium fluoride, and ammonium hydroxide are available from Sigma Aldrich for use in LC-MS systems.