Spectroscopy-03-01-2016

Were it not for the problem of photoluminescence, only one laser excitation wavelength would be necessary to perform Raman spectroscopy. Here, we examine the problem of photoluminescence from the material being analyzed and the substrate on which it is supported. Selecting an excitation wavelength that does not generate photoluminescence reduces the noise level and yields a Raman spectrum with a superior signal-to-noise ratio. Furthermore, we discuss the phenomenon of resonance Raman spectroscopy and the effect that laser excitation wavelength has on the Raman spectrum.

Continuing our theme of investigating the infrared spectra of hydrocarbons, we look at the nature of aromatic bonding and why aromatic rings have unique structures, bonding, and infrared spectra. Then we examine, in detail, the spectra of mono- and di-substituted benzene rings, and learn that infrared spectroscopy easily distinguishes between ortho-, meta-, and para- structural isomers. 

This month’s column presents an overview of the new 11th edition of the ACS Book of Reagent Chemicals and discusses some of the updated methods, and new procedures being adopted. In particular, we focus on new plasma based spectrochemical methodologies for the determination of heavy metals in reagent chemicals, which have replaced the 100 year-old test using precipitation and colorimetric measurement of the metal sulfides.

Analysis of Spectroscopy’s annual reader survey on salary, workload, and job satisfaction. The latest Spectroscopy salary survey shows that the average salary has dropped slightly, despite increasing workloads. But has this drop impacted job satisfaction? 

This article discusses emerging trends in the design and use of spectroscopic instrumentation. It focuses on recent research using new or modified spectroscopic techniques that are advancing scientists’ capability to obtain high-content, high-resolution data from ever-smaller sample sizes. To illustrate this trend, the article surveys novel approaches to complex measurement problems across a wide range of critical fields such as disease research, food safety, environmental monitoring, and drug development.

As was demonstrated by ESI and MALDI, and, more recently, ambient ionization approaches, successful new ionization methods can have an enormous impact on science. Novel ionization processes, such as inlet and vacuum ionization, are some of the latest of these approaches, and provide excellent alternatives to traditional approaches.

Click the title above to open the Spectroscopy March 2016 regular issue, Vol 31 No 3, in an interactive PDF format.