How to Select XRF Sample Cups
The traditional method of selecting a sample cup begins with taking the following three measurements of the sample cup holder or sample cup containment configuration provided with the x-ray instrumentation. A good caliper with the capability of measuring length, depth, inside and outside diameters in preferably metric units would be most helpful.
- THE INSIDE DIAMETER of the sample cup holder is required in order to determine the outside sample cup diameter size. Any ridges, ledges or tapers on the inside diameter of the sample cup holder must be considered as representing the inside diameter measurement. Record the inside diameter measurement since it will be the used to help you select a sample cup.
- THE INSIDE DIAMETER OF THE APERTURE represents the hole through which the primary excitation and secondary energies pass. Sample cup selection is also based on the size of the sample cup holder ledge formed by the aperture. It must be adequate in size to safely retain the sample cup and cover its edges from excitation exposure. If the aperture is larger than the sample cup it will not be retained and obviously fall through. If the aperture is smaller it might present a potential possibility of the excitation energy impinging upon the plastic sample cup that may be influential to analytical accuracy. Record this measurement for consideration in selecting a sample cup for a sample cup holder provided with your instrument.
- THE MAXIMUM INSIDE HEIGHT is defined as the distance measured from the ledge forming the aperture to the top open end of the sample cup holder. The importance of this measurement is to avert overextension of the sample cup that may potentially interfere with the operational mechanics of an automatic sample advance system or prevent a lid cover from effectively closing in accordance with the x-ray equipment manufacturer’s specifications.
With this information and reference to the "Quick Reference Chart" closely match a sample cup to the sample cup holder inclusive of selecting your attribute options such as “Snap-On Ring” or TrimLess® collar to affix thin-film, external or internal overflow reservoirs, vented “snap-on cap”, venting method, provision for mounting Microporous Film for equalizing pressure differentials between the interior of the sample cup and sample chamber, “serrated edge snap-on rings” for trimming extraneous thin-film from the assembled sample cup, SpectroMicro® sample cups and other interesting attributes.
® TrimLess and SpectroMicro are registered trademarks of Chemplex Industries Inc.