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X-Ray Fluorescence Analysis of Light Elements in Liquid Samples – EDX-8100 and Helium Purge Unit

Shimadzu’s EDX-8100 is an energy dispersive X-ray fluorescence spectrometer with high sensitivity for light elements and can be configured with an optional helium purge unit. The helium purge unit enables high-sensitivity analysis of light elements in samples that cannot be depressurized to a vacuum state such as solutions and samples that generate gas. As one effect, detection of fluorine (F) in liquid samples is possible with the EDX-8100. The detection limits of the elements F to K in liquid samples in a He atmosphere and differences depending on the film used to hold the samples were evaluated.

  • Elements and Samples

The samples are shown in Table 1. Pure water was used to calculate the background intensity.

Table 1 Elements, Contents, and Solutions

Element Content [ppm] Solution
Fa 94,962 Preparation
Ma 20,000 Preparation
Mg 20,000 Preparation
Al 20,000 Preparation
Si, P, S, Cl, K 1,000 Atomic Absorption Standard Solution
None - Pure Water
  • Sample Pretreatment

Approximately 5 mL of each sample was introduced directly into a film-covered sample container. The three films shown in Table 2 were used.

Table 2 Sample Holder Films

Name Thickness (µm) Compositional Formula
Prolene® (Chemplex) 4 C3H6
Polypropylene 5 C3H6
PET 6 C10H8O4
  • Detection Limits

(1) Atmosphere: Air/He

Fig. 1 shows the measured spectra in air and a He atmosphere when using the polypropylene film. Table 3 shows the detection limits calculated from the intensity and measurement conditions (current and integration time). The He atmosphere enabled detection of F and Na, and improved detection of Mg by 40 times, Al and Si by 8 times, and P and S by approximately 2 times.

Fig. 1: X-Ray Fluorescence Spectra for F to K [Blue: He Atmosphere, Red: Air] 

Table 3: Detection Limits (1) Differences Depending on Atmosphere [ppm]

Atmosphere 9F 11Na 12Mg 13Al 14Si 15P 16S 17Cl 19K
Air - - 3,300 210 91 25 16 2323 6.3
He 41,000 680 84 26 11 11 7.8 15 5.1

(2) Differences Depending on Film

 Three types of films were used in measurements in a He atmosphere. Fig. 2 (next page) shows the spectra, and Table 4 shows the detection limits. Prolene (Chemplex Inc.) with a thickness of 4 μm displayed the highest sensitivity, and the influence of the film thickness and composition on absorption increased with lighter elements.

Fig. 2: X-Ray Fluorescence Spectra for F, Al, and K [Blue: Prolene (Chemplex), Red: Polypropylene, Green: PET]

Table 4: Detection Limits (2) Differences Depending on Film [ppm]

Film 9F 11Na 12Mg 13Al 14Si 15P 16S 17Cl 19K
Prolene® 18,000 480 73 22 10 9.7 7.5 14 4.7
Polypropylene 41,000 680 84 26 11 11 7.9 15 5.1
PET - 5,400 340 55 54 25 24 18 5.8
  • Conclusion

Measurements of liquid samples by EDX are possible regardless of conditions such as concentration,    organic or inorganic material, suspension, and viscosity. This technique is not limited to solutions, but is also effective with samples such as the following, which are difficult or impossible to depressurize to a vacuum.

  • Teeth and other biomaterials (fracture, alteration)
  • Porous materials such as zeolite (time required to reach measurement vacuum)
  • Fibers and clothing (porous, wet)
  • Ultrafine particles such as graphite powder (scattering)
  • Sealed and enclosed materials (bursting)

This technique is effective for quickly determining the presence and content of light elements in the abovementioned materials.

Source: ETA

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