Thermodynamic Analysis Of Specimen Evaporation - Thermo Scientific Vitrobot Mk IV User Manual

Chapter | Introduction

1.2.2 Thermodynamic analysis of specimen evaporation

The underlying graph illustrates that the evaporation velocity is independent of film thickness
but that the evaporation depends on the relative humidity in the reaction/climate chambe r. A
constant ice thickness is therefore easier to achieve at higher humidity. Furthermore it is clear
that thin film preparation under room conditions (e.g. 20 °C and a relative humidity of 40 %)
may result in an appreciable loss of water; in the two seconds of a typical preparation 80 nm
of the thickness of the thin film is evaporated. This evaporation has not only an effect on the
temperature (preceding paragraph) but also on the solute concentration (N.B. osmotic
effects!) and the concentration of the suspended particles.
Inside the climate chamber of the Vitrobot, a small micro-thermocouple is present which
measures the temperature in the chamber. In the figure below the temperature of the
specimen was measured during the vitrification process i.e. during dipping in a vial,
withdrawal, blotting and the last moments before the freezing. The thermal history was
estimated with an environmental humidity of 40 % (blue) and > 99 % (magenta) respectively
while the chamber temperature was at 38°C. Also note the slow/insufficient equilibration of the
temperature of the sample in the vial.
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PN 103261 | Revision D | 23-Oct-2019
User Manual
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