Prepare Samples in Half the Time
Using a Fraction of the Solvent with dSPE
|By Michelle Misselwitz, Environmental Innovations Chemist, Julie Kowalski, Ph.D., Food Flavours and Frangrances Innovations Chemist, Mark Crawford, Applications Chemist, Michael Halvorson Ph.D., Senior Product Specialist, and Joan M. Stevens, Ph.D., Applications Manager|
Simplify and speed up sample preparation with Resprep dSPE tubes. Here we show the extraction and clean-up of pesticide residues from olive oil samples—twice as fast as GPC, with only a fraction of the solvent required for conventional SPE.
Olive oil is considered a healthy fat source and is a staple in many recommended diets. However, concerns about potentially negative health effects associated with pesticide residues have increased consumer interest in testing. While organophosporus pesticides are currently used in olive orchards to control pests, organochlorine pesticides are still tested for as persistent organic pollutants (residues), even though they are no longer in commercial use. There are several existing methods for measuring pesticide residues in olive oil, all of which involve sample extraction and clean-up.1 The common goal of these methods is to remove lipids that are harmful to the analytical system.2 Efficient sample clean-up procedures are critical to maximizing sample throughput and minimizing labor and material costs. Here we demonstrate the efficiency of a dSPE clean-up procedure, as well as the capabilities of both method-specific and general purpose analytical columns.
Sample extraction and clean-up can be accomplished with gel permeation chromatography (GPC), solid phase extraction (SPE), or dispersive solid phase extraction (dSPE) methods. However the dSPE method shown here is much less expensive than GPC (which requires specialized equipment) and uses substantially less solvent than comparable GPC or SPE methods (Table I).3 The method is simple to use and allows sample extraction and clean-up to be accomplished in half the time of other techniques (Table II).
Extraction and dSPE Clean-up for Pesticide Residues in Olive Oil
Extracts were analyzed using both Rtx®-CLPesticides2 and Rxi®-5Sil MS columns (Figure 1). The Rtx®-CLPesticides2 column is a method specific column that resolves all compounds. The Rxi®-5Sil MS column is a general purpose column that has one coelution that can easily be extracted by a mass spectrometer detector (MSD). Only ?-BHC was not detected, a subject of further investigation, however either column can be used effectively. Recoveries of 70%-80% were obtained, levels comparable to conventional SPE—without the necessity of vacuum manifolds or high pressure systems. The GPC method attained recoveries of > 95%. However this method requires large amounts of solvent and takes over twice as long as other methods.
The dSPE method shown here is an efficient, cost-effective way to clean up chlorinated pesticide residues in olive oil. With good recoveries and minimal matrix interference, it is an easy way to reduce solvent usage, compared to conventional SPE, and is more cost-effective than GPC.
|Table I: Resprep's dSPE method uses 42% and 89% less solvent than SPE and GPC methods respectively.|
|Table II: Cut extraction/clean-up time by 50% using a Resprep dSPE method.|
|Figure 1: Chlorinated pesticide residues in olive oil are easily separated on either Rtx®-CLPesticides2 or Rxi®-5Sil MS columns.|