Coupling of acetonitrile deproteinization and salting-out extraction with acetonitrile stacking for biological sample clean-up and enrichment of hydrophobic compounds (porphyrins) in capillary electrophoresis

Qi Li, Carmen W K HUIE*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)

Abstract

A new sample pretreatment approach in CE was developed for concurrent biological sample clean-up and the concentration of hydrophobic compounds based on the combination of ACN deproteinization with salting-out extraction. Further enhancement in concentration detection sensitivity was achieved by coupling (offline) salting-out extraction with an online CE sample enrichment technique known as "ACN stacking". By optimizing the pH of salting-out extraction, a number of model compounds (hydrophobic porphyrins with clinical significances), i.e. zinc-protoporphyrin, protoporphyrin, and coproporphyrin (CP) III and I, can be efficiently extracted from the aqueous sample into a smaller volume organic solvent (ACN) phase and an enrichment factor of ca. 100 can be obtained. The pressure injection of the enriched ACN phase (containing ca. 1% NaCl) into the CE capillary at 10% capillary volume resulted in additional concentration of the various hydrophobic porphyrins, allowing for a combined enrichment factor of ca. 1000 to be obtained. Calibration curves obtained for the determination of a pair of positional isomers with significant diagnostic value, urinary CPIII and CPI, were found to be linear between 10-300 ng/mL (with R2=0.999), and LODs (absorbance detection at 400 nm) were ca. 0.8 ng/mL (1.1 nmol/L of CPIII or CPI). Based on a single salting-out extraction, intraday precisions (nine consecutive injections) for both CPIII and CPI (at spiked concentrations of 10-300 ng/mL into urine) in terms of migration time and peak area were found to be within the range of 0.2-0.5 and 0.8-2.9%, respectively.

Original languageEnglish
Pages (from-to)4219-4229
Number of pages11
JournalElectrophoresis
Volume27
Issue number21
DOIs
Publication statusPublished - Nov 2006

Scopus Subject Areas

  • Analytical Chemistry
  • Biochemistry
  • Clinical Biochemistry

User-Defined Keywords

  • Acetonitrile deproteinization
  • Acetonitrile stacking
  • Capillary electrophoresis
  • Hydrophobic compounds
  • Salting-out extraction

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