Solid-Phase Microextraction (SPME) - - Chromatography Online
Solid-Phase Microextraction (SPME)

LCGC North America
Volume 30, Issue 10, pp. 904-911

Gas chromatography (GC) resolution and sensitivity are often limited by matrix effects in "real world" samples that originate outside of a laboratory. GC separation and detection may encounter interference from nonvolatile constituents, side-effects of large sample volumes, and the chemical activity of matrix compounds and derivatization residues. A number of sample preparation techniques increase analyte concentrations and detector response while reducing matrix effects, including classical liquid–liquid extraction, chemical derivatization, and sample preconcentration, as well as headspace, thermal desorption, and large-volume sample injection.

Solid-phase microextraction (SPME) is a relatively new sample extraction technique — first described in the 1990s by Pawliszyn (1,2) — that brings some unique capabilities to bear on the chromatographic analysis of dilute solutions in difficult matrices, both liquid and gaseous. Essentially, SPME consists of two discrete steps: solute absorption from the sample matrix into a thick layer of silicone or related adsorptive material, followed by transfer of the absorbed analytes into a chromatography inlet system by thermal or liquid desorption.

SPME has been applied to both GC and liquid chromatography (LC) separations. It eliminates the need for large-volume sample transfer into a GC column by concentrating analytes into the fiber coating while leaving the bulk of the solvent and nonvolatile residues behind. SPME uses orders of magnitude less solvent and has significant potential to greatly reduce or eliminate solvent consumption and the concomitant issues of used solvent disposal as part of sample preparation.

Chromatographers should not confuse SPME with solid-phase extraction (SPE), a related predecessor with similar applications. The principal difference is that SPE is carried out with a relatively large sorptive wafer the size of a small filter paper and requires post-sorption liquid-phase extraction of analytes; SPME is accomplished with a small fiber or tube coated with sorptive material. SPME is applied to both gas-phase and liquid-phase extraction, whereas SPE is limited to extraction from liquid-phase samples. This GC Connections installment primarily discusses SPME using absorptive polymeric coatings, although the principles also apply to adsorptive SPME onto active solid layers.

A related technique, stir-bar sorptive extraction (SBSE) uses a magnetic stir bar coated with a thick layer of absorptive polymer. The stir bar is exposed to sample solution for a time, during which solutes are absorbed into the polymer coating. Subsequently the stir bar is removed, dried, and then thermally desorbed for GC injection, or the absorbed analytes can be back-extracted with a different solvent. SBSE uses a larger volume of absorbent than SPME and, thus, is more efficient at extracting analytes with less absorbent solubility. Therefore, SBSE is generally more sensitive than SPME.

SPME applications cover a broad range that includes flower scents (3), chemical warfare agents (4), pharmaceutical process impurities (5), the determination of organochlorine pesticides in Chinese teas (6), volatile compounds in acidic media (7) and cheese (8), volatile phenols in wine (9), environmental pollutants in water samples (10), chloroanisoles in cork stoppers (11), volatile aliphatic amines in air (12), and phenylurea herbicides in aqueous samples (13).


blog comments powered by Disqus
LCGC E-mail Newsletters
Global E-newsletters subscribe here:



Column Watch: Ron Majors, established authority on new column technologies, keeps readers up-to-date with new sample preparation trends in all branches of chromatography and reviews developments. LATEST: When Bad Things Happen to Good Food: Applications of HPLC to Detect Food Adulteration

Perspectives in Modern HPLC: Michael W. Dong is a senior scientist in Small Molecule Drug Discovery at Genentech in South San Francisco, California. He is responsible for new technologies, automation, and supporting late-stage research projects in small molecule analytical chemistry and QC of small molecule pharmaceutical sciences. LATEST: HPLC for Characterization and Quality Control of Therapeutic Monoclonal Antibodies

MS — The Practical Art: Kate Yu brings her expertise in the field of mass spectrometry and hyphenated techniques to the pages of LCGC. In this column she examines the mass spectrometric side of coupled liquid and gas-phase systems. Troubleshooting-style articles provide readers with invaluable advice for getting the most from their mass spectrometers. LATEST: Radical Mass Spectrometry as a New Frontier for Bioanalysis

LC Troubleshooting: LC Troubleshooting sets about making HPLC methods easier to master. By covering the basics of liquid chromatography separations and instrumentation, John Dolan is able to highlight common problems and provide remedies for them. LATEST: How Much Can I Inject? Part I: Injecting in Mobile Phase

More LCGC Columnists>>

LCGC North America Editorial Advisory Board>>

LCGC Europe Editorial Advisory Board>>

LCGC Editorial Team Contacts>>

Source: LCGC North America,
Click here