1991 Pittsburgh conference

67

Vibrational Spectroscopy, 2 (1991) 67-68 Elsevier Science Publishers B.V., Amsterdam

MEETING REPORT 1991Pittsburgh Conference The Pittsburgh Conference & Exposition on Analytical Chemistry & Applied Spectroscopy has become the premier meeting for analytical instrument manufacturers to show their latest equipment. This year’s conference was held March 4-8, 1991 in Chicago. The conference was founded 42 years ago in Pittsburgh, and is still organized by volunteers from the Spectroscopy Society of Pittsburgh and the Society for Analytical Chemists of Pittsburgh. With nearly 1000 exhibitors and over 1500 technical papers presented, this year’s conference was the largest in the organization’s history. As usual, vibrational spectroscopists were present in abundance, checking out the latest inattending sessions, presenting strumentation, papers, and discussing spectroscopy with each other. Few other meetings bring together so many scientists and vendors who are actively involved in infrared and Raman spectroscopy. Although vibrational spectroscopy is just one of many areas represented at this meeting, two people cannot possibly do justice to all the Raman and IR advances presented there. There were 18 sessions and/or symposia specifically devoted to vibrational spectroscopy, with many other infrared and Raman talks scattered throughout the other sessions. There were mid-IR sessions on hyphenated techniques, reflection methods, apparatus and techniques, quantitative analyses, and microspectroscopy applications, spectrometric instrumentation, as well as several near-IR sessions and four award symposia. There were no notable discontinuities in infrared instrumentation introduced at this meeting, but rather, many refinements of existing approaches and numerous application examples. Perhaps the hottest new area for infrared spectroscopists at this year’s meeting was process control. Several companies exhibited equipment designed to monitor and control manufacturing

processes on line, and there was a session on process chemistry using mid- and near-IR spectroscopy. Time-resolved infrared spectroscopy seems to have attracted renewed attention this year, with some advances occurring in the development of both stroboscopic FT.IR and step-scan FT.IR approaches. Several applications of step-scan interferometry to photoacoustic spectroscopy were also discussed. Progress in GC/IR, LC/GC, and SFC/IR continues, with some significant sensitivity advances in each area, and more application examples being generated. Infrared microspectroscopy continues increasingly widespread application. More near- and mid-IR spectroscopic applications of fiber optics continue to emerge. Quite a few papers were given on applications of surface-enhanced Raman spectroscopy (SERS). Several focused on how materials such as peptides, amino acids, thiol compounds, and surfactants adsorbed on metal surfaces. Near-IR SERS on gold surfaces was used by several groups because of the superior inertness of gold compared to silver. SERS was also used for trace-level detection and for controlling the sampling depth of spectroscopic measurements. One group used surface enhancement to collect high-quality hyper-Raman spectra using as little as 100 mW of “ CW mode-locked” power at 1064 nm. Surfaceenhanced hyper-Raman spectroscopy was demonstrated on silver, gold and copper surfaces. Several papers reported applications of FT-Raman using 1064~nm excitation. Samples ranged from “real world” samples, such as metalloporphyrins and pharmaceuticals, to materials chosen to demonstrate instrument performance, such as rhodamine 6G and sulfur. Near-IR Raman spectroscopy was also demonstrated using two other types of instrumentation. An f/l.4 echelle spectrograph coupled to a CCD detector mea-

MEETING

sured a continuous 4500 cm-l spectral region simultaneously at l-2 cm-l resolution. A Hadamard transform Raman instrument using a fast liquid-crystal encoding mask was also described. Other impressive applications of Hadamard transform methods to Raman spectroscopy were presented. In each case, the entrance slit of a spectrograph was replaced by a Hadamard mask, allowing a larger area of the sample to be imaged onto the detector. One study used the larger sample area to greatly reduce the laser power density on the sample without a reduction in the signalto-noise ratio of the spectrum. Another study used this approach on spatially heterogeneous samples to collect two-dimensional Raman images. Threedimensional Raman images were created by collecting two-dimensional images from different focal planes and mathematically extracting depth information. Holographic Raleigh line-rejection filters were also discussed at this meeting. These filters have an extremely uniform transmission of about 80% for the Stokes Raman spectrum, and attenuate the Raleigh line by 4-6 orders of magnitude. Useful spectra can be collected as close at 50 cm-’ to the

REPORT

exciting line on the Stokes side of the spectrum. Some filters also allow an&Stokes spectra to be collected. Fewer resonance Raman papers were presented this year than in years past. Some of the applications included detection of aromatic materials or chlorinated ethylene in flames, detection of ethylenic end groups in polymers, and spectroscopy of bilirubin. One group used resonance Raman emission for detection in liquid chromatography. Another group attempted to do farUV resonance Raman studies with a single grating spectrograph, but severe scattering limited their success. This unique meeting continues to be a must for many vibrational spectroscopists. The 1992 edition will be held March 9-13 in New Orleans, Louisiana.

Curtis Marcott Michael J. Pelletier The Procter & Gamble Company Miami Valley Laboratories Cincinnati, OH USA