TY - JOUR

T1 - Effect of Thermal Lag and Measurement Precision in Differential Scanning Calorimetry

T2 - Theoretical Guidelines for Enzyme-Substrate Reactions by the Method of Orthogonal Collocation

AU - Whiting, L. F.

AU - Carr, P. W.

PY - 1978

Y1 - 1978

N2 - A simplified model of a differential scanning calorimeter (DSC) with large (40-120 µL) aqueous enzyme sample was simulated digitally by the mathematical technique called orthogonal collocation in order to observe the errors due to thermal lag (temperature and concentration gradients) in calculating the first-order Arrhenius kinetic parameters Zand ΔE. Only two dimensionless parameters were found to influence the determinate errors in the data, one related to the scan rate and the other related to the rate of diffusion relative to the rate of chemical reaction. The errors were independent of ΔH, C0, and Dm and also the parameters Z, ΔE, and To as long as the initial rate constant, k0, remained unchanged. Simulations also indicate that In Z and Δ can be obtained to within 5 % for an 80-µL sample at a scan rate of 5 K/min. An additional study was carried out involving the indeterminate errors incurred when one scans slowly relative to the rate of chemical reaction. Results indicate that random errors can easily be several times greater than the determinate errors related to thermal lag.

AB - A simplified model of a differential scanning calorimeter (DSC) with large (40-120 µL) aqueous enzyme sample was simulated digitally by the mathematical technique called orthogonal collocation in order to observe the errors due to thermal lag (temperature and concentration gradients) in calculating the first-order Arrhenius kinetic parameters Zand ΔE. Only two dimensionless parameters were found to influence the determinate errors in the data, one related to the scan rate and the other related to the rate of diffusion relative to the rate of chemical reaction. The errors were independent of ΔH, C0, and Dm and also the parameters Z, ΔE, and To as long as the initial rate constant, k0, remained unchanged. Simulations also indicate that In Z and Δ can be obtained to within 5 % for an 80-µL sample at a scan rate of 5 K/min. An additional study was carried out involving the indeterminate errors incurred when one scans slowly relative to the rate of chemical reaction. Results indicate that random errors can easily be several times greater than the determinate errors related to thermal lag.

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U2 - 10.1021/ac50036a017

DO - 10.1021/ac50036a017

M3 - Article

AN - SCOPUS:33947094451

SN - 0003-2700

VL - 50

SP - 1997

EP - 2006

JO - Analytical Chemistry

JF - Analytical Chemistry

IS - 14

ER -