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Versa User Manual www.teledynetekmar.com
Method Development • Page 6-4
samPLe eqUiLibration
Platen/sample temperature
One of the factors that has a direct influence on the K value is the platen/sample temperature. Typically, the higher
the temperature the lower the K value. As the sample temperature increases, the solubility of the analyte increases,
but the vapor pressure also increases. The vapor pressure increase will have a larger effect on the K value than the
solubility increase thus forcing the equilibration towards the gas phase. It should be noted that there are typically
limitations to the sample temperature due to the matrix. It is not recommended to exceed temperatures above
15°C below the boiling point of the matrix. For example, if the matrix is water, then it is not recommended to
exceed 85°C for the platen/sample temperature. Another negative effect associated with elevated platen/sample
temperatures, is sample degradation due to temperature. Thermally liable compounds can breakdown at high
temperatures causing reduced response. The Method Optimization Mode (M.O.M.) is best suited for identification
of the ideal sample equilibration temperature. Refer to the M.O.M. usage instructions in this manual for additional
information on this feature.
Platen/sample time
After the platen/sample temperature has been selected, it is critical to select a sample equilibration time that allows
the sample to reach equilibrium prior to the sampling step. Allowing the sample to reach equilibrium prior to
sampling allows for the method to be robust. In rare cases, mainly when working with solids that exhibit low diffusion
characteristics, the sample may never reach equilibrium. The sample equilibration time can easily be determined using
the M.O.M. function explained in this manual.
mix time
The last steps that comprise the total thermal exposure time are the mix functions, Mix Time and Mix Equilibration.
Mixing the sample typically helps reduce the total thermal exposure time needed to allow the sample to reach
equilibrium. This is especially true when analyzing liquid samples. The mixing step increases the gas to liquid interface
in the vial thus reducing the distance that an analyte needs to travel to reach the gas phase within the vial. Mix time is
never recommended to exceed more than 20% of the sample equilibration time.
mix Power and agitation mechanism
The RPM at which the Mixer turns can be adjusted by changing the mixer speed. The sample should never be mixed
hard enough to allow sample to be splashed onto the septa.
mix equilibration
Once the sample has been mixed, Mix Equilibration Mode can be used to allow the sample to re-equilibrate after the
mix step. This parameter is typically set between 30 seconds and 2 minutes.