Editing Titration (section)

===Gas phase titration===
Gas phase titrations are titrations done in the [[gas phase]], specifically as methods for determining reactive species by reaction with an excess of some other [[gas]], acting as the titrant.  In one common gas phase titration, gaseous [[ozone]] is titrated with nitrogen oxide according to the reaction

:O<sub>3</sub> + NO → O<sub>2</sub> + NO<sub>2</sub>.<ref>
{{Cite book
  | last = Hänsch
  | first = T.W.
  | title = Metrology and Fundamental Constants
  | publisher = IOS Press
  | year = 2007
  | pages = 568
  | isbn = 978-1-58603-784-0
}}</ref><ref>
{{Cite web
  | title = Gas phase titration
  | publisher = Bureau International des Poids et Mesures
  | url = http://www.bipm.fr/en/scientific/chem/gas_titration.html
  | access-date = 29 September 2001
}}</ref>

After the reaction is complete, the remaining titrant and product are quantified (e.g., by [[Fourier transform spectroscopy]]) (FT-IR); this is used to determine the amount of analyte in the original sample.

Gas phase titration has several advantages over simple [[spectrophotometry]].  First, the measurement does not depend on path length, because the same path length is used for the measurement of both the excess titrant and the product.  Second, the measurement does not depend on a linear change in absorbance as a function of analyte concentration as defined by the [[Beer–Lambert law]].  Third, it is useful for samples containing species which interfere at wavelengths typically used for the analyte.<ref>
{{Cite journal
  | last = DeMore
  | first = W.B.
  |author2=M. Patapoff
   | title = Comparison of Ozone Determinations by Ultraviolet Photometry and Gas-Phase Titration
  | journal = Environmental Science & Technology
  | volume = 10
  | issue = 9
  | pages = 897–899
  | date = September 1976
  | doi = 10.1021/es60120a012
| bibcode = 1976EnST...10..897D
  }}</ref>