Preprints
https://doi.org/10.5194/os-2020-120
https://doi.org/10.5194/os-2020-120

  16 Feb 2021

16 Feb 2021

Review status: a revised version of this preprint was accepted for the journal OS and is expected to appear here in due course.

Technical Note: Stability of tris pH buffer in artificial seawater stored in bags

Wiley H. Wolfe1, Kenisha M. Shipley1, Philip J. Bresnahan2, Yuichiro Takeshita3, Taylor Wirth1, and Todd R. Martz1 Wiley H. Wolfe et al.
  • 1Scripps Institution of Oceanography, University of California San Diego, La Jolla, 92093, USA
  • 2Department of Earth and Ocean Sciences, University of North Carolina Wilmington, Wilmington, 28403, USA
  • 3Monterey Bay Aquarium Research Institute, Moss Landing, 95093, USA

Abstract. Equimolar tris (2-amino-2-hydroxymethyl-propane-1,3-diol) buffer in artificial seawater is a well characterized and commonly used standard for oceanographic pH measurements. We evaluated the stability of tris pH when stored in flexible, gas impermeable bags across a variety of experimental conditions, including bag type, tris batch, and storage in air vs. seawater over 300 days. Bench-top spectrophotometric pH analysis revealed that the pH of tris stored in bags drifted at a rate of −0.0058 ± 0.0008 yr−1 (mean slope ± 95 % confidence interval of slope). Analyses of total dissolved inorganic carbon confirmed that a combination of CO2 infiltration and/or microbial respiration led to the observed decrease in pH. Eliminating bagged tris pH drift remains a goal, yet the pH drift rate of 0.006 yr−1 is lower than many processes of interest and demonstrates the value of bagged tris to sensor calibration and validation of autonomous in situ pH measurements.

Wiley H. Wolfe et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2020-120', Jens Daniel Müller, 11 Mar 2021
    • AC1: 'Reply on RC1', Phil Bresnahan, 05 May 2021
  • RC2: 'Comment on os-2020-120', Anonymous Referee #2, 18 Mar 2021
    • AC2: 'Reply on RC2', Phil Bresnahan, 05 May 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2020-120', Jens Daniel Müller, 11 Mar 2021
    • AC1: 'Reply on RC1', Phil Bresnahan, 05 May 2021
  • RC2: 'Comment on os-2020-120', Anonymous Referee #2, 18 Mar 2021
    • AC2: 'Reply on RC2', Phil Bresnahan, 05 May 2021

Wiley H. Wolfe et al.

Wiley H. Wolfe et al.

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Short summary
We tested the stability of a well-characterized seawater pH buffer, tris, during long-term storage in gas impermeable bags. Tris is used to validate pH measurements; it is critical that we understand how its chemistry changes over time. Correspondingly, we prepared multiple batches of tris buffer in artificial seawater, stored the buffer in multiple types of gas impermeable bags, and analyzed its pH over the course of 300 days, discovering an average drift of −0.006 yr−1.