Amicon
®
Ultra-4 Centrifugal Filter Devices
5
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. Before use, separately weigh the empty filter device, the centrifuge tube, and an empty tube for concentrate
collection.
2. Fill filter device with solution and reweigh.
3. Assemble device and centrifuge per instructions.
4. Collect the concentrate with a pipettor and dispense it into the preweighed concentrate collection tube.
5. Remove the device from the centrifuge tube and weigh the centrifuge tube and concentrate collection tube.
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
× C
c
W
o
× C
o
% filtrate recovery = 100 × W
f
×
C
f
% 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
Specifications
Maximum initial sample volume
Swinging-bucket and fixed-angle rotors (45º and 35º) 4.0 mL
Fixed-angle rotor (23º)
3.5 mL
Typical final concentrate volume
50 - 100 µL
Maximum relative centrifugal force
Swinging-bucket rotor
4,000 × g
Fixed-angle rotor
7,500 x g for 3K, 10K, 30K, and 50K
MWCO
5,000 x g for 100K MWCO
Active membrane area
3 cm
2
Dimensions
Filter device in tube (capped)
Length: 124 mm (4.9 in.)
Diameter: 17.3 mm (0.7 in.)
Filter device
Length: 73.4 mm (2.9 in.)
Diameter: 17.2 mm (0.7 in.)
Materials of Construction
Filter device
Copolymer styrene/butadiene
Membrane
Ultracel
®
low binding regenerated cellulose
Filtrate tube
Polypropylene
Filtrate cap and liner Polyethylene