Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Pyrolysis gas chromatography mass spectrometry

From Wikibooks, open books for an open world
Jump to navigation Jump to search

Pyrolysis gas chromatography mass spectrometry is a method of chemical analysis in which the sample is heated to decomposition to produce smaller molecules that are separated by gas chromatography and detected using mass spectrometry.[1]

How it works[edit | edit source]

Pyrolysis is the thermal dissociation of materials in an inert atmosphere or a vacuum. The sample is put into direct contact with a platinum wire, or placed in a quartz boat inside a platinum coil, and rapidly heated to 600 – 800 C. Large molecules cleave at their weakest points and produce smaller, more volatile fragments. Various methylating reagents, which increase the volatility of polar fragments, can be added to a sample before pyrolysis. These fragments can then be separated on a gas chromatograph (GC).

Not as well-known is the pyrolysis inside a Programmable Temperature Vaporizer (PTV) injector. The reason this technique is relatively unknown is that PTV injectors in general are of yet not often used. With some of the latest versions it is now possible to heat the sample very quickly until an end temperature of 600°C is reached. Some PTV's have a ramp rate of 30°C/sec. The fast ramp rate and the end temperature of 600°C are enough to make good pyrolysis. There are many advantages to using the injector as a pyrolyser. There is a price advantage, and switching from pyrolysing to normal GC injections can be done without changing the configuration of the hardware. Both liquid as well solid samples can be used when a PTV injector with a relative big liner is used. Real quantitative data can be acquired, and good results of derivatization inside the PTV injector are published.

Applications[edit | edit source]

Pyrolysis gas chromatography is very useful for the identification of synthetic polymeric media, such as acrylics or alkyds, and synthetic varnishes.[2] It can also be used for environmental samples.[3], including fossils.[4]

ref. to publications of in-injector pyrolysis:
- Erwin Kaal, Sjaak de Koning, Stella Brudin, Hans-Gerd Janssen Journal of Chromatography A, 1201 (2008) 169–175.
- Hyphenation of aqueous liquid chromatography to pyrolysis-gas chromatography and mass spectrometry for the comprehensive characterization of water-soluble polymers Erwin R. Kaal, Mitsuhiro Kurano, Margit Geißler, Hans-Gerd Janssen Journal of Chromatography A, 1186 (2008) 222–227

References[edit | edit source]

  1. Halket JM, Zaikin VG (2006). "Derivatization in mass spectrometry --7. On-line derivatisation/degradation". European journal of mass spectrometry (Chichester, England) 12 (1): 1–13. doi:10.1255/ejms.785. PMID 16531644. 
  2. "National Gallery of Art Conservation: Scientific Research". Retrieved 2007-08-21. 
  3. Janos P (2003). "Separation methods in the chemistry of humic substances". Journal of chromatography. A 983 (1-2): 1–18. doi:10.1016/S0021-9673(02)01687-4. PMID 12568366. 
  4. Poinar HN (2002). "The genetic secrets some fossils hold". Acc. Chem. Res. 35 (8): 676–84. doi:10.1021/ar000207x. PMID 12186573.