The shown chromatogram was recorded on a column of 30 m length and 0.32 mm internal diameter with a carrier gas flow rate of 2 mL/min. Determine the dead time of this column.
I keep getting a dead time that is really really small but I know it should be around 5 minutes...any hints to figure this out?
To determine the dead time of a chromatographic column, you need two pieces of information: the length of the column (L) and the average linear velocity of the carrier gas (u).
The average linear velocity (u) can be calculated using the formula:
u = Flow rate (F) / (cross-sectional area of the column)
In this case, the flow rate is given as 2 mL/min and the internal diameter of the column is 0.32 mm. To calculate the cross-sectional area of the column (A), you need to convert the diameter from millimeters to meters:
A = π * ((diameter / 2) ^ 2)
A = 3.1415 * ((0.32 / 2000) / 2) ^ 2
Once you have the cross-sectional area (A) and the flow rate (F), you can calculate the average linear velocity (u).
Once you have the average linear velocity, the dead time (t0) of the column can be determined using the formula:
t0 = L / u
Plugging in the values for the given length of the column (30 m) and the calculated average linear velocity (u), you can calculate the dead time.
If you are getting a dead time that is too small, double-check your calculations for the average linear velocity. Make sure you convert all units to the same system (e.g., meters instead of millimeters) and perform all calculations correctly.
By following these steps, you should be able to obtain the correct dead time for the chromatographic column.