Diamond ATR accessories are recognized for the range of samples that can be investigated, from hard, curved samples to liquids. Virtually unbreakable monolytic diamond crystals are used by some accessories, and highly fragile diamond wafers are used by others.
The pathlength through the diamond is usually as short as possible due to price considerations and the diamond lattice bands in the mid-infrared. These considerations limit the signal-to-noise ratio and affect performance. It is crucial to have as much of the incident light as possible reach the detector.
This article discusses the analysis of a range of samples using a compact high throughput diamond ATR accessory such as DiaMaxATR (Figure 1).
Figure 1. The DiaMaxATR
All spectra were collected using the DiaMaxATR single reflection diamond ATR installed in a commercial FTIR. The spectrometer coadded 32 scans obtained at 8 cm-1 resolution. The clean diamond ATR was used to collect the background single beam spectra.
The solid samples were compressed against the ATR crystal using the optimal force as limited by the built-in slip clutch in order to collect the sample spectra. A new PaperMate Profile® pen was used as the sample. It was disassembled for the analysis. The measurement was carried out by placing an ink drop over the crystal surface.
Results and Discussion
Figure 2 shows the pen analyzed, indicating the different sections examined. The resulting spectra are presented in Figures 3 through 7. Two methods to measuring the spectra of the ink are shown in Figure 3. The ink was analyzed as a coating by applying it on the curved metal surface close to the ball point, and as a liquid by placing a drop over the crystal surface.
Figure 2. The parts of a pen
The spectra collected from both approaches are nearly identical. More intense bands are observed in the spectrum showing the ink as a result of better contact with the ATR crystal and higher concentration. However, in the case of the ink in situ, the spectra collected differ slightly probably due to the presence of inhomogeneities in the sample, and the way the evanescent wave interacts with the underlying metal.
The spectra collected from other parts of the pen are shown in Figures 4 through 6. The library search feature included with the spectrometer was used to identify the composition of these components of the pen.
Figure 3. ATR spectrum of ink deposited on the crystal (blue) and ink on ball point (red)
Figure 4 shows the outside of the ink cartridge, which was conclusively identified as polypropylene. Similar spectra are observed for the body and push button of the pen, and spectral searching reveals that these parts are made up of polycarbonates with different formulations.
The spectrum of the pen clip is shown in Figure 6, clearly indicating that the clip is made up of polystyrene. The spectra of the grip and thrust device are shown in Figure 7.
Figure 4. ATR spectrum of the outside of the cartridge
Figure 5. ATR spectrum of the body (red) and the push button (blue)
Figure 6. ATR spectrum of the clip
Figure 7. ATR spectrum of blue grip (red) and the thrust device (blue)
This article has demonstrated the advantage of using the DiaMaxATR in the analysis of various parts of a pen. These parts represent a variety of samples, including curved plastics, curved metals, pliable materials and liquids.
This information has been sourced, reviewed and adapted from materials provided by Harrick Scientific Products, Inc.
For more information on this source, please visit Harrick Scientific Products, Inc.