1
Getting Familiar with Your TriPlus RSH
MHE Station
Thermo Scientific
TriPlus RSH User Guide
57
Procedure for Determining Acetone Content
The steps for determining the acetone content are outlined in the following example:
•
A
— Each of the six calibration standards is extracted five times for increasing the
quality
of the determination).
See
“A. Performing the actual MHE Measurements”
•
B
— For each of the six calibration samples, the five areas from the five extractions are
taken into account in determining the
total area
.
See
“B. Determination of the Total Area”
.
•
C
— An external standard calibration curve is established for acetone by plotting the
calculated total area as a function of the amount of acetone in the standard.
Remember that each of the
total areas
is a result of the MHE calculation for five
extractions.
See
“C. Construction of the Calibration Curve”
.
•
D
— The
total area
is determined for any one of the real samples. The total content of
the analyte is calculated from this value and the calibration curve.
See
“D. Calculation of the Analyte Content in Real Samples”
.
A. Performing the actual MHE Measurements
The parameters of the actual MHE measurements, such as incubation time, incubation
temperature, injection parameters, and so on, can be controlled using the MHE cycle that is
part of the MHE kit.
B. Determination of the Total Area
As you are performing a multiple headspace extraction to determine the total area, you can
expect a functional relationship of the type.
A = A(0) * exp(-k * n)
, where n is the extraction number
See
Therefore, by plotting the natural logarithm of the area as a function of the extraction
number, you can expect a linear relationship, from which the constants
A(0)
and
k
can be
directly determined by means of the standard linear regression techniques.
Finally, the
total area
can be determined as:
A = A(0)/(1-exp(-k))
.
The linear regression determination of the constants can be easily performed using a simple
Excel setup as well as the determination of the total area. The following Excel-sheet shows the
MHE-data for one of the calibration samples. See
.
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