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Food, Flavors & Fragrances \
~
Simplify and Speed Up Sample Preparation
With Res~re~ dSPE tubes!
Here we show the extraction and clean-up ofpesticide 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 abo ut po tent ially negative health
effects associated with pesticide resid ues have increased consumer interest in testin g. Wh ile organophospo rus pesticides are curre ntly used in
olive orcha rds to control pests, organoc hlor ine pesticides are still tested for as persistent orga nic po llut ants (residues), even though the y are
no lon ger in commercial use. There are several existing method s for measur ing pesticide residu es in olive oil, all of which involve sample
extracti on and clean-up.' The commo n goal of these methods is to remove lipids that are harmful to the analytical system.' Efficient sample
clean-up procedures are critical to maxim izing sample th roughput and mini mizing labor and materi al costs. Here we demon strate th e effi­
ciency of a dSPE clean-up pro cedure, as well as the capabilities of bot h method -specific and general purp ose analytical columns.
Simple Procedure UsesHalf the Time and Minimal Solvent
Sample extraction and clean-up can be accomplished with gel per mea tion chro ­
matography (GPC), solid phase extractio n (SPE), or dispersive solid phase extrac ­
tion (dSPE) method s. However the dSPE method shown here is mu ch less expen­
sive than GPC (which req uires specialized equ ipmen t) and uses substa ntially less
solvent th an comparable GPC or SPE methods (Table 0.' The method is simple to
use and allows sample extr action and clean- up to be accomplished in half the time
of ot her techniques (Table II).
Extraction and dSPE Clean-up for
Pesticide Residues in Olive Oil
Test sample : A 1.SmL sample of commercially obtained virg in olive oil
was spiked with a standard organochlorine pesticide mix. The spiked
sample was processed as follows.
1. Dilute with l .5mL hexane.
2. Add 6mL of acetonitrile (ACN).
3. Mix for 30 minutes on a shaker.
4. Allow layers to separate (approximately 20 minutes), t hen
collect the top (ACN) layer.
S. Repeat the liquid-liquid ext raction (steps 2-4) and combine
both ACN extract layers.
6. Place 1mL of the combined ACN extract in a l.5mL tube
containing lS0mg magnesium sulfate and SOmg PSA.
7. Shake the tube fo r 2 minutes.
8. Centrifuge at 3,000 U/min. for approximately Sminutes.
9. Remove the top layer and inject directly into th e gas
chromatograph system.
Extrac ts were analyzed using both Rtxv-Cl.Pesticidesz and Rxi®-SSil MS columns
(Figure 1). The Rtx®-CLPesticides2 column is a meth od specific column that
resolves all compounds. The Rxi®-SSil MS column is a genera l purpose column th at
has one coeluti on th at can easily be extr acted by a mass spectrometer det ector
(MSD). Only a -BHC was not detected, a subject of furt her investigation , however
either column can be used effectively. Recoveries of 70%-80% were obtained, levels
Global RESTEK Advantage · 8·
Table I Resprep dSPE method uses 42% and
89% lesssolvent th an SPE and GPCmethods
respectively.
140 .0 "1
_ 120.0
I
~ 100 .0
E­
m
VI
~ 80.0
Q)
Q.
-0
~ 60.0
~ 1
i 40.0 1
V> 20.0 I
~
0.0 Table II
Cut extraction /cl ean-up time by 50%
using Resprep dSPE method.
i 3.0 i
i 2.S t
VI 2.0 i
~ i
~ 1.
5 1
1.0
0.5
0.0
Website : E-mail : TelNo : 03 9762 2034 . . . in AUSTRALIA