Eliminating unwanted lipids from samples can be pretty difficult when you're trying to analyze lipid-soluble molecules. But with the new Enhanced Matrix Removal - Lipid kit (EMR-Lipid), it's easy to selectively remove them.
I've been solving sample preparations issues for almost 30 years and as an Agilent Senior Applications Chemist for about seven years. I do a lot of tough sample prep myself, and I am always looking for a technique that removes unwanted matrix while still offering detection of residue-level analytes. It was important to have a technique that integrates well with other methods, like QuEChERS and modified lipid extraction, yet was simple to use.
What it is
The new clean-up kit is very simple. An extraction tube is necessary for extraction of the sample whether using QuEChERS, protein precipitation or modified liquid extraction protocol. The EMR-Lipid dSPE (dispersive solid phase extraction) sorbent is activated with water and then a portion of the extract is added to perform the dSPE cleanup. The sample is then transferred a 50 mL centrifuge tube and the contents of a Polish pouch or tube is added for phase separation. The EMR-Lipid tube contains 1 g of material suitable for 5 mL of extract in most applications, and the Polish options are: Polish tube, containing NaCl/MgSO4, or the Polish pouch, containing MgSO4 only.
How it works
The EMR-Lipid Dispersive material is a sorbent with pores that selectively bind long unbranched hydrocarbon chains. Polar headgroups remain on the solvent-exposed side, while the analytes do not interact with the sorbent and remain in solution. The illustration at the right shows how this would be useful for removing lipids from a sample where you're interested in bulkier, non-linear organic molecules like pesticides, veterinary drugs, and polyaromatic hydrocarbons (PAHs).
The EMR-Lipid sorbent does not interact with bulkier compounds typical for the majority of analytes. This is even evident for some of our preliminary work with mycotoxins - specifically fumonisin B2 where the branched aliphatic group provides enough “bulk” to prohibit loss during dSPE treatment. Here are some examples of pesticides, PAHs, and veterinary drugs, and other compounds compounds we've shown we can now easily analyze because they are selectively excluded from the sorbent:
Integrating it with existing workflows
EMR-Lipid is a dispersive SPE clean-up that can be implemented into familiar workflows for food analysis. This allows for the use of existing sample preparation workflows and includes EMR-Lipid to provide lipid removal where needed.
QuEChERS: The first approach is the Quick, Easy, Cheap, Effective, Rugged, and Safe method (QuEChERS), which has been widely adopted for pesticide residue analysis and is expanding to other types of multiclass, multiresidue applications. EMR-Lipid can be used either in place of or in conjunction with a typical dSPE step for extremely complex matrices, providing dramatically cleaner samples. This method can be applied to a large number of commodities such as fruits, vegetables, and meat.
Modified Liquid Extraction: The second example is a modified liquid extraction method, which adds the EMR dSPE clean-up step. The first step is addition of acetonitrile, which serves as an extract solvent and “crashes” proteins out of solution. Depending on the application, this is the preferred methodology for EMR and can be applied to milk, meat, and seafood samples.
Here's an example where we helped someone analyze avocado extract - a VERY lipid-rich matrix! The figure at the right compares data from samples prepared with three different cleanup techniques:
You can see immediately how the EMR-Lipid clean-up method does a superior job of removing unwanted lipids - you can actually see and resolve the analytes in there, while injecting a cleaner extract into your system.
- Red: No cleanup, just solvent extraction
- Green: Solvent extraction with GPC (gel permeation chromatography) clean-up
- Blue: Solvent extraction with EMR-Lipid clean-up
Suggested ApplicationsHere are some of the cases where we know EMR-Lipid works really well:
|Fatty Samples||Analytes||Multiresidue Analysis|
- Finished foods
- Meat, fish, dairy
- Pet food, animal feed
- Vet drugs
- Mycotoxins, Aflatoxins
- Anything that does not resemble lipid
- Important to remove matrix and not analytes
- MS or QQQ detection where lipid interferences can cause ion suppression
Try it out!
I'm really excited to be able to offer this novel clean-up technique to researchers who have struggled with work-arounds for lipid removal. This kit has changed my vision of what is possible - so many difficult analytical problems are now possible to solve easily now! It's been good for my work, and I'm confident it will be good for yours, too.
Are you using EMR-Lipid now? Please share your own story in the comments below. I'm eager to hear how people are taking advantage of this new technology.
If you have any questions, please add a comment here. If you want detailed help about your particular project, feel free to start up a new Discussion in the area.
Related Application Notes: