Laboratory methods
Laboratory recovery: build a mass balance
Use blanks, fraction collection and volume records to distinguish adsorption, hold-up and analytical interference.
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Identify the fraction containing the target
Clarification commonly collects filtrate, whereas an ultrafiltration concentration step may target the retentate. Map feed, filtrate, retentate and rinse fractions before collecting them. Using a vague term such as supernatant for every device can lead to sampling the wrong fraction.
- Label each container by stream and expected target component.
- Reserve an unfiltered control from the same sample batch.
Multiply concentration by collected volume
Similar concentrations do not prove complete recovery. In a calculation example only, a 10 mL feed at 1 mg/mL contains 10 mg. Collecting 8 mL at the same concentration recovers 8 mg, or 80% of the input mass. This is arithmetic, not a product performance claim.
- Use measured collection volumes rather than nominal vessel capacities.
- Account separately for material removed for analytical sampling.
Use controls to locate the bias
An unfiltered control tracks sample changes, a solvent blank through the device reveals introduced background, and a spiked sample evaluates target loss. Keep vessels, holding time and analysis consistent; otherwise adsorption to a vial may be mistaken for adsorption to a membrane.
- Analyze controls after matched holding periods.
- Where the method permits, collect early and late filtrate fractions separately.
Revalidate changes to the preparation
More membrane area may improve throughput but also increase contact surface and hold-up. Preflushing may reduce background while changing dilution or recovery steps. Change one important variable at a time and use replicates to distinguish a real effect from analytical variability.
- Hold other conditions constant when comparing material, area or flushing.
- Retain recovery, blank background, processing time and repeatability results together.
Common technical questions
Does recovery above 100% mean better filtration?
First investigate volume, dilution, calibration, matrix effects and sample homogeneity.
Should the first fraction always be discarded?
No. The analytical method and fraction study should determine that step and account for the loss.
Related product approaches
Check materials, configuration and validation documents for the specific model.