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“ONE Sorbent,
ONE Method,
For ANY SPE application”
Demystifying Solid Phase Extraction for Toxicological Analysis of Biological Samples
Presented byMarc Boggeri
Technical Manager, Sample PreparationPhenomenex USA
Before We Start….a word on Non-commercial Intent.
My goal is to present you with tools to remove some of the mystery surrounding SPE.
• Fact. It’s 2004. New SPE tools do exist. • Fact. Not every manufacturer sells them due to patents and
commercial concerns.• Fact. Phenomenex pays my mortgage, so…• Fact. I will use Phenomenex products in my examples, more
as a practical matter than a commercial matter.• Fact. It’s 2004….I can get sued if I speak too much “on the
record” about other competitors… thank the lawyers for that!
So please bear with me as I try to navigate the minefield !
SDB Polymers
C18E
C18U
C8
Phenyl
CN
SI
NH2
FLPR
SCX / SAX
Non-Polar
Polar
Ionic
Strata X
Strata X-C
THIS….
+
PLUS
96-well Plate(96 little SPE tubes in a microtitre plate
footprint)
THIS
= Confusion!Which one to
choose?
Let me simplify.
Introduction to Solid Phase Extraction
What is “SPE” ?A “Sample Preparation” technique.
For our purposes Sample Preparation is“Manipulations performed to the sample, prior to analysis, that
are designed to facilitate chromatographic analysis.”
Common Sample Preparation Techniques:
HomogenizationDilutionWeighingSettling and DecantingCentrifugationFiltrationEnzymatic HydrolysisEvaporationLiquid / Liquid ExtractionProtein Crash/ PrecipitationSolid Phase Extraction
and many others.
Introduction to Solid Phase Extraction
Goals of SPE
“Cleanup”
“Concentrate”
“Solvent switch”
Introduction to Solid Phase Extraction
1 Liter Dirty Water
SPE Extraction
1 ml concentrated analtye
1. Clean-up
0 Minutes 100 Minutes 10
Why do we perform SPE?
Before (Liq /Liq)After SPE
2. Concentrate and 3. Solvent Switch
Introduction to Solid Phase Extraction
The REAL GOAL !
Introduction to Solid Phase Extraction
HOW SPE WORKS
The sample is passed through a SPE device. Analyte(s) is retained onto the sorbent.
The contaminants are washed out of the tube.
Analyte is eluted from the tube.
Note: Step 1: Conditioning / Solvation omitted for visual simplicity.
Introduction to Solid Phase Extraction
What Type of Interactions?
SPE relies upon the same basic chromatographic retention mechanisms as
HPLC, GC and TLC.
Introduction to Solid Phase Extraction
SPE and HPLC differ in the strength of the interactions between the analyte and the stationary phase.
– SPE: Strong interactions, 100% retention of analyte, or 100% elution.
– HPLC: Weaker partial interactions that allow each of the analytes todifferentially migrate along the length of the column.
Introduction to Solid Phase Extraction
4 Main Steps
1. Mechanism2. Chemistry3. Sorbent Mass in tube4. Tube Size / Format
Choosing a SPE Product
1.a. Non-Polar / Reverse Phase: HydrophobicTypical phases: C18, C8, C4, CH
Step 1. Mechanism
1.b. Non-Polar / Reverse Phase: AromaticTypical phases: Strata X, SDBL, styrene divinylbenzene polymers, PH.
Step 1. Mechanism
Reverse Phase: Aromatic Selectivity
2. Hydrophilic / Polar / Normal PhaseTypical phases: Silica, NH2, CN, FL., X
Step 1. Mechanism
3. Ionic / Ion Exchange / (hydrophilic)Typical phases: SCX, SAX, NH2,
Plus: Mixed-mode sorbents: X-C, Screen C & Screen A.
Step 1. Mechanism
SDB Polymers
C18E
C18U
C8
Phenyl
CN
SI
NH2
FLPR
SCX / SAX
Non-Polar
Polar
Ionic
Strata X
Strata X-C
Step 1. Mechanism
SPE offers a wide-range of extraction “tools”!
Beware of The “Hidden” Strong Ion Exchangers
• Strata X-C: SCX on a aromatic resin.“For just about anything!”
• Strata Screen C: C8 + SCX“for screening of cationic compounds”
• Strata Screen A: C8 + SAX“for screening of anionic compounds”
Method Development
Before we get too far: A Practical View
The most common Method Development Mistakes are1. Choosing the wrong SPE product ( sorbent or mass)2. Using the wrong solvents or volumes3. Not setting realistic goals for the sample prep.
Ie, Which is most important to your overall analysis?
– Absolute highest recovery ?– Greatest clean-up?
Typically some compromise is required.
Method Development
Historical Information
• How do you extract now or in the past? Ie, Liquid/Liquid Data. • “Bases” = cationic amines • “Acids” = anionic organic acids• “Neutrals” = general non-polar structure
• Any SPE methods that did not work well? What did not work is almost as useful as knowing what did!
Method Development
Summarizing: Analyte Polarity vs Retention Mechanism
Analyte Polarity RetentionMechanism
Hydrophobic Non-Polar
Hydrophilic Polar
Ionized (+ or -) Ion Exchange
“Like dissolves Like”
For Ion Exchange: “ Opposites Attract”
Method Development
Classify the Matrix / Sample
• Liquid, Solid or Suspension?• Composition: Aqueous, Organic, Solids, Fatty.• Liquid: pH, Ionic strength• Solubility: Aqueous, Organic• Impurities and known interferences • Expected Concentration of Analyte:
= volume needed to extract to reach Method Detection Limit?
But that’s only ½ the Story!
Summarizing Matrix Effects and SPE Mechanism
Sample Matrix Composition Likely SPE Retention Mechanism
Aqueous: Water, biological fluids, aqueous homogenates. Non-Polar
Organic: Non-polar organic solvents Polar
Aqueous or Organic Ion Exchange
Method Development
3. Identify Extraction Mechanism
Putting it all together.
Method Development
3. Identify Extraction MechanismAnalyte + Matrix = Mechanism !
Analyte Polarity Sample Matrix Polarity SPE Mechanism Sorbents
Non-Polar Aqueous Non-PolarC18E, C18U, C8, PH,
SDBL, X "Universal" Polymeric Sorbent
Polar Non-polar organic Polar SI-1, Si-2, NH2, CN, FLPR
Ionic Aqueous or Organic: Ion Exchange (Strong and Weak)
SCX, WCX, SAX, NH2, Mixed-mode w/
IEX
Once you identify the mechanism: then you select a specfic sorbent
Method Development
In reality this happens:
AqueousWaterUrinePlasmaBloodAq. Tissue Preps
Organic H2O Misc.
MeOH
Acetonitrile
IPA
Organic NOT H2O Misc.
Hexane
DCM
Reverse Phase
Strata X, C18E, C8
Mixed Mode-Ion Exchange
Strata X-C, SAX, WCX, etc.
Ion Exchange
Strata SCX, SAX, WCX
Normal Phase
Strata NH2, CN, SI, FLPR
Ion Exchange
Strata SCX, SAX, WCX
+ H2O
+ Hexane
Method Development
Method Development
SDB Polymers
C18E
C18U
C8
Phenyl
CN
SI
NH2
FLPR
SCX / SAX
Non-Polar
Polar
Ionic
Strata X
Strata X-C
4. a) Chemistry
Step 2. Choose Sorbent Chemistry
Mixed Mode sorbents should be classified by their
ion exchange group!
Step 3. Choose Sorbent Mass in Tube
Selection of the proper sorbent mass is critical:
• Not Enough Sorbent = Overloading = Sample BreakthroughOverloading results in Poor Irreproducible Recovery.
• Too Much Sorbent = Sufficient Capacity = Safe but Economically Undesirable.
Larger tubes more expensive, need more solvent and sometimes dirtier extracts.
Step 3. Choose Sorbent Mass in Tube
FACT #1: The sorbent packed inside the tube performs the extraction .
FACT #2: Sorbent mass selection is NOT an exact science. Lots of matrix effects!
Si-based Sorbent Capacity: A Theoretical Approach:– Non-polar and polar sorbents: Equivalent to 5% of the sorbent mass.– Ion Exchange Sorbents: Typically from 0.5 to 1.0 milliequivalents per gram of
sorbent (meq / g ). Values are commonly reported by the manufacturer.
Biological:Blood, serum and plasma:
Resin (Strata X or X-C) 30 mg per 250 ul sampleSilica-based: 50 mg per 250 ul sample.
Urine: Resin (Strata X or X-C) 30 mg per 1 ml sampleSilica-based: 50 mg per 1 ml sample.
Filtered Tissue homogenates: 60 mg Resin or 100 mg Si-based per 100 mg tissue.
Summary: Be safe. Round Up.
Step 3. Choose Sorbent Mass in TubeSorbent Capacity: A Practical Approach
For Example:
“How much sorbent do I need to extract a 500 ul plasma sample?”
For strata X: “ 30 mg per 250 ul sample”
2 x 30 mg = 60 mg strata X
For C18E: “50 mg packing per 250 ul sample”
2 x 50 mg = 100 mg C18E
Do the Math…. scale up or down as necessary.
Step 3. Choose Sorbent Mass in Tube
4. b) Sorbent Mass
Step 4. Choose Tube Format / Size.
• Typically the required sorbent mass is available in a limited number of tube sizes, or volumes. Choose the closest available mass.
• Remember: tube “size” in ml ( or cc) is of secondary importanceunless you have some hardware/robotic requirements. The sorbent does the work.
96-well Plate(96 little SPE tubes in a microtitre plate
footprint)
Step 4. Choose Tube Format / Size.
Step 4. Choose Tube Format / Size.
Sample volume > than Tube ?
Sorbent Mass
Theoretical Minimum 2 bed volumes Not Recommended ! )
Practical Minimum Wash and Elution Volume 8 bed volumes
Recommended Wash and Elution Volume 16 bed volumes ( Safe Starting Point)
10 mg * 50 ul 200 ul 400 ul 25 mg 75 ul 250 ul 500 ul 30 mg * 125 ul 500 ul 1 ml 50 mg 125 ul 500 ul 1 ml 60 mg * 250 ul 1 ml 2 ml 100 mg 250 ul 1 ml 2 ml 150 mg 375 ul 1.5 ml 3 ml 200 mg 500 ul 2 ml 4 ml 500 mg 1.25 ml 5 ml 10 ml 1 g 2.5 ml 10 ml 20 ml 2 g 5.0 ml 20 ml 40 ml 5 g 12.5 ml 50 ml 100 ml 10 g 25.0 ml 100 ml 200 ml
Method Development
* = resin sorbents. Strata X and X-C
Practical Tool: Solvent Volumes for SPE Processing
Introducing Secondary Interactions:
Primary Interaction = Strongest Interaction between analyte and sorbent.
Secondary Interaction = Weaker Interaction…
For ion exchangers: – Ionic = primary & very strong
– Hydrophobic = secondary & weaker… but still there.
Lets’ have a closer look…
Method Development
Secondary Interactions on Ion Exchangers
Primary
Secondary
For Elution: Must disrupt both !
Hydrophobic
Method Development
Practical Suggestion: Ion Exchange Elution Solvents:
Because of Secondary Non-polar interactions.
• The MEOH + acid or base (98:2) may be the best choice.• Efficient Low volume elution.• Volatile.• Simple to make.
For Strata X-C: MeOH : Acetonitrile : NH4OH (sat.) (49:49:2)
Note: For X-C and Screen C mixed-mode ion exchangers… organic is a MUST!
Method Development
Method Development Update: 6 / 04
New Resin Technology Greatly Simplifies Method Development from Bio samples and Aqueous Matrices.
•Strata X. Simple reverse phase SPE method is very simple and rugged.
•Strata X-C mixed-mode cation exchange for super cleanup from dirty biomatrices.
Not Marketing hype!
Feeling BOMBARDED with the following claims?
“Deconditioning Resistant”
“Superior recovery for Acidic,Basic and Neutral Compounds”
“Automation Friendly”
“Water-wettable”
“Hydrophilic-Lipophilic Balance”
“Fast and Simple Method Development”
And the Mother of All Marketing Claims….
“ONE Sorbent,
ONE Method,
For ANY SPE application”
Does it justify such wild claims?
• Short Answer:
Yes !• Long Answer
Let’s have a closer look….
First: Recall the Deficiencies of traditional SPE sorbents
• Residual silanol / uncontrolled secondary interactions (end capping
effect)
• pH limitations of base silica
• Base silica fragile: crushing = fines
•Lot to lot reproducibility
•Must keep “wet”after conditioning
• Narrow selectivity range: limited retention of polar metabolites
With that in mind…
Most Popular are: Styrene-divinyl benzene polymers modified by the addition of a “ polar”
functional group. N-vinylpyrrolidone.
– Phenomenex Strata X : surface coated resin– Competitor OW: copolymerized resin
Phenomenex Strata X is a unique patented sorbent chemistry only available from Phenomenex.
What are these new “ wonder” resins?
Strata X and X-C Offer Three Primary Benefits Over Silica Based Sorbents.
1. Aromatic selectivity2. Worry-free processing. 3. Non-halogenated Elution Solvent
Plus:– Exceptional cleanup– Superior Lot to lot reproducibility
How does Strata X compare to traditional Si-based ?
Structure of Strata X
Reverse Phase: Aromatic Selectivity
Polar / HydrophillicSelectivity
The Strata X resin family.
SDBL X
X-C+ SCX group
+ SAX group X-A ( ? )
X-CW
+ WCX group
(coming soon !)
X-WA
+ NH2 group
( ? )
Benefit #1. Unique SelectivityMulti-mode Retention Mechanism: π - π, hydrogen bonding and
hydrophobic
Styrene divinylbenzene: Aromatic reverse phase selectivityPlus
N-Vinylpyrrolidone: Hydrophilic – polar.
Think about it. How many of your analytes have aromatic regions?How many have some polar/charged functional groups?
The majority.
Some common analyte structures.
O
O H
H
H
O
O H
THC-COOH
NH2
Amphetamine
O
O N
Acidic Probes
X
X=OH (Salicylic acid)X=OCOCH3 (Aspirin)
COOH
CH3O
Naproxen
COOH
Ketoprofen
Basic ProbeC2H5
C2H5H2NProcaine
COOH
OHOH
OOH
O
H
H
H
Prednisolone
Example of basic compounds
O
N
OH
O
H
NH
OH
NH2
NH
O
OH
NH
O
NH2
OH
C18 “De-Conditioning” / Chain collapse reduces (destroys!) sorbent efficiency.
Unconditioned Conditioned
> 2 min @ 5 in Hg Vacuum
Benefit #2. Worry-free Processing.“ Deconditioning”: What it is and how it can effect your work.
Note dye band on C18 vs Strata X after drying for 10 minutes.
Silica C18 sorbent dried after conditioning with
methanol
Strata X
Benefits of strata-X: resistant to deconditioning
BAD ! Good !
Structure of Strata X
Reverse Phase: Aromatic Selectivity
Polar / HydrophillicSelectivity
No “Chains” to collapse !
Polar Modifier “holds” conditioning solvents!
Sorbent Chain Collapse from an Extraction Recovery Perspective.
ProcainamideTheophyllineCaffeine
RanitidineDoxepin
0
20
40
60
80
100
0 2 4 6 8 10Drying time (min)
% R
ecov
e ry
Both dried at 10” Hg after conditioning with MeOH.
0
20
40
60
80
100
120
0 2 4 10
% R
ecov
ery
Drying time (min)
Silica C18 Strata-X
In the Lab: Benefits of Strata X
• No need to use stopcocks with tubes
• Higher throughput. • Turn the vacuum on and leave it on!
• Worry-free automation. • Program vacuum and flow rates for the “slow flow” samples
• Super rugged / Super reproducible
• Best sorbents for 96-well plate SPE!
Fewer Headaches !
Conditionmethanol
Equilibratewater or buffer
Load Sample
Wash1. buffer
2. acidified water3. methanol
Elutemethanol/AcN + base
Halogen-free elution!
Benefit #3. Halogen-free Elution with Strata X-C for Bases
Strata X: So does it really perform?
Bases
Neutrals
Acids
0
20
40
60
80
100
Nor
doxe
pin
Am
itrip
tylin
e
Nor
tript
ylin
e
Dox
epin
Pro
cain
amid
e
Ace
tam
onop
hen
Theo
brom
ine
Theo
phyl
line
Caf
fein
e
Cim
itidi
ne
Ibup
rofe
n
Nap
roxn
Feno
prof
en
Indo
met
haci
ne
% R
ecov
ery
RSD: 2-5%
Clean up of analytes from serum
Recovery of a wide spectrum of analytes
strata-X in pharmaceutical applications: extraction of steroids from plasma
F
OHOH
O
OOH
H
H
OHOH
OOH
O
H
H
H
Betamethasone
Prednisolone
0
20
40
60
80
100
% R
ecov
ery
Pred
nisolo
ne
Betha
met
haso
ne
Greater than 90% Recovery
Strata X: So does it really perform?
strata-X in biological applications: selective elution of peptides from a salt matrix
Selective Elution Based on their Acidity by Different Elution Solvents
Eluent ACTH Bradykinin Angiotensin I HGRH
40:60 ACN/water 0.0% 5.1% n/a 101.5%
70:30 ACN/water 0.0% 44.1% 98.4% n/a
70:30 ACN/1.0% formic acid 78.8% 92.5% 98.5% n/a
Absolute Recovery from strata-X, 30mg. Vol of eluents = 250uL.
Basic Neutral Acidic
Strata X: So does it really perform?
strata-X-C in veterinary applications: extraction of sulfa drugs from plasma
NH2
S
O O
NH
ONCH3
Sulfamethoxazole
N
N NH
SNH2
O O
Sulfaquinoxaline
0
20
40
60
80
100
% R
ecov
ery
sulfa
thiaz
olesu
lfam
etho
xazo
le
sulfa
quino
xalin
e
Greater than 90% Recovery
strata-X-C in toxicological applications:extraction of diuretics from plasma
S
NH
NH
O O
S
Cl
NH2
O O
NH
OHO
S
ClNH2
O
O
O
0
20
40
60
80
100
% R
ecov
ery
Hydr
ochlo
rothi
azid
e
Furo
sem
ide
hydrochlorothiazide
furosemide
Greater than 90% Recovery
strata-X-C in toxicological applications:extraction of drugs of abuse from urine
020406080
100
% R
ecov
ery
THC-
COOH
Amph
etam
ine
Met
ham
phet
amine
NH2
O
O H
H
H
O
O H
THC-COOH
Amphetamine
Greater than 90% Recovery
strata-X-C
strata-X-C: Your best choice for toxicological analysis :
Bases: strong cation exchanger + powerful secondary interactions including π- π and hydrogen bonding
Acids and Neutrals too ! Utilize the π- π and hydrogen bonding for retention.
No pH limitations
Deconditioning resistant.
No Methylene Chloride needed!
2004…Reverse Phase
New Simplified :
Surface-modified, resin based:
• strata X
Old / Historical:
Predominantly silica based, linear hydrocarbon.
• C18E, C18U, C8, C1, PH.
2004… Ion Exchange and Mixed-mode
Old:
Silica based: SCX, WCX, SAX, NH2
Mixed Mode: Screen C and Screen A.
New Simplified:Resin based:
•Strata X-C (mixed-mode, strong cation exchange)
•Strata X-A ( mixed-mode, strong anion exchange)
Silica based•WCX (weak cation exhange)•NH2 (weak anion exchange)
Thank You !Questions?