Application of magnetic nanoparticles for the extraction of radium-226 from water samples

Bare (unmodified) and crown ether (CE)-modified Fe3O4 magnetic nanoparticles (MNPs) were investigated for the rapid extraction of 226Ra from water samples. It involved synthesizing the MNPs, introducing them into the sample solutions, ultrasonicating and agitating the suspension, magnetically separating the nanoparticles from solution, and measuring the 226Ra content in the supernatant. Experimental parameters such as salt choice, salt concentration and pH were optimized to achieve maximum extraction of 226Ra onto the MNPs. 226Ra content was determined using a Hidex 300SL liquid scintillation counter with α/β separation capability, or a gamma spectrometric detection system. The bare Fe3O4 nanoparticles showed significant pH dependence for the extraction of 226Ra from an aqueous solution over a pH range of 2-10. They gave an extraction of 95 ± 1 and 98 ± 1 % at pH 9 in 0.1 M NaCl and 0.1 M NaClO4, respectively, whereas an extraction of 8-24 % was obtained, over the pH ranges from 2 to 5. The CE-modified MNPs yielded extraction efficiencies as high as 99 ± 1 % in the presence of 0.01 M picric acid at pH 4. This study demonstrates that the surface functionalization of Fe3O4 MNPs with suitable ligand modification can offer a selective mode of extraction for 226Ra in the presence of its daughter progenies

Selective extraction of 90Sr in urine using 4′4″(5″)di-tert-butyl dicyclohexano-18-crown-6 ether immobilized on polyacrylamide-coated magnetic nanoparticles

4′4″(5″)di-tert-butyl dicyclohexano-18-crown-6 ether was immobilized onto the surface of iron oxide magnetic nanoparticles coated with divinylbenzene-crosslinked polyacrylamide. The coated magnetic nanoparticles were successful in selectively extracting 90Sr from human urine samples, as confirmed by the liquid scintillation counting spectra. This method offers excellent repeatability for 90Sr in urine bioassay, with a relative precision of 8 % when five urine samples collected from different donors were spiked with1.58 Bq of 90Sr and analyzed

Preliminary studies of an 18-crown-6 ether modified magnetic cation exchange polymer in rapid 90Sr bioassay

A cation exchange polymer resin embedded with magnetic nanoparticles and modified with crown ether was developed for urinalysis to rapidly monitor levels of 90Sr exposure in humans who have been involved in a nuclear event. Invention of the resin matrix of 2-acrylamido-2-methyl-1-propanesulfonic acid cross-linked with divinylbenzene incorporated a Sr2+ chelating agent, di-tert-butyl-cyclohexano-18-crown-6 through surface immobilization using a molecular modifier 1-octanol. The performance of these magnetic cation exchange resin particles was investigated by separating 90Sr in the presence of 90Y progeny. Masking agents and precipitants were examined to ascertain that sodium hydroxide at pH 7.5 was capable of selectively removing 89 ± 2% 90Y before subsequent 90Sr uptake. Preliminary investigations in rapid urinalysis were successful in isolating 83 ± 2% 90Sr when pH was optimized to 9, with a sample turnover time <2 h, which is promising for radiological emergencies

A comparative study of magnetic transferability of superparamagnetic nanoparticles

The aspect of magnetic transferability was established using an automated magnetic particle transfer workstation. Maghemite (γ-Fe2O3) nanoparticles were synthesized via conventional co-precipitation procedure. Their transferability was determined in addition to several commercial nanoparticles that ranged in diameter, surface functionality, and composition. Transmission and scanning electron micrographs and infrared spectrum, respectively, provided size and surface information on the synthesized particles for comparison to commercially available magnetic nanoparticles

Synthesis of crown ether modified cation exchange polymer particles for 90Sr urinalysis

Cation exchange polymer particles have been synthesized for urinalysis to monitor levels of strontium-90 ( 90Sr) exposure in humans. Two techniques were utilized in the incorporation of a Sr 2+ selective chelating agent, di-tert-butyl-cyclohexano-18-crown-6 (DtBuCH18C6). The ion imprinting technique involved entrapment of DtBuCH18C6 during the formation of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) polymer particles. In the surface immobilization technique, adsorption of DtBuCH18C6 onto the surface of AMPS polymer particles was assisted by a molecular modifier. Ethylene glycol dimethacrylate (EGDMA) and divinylbenzene (DVB) were evaluated as cross-linking agents to provide better support for DtBuCH18C6. These polymer particles were characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Radiometric binding assays demonstrated that surface immobilization, in comparison to matrix imprinting, achieved greater Sr 2+ uptake. Application of the surface immobilized particles in urinalysis was successful, attaining 86 ± 2% 90Sr uptake at pH 9

Molecularly imprinted polymers for 90Sr urine bioassay

A molecularly imprinted polymer (MIP) comprising dicyclohexano-18-crown-6 (DCH18C6) was synthesized as a Sr-selective sorbent for urine bioassay purposes. MIP particles (326 ± 2 nm diameter) were formed using acetone and acetonitrile (1:3 v/v) as the porogen, methacrylic acid (MAA) as the functional monomer and ethylene glycol dimethacrylate (EGDMA) as the cross-linker. The DCH18C6-MIP particles were impregnated with additional DCH18C6 and treated further with NaOH to attain better binding affinity for Sr2+. The effects of pH, ionic strength and amount of particles were evaluated for optimal extraction of 90Sr2+ from urine samples, as measured by liquid scintillation analysis (LSA). After up to 94% of 90Y was removed by precipitation with TiO2, DCH18C6-MIP particles were applied for selective SPE of 90Sr remaining in the urine matrix for final LSA

Selectivity of 90Sr urine bioassay technique over 241Am, 238/239Pu, 210Po, 137Cs and 60Co

The selectivity of a rapid 90Sr bioassay technique over 241Am, 238/239Pu, 210Po, 137Cs and 60Co has been investigated. Similar to 90Sr, these radionuclides are likely to be used in radiological dispersive devices. The purpose of this study was to demonstrate the degree to which the 90Sr bioassay technique is free from interference by these radionuclides if present in a urine matrix. The interfering radionuclides were removed (from 90Sr) by their retention on an anion exchange column. While, recovery of the target radionuclide (90Sr) was found to be ≥ 90 %, contributions from 241Am, 242Pu and 208Po were found to be ≤ 3 % indicating minimal interference from these radionuclides. The breakthrough for 60Co, however, was found to be ≤19 % indicating that it will have some interference contribution to the 90Sr measurement if present in the urine sample. As 137Cs was not retained at all by the anion exchange column, the method as such was not selective over 137Cs. However, a slight modification of the method through the ammonium molybdophosphate treatment quantitatively removed Cs from the urine sample, thereby; making it selective for 90Sr despite any 137Cs that is present

Polymer-coated magnetic nanoparticles for rapid bioassay of 90Sr in human urine samples

A rapid bioassay for 90Sr was developed involving preconcentration of 90Sr/ 90Y from human urine samples with a cation exchange polymer (poly-acrylamido-methyl-propanesulfonic acid) coated onto magnetic nanoparticles, followed by selective elution of 90Sr (over 90Y) with phosphate for determination by liquid scintillation analysis. The minimum detectable activity for this method (4.9 ± 0.5 Bq/L) is lower than the required sensitivity of 19 Bq/L for 90Sr in human urine samples, as defined in the requirements for radiation emergency bioassay techniques for the public and first responders based on the dose threshold for possible medical attention recommended by the International Commission on Radiological Protection. The relative bias was 9.2%, the relative precision was 3.2%, and the linear dynamic range covered 12-600 Bq/L. This simple and rapid bioassay method is found to be in compliance with the HPS ANSI N13.30 performance criteria for radiobioassay

Cd2+, Cu2+, Pb2+, Sr2+, and Y3+ binding characteristics of 17β-estradiol molecularly imprinted polymer particles incorporated with dicyclohexano-18-crown-6 for urine bioassay

The metal ion binding characteristics of molecularly imprinted polymer (MIP) submicron particles prepared using 17β-estradiol (E2) as a template, and incorporated with dicyclohexano-18-crown-6 (DCH18C6), were studied using differential pulse anodic stripping voltammetry. When Sr2+ was added to DCH18C6-E2-MIP particles already occupied by Cd2+, Cu 2+, and Pb2+ inside the binding sites, a displacement reaction was observed: Cd2+/Cu2+/Pb2+-DCH18C6- E2-MIP + Sr2+ = Sr2+-DCH18C6-E2-MIP + Cd 2+/Cu2+/Pb2+. This demonstrated that DCH18C6 had stronger binding affinity for Sr2+ than Cd2+ Cu 2+ or Pb2+. Strong DCH18C6 binding affinity was also observed for Y3+. Atomic emission spectrometry showed that DCH18C6-E2-MIP particles (150 mg/mL) resulted in 52% binding of Sr2+ (2000 ppm, at pH 6.3 ± 0.1 and ionic strength of 0.1M NaNO2)