Answer:
D) To minimize plate height, the optimal flow rate is the maxima for the plot of plate height versus flow rate.
Explanation:
Van Deemter equation in chromatography, relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation.
The formula is:
H = A + B/u + C×u
Where:
H = HETP (plate height)
A = Eddy diffusion term . Â
B = Longitudinal diffusion.
C = Resistance against mass transfer.
u = Linear velocity .
A) A takes into account multiple pathways through the column. The value of A is column specific and independent of linear flow. Â TRUE. Eddy difussion term depends of column packing
B) B takes into account longitudinal diffusion of the analyte in the mobile phase. The value of B is column specific and the impact of B on the plate height is inversely proportional to the linear velocity. TRUE. Longitudinal difussion is another term that is specific to a column. Also, as the formula is H = A + B/u + C×u, the impact of B on the plate height is inversely proportional to the linear velocity.
C) C takes into account equilibrium time between the stationary and mobile phase. The value of C is column specific and the impact of C on plate height is proportional to the linear velocity. Â TRUE. C is the time that system needs to equilibirum. Based on the formula, the impact of C on plate height is proportional to the linear velocity
D) To minimize plate height, the optimal flow rate is the maxima for the plot of plate height versus flow rate. Â FALSE. The optimal flow is the minimum of the graph
E) Linear velocity is the flow rate of the mobile phase. TRUE. The Van Deemter equation describes u as the linear velocity of the mobile phase.
I hope it helps!
