Research at ORNL is Coupling Mass Spectrometry and Planar Separations
ORNL researchers have been looking for ways to improve Ambient Surface Sampling and Ionization Techniques, which are ways to analyze samples by mass spectrometry (MS) without having to first place them in the high vacuum environment of the mass spectrometer. As part of this work, they have teamed up with the Thin-Layer Chromatography (TLC) companies Camag and Merck KGaA. TLC, an important type of planar separation, is often underestimated by chemists, who are introduced to it in undergraduate Organic Chemistry labs as a simple and cheap low resolution separation technique. Continued improvement over the years in separation media and instrumental sample application and in development techniques for the plates used in TLC has turned TLC into a technique capable of high performance, high resolution separations (HPTLC).
However, it doesn’t interface well with identification techniques like MS. Gary J. Van Berkel, head of the organic and biological mass spectrometry group at Oak Ridge National Laboratory, and his collaborators are working to change that. The Ambient Surface Sampling and Ionization Techniques developed by Van Berkel and his colleagues can be used with HPTLC for high sensitivity qualitative identification of unknowns or quantitative determination of targeted analytes. The direct surface sampling and analysis approach is beginning to be successful with larger biological molecules, like peptides and proteins, separated by HPTLC. Mass spectrometric analysis of these same biological molecules from alternative planar separation media like electrophoretic gels requires each component to be removed in gel, extracted from the gel, thoroughly cleaned, and then put in the mass spectrometer; a time-consuming and costly process.
HPTLC is used to analyze small samples by separating the components of each sample on a TLC plate. For example, as reported in C&E News, in Zurich it is used to check food products for a toxic dye that is sometimes illegally put in spices to enhance their color. It is also important in Asia, where Artemisia annua plants are grown in large pots. These plants contain artemisinin, which is used to treat malaria, and local labs need to quickly identify when the artemisinin levels are highest. HPTLC allows this speed. It also allows multiple samples to be analyzed simultaneously, saving both time and resources. In addition, HPTLC makes it easy to analyze samples side-by-side as opposed to sequentially, and compounds in the sample that weren’t separated out are left on the plate and can be analyzed through other methods.
Well Defined The components of common horsetail, a dietary supplement used as a diuretic or for osteoporosis, can be separated by high-performance TLC.
C&E News, May 18, 2009, Vol. 87, Issue 20, pp. 11-18