Inconsistent PFAS results can be a nightmare, especially when you’re working at ultra-trace levels. These compounds are everywhere, and even the tiniest bit of background contamination can throw off your data. Here are a few things that might help:
1. Audit Your Lab for PFAS Sources: PFAS are sneaky. They’re in lab gloves, PTFE tubing, sample containers, and even some lab coats. Switch to PFAS-free materials—polypropylene or high-purity glass for sample storage, nitrile gloves (avoid the powder-coated ones), and PTFE-free pipette tips. Also, check your solvents—some brands of methanol and water can have background PFAS contamination.
2. Rethink Sample Prep: A lot of background contamination creeps in during extraction and cleanup. If you’re using SPE cartridges, make sure they’re explicitly labeled as PFAS-free. Run blanks through your entire workflow (including extraction and cleanup) to see where contamination might be coming from.
3. Contamination-Free Water: This one’s big. Your ultrapure water source must be PFAS-free—some lab water systems leach trace amounts. If you haven’t already, test your lab water for PFAS contamination. You might need an additional filtration step, like a carbon filter, before your ultrapure system.
4. Negative Controls Are Your Best Friend: Run procedural blanks with every batch. If you see PFAS in your blanks, you’ve got a contamination issue, not a real sample problem. Compare blank levels to your sample results—if they’re close, your data might be compromised.
5. Check Your Instrumentation: LC-MS/MS systems are sensitive but can be a source of contamination if not maintained properly. Make sure your mobile phase solvents, tubing, and injection ports are cleaned regularly and PFAS-free. Running a high-purity methanol blank before your batch can help flush out any lingering PFAS.
6. Standardize Your Workflow with a LIMS: This one’s often overlooked, but if you’re running multiple batches over time, an advanced environmental LIMS can help track patterns in contamination such as when some reagents are linked to variability, if certain analysts introduce bias, or if specific days tend to produce worse results.
At the end of the day, PFAS work is all about controlling every possible source of contamination. Hope this helps!
If you’ve already ruled out the common culprits, let me know—I’d be curious to hear what’s still causing issues in your lab.