Page 237 - Tandem Techniques

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transfer capillaries were constructed from deactivated fused silica tubes, 0.32 mm I.D. The water
formed by combustion was removed by a tubular Nafion membrane, which was mounted coaxially in a
stainless steel tube. The annular volume round the transfer tube was purged free of water vapor by
means of a stream of helium gas. The flow of eluent from the water separator to the mass spectrometer
was controlled by an open split valve, similar to that described on page 154, in Chapter 4. The mass
spectrometers used were the Delta S and the Finnigan MAT 252.

It was found that the organic carbon contained in peaks, 5 sec or more in width, containing as much as
40 nmol of carbon, could be quantitatively converted to C02, in tubular combustion reactors 200 x 0.5
mm, packed with either copper oxide or nickel oxide. No auxiliary supply of oxygen was required, the
necessary oxygen for oxidation being provided by the oxides. Due to the relatively high partial pressure
of oxygen over copper oxide at high temperatures, this material could not be used above 850°C.
Combustion was complete using nickel oxide at 1150°C and, if some free oxygen was present, the
reaction temperature could be reduced to 1050°C. It was found that the standard deviation of the data
for the measurement of C/ C was less than twice the shot noise, and so the combustion system did not
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affect the analytical precision. It was also found essential to remove all the water produced during
combustion, otherwise protonation of the CO would result in significant inaccuracies.
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Pyrolysis GC/MS of Biological Particulates Collected During Space Shuttle Missions

The absence of significant gravitational forces when in orbit allows particles of human food, skin
flakes, paint chips, lint, dust etc., to remain suspended in the shuttle atmosphere, until removed by air
filters. These free-floating particles, and those arising from in-space experiments, are potential sources
of eye, skin and other forms of irritation, and could also transport and spread infectious diseases and
possibly produce other types of hazard. Concern over the possible release of particles from animal and
other experiments, and the likely and consequent effects on health has