Practical considerations for amino acid isotope analysis

Silverman, Shaelyn N.; Phillips, Alexandra A.; Weiss, Gabriella M.; Wilkes, Elise B.; Eiler, John M.; Sessions, Alex L.

doi:10.1016/j.orggeochem.2021.104345

Practical considerations for amino acid isotope analysis

Journal Article · Tue Dec 28 00:00:00 EST 2021 · Organic Geochemistry

DOI:https://doi.org/10.1016/j.orggeochem.2021.104345· OSTI ID:1977525

Silverman, Shaelyn N. ^[1]; Phillips, Alexandra A. ^[2]; Weiss, Gabriella M. ^[3]; Wilkes, Elise B. ^[2]; Eiler, John M. ^[2]; Sessions, Alex L. ^[2]

California Institute of Technology (CalTech), Pasadena, CA (United States); OSTI
California Institute of Technology (CalTech), Pasadena, CA (United States)
California Institute of Technology (CalTech), Pasadena, CA (United States); Pennsylvania State University, University Park, PA (United States)

Over the last few decades, isotopic analysis of amino acids at the compound- and position-specific levels has been rapidly advancing across diverse fields. As these techniques progress, evaluation of isotopic fractionation associated with sample workup is essential. This critical review of analytical methods through the lens of isotope geochemistry provides a benchmark for researchers across disciplines seeking to make compound- and position-specific amino acid isotope measurements. We focus on preparation, acid hydrolysis, clean-up, derivatization, separation, and C, H, N, and S isotope measurement. Despite substantial customizability across these steps, the following general recommendations should maximize recovery while minimizing isotopic fractionation. Samples should be freeze-dried and stored anoxically at ≤ –20 °C prior to conventional acid hydrolysis (6N HCl, 110 °C, 20–24 h, anoxic), which suffices for many residues. Both gas and liquid chromatographic (GC and LC, respectively) techniques are well-established and separate about 15 amino acids; LC bypasses the need for derivatization, while GC provides higher sensitivity. Furthermore, when derivatization is needed, n-acetyl and alkoxycarbonyl esters provide the most reproducible C isotope ratios. For compound-specific analyses, online GC–IRMS and LC–IRMS systems offer the easiest workflow, but EA–IRMS enables potential multi-element isotope analysis. Emerging techniques like high-resolution mass spectrometry are also promising for multi-element analysis and recover position-specific isotopic information. Looking forward to the next decade of innovation, isotope geochemists and ecologists can improve amino acid isotope analysis by focusing on streamlining multi-element analysis and standardizing calibration practices across laboratories.

View Accepted Manuscript (DOE)

Research Organization:: California Institute of Technology (CalTech), Pasadena, CA (United States)

Sponsoring Organization:: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Simons Foundation; USDOE; USDOE Office of Science (SC)

Grant/Contract Number:: SC0016561

OSTI ID:: 1977525

Alternate ID(s):: OSTI ID: 1845165

Journal Information:: Organic Geochemistry, Journal Name: Organic Geochemistry Journal Issue: C Vol. 164; ISSN 0146-6380

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Acid hydrolysis
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