Calibrating ITC instruments : problems with weak base neutralization

Medoš, Žiga (avtor), Bešter-Rogač, Marija (avtor), Leontidis, Epameinondas (avtor), Tellinghuisen, Joel (avtor)

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.

• Jezik: Angleški jezik
• Ključne besede: calorimetry, isothermal titration calorimetry, calibration, acid-base reaction, diffusion
• Vrsta gradiva: Članek v reviji
• Tipologija: 1.01 - Izvirni znanstveni članek
• Organizacija: FKKT - Fakulteta za kemijo in kemijsko tehnologijo
• Status publikacije: Objavljeno
• Različica publikacije: Objavljena publikacija
• Leto izida: 2024
• Št. strani: 9 str.
• Številčenje: Vol. 694, art.115602
• PID: 20.500.12556/RUL-160001
• UDK: 543.57:536.6
• ISSN pri članku: 0003-2697
• DOI: 10.1016/j.ab.2024.115602
• COBISS.SI-ID: 201903875
• Datum objave v RUL: 07.08.2024

Gradivo je del revije

• Naslov: Analytical biochemistry
• Skrajšan naslov: Anal. biochem.
• Založnik: Elsevier
• ISSN: 0003-2697
• COBISS.SI-ID: 6506759

Licence

• Licenca: CC BY-NC 4.0, Creative Commons Priznanje avtorstva-Nekomercialno 4.0 Mednarodna
• Povezava: http://creativecommons.org/licenses/by-nc/4.0/deed.sl
• Opis: Licenca Creative Commons, ki prepoveduje komercialno uporabo, vendar uporabniki ne rabijo upravljati materialnih avtorskih pravic na izpeljanih delih z enako licenco.

Sekundarni jezik

• Jezik: Slovenski jezik
• Ključne besede: kalorimetrija, izotermna titracijska kalorimetrija, kalibracija, kislinsko-bazna ravnotežja, difuzija

Projekti

• Financer: ARIS - Javna agencija za znanstvenoraziskovalno in inovacijsko dejavnost Republike Slovenije
• Številka projekta: P1-0201
• Naslov: Fizikalna kemija

• Financer: ARIS - Javna agencija za znanstvenoraziskovalno in inovacijsko dejavnost Republike Slovenije
• Številka projekta: N1-0186
• Naslov: Metalcarborani kot edinstveno izhodišče za pripravo funkcionalnih nanostrukturiranih in polimernih materialov