Editing Electron ionization (section)

=== Gas chromatography mass spectrometry ===
[[Gas chromatography]] (GC) is the most widely used method in EI-MS for sample insertion. GC can be incorporated for the separation of mixtures of thermally stable and volatile gases which are in perfect match with the electron ionization conditions.

==== Analysis of archaeologic materials ====
The GC-EI-MS has been used for the study and characterization of organic material present in coatings on Roman and Egyptian [[amphora]]e. From this analysis scientists found that the material used to waterproof the amphorae was a particular type of resin not native to the archaeological site but imported from another region. One disadvantage of this method was the long analysis time and requirement of wet chemical pre-treatment.<ref name=":1" />

==== Environmental analysis ====
GC-EI-MS has been successfully used for the determination of pesticide residues in fresh food by a single injection analysis. In this analysis 81 multi-class [[pesticide]] residues were identified in vegetables. For this study the pesticides were extracted with [[dichloromethane]] and further analyzed using gas chromatography–[[tandem mass spectrometry]] (GC–MS–MS). The optimum ionization method can be identified as EI or [[chemical ionization]] (CI) for this single injection of the extract. This method is fast, simple and cost effective since high numbers of pesticides can be determined by GC with a single injection, considerably reducing the total time for the analysis.<ref>{{Cite journal|last1=Arrebola|first1=F. J.|last2=Martı́nez Vidal|first2=J. L.|last3=Mateu-Sánchez|first3=M.|last4=Álvarez-Castellón|first4=F. J.|date=2003-05-19|title=Determination of 81 multiclass pesticides in fresh foodstuffs by a single injection analysis using gas chromatography–chemical ionization and electron ionization tandem mass spectrometry|journal=Analytica Chimica Acta|volume=484|issue=2|pages=167–180|doi=10.1016/S0003-2670(03)00332-5|bibcode=2003AcAC..484..167A }}</ref>

==== Analysis of biological fluids ====
The GC-EI-MS can be incorporated for the analysis of biological fluids for several applications. One example is the determination of thirteen synthetic [[pyrethroid]] [[insecticide]] molecules and their [[Stereoisomerism|stereoisomers]] in whole blood. This investigation used a new rapid and sensitive electron ionization-gas chromatography–mass spectrometry method in [[Gas chromatography–mass spectrometry|selective ion monitoring]] mode (SIM) with a single injection of the sample. All the pyrethroid residues were separated by using a GC-MS operated in electron ionization mode and quantified in selective ion monitoring mode. The detection of specific residues in blood is a difficult task due to their very low concentration since as soon as they enter the body most of the chemicals may get excreted. However, this method detected the residues of different pyrethroids down to the level 0.05–2&nbsp;ng/ml. The detection of this insecticide in blood is very important since an ultra-small quantity in the body is enough to be harmful to human health, especially in children. This method is a very simple, rapid technique and therefore can be adopted without any matrix interferences. The selective ion monitoring mode provides detection sensitivity up to 0.05&nbsp;ng/ml.<ref>{{Cite journal|last1=Ramesh|first1=Atmakuru|last2=Ravi|first2=Perumal Elumalai|date=2004-04-05|title=Electron ionization gas chromatography–mass spectrometric determination of residues of thirteen pyrethroid insecticides in whole blood|journal=Journal of Chromatography B|volume=802|issue=2|pages=371–376|doi=10.1016/j.jchromb.2003.12.016|pmid=15018801}}</ref> Another application is in [[protein turnover]] studies using GC-EI-MS. This measures very low levels of [[Phenylalanine|d-phenylalanine]] which can indicate the enrichment of [[amino acid]] incorporated into tissue protein during studies of human protein synthesis. This method is very efficient since both free and protein-bound d-phenylalanine can be measured using the same mass spectrometer and only a small amount of protein is needed (about 1&nbsp;mg).<ref>{{Cite journal|last1=Calder|first1=A. G.|last2=Anderson|first2=S. E.|last3=Grant|first3=I.|last4=McNurlan|first4=M. A.|last5=Garlick|first5=P. J.|date=1992-07-01|title=The determination of low d5-phenylalanine enrichment (0.002–0.09 atom percent excess), after conversion to phenylethylamine, in relation to protein turnover studies by gass chromatography/electron ionization mass spectrometry|journal=Rapid Communications in Mass Spectrometry|language=en|volume=6|issue=7|pages=421–424|doi=10.1002/rcm.1290060704|pmid=1638043|issn=1097-0231|bibcode=1992RCMS....6..421C}}</ref>

==== Forensic applications ====
The GC-EI-MS is also used in [[forensic science]]. One example is the analysis of five local [[Anesthesia|anesthetics]] in blood using [[Headspace gas chromatography for dissolved gas measurement|headspace]] solid-phase [[Microextraction by packed sorbent|microextraction]] (HS-SPME) and gas chromatography–mass spectrometry–electron impact ionization selected ion monitoring (GC–MS–EI-SIM). Local anesthesia is widely used but sometimes these drugs can cause medical accidents. In such cases an accurate, simple, and rapid method for the analysis of local anesthetics is required. GC-EI-MS was used in one case with an analysis time of 65 minutes and a sample size of approximately 0.2 g, a relatively small amount.<ref>{{Cite journal|last1=Watanabe|first1=Tomohiko|last2=Namera|first2=Akira|last3=Yashiki|first3=Mikio|last4=Iwasaki|first4=Yasumasa|last5=Kojima|first5=Tohru|date=1998-05-29|title=Simple analysis of local anaesthetics in human blood using headspace solid-phase microextraction and gas chromatography–mass spectrometry–electron impact ionization selected ion monitoring|journal=Journal of Chromatography B|volume=709|issue=2|pages=225–232|doi=10.1016/S0378-4347(98)00081-4|pmid=9657219}}</ref> Another application in forensic practice is the determination of [[date rape drug]]s (DRDs) in urine. These drugs are used to incapacitate victims and then rape or rob them. The analyses of these drugs are difficult due to the low concentrations in the body fluids and often a long time delay between the event and clinical examination. However, using GC-EI-MS allows a simple, sensitive and robust method for the identification, detection and quantification of 128 compounds of DRDs in urine.<ref>{{Cite journal|last1=Adamowicz|first1=Piotr|last2=Kała|first2=Maria|title=Simultaneous screening for and determination of 128 date-rape drugs in urine by gas chromatography–electron ionization-mass spectrometry|journal=Forensic Science International|volume=198|issue=1–3|pages=39–45|doi=10.1016/j.forsciint.2010.02.012|pmid=20207513|date=May 2010}}</ref>