This application note shows that the Epsilon 4 - a high-performance benchtop energy dispersive X-ray fluorescence spectrometer – is fully capable of identifying small differences in materials. The finger printing technique is applicable to all materials including liquids, powders and solids. FingerPrint software is available for all Epsilon 4 products.
In recent years it has become common practice to screen incoming materials and finished products within the health care and pharmaceutical community. This practice limits both waste and product liability and helps to identify counterfeit from innovator products. As the EDXRF technique does not significantly heat samples it is applicable for both organic and inorganic material testing. Furthermore, as a simultaneous technique, detecting all elements (from F to Am), it is well suited for rapid material identification.
Measurements were performed using an Epsilon 4 EDXRF spectrometer, equipped with a rhodium anode X-ray tube, a 10W, 50 kV and 2 mA generator, 6 filters, a helium purge facility (not necessary for all applications), a high-resolution silicon drift detector, a spinner and a 10-position removable sample changer.
Each toothpaste sample was weighed to approximately 10 g and simply placed into disposable P1 sample cups. Each P1 cup was constructed with a 4 micron Prolene X-ray support film. A clean plastic spatula was used to lightly press the material to the bottom of each cup and remove air voids. Total sample preparation time was less than 2 minutes per sample.
Toothpaste spectrum library
Using the spectrum viewing function it is possible to view sample and standard material spectra. This step is not necessary but illustrates the resolving power of the Epsilon 4. A selection of 5 toothpaste spectra is shown in Figure 1.
Figure 1. Comparison of 5 representative toothpastes
The optimal FingerPrint conditions were determined using the standard feature: Optimize conditions. Measurement times were 3 minutes per sample. For the analysis, default Epsilon 4 settings were used. The FingerPrint application was chosen by toggling the FingerPrint button and using the default settings.
Create a library - measure standards
It was not necessary to perform any spectral interpretation or deconvolution. The library consisted of 58 entries including 30 different brand types and replicates from Asia, Europe and North America. All materials were simply loaded and measured.
Unknown samples were placed on the sample tray. A fresh preparation of Arm & Hammer toothpaste was measured as an unknown. Measurements were started after the corresponding sample positions were identified.
Instant identification – results
The identification of likely candidates is instantly reported where the Chi2 values are below 3. In this example, only one toothpaste from the library was identified as it was the only material with Chi2 value less than 3. For illustration purposes an expanded list is shown in Table 1. The result was a correct match and this demonstrates the distinguishing power of the FingerPrint software with Epsilon 4.
Table 1. Measurement conditions
Fingerprint software - Capturing subtle differences
The FingerPrint software employs a sophisticated statistical algorithm that examines the entire scan. This includes features such as peak shape and background profiles. A key advantage is that fingerprinting is a fully automated method without the need for interpretation.
This work clearly illustrates that the Epsilon 4 can be used for rapid FingerPrint identification of all materials including raw materials, reagents, excipients and health care products.