Individuals may try to beat their drug test by adding various substances into urine specimens in order to have negative drug screen results to pass workplace drug testing. Many Internet-based companies have been selling in vitro adulterants containing potassium nitrite, glutaraldehyde, pyridinium chlorochromate, and stealth (a combination of peroxidase and hydrogen peroxide). These chemicals are effective in modifying structures of certain drug/metabolites, especially marijuana metabolites, and may cause false negative test results in both immunoassay screening and mass spectrometry (MS) confirmation. Unfortunately, clinical laboratory drug testing for specimen validity and adulteration cannot detect the presence of all these compounds in urine specimens. However, there are special dipstick tests and other tests available to detect these adulterants in the urine prior to the analytical step.