Introduction
Solid phase microextraction (SPME) is a fast, environmentally friendly, field-compatible method of sample preparation for chemical analysis. In 2001, Chem 13 News published an introductory article about the newly developed technique, and since then its popularity has grown, expanding to scientists in many disciplines. While the previous article described the method, this article will focus on the applications and developments of the science, and how SPME is improving the quality of our society and life.
To refresh your memory, SPME was developed as an alternative to liquid extraction, which is an exhaustive technique that involves the use of large quantities of organic solvent. SPME employs a syringe design of a retractable fused-silica, polymer or metal fiber core, coated with the extraction phase. As the fiber is submerged in the sample, the analyte equilibrates between the two phases. The fiber can then be drawn back into the needle for safe storage, and can be directly analyzed by GC (gas chromatography) and HPLC (high-performance liquid chromatography) without any loss of the sample. The benefits of this method are its ease of use, sensitivity, selectivity, integration of sampling and sample preparation steps and field compatibility.
Non-lethal sampling in fish
An interesting application of this technique is its use in environmental testing of fish tissue. A growing concern is the releasing of organic compounds, such as pharmaceuticals, into surface water. These chemicals have been shown to accumulatein fish tissues and have the potential to impact human health. There is a demand to study fish tissue, to investigate the pollution effects, but in order to do this the present analytical methods involve sacrificing the animal. Recently, SPME coupled with LC-MS (liquid chromatography–mass spectrometry) was used as a rapid and non-lethal sample preparation method for determination of the contaminants in live fish. By applying appropriate SPME with highly a sensitive MS system, very low concentration of the pollutants can be detected in live fish tissue.
SPME applications in medicine
SPME has been applied to pharmaceutical and medical research to evaluate pharmacokinetics and metabolism of drugs. Typical biological samples are very complex and may contain numerous components while the analytes of interest may be present at low concentration. Due to its sensitivity and selectivity, SPME is a good candidate to extract such analytes. The results obtained through this method measure only the concentration of the analyte that is bioavailable, allowing further research into its uses and properties within the system. Furthermore, SPME eliminates the need for blood or tissue removal, which permits repeated studies of processes at different times or localizations within the same organism. This has ethical benefits, enabling studies in small rodents without the need to sacrifice multiple animals. Another developing application of SPME is its use in detection and diagnosis of disease through biomarker analysis. By analyzing a patient’s breath, skin, tissue, feces or urine, SPME can detect markers associated with several cancers and bacterial infections. SPME-GC-MS, mainly used for studies of human breath, has recently proved that profiles of volatile organic compounds in patients with lung cancer remain constant through all stages of the disease. This can provide doctors with a method of early detection, and allow treatment to begin sooner. Studies of urine are currently being done to identify biomarkers for prostate, breast, leukemia, colorectal, and lymphoma cancers. Infections caused by bacteria have also been shown to exhibit
Liver sampling with SPME probes prior to organ transplantation.
biomarkers. Pathogens such as P. aeruginosa in cystic fibrosis patients, H. pylori in stomach cancer patients, and other pathogens associated with gastrointestinal infection can be identified by associated biomarkers and detected by SPME.
Conclusion
With its unique properties and benefits, SPME is quickly becoming a trusted method in industrial and clinical analysis. Recent research has resulted in many advancements such as full automation of the process, development of biocompatible and in vivo analysis, and improvements of efficiency and sensitivity. These advancements in biological studies provides a powerful tool in ecology, pharmacy and medicine, and
Diagram of in-vivo SPME microextraction from blood vessel in tissue (as described in In vivo sampling with solid phase microextraction, Musteata and Pawliszyn, 2007,Journal of Biochemical and Biophysical Methods. Vol. 70 (2), pages 181-193.
meets the demand for environmentally friendly technology. With continuing research, SPME will allow us to observe and detect molecules in our environment so that we can live better and healthier lives.
