Conference Agenda

Orbitrap-based Isotope Ratio MS provides a unique and complimentary tool to classical Isotope Ratio MS techniques to measure the relative abundance of isotopologues. The soft Electrospray Ionization of the Thermo Scientific™ Orbitrap Exploris™ MS produces intact molecular ions that can optionally be fragmented by higher energy collisional dissociation. Combining these features with the high-resolution accurate mass of Orbitrap analyzers gives insights into compound specific as well as position specific isotope ratios.

Precision and accuracy of Orbitrap-based isotope ratio analysis can be significantly improved by utilizing sample-standard bracketing to correct for instrument drift and inaccuracies via isotope ratio calibration. This is currently achieved either by the dual syringe inlet approach, which uses a diverter valve switching between two syringes filled with a sample and a standard or using an HPLC autosampler for alternating injections of sample and standard solutions.

Here we present an optimized workflow to increase system productivity while improving isotope ratio standardization. This workflow utilizes two flows of liquid controlled by a switching valve with one flow from the HPLC autosampler for sample introduction and a second flow from a syringe for standard introduction. This fully automated setup allows the injection of a standard during the washout period of the HPLC autosampler loop, reducing idle time while improving the quality of the measurements. Precision and accuracy can now be verified more easily by drift correction and one- or two-point calibration.

Isotope ratio calibration using the novel strategy for sample and standard introduction will be demonstrated on latest applications for inorganic (e.g. sulfate) and organic (e.g. amino acids, vanillin) samples showcasing unique insights into the isotopic anatomy of molecules.

The greenhouse gas research community faces a growing demand for simple and efficient isotopic analysis of discrete gas samples (e.g., carbon isotopes of CO₂ and CH₄). Conventional techniques such as Isotope Ratio Mass Spectrometry (IRMS) often involve high initial and maintenance costs, complex deployment procedures, and limited fieldwork adaptability. In contrast, the new Sage Gas Autosampler from Picarro offers an efficient and reliable solution when paired with a Picarro isotopic carbon analyzer. This system features a 150-position vial rack designed for 12mL headspace vials, each pressurized with approximately 30mL of gas. The measurement of each vial takes about 5min. At atmospheric concentrations, the δ¹³C precision for both CO₂ and CH₄ is approximately 0.3‰. Here, we detail the operational workflow of the Sage Gas Autosampler and present its performance data when integrated with the Picarro G2201-i carbon isotope analyzer. We will also discuss best practices for discrete isotope gas and concentration analysis when working with this analytical system.