Laboratory filtration: 7 mistakes that can affect your results

1. Assuming any 0.45 µm filter is the same as any other

Material, extractables, and construction vary between products at the same nominal pore rating. Two "0.45 µm" filters from different lines can behave differently with your specific sample. Confirm the full specification, not just the pore size.

2. Using a hydrophobic membrane for an aqueous sample without pre-wetting

Standard PTFE won't pass an aqueous sample without help. See our hydrophilic vs. hydrophobic guide for how to avoid this exact mismatch.

3. Ignoring analyte binding to the membrane

Nylon and some other materials can adsorb certain compounds—an easy way to silently lose analyte and skew a trace-level result. Check binding behavior for your specific analyte before standardizing a method.

4. Skipping the final pre-injection filtration step

A single missed filtration step before HPLC or GC injection can foul a column or introduce noise into a result that would otherwise be clean. See our sample prep filtration guide.

5. Using a generic filter for a trace-level or MS-detected method

Extractables from an ordinary filter can show up as background noise or ion suppression in sensitive methods. Low-extractable/HPLC-certified lines exist for exactly this reason.

6. Mismatching diameter to hardware

An undersized membrane in a vacuum or standalone funnel setup won't seal properly and can let sample bypass the filter entirely, silently invalidating the step.

7. Not documenting the specific product and lot for regulated work

When a result gets questioned later, being able to state exactly which filter (material, pore size, lot) was used is often the difference between a quick answer and a scramble.