Thermo Scientific TriPlus RSH, Руководство пользователя

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1
Getting Familiar with Your TriPlus RSH
MHE Station
52 TriPlus RSH User Guide Thermo Scientific
A(ref ) — Area that would be measured if all of the analyte were present in the headspace
(again corresponding to the measured signal from a similar gas standard).
A(0) — Actual area measured from the first extraction with 75% of the analyte in the gas
phase:
A(0) = ¾ * A(ref )
The total area determined by the MHE procedure is:
A(tot) = A(0) + ¼ * A(0) + 1/16 * A(0) + …… , or
A(tot) = A(0) / (1-¼) = 4/3 * A(0)
However, A(0) = ¾ * A(ref ) and therefore:
A(tot) = A(ref )
In this case, you also arrive at the correct value by determining the total amount of analyte by
comparing the measured sum of analyte areas to a calibration measurement using data from a
single determination of a gas standard.
The conclusion is, when in equilibrium, the relative ratio of the condensed phase versus the
headspace plays no role in the amount of analyte content that is determined from an
MHE-series.
Furthermore, it can be concluded that quantification based on a single determination from a
gas standard will, in this particular case, yield the correct result, assuming that the entire
headspace is removed/exchanged during each extraction step.
Situation 3
The equilibrium between the condensed phase and the headspace is assumed to be 50/50.
Furthermore, we assume that only a part of the headspace is removed between each sampling.
The relative amount of the headspace removed between each successive extraction constant
and is denoted
α.
The measured area of the analyte peak is A .
A(ref ) — Area that would be measured if all of the analyte were present in the headspace
(again corresponding to the measured signal from a similar gas standard).
A(0) — Actual area measured from the first extraction with 50% of the analyte in the gas
phase:
A(0) = ½ * A(ref )
The total area determined by MHE is:
A(tot) = A(0) + (1-? * ½) * A(0) + (1-? * ½)2 * A(0) + …… , or
A(tot) = A(0) / (1-(1-? * ½)) = A(0) * 2/
α