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SPE for Environmental Samples - for Environmental Samples ... –extract with...

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  • 2012 Waters Corporation 1

    Sample Preparation Strategies for

    Complex Environmental Analysis

    SPE for Environmental Samples

  • 2012 Waters Corporation 2

    Outline

    Introduction Why is Sample Prep Done Why SPE

    Strategies

    Traditional approaches o Normal Phase o Reverse Phase o Mixed Modes

    Modern approaches o Mixed Modes o Reverse phase

    Summary

  • 2012 Waters Corporation 3

    Sample Preparation Techniques

    Sample Preparation- The simplification of sample

    matrix and enrichment of target analyte(s)

    Types of Sample Prep include:

    Dilution (simple, fast, no cleanup, no enrichment)

    Centrifugation (cleanup, no enrichment)

    Filtration (simple, fast, cleanup, no enrichment)

    Liquid/Liquid Extraction (cleanup, enrichment, cumbersome)

    Solid Phase Extraction (cleanup, fast, enrichment)

  • 2012 Waters Corporation 4

    For high sensitivity analyses, such as those employing LC/MS/MS, proper sample preparation can be critical for minimizing matrix effects and concentrating analytes of interest.

    Why is Sample Prep Done?

    60% of the work activity and operating cost is spent on sample preparation

    for introduction into the analytical system

    Three Purposes:

    Removes interferences from sample matrix

    Concentrating analytes of interest

    Present sample matrix not compatible with analytical system

  • 2012 Waters Corporation 5

    Why Use SPE in Environmental Analysis ?

    Sample Enrichment

    To achieve low ppt detection limits, usually the sample must be

    concentrated 10-1000 times

    o using liquid extraction (LE), up to 500 mL of solvent must be

    evaporated after cumbersome manual extraction

    o using SPE, only 10 mL of solvent must be evaporated after more

    user friendly procedure

    Sample Cleanup

    Cleanup steps can often be incorporated into the SPE experiment

    this cannot be done using LE

    SPE cartridges can be used to further cleanup extracts obtained from

    either SPE or LE

  • 2012 Waters Corporation 6

    SPE Sorbents for Environmental Analysis

    Normal-Phase Sorbents

    Silica, Alumina, Florisil, Aminopropyl silica, PSA, Diol silica,

    Reversed-Phase Sorbents

    Oasis HLB

    C18, C8 etc (alkyl silica's)

    Graphitized carbon and activated carbon

    Ion Exchange

    Accell Plus CM, QMA

    Mixed Mode (ion-exchange/reversed phase)

    Oasis MAX, Oasis WAX (strong and weak anion-exchange)

    Oasis MCX, Oasis WCX (strong and weak cation-exchange)

  • 2012 Waters Corporation 7

    Specialty Products for Environmental & Food Analysis

    Sep-Pak DNPH (air samples, aldehydes and keytones)

    XPoSure Aldehyde Sampler (air samples, large particle size for personal air monitors)

    Ozone Scrubber (removes ozone interference)

    Sep-Pak Dry (high capacity desiccant, removes water from normal phase extracts)

    PoraPak RDX (explosives, EPA Method 8330)

    Sep-Pak PS2 (multi-residue pesticide analysis in water)

    Sep-Pak AC2 (removes/enriches polar organic molecules in water)

    Carbon Black / Aminopropyl (pesticide clean-up in food)

    Carbon Black / PSA (two layer sorbent bed, pesticide cleanup in food)

    DisQuE dispersive SPE QuEChERS multiresidue pesticide analysis

    SPE Sorbents for Environmental Analysis

  • 2012 Waters Corporation 8

    Waters SPE History

    1978

    Sep-Pak

    (silica based SPE introduced)

    1980s

    Sep-Pak

    (additional silica

    bonded phases)

    1994

    Oasis HLB

    (co-polymeric

    resin)

    1999

    Oasis MCX, MAX

    (mixed-mode, strong

    ion exchange)

    2002

    Oasis WCX, WAX

    (mixed-mode, weak

    ion exchange)

    2005

    Sep-Pak

    (GCB/Amino)

    2008

    PSA

    (Primary-secondary

    amine silica)

    2008

    DisQuE

    (Dispersive SPE

    QuEChERS)

  • 2012 Waters Corporation 9

    Outline

    Introduction Why sample Prep Considerations

    o Choices of tools Why SPE

    SPE Strategies Traditional approaches

    o Normal Phase o Reverse Phase o Mixed Modes

    Modern approaches o Mixed Modes o Reverse phase

    Summary

  • 2012 Waters Corporation 10

    SPE Strategies

    1. Strategy #1

    Pass-through cleanup

    2. Strategy #2

    Retention, cleanup, elution

    3. Strategy #3

    Dispersion Cleanup (DisQuE for QuEChERS)

  • 2012 Waters Corporation 11

    SPE Strategy #1 Pass-Through Cleanup

    1. Sample is passed through sorbent and collected

    no sample enrichment

    2. Matrix interferences are retained on sorbent

    pass through

    Blue = Compound of interest

    Purple = Sample

    Sample is not concentrated

  • 2012 Waters Corporation 12

    1. load 2. wash 3. elute

    1. Sample is loaded onto SPE sorbent Analyte(s) of interest

    are retained on sorbent

    2. Matrix interferences are washed off sorbent

    3. Analytes are eluted from sorbent

    SPE Strategy #2 Retention-Cleanup-Elution

    Blue = Compound of interest

    Purple = Sample

    Sample Concentrated

  • 2012 Waters Corporation 13

    SPE Strategy #3 Dispersive SPE

    Bulk sorbent is added to sample with agitation

    Sample is filtered or centrifuged

    Supernatant is collected for analysis

    Quicker

    Easier

    Cheaper

    Effective enough in many cases

    Accepted for Agro analysis of pesticides applications for Environmental analysis include soil and water screening

  • 2012 Waters Corporation 14

    Outline

    Introduction Why sample Prep Considerations

    o Choices of tools Why SPE

    SPE Strategies

    Traditional approaches o Normal Phase o Reverse Phase

    Modern approaches o Mixed Modes

    Summary

  • 2012 Waters Corporation 16

    Isolation of Aromatic Hydrocarbons Contaminated Soil

    Prepare Sample

    Condition/Equilibrate 4 mL DCM

    10 mL hexane

    Load Sample 0.25 mL of pre-extract in hexane

    Elute 1 3 mL hexane

    Elute 2 2 mL DCM

    Evaporate to Final Volume

    Sep-Pak Silica

    SPE Protocol

    Pre-extraction Soils are mixed with sodium sulfate and

    extracted with DCM or DCM/acetone.

    The extract is exchanged to hexane (weak

    solvent). The extract must be water-free.

    Aliphatic hydrocarbons are removed.

    This fraction may be collected and

    analyzed if desired.

    Aromatic hydrocarbons are eluted with

    strong solvent.

    Conditions for 6 cc 500 mg cartridges

  • 2012 Waters Corporation 17

    Hydrocarbons Recovered from Diesel Contaminated Soil (spiked)

    Diesel

    Diesel Elute 1

    Aliphatic (hexane) fraction

    Diesel Elute 2

    Aromatic (DCM) fraction

  • 2012 Waters Corporation 18

    Aromatic Hydrocarbons Recovered from Diesel Contaminated Soil (GC-FID)

    Elute 2:

    Sep-Pak Silica SPE

    (aliphatic hydrocarbon

    interference eliminated)

    Minutes 0 5 10 15 20 25 30 35

    naphthalene

    2-methylnaphthalene

    1-methylnaphthalene

    phenanthrene

    Diesel:

    No SPE

    FID

    Gas Chromatography Column: RTX-5, 30 m x 0.25 mm (ID) 0.25 m film 1 mL/min Helium carrier gas 35o C for 1 min, then 8oC/min to 320

  • 2012 Waters Corporation 19

    Normal Phase Pass-Thru Cleanup (additional applications)

    Chlorinated Pesticides in Soil or Water

    Liquid extraction

    exchange to hexane

    pass-thru cleanup on Florisil or Alumina

    GC-MS Pesticides in fruit and vegetables

    extract with acetonitrile/toluene

    pass-thru cleanup on aminopropyl silica

    o often performed with Graphitized carbon

  • 2012 Waters Corporation 20

    Outline

    Introduction Why sample Prep Considerations

    o Choices of tools Why SPE

    SPE Strategies

    Traditional approaches o Normal Phase o Reverse Phase

    Modern approaches o Mixed Modes

    Summary

  • 2012 Waters Corporation 21

    Reversed Phase Retention SPE Typical Protocol

    Condition cartridge strongest solvent first (DCM, MTBE,

    ethyl acetate)

    intermediate solvent next (methanol)

    weak solvent last (water)

    Load Sample dissolve in or exchange to weak

    solvent (water or water/methanol)

    Wash Cartridge use strongest possible solvent without

    eluting analyte (methanol/water)

    Elute Cartridge with strong solvent* methanol, IPA,MTBE, DCM

    *Oasis HLB elute solvent should have at

    least 5 % methanol or IPA as polar modifier

    Prepare Sample

    Condition/Equilibrate 1 mL methanol, 1 mL water

    Load Sample

    Wash 1 mL 5% methanol/water

    Elute 2 mL methanol

    Evaporate, Reconstitute

    Oasis HLB

    SPE Protocol

    Conditions for 3 cc 60 mg cartridges

  • 2012 Waters Corporation 22

    Reversed-Phase SPE

    Sorbent surface is relatively hydrophobic Sep-Pak C18 Silica, other alkyl silica, Oasis HLB

    Sample is prepared for SPE in aqueous or other polar sorbent

    Oasis HLB is better pH stable from 1-14

    Doesnt de-wet

    Examples:

    Isolation and enrichment of organic contaminants from surface

    waters

    Simple method for aromatics in groundwater

    Advanced method fo

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