Application Notebook-02-01-2016

Click the title above to open the Spectroscopy February 2016 Application Notebook, Vol 31 No 2, in an interactive PDF format.

The elegant design of the Elegra results in a very compact accessory (Figure 1), making it easy to fit every ICP model without overcrowding the sample compartment. The Elegra utilizes highly efficient membrane technology to add moisture to the argon as it flows through the inert metal-free construction. The device runs at atmospheric pressure and does not require heating or electric power. The Elegra is also configured with a bypass switch so that the operator can turn humidification on and off without connecting or disconnecting any tubing. For easy installation on any ICP instrument and nebulizer, each Elegra Kit is packaged with customized gas connectors.

As the temperature increases, significant changes in the myoglobin secondary structure are observed. Between 25 °C and 70 °C, the 1649 cm-1 peak height decreases and linewidth increases. These changes in the amide I band reflect increased protein structural disorder. A temperature increase from 70 °C to 75 °C causes a drop in the 1649 cm-1 band intensity. Simultaneously, two peaks grow in at 1683 and 1637 cm-1. These changes indicate conversion of random coil/α-helix to intermolecular β-sheet. Further conversion to β-sheet is observed as the temperature rises to 90 °C. The final β-sheet structure is an insoluble aggregate. This aggregation process is not reversed when the temperature is driven back to 25 °C.

To optimize the mapping collection parameters, it is important to factor the size of the mapping area, the beam diameter, and the desired beam spacing. For this sample, the area being mapped is shown in red outline in Figure 2, approximately 50.4 x 3.5 mm.

Moxtek's MAGPRO miniature X-ray source is capable of up to 60 kV 200 µA and down to 4 kV and 1000 µA, and limited to an output power of 12 watts. The 12 W source is meant for use in small bench top systems where small size is valued.

The Rigaku NEX CG combines secondary and polarization target excitation, with a high performance SDD detector, to deliver optimal EDXRF sensitivity. In conjunction with UltraCarry, the NEX CG is an ideal tool for the trace elemental analysis of aqueous solutions down to parts-per-billion levels. This technique is suitable for many applications, including: 1) monitor effluents, waste streams, and discharge waters; 2) screen for common metals; 3) measure hazardous elements; 4) QC of production rinse waters; 5) pavement run-off; 6) storm water run-off; 7) agricultural run-off; 8) site remediation; and 9) soil leachates.

The United States Pharmacopeia (USP) is in the process of developing new USP chapters and for the measurement of inorganic contaminants in pharmaceutical samples. While samples can be dissolved in aqueous or organic solvents, the large majority will require digestion, and closed vessel microwave digestion is stipulated by USP. Single reaction chamber (SRC) microwave digestion is a new type of closed vessel digestion that was developed by Milestone and offers many advantages over closed vessel digestion-particularly for pharmaceutical sample types.

Single reflection ATR spectroscopy is valuable for examining thermally induced changes in materials. Changes in the water concentration and amide bands of egg yolk were observed using the Harrick DiaMaxATR accessory. Further analysis is possible to obtain more rigorous identification of the heat-induced structural changes.

The Z-500 also analyzes base metals and trade elements, including Mg, Ti, V, Cr, Fe, Mn, Cu, Ni, and others. Trace metals of commercial interest or as pathfinders including Li, Be, B, C, and halogens including F, Cl, and Br are also analyzed. Figure 2 shows results for Li analysis, as an example. The results for lithium analysis were reasonably good. While there is some scatter in the data, the HH LIBS is measuring very low concentrations, in the 10–30 ppm concentration range. In general, the results for B, Be, Mg, Ba, and other elements were comparable, in terms of correlation, with the Li data.

The flavonoids that dominate the fluorescence spectra for honey shown in Figure 1 are polyphenols. These plant metabolites determine the color, aroma, and flavor of the honey, and provide antioxidant and other health benefits. The fluorescence spectrum for each honey sample illustrates the sensitivity of fluorescence spectroscopy for characterizing honey.

The LUMOS FT-IR microscope is an all-in-one solution with an integrated spectrometer, a high degree of automation, and a dedicated user interface. The innovative motorized attenuated total reflectance (ATR) crystal allows performing the complete measurement procedure fully automated including background and sample measurements. The dedicated OPUS software Wizard guides the user through the whole measurement procedure. For identification of unknown compounds, spectrum search and mixture analysis are applied using the functionality of the OPUS/SEARCH package. Chemical images of the spectral data are generated from univariate and multivariate analysis results.

RISE microscopy, the combination of Raman imaging and scanning electron microscopy, is a powerful new analytical method for the analysis and interrelation of the structure and composition of microscopic samples. The integration of both imaging techniques in one instrument avoids shuttling the sample from one microscope to another. Here we demonstrated its usefulness in the identification, discrimination, and localization of polymorphs of titanium dioxide.