Oxygen and hydrogen isotopes in fossil insect chitin as paleoenvironmental indicators

Abstract

Isotopic analyses of the minute quantities of chitin typically available from a fossil locality is facilitated by a new method of extracting 8180 and 82H values from a single organic sample. This involves the pyrolysis of materials in quartz-encapsulated nickel tubes. When heated to 1050*C hydrogen diffuses through the nickel and is held in the surrounding evacuated quartz envelope. This is transferred to a mass spectrometer for analysis, then CO2 is extracted from the nickel tube on a vacuum-separation line and analyzed for 818O.

Compensation for exchangeable hydrogen is achieved through equilibration with water of known 82H at 0*C. In this procedure, purified chitin or cellulose is soaked in NaOH solution at about 0*C to open up the structure and make the maximum number of hydrogen atoms available for exchange.This method allows compensation for the influence of non-conservative, oxygen-bonded hydrogen in measured 82H values.