MEPS (Micro Extraction by Packed Syringe) Components

MEPS (Micro Extraction by Packed Syringe)

• A miniaturization of SPE (Solid Phase Extraction) with differences:
  • Allows working with smaller sample volumes (10µL vs hundreds/thousands of µL in SPE)
  • Can be fully automated for extraction and injection using a syringe and autosampler for LC or GC
  • Reduces solvent volume and sample handling
  • Allows concentrating larger sample volumes through multiple 100µL or 250µL portions
  • Cartridges are reusable (40-100 samples depending on the matrix)
• Phase can be efficiently washed out between extractions, eliminating potential carry-overs

MEPS Cartridge Scheme

• Cartridge contains SPE phase (C18, C8, C2, SCX e Sil with 45µm diameter particles)
• Inserted in the syringe needle, prepared for GC or HPLC

MEPS Applications

• Phenols in residual waters:
  • Cartridge: BIN - C18 MEPS
  • Conditioning: 30 µL MeOH
  • Re-equilibration: 30 µL H2O
  • Extraction: 10 x 100 µL of the sample at 5 µL/seg
  • Dry step: with air (3 x 80 µL at 50 µL/seg)
  • Elution: 10 µL MeOH
  • Analysis: directly; 2 µL for GC/MS; column BPX5
• Biological samples:
  • Urine:
    • Sample: 100µL
    • Cartridge: BIN - C18
    • Conditioning: MeOH
    • Re-equilibration: H2O
    • Elution (xanthines): 30µL MeOH
    • Analysis: 2µL; BPX5; GC/MS
  • Plasma:
    • Sample: 50 µL
    • Cartridge: BIN - C2
    • Conditioning: MeOH
    • Re-equilibration: H2O
    • Elution: 30µL 0.1% HCOOH in ACN/H2O (75:25)
    • Analysis: HPLC; C18,100 x 2.1 mm

Comparison of MEPS, SPME, and SPE

• MEPS: solid phase extraction in a syringe, with benefits of miniaturization and automation
• SPME: solid phase microextraction, using a fiber for extraction and desorption
• SPE: solid phase extraction, using a cartridge or column for extraction and elution

Chromatographic Parameters

• Resolution (Rs): ratio of difference in retention times and average peak width
• Efficiency (N): plate number, a measure of column performance
• Selectivity (α): ability to separate two compounds
• Peak capacity: number of peaks that can be separated in a chromatogram
• Kinetic plots: a graph of peak width vs. retention time
• Giddings statements: a set of equations describing chromatographic performance

Liquid Chromatography (LC)

• Types:
  • Reversed phase (RP)
  • Normal phase (NP)
  • Hydrophilic interaction (HILIC)
• Parameters:
  • Column: stationary phase and dimensions
  • Mobile phase: solvent composition and flow rate
  • Detection: UV, MS, or other methods

Mass Spectrometry (MS)

• Principles:

  • Ionization: converting molecules into ions
  • Separation: based on mass-to-charge ratio
  • Detection: measuring ion intensity

• Types:

  • Single quadrupole
  • Triple quadrupole
  • Time-of-flight (TOF)
  • Orbitrap### Solid-Phase Microextraction (SPME)

• SPME fibers have polarity, with options including PDMS and PA

• PDMS is a type of SPME fiber

• Analyte molecular weight (MW) is a factor in SPME

• Supelco is a brand-name related to SPME

SPME Extraction Time

• Extraction time is a parameter in SPME
• Supelco is also relevant to SPME extraction time

SPME Stirring

• Stirring is an optional step in SPME
• Options for stirring include no stirring and stirring

Stir Bar Sorptive Extraction (SBSE)

• SBSE was introduced in 1999 by Erik Baltussen and Pat Sandra
• SBSE is based on the same principles as SPME
• Instead of a fiber, SBSE uses 10 mm stir bars with a layer of 24 to 500 µL of PDMS for analyte extraction
• Twister, GERSTEL is a brand-name related to SBSE
• SBSE has a lower phase ratio (β) compared to SPME, which can lead to higher recoveries
• The typical volume of PDMS in SPME is greater than in SBSE