Molecular Average and Intramolecular δC Measurements of Pyruvic Acid and Acetic Acid Using Gas Chromatography Orbitrap Mass Spectrometry (GC Orbitrap-MS).

We developed a novel method using gas chromatography - Orbitrap mass spectrometry (GC Orbitrap MS) to measure the intramolecular carbon isotope value of pyruvic acid and acetic acid with high mass accuracy and mass resolution with nanomole (10-100) injections of analyte. Previous efforts to analyze intramolecular isotope patterns of small organic acids have been limited by labor-intensive chemical degradation steps, a narrow potential analyte pool, or large sample mass requirements. We present a new way to trap an analyte peak, which is then tested by measuring the molecular average and intramolecular carbon isotope values of pyruvic acid and acetic acid standards.

Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu.

Organic matter in meteorites reveals clues about early Solar System chemistry and the origin of molecules important to life, but terrestrial exposure complicates interpretation. Samples returned from the B-type asteroid Bennu by the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer mission enabled us to study pristine carbonaceous astromaterial without uncontrolled exposure to Earth's biosphere. Here we show that Bennu samples are volatile rich, with more carbon, nitrogen and ammonia than samples from asteroid Ryugu and most meteorites.

Sequential measurement of C, N, and S isotopic composition on nanomolar quantities of carbon, nitrogen, and sulfur using nano-elemental analysis/isotope ratio mass spectrometry.

Rationale: We report modifications to a commercial elemental analyzer-isotope ratio mass spectrometer that permit high-precision isotopic analysis of nanomoles of carbon (C), nitrogen (N), and sulfur (S) on a single sample without chemical or cryogenic trapping of gases. The sample size required for measurement by our system is about two orders of magnitude less than that for conventional analyses.

Methods: Our system builds on the analytical advancements offered by the EA IsoLink IRMS System and employs simple modifications to reduce the diameter of the flow path (reactors, water trap, and transfer lines), enhance peak separation (gas chromatography capillary column), and improve sample transfer to the ion source of the mass spectrometer (reduced flow rates).

Picomolar-scale compound-specific isotope analyses.

Rationale: We report modifications to compound-specific isotope analyses (CSIA) to enable high-precision isotopic analyses of picomoles of carbon for intact organic molecules. This sample size is two orders of magnitude below the amounts required for commercial systems. The greatly enhanced sensitivity of this system expands molecular isotope studies and applications previously prohibited by low concentrations and small samples.