Hplc Column Volume Calculator

HPLC Column Volume Calculator

Calculate Geometrical Volume and Void Volume based on column dimensions.

Measured in millimeters (mm)

Measured in millimeters (mm)

Usually 0.60 – 0.70 for fully porous particles

Understanding HPLC Column Volume

In High-Performance Liquid Chromatography (HPLC), knowing the column volume is essential for method development, scaling separations between different column sizes, and calculating parameters like gradient delay and dwell volume. This calculator determines both the Geometrical Volume and the estimated Void Volume (Dead Volume).

Geometrical Volume vs. Void Volume

It is important to distinguish between the two types of volumes calculated:

• Geometrical Volume (V_c): This is the total volume of the empty cylinder that makes up the column. It is calculated purely based on the physical dimensions (Length and Internal Diameter).
• Void Volume (V₀): Also known as Dead Volume or Hold-up Volume, this represents the volume of the mobile phase inside the column. It accounts for the space between the stationary phase particles (interstitial volume) and the pore volume within the particles.

Typical Porosity Values: For fully porous packing materials (e.g., standard silica C18), the total porosity is typically between 0.60 and 0.70 (defaulting to 0.68). For core-shell (superficially porous) particles, porosity is generally lower, often around 0.50 to 0.55.

The Formulas

The calculator uses the standard cylinder volume formula for the Geometrical Volume:

$$ V_c = \pi \times r^2 \times L $$

Where:

• $r$ = Radius (Internal Diameter / 2) in mm
• $L$ = Column Length in mm
• Result is in cubic millimeters ($mm^3$), which is equivalent to microliters ($\mu L$).

The Void Volume is estimated using the total porosity ($\epsilon$):

$$ V_0 = V_c \times \epsilon $$

Why is this Important?

1. Method Transfer: When moving a method from a standard HPLC to a UHPLC, or scaling up to preparative chromatography, you must maintain the ratio of sample volume to column volume to ensure consistent resolution.

2. t₀ Determination: The void volume allows you to calculate the dead time ($t_0$), which is the time it takes for an unretained compound to pass through the column at a given flow rate ($F$):

$$ t_0 = \frac{V_0}{F} $$

3. Gradient Scaling: When changing column dimensions, the gradient time must be adjusted relative to the column volume to maintain separation selectivity.