Analysis of Liquid and Powder Samples by Benchtop WDXRF Spectrometer Supermini200 without Helium Gas

Conventional WDXRF typically measures liquids and loose powders under a helium atmosphere because these samples cannot tolerate evacuation or may be disturbed during vacuum pumping. Helium shortages and rising costs have made this approach increasingly difficult. An air/vacuum configuration allows the sample chamber to remain at atmospheric pressure while maintaining a vacuum in the optical chamber, eliminating the need for helium while preserving good analytical performance for many elements.

A sealing unit physically isolates the sample chamber from the optical chamber. The sample remains in air while X-rays travel through a vacuum in most of the optical path, minimizing X-ray absorption compared with a system operating entirely in air. This design significantly improves sensitivity for many low-energy element lines while avoiding the use of helium gas.

The configuration provides practical measurement capability for silicon and heavier elements. Compared with measurements made entirely in air, signal intensities for low-energy elements are substantially improved, allowing routine analysis of elements such as silicon, phosphorus, sulfur, chlorine, calcium, and heavier transition metals. Elements lighter than silicon remain difficult to quantify because of greater X-ray absorption in air.

The chlorine Kα emission line lies very close to the sulfur Kβ line. WDXRF provides sufficient spectral resolution to separate these overlapping peaks, enabling accurate determination of trace chlorine even when sulfur is present at much higher concentrations. EDXRF generally cannot resolve these peaks adequately, making trace chlorine analysis much more challenging.

Specialized high-sensitivity analyzing crystals, such as RX9 and RX9C, increase detection efficiency for these low-energy elements. Compared with a standard PET crystal, the RX9 provides roughly three times higher sensitivity, while the RX9C offers approximately 3.6 times higher sensitivity, helping offset the signal loss associated with air/vacuum measurements.

The approach is especially valuable for liquid samples, such as petroleum products and oils, and loose powder materials that cannot easily be pelletized. Fine powders such as petroleum coke can be analyzed without the risk of particle disturbance caused by evacuating the sample chamber, while liquids can be measured without requiring a helium atmosphere.

Laboratories can choose among vacuum, helium, and air/vacuum operating modes according to the sample type and analytical requirements. Samples that no longer require helium can be analyzed without consuming the gas, reducing dependence on an increasingly expensive and limited resource while retaining conventional measurement modes when necessary.