Calibrating ITC instruments

problems with weak base neutralization

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

Povzetek

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.

Ključne besede

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

Podatki

Jezik:	Angleški jezik
Leto izida:	2024
Tipologija:	1.01 - Izvirni znanstveni članek
Organizacija:	UL FKKT - Fakulteta za kemijo in kemijsko tehnologijo
UDK:	543.57:536.6
COBISS:	201903875
ISSN:	0003-2697
Št. ogledov:	48
Št. prenosov:	0
Ocena:	0 (0 glasov)
Metapodatki:

Ostali podatki

Sekundarni jezik:	Slovenski jezik
Sekundarne ključne besede:	kalorimetrija;izotermna titracijska kalorimetrija;kalibracija;kislinsko-bazna ravnotežja;difuzija;
Vrsta dela (COBISS):	Članek v reviji
Strani:	str. 1-9
Zvezek:	ǂVol. ǂ694, [article no.] 115602
Čas izdaje:	Nov. 2024
DOI:	10.1016/j.ab.2024.115602
ID:	24676138