Spectroscopy-07-01-2015

Continuing the theory and practice themes from previous columns, the theory portion of this column will be a discussion of the proper way of handling the infrared spectral interpretation of mixtures. In my opinion, mixtures are the biggest obstacle to interpreting infrared spectra, and I will share with readers five tried-and-true techniques for dealing with them. The practice portion of the column will give the answer to the last installment’s problem, and complete the spectral analysis of straight chain alkanes.

This installment describes the development of two novel X-ray diffraction (XRD) techniques that enable the rapid analysis of samples using handheld instrumentation for remote applications. Both techniques can be applied to unprepared samples in the field, which is a highly favorable characteristic in many applications since the time required for laboratory-based sample preparation is avoided.

The archnemesis of calibration modeling and the routine use of multivariate models for quantitative analysis in spectroscopy is the confounded bias or slope adjustments that must be continually implemented to maintain calibration prediction accuracy over time. A perfectly developed calibration model that predicted well on day one suddenly has to be bias adjusted on a regular basis to pass a simple bias test when predicted values are compared to reference values at a later date. Why does this problem continue to plague researchers and users of chemometrics and spectroscopy?

The speciation of trace elements has become much more common in recent years, and in some cases is now required by certain regulatory bodies - such as for the analysis of hexavalent chromium in drinking water. At the same time, speciation methods are becoming sophisticated as researchers try to address more complex questions about how different metal species are transported and interact with the environment and specifically with plants, animals, and humans, often forming complexes with other compounds that are more complicated to analyze. Prof.

The new Mars rover that is being developed for launch in 2020 by the National Aeronautics and Space Administration (NASA) will include a micro-X-ray fluorescence instrument called “PIXL,” for Planetary Instrument for X-Ray Lithochemistry. PIXL will be mounted at the end of the rover’s robotic arm and is designed to provide fine-scale identification of the elemental composition of rocks and soils on Mars. It is one of seven instruments on the Mars 2020 rover to seek evidence of past life on Mars.

Surface-enhanced Raman scattering (SERS) has been applied to the determination of the antioxidant butylated hydroxyanisole (BHA), commonly used in fatty foods and oils to prevent their oxidation. The use of SERS-Raman microscopy with an inexpensive homemade silver substrate allowed the direct determination of BHA in oils without any sample handling. Several edible and essential oils (used as flavorings) have been considered for this purpose.

The ChemDoodle Mobile app is designed to allow users to draw chemical structures, view 3D graphics, and generate IUPAC names.

Click the title above to open the Spectroscopy July 2015 regular issue, Vol 30 No 7, in an interactive PDF format.