PerkinElmer Clarus SQ 8 MS Series, Hardware Manual

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Maintenance
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Analytical Column
The analytical column inside the Clarus GC oven provides the sample separation.
Make sure you select the proper column for your analysis. PerkinElmer offers a
wide range of columns in the
Gas Chromatography Column Catalog. The
TurboMass Tutorial provides additional column selection tips.
There are several things to consider when choosing an analytical capillary column:
1.
Know the types of samples you will be analyzing. Are they volatile, semi-volatile,
pesticides, solvents, etc?
2.
Select a stationary phase based on polarity of the sample. A very general rule in
column selection is that like dissolves like. Column polarity has the greatest effect
on how the column separates the compounds of interest as the sample interacts with
the stationary phase. There are different degrees of polarity from non-polar to very
polar. When compounds are separated primarily on their boiling points the phase is
considered to be non-polar. Polar phases typically separate compounds based on the
chemical interactions between the sample components and the stationary phase.
3.
The inside diameter of the capillary column has an effect on the column’s resolving
power and its capacity or concentration range. In general, the larger the inside
diameter of the column, the larger the sample capacity. However, the larger the
inside diameter, the higher the flow necessary to achieve good performance.
4.
The next parameter is the phase or film thickness. Film thickness will primarily
affect the retentive character and the capacity of the column. Increasing the film
thickness will cause an increase in the retention of the compounds being analyzed.
Thick film columns are primarily used for extremely volatile compounds. The
thicker phases will retain components longer, allowing them to interact longer with
the stationary phase, thereby increasing the separation of closely eluting compounds.
5.
The last variable to consider is column length. The effect of column length on a
separation becomes less important as column length increases. Resolution is a
function of the square root of the column length. An example of this relationship is
that, if you want to double the separation between two peaks without changing the
stationary phase, inside diameter, film thickness, or GC conditions, it would take a
four-fold increase in the column length. A 30 meter column is the most common
length and is usually sufficient for analyzing most samples. Typically, users doing
environmental EPA type analysis will use a 30 meter column for semi-volatile
compounds and 60 to 105 meter columns for volatile compounds.