The first Richard Payling Prize was awarded to Gerardo Gamez in 2005 during the European Winter Conference on Plasma Spectrochemistry in Budapest, Hungary, for his poster presentation entitled "Analysis of gel electropherograms and blotting membranes via spatially resolved glow discharge optical emission spectrometry" (1). This work was part of Dr. Gamez' PhD work performed in Prof. Dr. G. M. Hieftje's laboratory at Indiana University-Bloomington, USA, in collaboration with Dr. S. J. Ray, Dr. F. J. Andrade, and M. R. Webb.
It was the first time a GD in pulsed RF power mode was used for obtaining laterally resolved information of the sample from within the anode. Earlier work from Hoffmann and Ehrlich had shown that in heterogeneous samples the optical emission from a GD, powered in continuous dc mode, had some memory of the place of origin of the analyte in the sample within the limits of the anode(2). However, the degree of lateral resolution observed under such conditions was very poor. In a later study by Webb et al. it was shown that operating the discharge in pulsed dc mode improves significantly the lateral resolution (3). Nevertheless, no applications were pursued. The poster for which G. Gamez got the Payling Prize in 2005 showed the first preliminary studies for an application of laterally resolved GDOES to real samples such as gel electropherograms (Figure 1). This work also served as the basis for a manuscript published at a later date (4). Gel electrophoresis is still by far the most popular separation technique for biological compounds (proteins, biopolymers, etc.). These compounds can be separated according to their electrophoretic mobility along one direction and their isoelectric point along another direction to yield a two dimensional separation map. The end goal is to obtain laterally resolved atomic emission maps from entire electropherograms in order to identify and quantify the biological compounds containing metal atoms or which have been tagged or dyed with other compounds to enhance their specificity or sensitivity. For example, in this study the use of a silver-enhanced colloidal gold dye was explored. This type of protein dying technique is very popular and in the case of the GDOES analysis provides for a great sensitivity enhancement because for every protein there will be many more silver atoms and by following the spatially resolved silver atomic emission one can easily identify and quantify the proteins of interest.
Figure 1. Spatially resolved emission from PVDF blot membrane sample at 328nm: with Ag particles dot smears during continuous mode (A,B) and during pulsed mode (C,D) of operation at 1Khz and 50% duty cycle. Operating conditions: 30 mm cathode, 3Torr, 100W forward RF power (1).
Gerardo Gamez obtained his Bachelor and Master of Science degrees at the University of Texas at El Paso where he performed research in environmental chemistry pertaining to the use of plant tissues to filter aqueous media from heavy metal contamination. He obtained his PhD in Analytical Chemistry at Indiana University-Bloomington where he employed laser and optical emission diagnostic techniques in fundamental studies of plasmas used in analytical spectrochemistry. His postdoctoral work at the Swiss Federal Institute of Technology, ETH, Zurich, involved developing methods for ambient ionization mass spectrometry and exploring the possibilities of near-field laser ablation techniques. He is currently in the Microanalysis group at the Swiss Federal Laboratories for Materials Science and Technology, EMPA, Thun, where he develops methods and instrumentation in glow discharge spectroscopy and serves as the coordinator for the Analytical Glow Discharge Marie Curie Research Training Network, GLADNET.
- G. Gamez, S. J. Ray, F. Andrade, M. R. Webb, G. M. Hieftje, Analysis of gel electropherograms and blotting membranes via spatially resolved glow discharge optical emission spectrometry, 2005 European Winter Conference on Plasma Spectrochemistry, 30th January - 3rd February 2005, Budapest, Hungary.
- V. Hoffmann, G. Ehrlich, Spectrochim. Acta Part B, 1995, 50B, 607-616.
- M. R. Webb, V. Hoffmann, G. M. Hieftje, Spectrochim. Acta Part B, 2006, 61, 1279-1284.
- G. Gamez, S. J. Ray, F. Andrade, M. R. Webb, G. M. Hieftje, Anal. Chem., 2007, 79 (4), 1317-1326.