ALBERT

Description: The automated measurement of δ13C and δ18O from solid carbonate samples has been demonstrated using a ThermoScientific™ Delta Ray™ IRIS with URI Connect. The measurement of certified reference materials confirms the high achievable accuracy and a precision of 〈0.1‰ for both δ13C and δ18O.

Description: For many decades different instrumental methods, involving generations of the Thermo Fisher Scientific isotope ratio mass spectrometers with Kiel Carbonate device, and the continuous flow Gas Bench II with the Carbonate-Option, offered the scientifically required high precision and high throughput of samples for these applications. The Thermo Scientific Delta Ray Isotope Ratio Infrared Spectrometer (IRIS) Analyzer with the Universal Reference Interface (URI) Connect and TELEDYNE Cetac ASX-7100 autosampler, now extends the traditional offerings with a system that can be used in the laboratory or field and offers high precision and throughput of samples. Delta Ray IRIS uses isotope ratio infrared spectroscopy (IRIS) to determine isotope ratios. The laser light is generated by a difference frequency generation (DFG) mid-infrared laser which operates at 4.3 µm. Calculation of different carbon dioxide isotopologues and determination of stable isotope ratios from spectrum is possible due to absorption lines which are shifted relative to each other. The system can measure up to 100 samples per day, with a δ13C precision better than 0.15‰. Here we present sample preparation and sample processing method for determination of isotopic composition of carbon (δ13C) in dissolved inorganic carbon (DIC) and carbonate material with Delta Ray Connect, and comparison with traditional mass spectrometry methods. We analyzed carbonate material of several different calcifying organisms and seawater samples collected from coral culturing tank at GEOMAR. The preparation of the samples for analysis on the Delta Ray IRIS is similar to the previously mentioned Gas Bench II method. Both carbonate and water samples were acidified using a few droplets of 104% H3PO4 and left for equilibration to finish. Carbonates were measured at 80°C while water samples were measured at room temperature. Sample processing was identical. The CO2 gas generated by reaction was flushed into the Variable Volume inside the URI Connect through the Nafion based built-in water trap. As part of the workflow, reference gas was regularly measured at the same concentration as the sample to allow automatic drift and linearity correction. Sampling and measurement procedure were driven automatically from Qtegra Software. With each batch of samples, NBS 18 and IAEA-603 were measured and used as reference material for calibration. The obtained isotope ratios for NBS 18 and IAEA-603 were averaged and used to generate two-point calibration curves for the 13C/12C ratio. The calibration function was then applied to measured isotope ratios of the samples. Results gained with above described method are in a good agreement with data obtained using traditional IRMS methods, performed in two independent laboratories in Kiel, Germany and Graz, Austria.

Description: Carbonates represent one of the most important reservoir rocks for groundwater, geothermal energy and hydrocarbons. Since carbonates are mainly biological sediments, their depositional environment is often complex and frequently changing. Furthermore, they are often subjected to numerous diagenetic processes like dolomitization and karstification due to their high reactivity with acidic water. This heterogeneity is the main reason for their suitability as a reservoir rock, but also complicates their stratigraphic classification. Stable carbon and oxygen isotopes of carbonates might be a suitable tool to classify these rocks, because processes like dolomitization or shifts from inorganic to biologically driven deposition as well as global sea level changes due to climate change leave a unique isotope signal within their 13C and 18O isotope signature. The aim of our study is to calibrate a chemo-stratigraphic curve on a drill core representing a complete succession of Upper Jurassic carbonate rocks from Southern Germany. For our study we used Thermo Scientific™ Delta Ray™ Isotope Ratio Infrared Spectrometer (IRIS) with the Universal Reference Interface (URI) Connect, which allows fast and cost effective isotope analysis, even under field conditions. The Delta Ray Connect is based on direct absorption spectroscopy and is used for simultaneous determination of δ13C and δ18O. The results will help to validate, if stable isotopes of carbonate rocks are useful tools for stratigraphic analysis within the Upper Jurassic in Southern Germany and might allow classification of disintegrated drilling samples like cuttings. This will help to gain more information about the structure of the Upper Jurassic in the subsurface and might add important information e.g. for sequence stratigraphic purposes.