Instruments and IRMS Techniques

For δ13C and δ18O measurements, Isotope Ratio Mass Spectrometry (IRMS – Delta V) is employed. In this method, samples are converted to CO2 gas, typically through a reaction with phosphoric acid. The resulting CO2 gas is then analyzed in the mass spectrometer to determine the isotopic ratios.

Sample preparation and powder sampling

For carbon and oxygen isotope measurements by IRMS, approximately 1-2 mg of carbonate powder is required. The samples should be clean, free of contaminants, and representative of the mineral phase of interest to ensure accurate results. The measurement of carbonate oxygen and carbon isotopes can be done at different scales and using various sampling techniques. Here’s an overview of the main methods used:

Conventional IRMS on Powder Samples collected with a Dremel:  Using a Dremel tool, samples are collected as powder from a 2 mm wide area. This method is useful for obtaining bulk measurements of isotopic ratios from a relatively large sample area. It is quick and easy to perform, making it suitable for homogenised or large-scale samples. However, it has less spatial resolution and may mix isotopic signals from different growth layers or phases within the sample.

Conventional IRMS on micro-powder sample collected with a Micro-mill System: The micro-mill system allows for targeted sampling of very small areas, ranging from sub-millimeter to millimeter scale. This method is ideal for extracting samples from specific microstructural features within a carbonate, such as growth layers or distinct mineral phases. It offers higher spatial resolution compared to macro-sampling, enabling detailed study of isotopic variations within a sample. Although it is more time-consuming and requires careful handling to avoid contamination, it provides a more precise analysis.

Precision and accuracy

Isotope Ratio Mass Spectrometry (IRMS) for carbon and oxygen isotopes can achieve a precision of ±0.1‰ for δ13C and ±0.2‰ for δ18O. These high levels of precision are essential for reliable isotopic measurements and subsequent geological interpretations.

Figure 1. This figure illustrates the GeoMill 360 used for precise sampling of carbonate samples. The top and bottom left images show the GeoMill 360 extracting ‘in-situ’ samples on a thin section under a camera. The bottom middle image displays the full setup of drilling with computer monitoring. The right image depicts sample preparation for isotope ratio mass spectrometry (IRMS) using a Thermo Fisher Delta V.

Cost of δ13C and δ18O Analysis and delay

To provide accurate pricing and an official quote, please specify the number of samples along with the name and billing address of the paying institution. Nor­mally, the turnaround time is in­ the or­der of two to four weeks, de­pend­ing on the number of new samples ­sub­mitted­ and those already on the waiting list.

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At H-Expertise Services, we leverage advanced techniques, state-of-the-art equipment, and the expertise of our geochemist with decades of practical experience to ensure you receive precise and insightful data, deepening your understanding of geological systems.  Partner with us for unmatched expertise and impactful results. Please contact our specialist, Xavier Mangenot, at xavier.mangenot@h-expertise-services.com to discuss your operational needs, pricing, and to design a customised analytical strategy tailored to your requirements.

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