Purchase of an automated 15N, 13C analyzer for the University of Texas Marine Science Institute to replace a >25 year old isotope ratio mass spectrometer and associated high vacuum sample preparation lines is proposed. Although tens of thousands of samples have been analyzed using the present system, it is currently inoperable and requires a major overhaul. However, because of the system's age, its relatively primitive technology, and demand by several users, any repairs to the instrument are unlikely to be cost effective over the long term or meet the expectations of the scientific research staff at the Institute. Instead, the purchase of a new analyzer represents a substantial advance in technological capabilities which will open additional avenues of research for the scientists at the Institute as well as providing isotopic data for currently funded research programs. The proposed and currently funded research avenues include microbiological, ecological, physiological and chemical studies. This research will use the stable isotope compositions of bioactive elements, such as C and N, to delineate metabolic pathways, understand food webs in natural environments, and determine the sources, transformations and fates of these elements in ecosystems. The proposed analyzer is a compact instrument which determines the carbon and nitrogen isotopic ratios of gases, solids and liquids in their natural state with minimal sample preparation. Expensive and time consuming sample preparation on high vacuum lines with subsequent transfer of purified sample gases to a mass spectrometer is avoided in the proposed system since sample processing and isotopic analysis are integrated into one unit. An additional advantage of the proposed system over those presently available to Institute scientists is that samples with natural abundance of the 13C and 15N isotopes as well as isotopically amended samples used in tracer studies can be analyzed on one instrument.
