On-line delta O-18 measurement of organic and inorganic substances

A method for the automated sample conversion and on-line oxygen isotope rat io (delta(18)O) determination for organic and inorganic substances is prese nted. The samples are pyrolytically decomposed at 1400 degrees C in the pre sence of nickelized graphite. With the system presented organic as well as inorganic samples such as nitrates, sulphates and phosphates of 50-100 mu g O can be analyzed for their delta(18)O values with a standard deviation us ually better than 0,5 parts per thousand, Additionally, carbon isotope rati os of organic substances and nitrogen isotope ratios of inorganic nitrogeno us compounds are available in the same sample run. Data for international a nd some inter-laboratory reference materials are presented to show the accu racy and reliability of the method. The effect of some additives on the CO yield was checked for substances which do not pyrolyze completely. Copyrigh t O 1999 John Whey & Sons, Ltd.