The scanning of broad mass ranges is known as full scan analysis. A full scan MS gives extensive details of molecule’s structure as it provides a record of all the fragments and their abundance. Many libraries utilize spectral matches to give unambiguous identification regarding the compound. Many forensic laboratories also depend on full scan analysis of mass spectrums in order to detect unknown compounds. Therefore, their usage is generally acceptable in the legal system to identify various drugs.
Even though, full scans give the best information as far as identification is concerned, it however, has many disadvantages. Firstly, all the ions that are being monitored from the analyte might not be of the investigator’s interest. Some ions, found in the background are from the system (column bleed0 or come via matrix interferences such as from extraction.. this causes poor match from the library and decrease the sensitivity of the test. Many times, the background can be removed to give a background minus mass spectrum. Moreover, due to the dc/RF i.e. direct current/radio frequency being swept throughout the mz range, the m/z ions can be gathered for same time period regardless of whether they are from the analyte the investigator needs or not. This also reduces the sensitivity of the test as time is wasted to scan the m/z ions that are of no interest to the investigator.
Acidic, basic or neutral extraction after which GC-MS analysis is performed can recognize variety of drugs and metabolites singly. This can be an expensive and a tedious procedure but many laboratories utilize it.