Work

Kinetically tunable, subzero-active, visual time–temperature indicators based on the permanganate–oxalate reaction

Year: 2025

Type: article

Abstract: , we depressed the melting points of the reaction mixtures to -18 °C, -37 °C, and -67 °C, respectively. The incorporation of perchlorate salts as antifreeze systems did not derail the kinetic behavior of the permanganate-oxalate reaction and allowed the reactions to pause below their melting points. Here, we developed and characterized eight customized TTIs, running from five minutes at 25 °C to 7 days at -20 °C. Temperature sensitivity was consistent with Arrhenius behavior (i.e., exponential increases in run time with linear decreases in temperature). The TTIs exhibited good accuracy and reproducibility, with within-batch and between-batch run-time precision at the targeted temperatures of ≤ 4.8% CV and ≤ 7.5% CV, respectively. The average absorbance vs. time trajectories, expressed as RMSD %CVs, were 4.5% for intra-batch and 10.4% for inter-batch runs. Indicators withstood multiple freeze/thaw cycles or extended pre-freezing periods with minimal impact on reaction kinetics. Once activated and stored below their melting points, TTIs maintained color intensity for at least 12 months. This work establishes the permanganate-oxalate system in eutectic perchlorate-based antifreeze solutions as a simple, inexpensive approach for ultracold-active TTIs, offering customizable kinetics and robust performance. The described TTIs can serve to improve quality monitoring of biologicals and biospecimens during ultracold storage and handling.

Source: Reaction Chemistry & Engineering

DOI: 10.1039/d5re00192g

Authors: Jorvani Cruz Villarreal, Emil Ljungberg, Nilojan Jehanathan, Milap Owens, Anika Li, Chad R. Borges

Institution: Arizona State University

Language: English

Topic: Thermal and Kinetic Analysis

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: green

Funder: National Cancer Institute

Award: G1568072917