Liquid chromatography methods using different techniques of mass spectrometry were also reported. Pyridine is conventionally detected by the gas chromatography and mass spectrometry methods. These included mass spectrometry and gas chromatography instruments. BRs can be detected by gas chromatography mass spectrometry and bioassays. Testing for formaldehyde is by blood and/or urine by gas chromatography-mass spectrometry. SRM can be used for targeted quantitative proteomics by mass spectrometry. Several recent methods allow for the quantitation of proteins by mass spectrometry (quantitative proteomics). These ionization techniques are used in conjunction with mass analyzers such as tandem mass spectrometry. This is verified through the use of gas chromatography-mass spectrometry. Gas chromatography, preferably coupled to mass spectrometry (GC-MS), is considered a minimum requirement. EI was one of the first ionization techniques developed for mass spectrometry. The test is performed by Isotope Ratio Mass Spectrometry (IRMS). Duoplasmatrons are used for secondary ion mass spectrometry. Mascot identifies proteins by interpreting mass spectrometry data. QqTOFs are used for the mass spectrometry of peptides and other large biological polymers.