Void volume

Void Volume Calculation for chromatography.

1. Void Volume Presented By MD. MORSHEDUL H AQUE 4 th year student Department of Environmental Sciences Jahangirnagar University, Savar , Dhaka.

2. Definition - What does Void Volume mean? Void volume is the volume of the pores or space between particles in: Ion exchanger Filter media Other granular material This is often expressed as a percentage of the total volume occupied by the material . Void volume refers specifically to the volume of the liquid phase contained inside a column. The same term is sometimes also used informally to refer to the volume of a cavity in the column/tubing or fittings . Void volume is also known as dead volume .

3. Determination of Void Volume Void volume is the volume of mobile phase ( Vm or V0) in a column. In an ideal case, it is equal to the mobile phase hold-up volume . For example, if the stationary phase occupies 40% of the total column volume, the void volume would be 60% of the total column volume. In column chromatography, the volume of the mobile phase is the total bed volume of the column minus the volume occupied by the support particles.

4. Calculation of Void Volume The equation of determination of void volume: V L Where, V = Column Volume r = inner diameter L = length of column   r L

5. Example Consider a column that is 25 cm long with an inner diameter of 1 cm. V L = 3.14 = 19.6 mL The total column volume is 19.6 mL. If the mobile phase occupies 60% of the column volume T he void volume is 60% of 19.6mL=11.8 mL.  

6. Estimation of total Void Volume Various methods to estimate the total void volume include: Pycnometry Minor disturbance method Tracer pulse method Hold-up volume based on unretained compounds Accessible volume based on Martin's rule and its descendants

7. Reference https:// www.corrosionpedia.com/definition/1150/void-volume VOGEL’S, Textbook of Quantitative Chemical Analysis, Sixth Edition.

8. Thank You