Page 370 - Academic Press Encyclopedia of Physical Science and Technology 3rd Analytical Chemistry

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Encyclopedia of Physical Science and Technology EN0011A-541 July 25, 2001 17:27

Organic Chemistry, Compound Detection 473

spectrometry (Py/MS) technique such as the Curie point The thermal reactions that accompany the smoking of
system offers considerable advantages: rapid analysis, au- tobacco and cannabis furnished important structural in-
tomation of the system, and direct chemical information. formation on tobacco alkaloids. The pyrolysis of tobacco
Laser microprobe mass analysis (LAMMA) on milligram alkaloids yielded products such as quinoline and isoquino-
amount of sample has been reported. An alternative ap- line and nicotinonitrile which are probably derived from
proach is the detection of very small (picogram) amounts nornicotine and mysomine. Pyrolysis of natural polyenes
of organic matter by direct ionization due to laser irradia- such as β-carotene yielded ionene and small amounts of
tion. Thus, digitonin (MW 1228) and sucrose (MW 342) toluene, m-xylene, and 2,6-dimethylnaphthalene.
were readily detected. Although the identification and quantitation of drugs,
New techniques such as Py/GC/MS/DS (pyrolysis/gas e.g., narcotics and alcohol blood levels, are of forensic
chromatography/mass spectrometry–data system) and interest, the major impact of analytical pyrolysis in foren-
Py/MS/DS have been applied for detection and structural sic science is in the identification of complex natural and
elucidation of complex organic compounds. synthetic substances such as blood, skin, hair, wood, soil,
fibers, plastics, and waxes, which might be associated with
a suspect and found in the scene of the crime.
1. Pyrolysis of Synthetic Polymers

The thermal degradation of synthetic polymers has proven
to be an extremely important analytical technique for re- 4. Pyrolysis of Organic Geopolymers
vealing composition, structure, and stability profiles. It
Pyrolysis methods are used for detection and identification
actually causes unzipping of the polymer chain to yield
of natural organic polymeric products in the geosphere
sequential monomer units. Thus, thermal depolymeriza-
(such as humic substances and kerogens). The impetus
tion of rubber (at 700 C and atmospheric pressure) yielded for much of this work has been provided by the US space
◦
isoprene and dipentene, whereas polystyrene yielded a se-
exploration program, when the efforts in taxonomy, bio-
ries of monomeric and dimeric hydrocarbons.
logical molecules, and organic geochemistry which have
resulted in Py/GC/MS studies, were undertaken on the sur-
2. Pyrolysis of Biological Molecules face of the planet Mars. The pyrolysis technique is also
being used in the study of environmental pollutants (indus-
The rapid extension of analytical pyrolysis into diverse
trial processes, power stations, and fires). The use of the
fields such as taxonomy and soil chemistry has been
Py/GC/MS technique furnished important information on
largely due to progress in the pyrolysis of biological
the structure of humic substances, melanoidins and coals.
molecules. Such work has shown that the various classes
The Rock–Eval method uses a special pyrolysis device
of molecules with the possible exception of nucleic acids
(coupled with GC) in which a small sample of sedimentary
give highly characteristic pyrograms and has enabled the
rock (containing organic matter) is progressively heated
detection of the origin of fragments of complex samples
◦
to 550 C. During the assay the hydrocarbons already
such as bacteria and soil constituents. Interest in the py-
present in the rock (S 1 ) are first volatilized; pyrolysis of
rolysis of biological molecules is also due to the commer-
kerogen then results in the generation of hydrocarbons,
cial importance of thermal degradation processes, such
hydrocarbon-like compounds (S 2 ), and oxygen contain-
as flame retardation, use of biomass such as algae for
ing volatiles, i.e., CO 2 (S 3 ) and water. Thus, S 1 + S 2 ,ex-
production of oil and gas (energy), and thermal transfor-
pressed in kilograms of hydrocarbons per ton of rock, is
mations of organic constituents of food during cooking.
an evaluation of genetic potential (abundance and type of
Thus, the sensitivity and specificity of Py/GC/MS has en-
organic matter) of the rock.
abled octapeptides in infusion fluids and two closely re-
lated hormones, lypressin and felypressin to be detected
in nanogram amounts in aqueous solutions.
5. Extraterrestrial Matter
Coupled pyrolysis techniques have been used for the anal-
3. Pyrolysis of Drugs and Natural Products
ysis of extraterrestrial organic matter to provide evidence
Py/GC, Py/GC/MS, and HPLC/MS are routinely used for on molecular evolution within the solar system. Samples
the analysis of pure and formulated drugs or for the de- analyzed so far included meteorites collected on the sur-
tection of active principles and metabolites in body fluids. face of the earth, lunar rocks transported to earth and cer-
The Py/GC method is used for detection of sulfonamides, tain soils analyzed on the surface of that planet. The fully
barbiturates, and alkaloids such as morphine; heroine, automated Py/GC/MS/DS analysis of Martian soils re-
phenacetin and caffeine (often used in forensic science). vealed only the presence of water and CO.