Amicon
®
Ultra-2 Centrifugal Filter Devices
7
How to Quantify Recoveries
Calculate total recovery, percent concentrate recovery, and percent filtrate recovery using the method below. The procedure
provides a close approximation of recoveries for solutions having concentrations up to roughly 20 mg/mL.
NOTE
: Appropriate assay techniques include absorption spectrophotometry, radioimmunoassay, refractive index, and
conductivity.
Direct Weighing Procedure
The density of most dilute proteins is nearly equal to the density of water (i.e., 1 g/mL). Using this property, the concentrate and
filtrate volumes can be quantified by weighing them and converting the units from grams to milliliters. This technique is valid only
for solutions with concentrations of approximately 20 mg/mL or less.
1.
Separately weigh the empty filter device, filtrate collection tube, and concentrate collection tube before use.
2.
Fill filter device with solution and reweigh.
3.
Assemble device in filtrate collection tube and centrifuge per instructions.
4.
Collect the concentrate by reverse spin into the pre-weighed concentrate collection tube.
5.
Remove the device from the concentrate collection tube and weigh the filtrate and concentrate collection tubes.
6. Subtract weight of empty device/tubes to calculate weights of starting material, filtrate, and concentrate.
7. Assay the starting material, filtrate, and concentrate to determine solute concentration.
8.
Calculate recoveries using the weight/volume data and the measured concentrations as follows:
% concentrate recovery = 100 × W
c
x C
c
W
o
x C
o
% filtrate recovery = 100 × W
f
x C
f
W
o
x C
o
% total recovery = % concentrate re % filtrate recovery
W
c
= total weight of concentrate before assay
W
o
= weight of original starting material
W
f
= weight of filtrate
C
c
= concentrate concentration
C
o
= original starting material concentration
C
f
= filtrate concentration