problems with weak base neutralization
Žiga Medoš (Author), Marija Bešter-Rogač (Author), Epameinondas Leontidis (Author), Joel Tellinghuisen (Author)

Abstract

Modern isothermal titration calorimetry instruments give great precision, but for comparable accuracy they require chemical calibration. For the heat factor, one recommended process is HCl into the weak base TRIS. In studying this reaction with a VP-ITC and two Nano-ITCs, we have encountered some problems, most importantly a titrant volume shortfall Δv ≈ 0.3 μL, which we attribute to diffusive loss of HCl in the syringe tip. This interpretation is supported by a mathematical treatment of the diffusion problem. The effect was discovered through a variable-v protocol, which thus should be used to properly allow for it in any reaction that similarly approaches completion. We also find that the effects from carbonate contamination and from OH− from weak base hydrolysis can be more significant that previously thought. To facilitate proper weighting in the least-squares fitting of data, we have estimated data variance functions from replicate data. All three instruments have low-signal precision of σ ≈ 1 μJ; titrant volume uncertainty is a factor of ∼2 larger for the Nano-ITCs than for the VP-ITC. The final heat factors remain uncertain by more than the ∼1 % precision of the instruments and are unduly sensitive to the HCl concentration.

Keywords

kalorimetrija;izotermna titracijska kalorimetrija;kalibracija;kislinsko-bazna ravnotežja;difuzija;calorimetry;isothermal titration calorimetry;calibration;acid-base reaction;diffusion;

Data

Language: English
Year of publishing:
Typology: 1.01 - Original Scientific Article
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
UDC: 543.57:536.6
COBISS: 201903875 Link will open in a new window
ISSN: 0003-2697
Views: 48
Downloads: 0
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Other data

Secondary language: Slovenian
Secondary keywords: kalorimetrija;izotermna titracijska kalorimetrija;kalibracija;kislinsko-bazna ravnotežja;difuzija;
Type (COBISS): Article
Pages: str. 1-9
Issue: ǂVol. ǂ694, [article no.] 115602
Chronology: Nov. 2024
DOI: 10.1016/j.ab.2024.115602
ID: 24676138