A rapid online estimation method for radiostrontium in soil samples using crown ether and supercritical fluid...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Radiochemistry

Background:

• Crown ethers are effective in extracting metal cations from aqueous to organic phases.
• Di-tert-butyl-cyclohexano18crown6 (DTBDCH18C6) shows selectivity for Strontium (Sr(II)).
• Supercritical Fluid Extraction (SFE) offers a potential route for radionuclide recovery from environmental matrices.

Purpose of the Study:

• To evaluate the feasibility of recovering Strontium-89/90 ((85,89)Sr) from synthetic soil samples using SFE.
• To optimize experimental parameters for efficient (85,89)Sr extraction with DTBDCH18C6.
• To assess the selectivity of the SFE method for (85,89)Sr over Cesium-137 (137Cs).

Main Methods:

• Supercritical Fluid Extraction (SFE) was employed using DTBDCH18C6 dissolved in methanol/nitric acid as a phase modifier.
• Optimization of parameters included extraction mode (static/dynamic), equilibration time, nitric acid concentration, and crown ether concentration.
• Analysis of (85,89)Sr and (137)Cs recovery from synthetic soil samples (<100 μm particle size).

Main Results:

• Near-quantitative recovery (>95%) of (85,89)Sr was achieved using optimized static mode SFE with 2×10⁻⁴ M DTBDCH18C6 in methanol/4M HNO₃ after 30 min equilibration.
• Dynamic mode SFE also yielded near-quantitative (>95%) recovery of (85,89)Sr within 1 hour under identical conditions.
• Minimal extraction (~10%) of (137)Cs was observed, indicating high selectivity for (85,89)Sr.

Conclusions:

• SFE using DTBDCH18C6 is a highly effective and selective technique for the recovery of (85,89)Sr from soil samples.
• The method demonstrates significant potential for the environmental analysis of (90)Sr in various sample types.
• The observed selectivity suggests applicability in complex environmental matrices where differentiation between radionuclides is crucial.