Suppose you have a 14.3 cm long chromatography column with an inner diameter of
ID: 558283 • Letter: S
Question
Suppose you have a 14.3 cm long chromatography column with an inner diameter of 4.58 mm that is packed with a stationary phase that occupies 60.0% of the volume. What is the linear flow rate, ux, in cm/min, if the volumetric flow rate, uv, is 1.49 mL/min?
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Suppose you have a 14.3 cm long chromatography column with an inner diameter of 4.58 mm that is packed with a stationary phase that occupies 60.0% of the volume. What is the linear flow rate, ux, in cm/min, if the volumetric flow rate, uv, is 1.49 mL/min? Incorrect You have used the fraction of the column occupied by the stationary phase in your calculation of the volume occupied by the mobile phase, Vm The fraction occupied by the mobile phase is equal to (100%-60.0%)/100. Number cm/ min b 11 = 15.1 x How long will it take, in minutes, for the solvent to pass through the column? Number tm | | 0.95 min What is the retention time, in minutes, on this column for a solute with the retention factor, k, of 11.0? Number minExplanation / Answer
Inner diameter = 4.58 mm = 0.458 cm
Radius = Diameter/2 = 0.458/2 = 0.229 cm
Volume = pi * r^2 * L = pi * (0.229)^2 * 14.3 = 2.355 cm^3
Volume of mobile phase = 40% of total volume = 0.40 * 2.355 cm^3 = 0.942 cm^3 = 0.942 mL
Fraction of column swept by mobile phase/min = 1.49/0.942 = 1.581 min^(-1)
Flow rate = 1.581 min^(-1) * 14.3 cm = 22.618 cm/min
Time taken = Column length/Flow rate = 14.3/22.618 = 0.6322 min
k = tR'/tm
tR' = 11tm = 11(0.6322) = 6.9542
Retention time = tR' + tm = 6.9542 + 0.6322 = 7.5864 min
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