Low-Cost, High-Performance Sample Cell for X-Ray Spectroscopy of Solutions and Gels Made from Plastic Straw

Low-cost tube-type sample cells for X-ray spectroscopy of solutions, sols, and gels were made from plastic straws. Energy-dispersive X-ray fluorescence (XRF) experiments showed that the X-ray transparency of the straw cells is ∼50% superior to that of quartz capillary cells for 6 - 7 keV XRF and is almost uniform over the entire range, allowing its use for position-dependent measurements. Wavelength-dispersive XRF experiments showed that the difference in the surface curvature between the straw cells and pellet samples leads to an apparent ∼1.5 eV shift of the Fe Kβ_1,3 peak; however, chemical effects of Fe Kβ_1,3 spectra can be studied if all the samples (including standards) are evenly set in the straw cells. Additionally, the application of the straw cell in studying precipitation band formation in gels was shown on two gel samples containing 0.004 M [Fe(CN)₆]^3-/[Fe(CN)₆]^2- in 2 mass% κ-carrageenan and 0.040 M Fe²⁺/Fe³⁺ in 1 mass% agarose, respectively.