Thin-Film Selection Guide
Thin Film Short Description
The following selection guide lists all of the Thin-film sample supports manufactured by Chemplex® Industries, Inc. Use of the table is quite simple, just click on the heading of the column of interest and the table will be refreshed, and sorted by the values selected in the column. Click on the column heading again and it will be sorted in the reverse order. This will allow grouping of the Thin-film support windows by the parameters of interest to suit your needs. For example, when looking for all Chemplex® Thin films with a thickness of 7.5µm, click on the column heading of “Thickness” and then scroll to the entries with the value of 7.5 µm. All of them will be listed together.
XRF Sample Cups and Thin-Film Sample Support Windows are the basic necessities for containing and analyzing samples by XRF spectroscopy. Superficially, the procedure appears relatively simple. Attach a thin-film to one end of a new sample cup, introduce the sample and insert it in an x-ray machine for elemental analysis.
Selection of a suitable thin-film sample support window is mostly based on satisfying primary important laboratory requirements:
• Convenience of use
• Contamination avoidance
• Chemical Resistance to samples
• Analyte-line transmittance and intensity
The information presented entails the main packaging forms of thin-films that are offered, the various types of thin-films, a methodology for evaluating an appropriate thin-film for maximizing analyte-line percent transmittance and the resistance to sample chemical attack. Other issues of laboratory concern may include sample weight retention strength, performance under differential pressure conditions, integration time, excitation potential and related heat generation.
CONVENIENCE OF USE AND CONTAMINATION AVOIDANCE Dispensing and handling of thin-film in attempt to prepare a sample cup with a sample support window is frustrating, inconvenient and a source for contamination. This is attributed to the static electrical charges inherent to the thin-films that create static cling. The thin-film tends to stick to any surrounding object and one’s person. This phenomenon presents the potential of contaminating the thin-film and affecting analytical x-ray data.
With the advent of SpectroMembrane® Sample Support Carrier Frames, there is no annoying static cling or potential contamination risk to the thin-film through handling or attraction of airborne particles. With the exception of the sample cup, the thin-film is never in intimate contact with anything else. Thin-film handling is performed by the use of the integrated carrier frames that automatically detach during the assembly process leaving taut thin-film sample planes.
TRANSMITTANCE OF SPECTRAL LINES The transmittance properties of a thin-film are functions of gauge thickness, density and mass attenuation coefficients of the constituent chemical elements. The Analyte-Line Transmittance chart, above with the photographs, may aide in selecting the correct thin-film for a given sample of analytical interest. Simply refer to the spectral line of the element in the sample having the lowest energy, KeV, or the longest wavelength, Å. Then choose a curve with the highest percentage of transmittance. Finally use the Legend to determine which material and thickness.
CHEMICAL RESISTANCE In conjunction with selecting a thin-film providing a high % Transmittance value for an element analyte-line of interest, evaluation of resistance to chemical attack by a sample is an appropriate consideration. Liquid samples are generally more prone to thin-film degradation and rupture than other sample forms. Refer to the “Resistance of Thin-Film Substances to Chemical Attack” table.
Other factors equally influential to the integrity of a thin-film substance are:
• Integration time - extended analysis time
• Excitation potential - intense x-ray exposure
• Heat generatoin - from the sample and x-ray source
It is strongly urged that thin-film substances are subjected to judicious testing and evaluation prior to actual use to avoid inadvertent mishaps during analysis and potential damage to the x-ray instrumentation and costly ensuing clean-ups.
IMPORTANT: The chemical resistances of thin-films contained in the following table are provided as a matter of informational purposes only. They are not intended to preclude actual testing and suitability of use and applications. The responsibility of acceptance, suitability, testing, evaluation and safety resides totally with the user. Chemplex® Industries, Inc. assumes no liability whatsoever in using any thin-film sample support window substances and assumes no liability whatsoever for any information, advertisement, inferences, reports or any other form of communication written or orally presented.
Our 7.5µm Kapton® thin-film available from Chemplex® exhibits similar properties as the previous traditionally used type: 7.5µm gauge, high sample retention tensile strength, equivalent % Transmittance values of x-rays, chemical resistance and melting points. The difference between the other Kapton® films and the Chemplex® 7.5µm Kapton® thin-film is “it is not subject to the U.S. International Traffic in Arms Regulations (ITAR).” Reportedly, an unknown slight difference between the ITAR controlled and the new 7.5µm Kapton® thin-film may affect the reliance on previously established calibration data. Chemplex® suggests judiciously re-examining this issue for verification prior to implementing an analytical program.
IMPORTANT: Some window materials may not be suitable for analyzing sulfur in diesel fuel, gasoline and other petroleum products containing aromatic hydrocarbons. ASTM D-6445-99 (Reapproved 2004) e1: "Samples of high aromatic content may dissolve polyester and polycarbonate films. In these cases, other materials besides these films may be used for X-ray windows, provided that they do not contain any elemental impurities. ASTM D 4294-08a: "Any film that resists attack by the sample, is free of sulfur, and is sufficiently X-ray transparent can be used. Film types can include polyester, polypropylene, and polycarbonate. However, samples of high aromatic content can dissolve polypropylene, polycarbonate and polyester."
® SpectroCertified, Prolene, Etnom, Ultra-Polyester and Chemplex are registered trademarks of Chemplex Industries, Inc.
® Mylar and Kapton are registered trademarks of E. I. DuPont de Nemours & Co., Inc.