There’s nothing more satisfying than successfully extracting a really challenging sample. Solid phase extraction (SPE) is a powerful technique for extracting semi-volatile organic compounds and hexane-extractable materials (HEMs). When the chemistry is tailored to meet the requirements of the application, literally hundreds of compounds can be extracted with a single pass of solution through an SPE disk.
That feeling of success is magnified when you’ve battled and successfully processed a really challenging sample – like dirty wastewater or TCLP leachates. Those of you who process wastewater samples know what I mean – the foul-smelling, sludge-like samples with lots of particulates and even larger objects such as pebbles, sticks and leaves. They’re so dirty, you almost feel badly exposing your extraction system to them.
Believe it or not, you can process all your wastewater samples without clogging your disk, losing any sample, or reducing your analyte recoveries, but preparation is the key to that success. If you use what you know about your sample to select an appropriate disk, holder, pre-filters and filter aids, you should be able to process each sample completely.
I know what you’re thinking – your customers don’t tell you much about the sample matrices they send you. They just tell you the general matrix type (wastewater, industrial discharge, etc) and that they need results processed against a certain method (8270, 625.1, 1664, or 608, for example). Not to worry. You can learn a surprising amount about your sample matrix just by looking at it. Is it opaque or transparent? Does it have large items in it (pebbles, sticks, leaves, etc)? Does it seem oily or soapy? Asking and answering questions about the appearance of your sample often point you in the right direction in terms of building your pre-filter and/or filter aid stack. Finding the right guide will steer you toward the right media, disk size, and should tell you how to condition, load and elute that disk to help ensure adequate recoveries.
In an attempt to process a range of difficult samples, I’ve consulted my fair share of guides – eBooks, white papers, blogs, application notes, journals and textbooks. If I can find one that’s written for my specific application or my specific laboratory challenge, they usually have what I like to call “the secrets to my success.”
The most recent guide I’ve come across is an eBook that provides detailed guidance in overcoming sample preparation challenges for wastewaters, when processing them for EPA Methods 8270 and 625.1. Check it out if you get the chance – hopefully it’ll become a secret to your success!
Leave a comment to share useful guides you’ve used to overcome your preparation challenges!