Occurrence of and radioanalytical methods used to determine medical radionuclides in environmental and biological samples. A review

Amide-decorated reusable C18 silica-packed columns for the rapid, efficient and sequential separation of lanthanoids using reversed phase-high performance liquid chromatography

The current work focuses on the sequential separation of trivalent lanthanides (except Pm3+) using modified C18 silica-packed supports through the reversed-phase high-performance liquid chromatography (RP-HPLC) technique. In the current research, four indigenously synthesized amphiphilic aromatic triamide derivatives, namely N1, N1, N3, N3, N5, N5-hexa(alkyl) benzene-1,3,5-tri carboxamide (alkyl = butyl, hexyl, octyl, and decyl), were employed as column modifiers. The results show that the separation of Ln3+ can be achieved systematically (< 12 min) by tuning the modifiers' functional group and hydrophobic chain and fine-tuning the column modification procedure and separation parameters. The chromatographic studies revealed that the use of 0.168 mmol of N1, N1, N3, N3,N5, N5-hexa(hexyl)benzene-1,3,5-tricarboxamide (HHBTA) coated column and 0.419 mmol of N1, N1, N3, N3, N5, N5-hexa(octyl) benzene-1,3,5-tricarboxamide (HOBTA) modified columns offered excellent separation for the lanthanoids, using 0.1 M α-hydroxyisobutyric acid (HIBA), as mobile phase. The separated lanthanoids were quantified by post-column derivatization reaction (after the separation process) using Arsenazo (III) as the post-column reagent by integrating with a UV-Visible detector fixed at 655 nm (λmax). A systematic study on the influence of various analytical features, such as the effect of the modifier's chain length and its concentration, mobile phase composition and pH, was performed and optimized for achieving the best separation protocols.

Fast and selective reversed-phase high performance liquid chromatographic separation of UO2 2+ and Th4+ ions using surface modified C18 silica monolithic supports with target specific ionophoric ligands

Reprocessing nuclear-spent fuels is highly demanded for enhanced resource efficacy and removal of the associated radiotoxicity. The present work elucidates the rapid separation of UO₂ ²⁺ and Th⁴⁺ ions using a reversed-phase high-performance liquid chromatographic (RP-HPLC) technique by dynamically modifying the surface of a C₁₈ silica monolith column with target-specific ionophoric ligands. For the dynamic modification, four analogous aromatic amide ligands, N ¹,N ¹,N ³,N ³,N ⁵,N ⁵-hexa(alkyl)benzene-1,3,5-tricarboxamide (alkyl = butyl, hexyl, octyl, and decyl) as column modifiers were synthesized. The complexation properties and retention profiles of the amide-based column modifiers for the selective and sequential separation of UO₂ ²⁺ and Th⁴⁺ ions were investigated. In addition, the selective separation of UO₂ ²⁺ and Th⁴⁺ ions among the competitive ions of similar chemical properties were also studied. The ionophore immobilized C₁₈ silica monolith columns demonstrated a varying degree of retention behavior for UO₂ ²⁺ and Th⁴⁺ ions (UO₂ ²⁺ is retained longer than Th⁴⁺ under all analytical conditions), eventually leading to rapid separations within a period of ≤5 min. A 0.1 M solution of 2-hydroxyisobutyric acid (HIBA, 1 mL min^-1) served as the mobile phase, and the qualitative and quantitative assessment of the sequentially separated 5f metal ions was achieved through post-column derivatization reaction, using arsenazo(iii) as a post-column reagent (PCR; 1.5 mL min^-1) prior to analysis using a UV-vis detector, at 665 nm (λ _max). The developed technique was further evaluated by standardizing various analytical parameters, including modifier concentration, mobile phase pH, mobile phase flow rate, etc., to yield the best chromatographic separation. Also, the conceptual role of alkyl chain length (in the modifier) on the retention behavior of the studied metal ions was evaluated for cutting-edge future applications.

Determination of 131I activity concentration and rate in main inflows and outflows of Salitre wastewater treatment plant (WWTP), Bogota

Samples were collected for several weeks to determine the evolution of the ¹³¹I (Iodine-131) activity concentration in the inflow water processed at the Salitre wastewater treatment plant (WWTP) in Bogota, Colombia, derived from medical facilities for thyroid cancer diagnosis and treatment. Mass balances on ¹³¹I were performed based on the activity rates at the main inflow and outflow of the plant. The ¹³¹I activity concentration in the raw water stream was observed to increase significantly from Monday onwards throughout the week, while the daily activity concentration was highest in the morning and then continuously decreased over the rest of the day. The ¹³¹I activity concentration in the raw water exceeds the reference value for drinking water and is very close to the discharge limit in water bodies in Colombia. A mass balance calculation showed that the activity rate for the inflow and outflow waters of the WWTP is about 15% of the authorized activity to use for facilities discharging water into the basins and the use of bio-sludge stream for organic fertilizer production does not represent a significant risk of external irradiation for the population. The results of this work are the first of its kind in Colombia, which ones contribute significantly to determinate the radiological risk to public health due to utilization of treated water and sludge, know the ¹³¹I behavior in the city sewage systems, and give information for the performance review of regulatory control on ¹³¹I management in the country.

Automatic multicommuted flow systems applied in sample treatment for radionuclide determination in biological and environmental analysis

The presence of artificial and natural radioactivity in the environment is currently a topic of great relevance and ecological interest, even in human health issue, due to the increase of different anthropogenic activities. The use of multicommuted flow analysis techniques (e.g. Multi-Syringe Flow Injection Analysis - MSFIA, Lab-On-Valve - LOV and Lab-In-Syringe - LIS) has allowed the automation of radiochemical procedures to separate and preconcentrate radionuclides in environmental and biological samples. In comparison with the manual approach commonly used in routine analysis for radioactivity monitoring, the automation has enabled the development of highly reproducible methodologies with a great analysis frequency. Moreover, during the analytical procedure, the intervention of the analyst is drastically reduced, minimizing the radiological risk. The automation also offers significant advantages such as minimum consumption of time and reagents, reducing the cost and the generation of waste, contributing to the green chemistry. In this review, several multicommuted flow analysis techniques (MSFIA, LOV and LIS) reported in the last decade applied for the development of automatic sample treatment methodologies, used to separate, preconcentrate and quantify ⁹⁰Sr, ⁹⁹Tc, natural U and ²²⁶Ra in biological and environmental samples are described and critically compared.