Uncertainty propagation through correction methodology for the determination of rare earth elements by quadrupole based inductively coupled plasma mass spectrometry

Determination of rare earth elements by quadrupole based inductively coupled plasma mass spectrometry (ICP-QMS) shows several spectroscopic overlaps from M⁺, MO⁺ and MOH⁺ ions. Especially, the spectroscopic interferences are observed from the atomic and molecular species of lighter rare earth elements including Ba during the determination of Eu, Gd and Tb. Mathematical correction methods, knowing the at.% abundances of different interfering isotopes, and the extent of formation of molecular species determined experimentally, have been used to account for various spectroscopic interferences. However, the uncertainty propagated through the mathematical correction limits its applicability. The uncertainty propagation increases with the increase in contribution from interfering species. However, for the same extent of total contribution, the overall error decreases when the interfering species are more than one. In this work, chondrite as well as a few geological reference materials containing different proportions of various rare earth elements have been used to study the contributions of different interfering species and the corresponding uncertainty in determining the concentrations of rare earth elements. A number of high abundant isotopes are proposed for determining the concentrations of various rare earth elements. The proposed isotopes are tested experimentally for determining the concentrations of different rare earth elements in two USGS reference materials AGV-1 and G-2. The interferences over those isotopes are corrected mathematically and the uncertainties propagated due to correction methodology are determined for those isotopes. The uncertainties in the determined concentrations of rare earth elements due to interference correction using the proposed isotopes are found to be comparable with those obtained by the commonly used isotopes for various rare earth elements.     

Elimination of the spectral interference from polyatomic ions with rare earth elements in inductively coupled plasma mass spectrometry by combining algebraic correction with chromatographic separation

A simple and effective procedure is developed to avoid the spectral interference from light rare earth elements (REEs) and barium polyatomic ions on some rare earth elements in inductively coupled plasma mass spectrometry (ICP-MS) by combining algebraic correction with AG50W-×8 cation exchangeable chromatography. Algebraic correction is made to reduce the spectroscopic overlap interference of ¹⁴¹Pr¹⁶O and ¹⁴³Nd¹⁶O on ¹⁵⁷Gd and ¹⁵⁹Tb. The spectroscopic overlap interference of BaO⁺ and BaOH⁺ on some middle REEs are overcome by separation of REEs from barium with AG50W-×8 cation exchangeable chromatography. Prior to the determination, REEs are separated from complicated matrix samples using AG50W-×8 cation exchangeable resin. Ba is eluted with 2 mol/l HNO₃ solution. REEs are retained and could then be eluted with 5 mol/l HNO₃ solution. Recoveries for REEs are from 96 to 110%. More than 99.5% of Ba in the sample is removed, ensuring that the spectral interference from barium polyatomic ions on some middle REEs such as Nd, Sm, Eu and Gd are eliminated. The potential of the proposed method is evaluated by analysis of Certified Reference Materials (CRMs). Results show that experimental data are in good agreement with the certified values. The new technique has been successfully employed for the determination of REEs in practical soil and plant samples.     

Reaction chemistry and collisional processes in multipole devices for resolving isobaric interferences in ICP–MS

A low-level review of the fundamentals of ion-molecule interactions is presented. These interactions are used to predict the efficiencies of collisional fragmentation, energy damping and reaction for a variety of neutral gases as a function of pressure in a rf-driven collision/reaction cell. It is shown that the number of collisions increases dramatically when the ion energies are reduced to near-thermal (< 0.1 eV), because of the ion–induced dipole and ion–dipole interaction. These considerations suggest that chemical reaction can be orders of magnitude more efficient at improving the analyte signal/background ratio than can collisional fragmentation. Considerations that lead to an appropriate selection of type of gas, operating pressure, and ion energies for efficient operation of the cell for the alleviation of spectral interferences are discussed. High efficiency (large differences between reaction efficiencies of the analyte and interference ions, and concomitant suppression of secondary chemistry) might be required to optimize the chemical resolution (determination of an analyte in the presence of an isobaric interference) when using ion-molecule chemistry to suppress the interfering ion. In many instances atom transfer to the analyte, which shifts the analytical m/z by the mass of the atom transferred, provides high chemical resolution, even when the efficiency of reaction is relatively low. Examples are given of oxidation, hydroxylation, and chlorination of analyte ions (V⁺, Fe⁺, As⁺, Se⁺, Sr⁺, Y⁺, and Zr⁺) to improve the capability of determination of complex samples. Preliminary results are given showing O-atom abstraction by CO from CaO⁺ to enable the determination of Fe in high-Ca samples.     

Investigation and quantification of spectroscopic interferences from polyatomic species in inductively coupled plasma mass spectrometry using electrothermal vaporization or pneumatic nebulization for sample introduction

A new method for quantification of spectral interferences based on analyte isotope ratio measurements in the presence of various concentrations of a specific matrix is presented. Within the method, a tolerance level is used, defined as the matrix concentration at which the ratio between analyte isotopes with and without interferences is altered by 10% compared to a pure water reference standard, normalized with respect to the analyte concentration in the solutions. This can be used to estimate the lowest analyte concentration which can be determined with a defined accuracy in the presence of a known concentration of a specific matrix. Regarding spectroscopic interference effects, comparative results for sample introduction into the ICP–MS by electrothermal vaporization, ETV, and nebulization are presented for common matrix — (Ca, Na, K, Cl, P, O) and analyte (Cr, Ni, Cu, As, Se) elements. With the exception of the spectral overlap of ³¹P₂⁺ on ⁶²Ni⁺, spectroscopic interferences were reduced by 1–2.5 orders of magnitude when using ETV for sample introduction. Reasons for the increase in the spectral interference of ³¹P₂⁺ on ⁶²Ni⁺ are discussed. For sample introduction by nebulization, it was found that spectral interferences from CaO⁺ on ⁵⁸Ni⁺ and ⁶⁰Ni⁺ were reduced in the presence of phosphate.     

ICP emission spectrometric analysis of rare earth elements in permanent magnet alloys

An analytical method for the determination of rare earth elements (REE) in a NdFeB permanent magnet alloy by ICP emission spectrometry is described. Spectral interferences, arising from overlapping, as well as matrix effects have been studied. Considering spectral interferences, sensitivities of spectral lines, background intensities and the chemical composition of the sample investigated, optimum spectral lines for each REE have been selected. Because of an unfavourable concentration ratio in samples of a NdFeB permanent magnet alloy, a preliminary separation of matrix elements from rare earth elements by ion chromatography is necessary. Different modes of elution (isocratic and gradient) with -hydroxy-isobutyric acid and different columns (NUCLEOSIL, SULFOPROPYL SI-100, DIONEX HPIC-CS3) have been tested. Optimum separation conditions have been chosen for each element and the separation efficiency at equal or different concentrations of the selected elements have been established. Although the separation of REEs resulted in partly overlapping peaks, the ratio between analyte and interferent is improved and the spectral interferences are diminished. The results obtained are in good agreement with certified values.     

Comparing the capability of collision/reaction cell quadrupole and sector field inductively coupled plasma mass spectrometers for interference removal from 90Sr, 137Cs,and 226Ra

Here we report a quantitative comparison of sector field inductively coupled plasma mass spectrometry (ICP-SFMS) and collision/reaction cell inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for the detection of ⁹⁰Sr, ¹³⁷Cs, and ²²⁶Ra at ultra-trace levels. We observed that the identification and quantification of radioisotopes by ICP-MS were hampered by spectral (both isobaric and polyatomic ions) and non-spectral (matrix effect) interferences. ICP-QMS has been used to eliminate the isobaric ⁹⁰Sr/⁹⁰Zr interference through the addition of O₂ into the collision cell as a reactant gas. Zr⁺ ions were subsequently converted into ZrO⁺, whereas Sr⁺ ions were not reactive. In addition, the isobaric interference of ¹³⁷Ba on ¹³⁷Cs was eliminated by the addition of N₂O gas in the cell, which led to the formation of BaO⁺ and BaOH⁺ products, whereas Cs⁺ remained unreactive. Furthermore, He and H₂ were used in the collision/reaction cell to eliminate polyatomic ions formed at m/z 226. A comparison of the results obtained by ICP-SFMS after a chemical separation of Sr from Zr and Cs from Ba was performed. Finally, to validate the developed analytical procedures, measurements of the same samples were performed by γ-ray spectroscopy.     

Mathematical Correction for Polyatomic Isobaric Spectral Interferences in Determination of Lanthanides by Inductively Coupled Plasma Mass Spectrometry

The determination of lanthanides by Inductively Coupled Plasma Mass Spectrometry (ICP‐MS) is complicated by several spectral overlaps from M⁺, MO⁺ or MOH⁺ ions formed in the ICP. Especially, it is essential to avoid the spectral interferences from lighter lanthanide and Ba polyatomic ions on middle or heavier lanthanides. To tackle this problem, we have developed a mathematical correction method, which reduces all the spectral overlaps from oxide species of Pr, Nd, Ce and Sm over Gd, Tb, Dy and Ho, and Gd, Tb over Yb and Lu. It can also successfully correct the oxide and hydroxide interference of Ba over Eu. The effectiveness of the proposed the mathematical correction scheme is demonstrated for the USGS Standard Rock samples AGV‐1 and G‐2. The results show that the experimental data obtained by applying the mathematical correction scheme for lanthanides is in good agreement with the reported values, using pneumatic and ultrasonic nebulisation methods, for their ICP‐MS analysis.     

环烷酸类载体液膜体系对金属离子传输机理的研究

本文先在大块液膜体系中以环已烷甲酸为载体,通过正交设计,系统地研究了各种因素对希土离子输送作用的影响规律。比较了相同条件下RE~(3+)(希土)同Na~+,NH_4~+、Ca~(2+)和Fe~(3+)等离子的输送作用。发现在适当条件下,无皂化的羧酸载体对RE~(3+)离子具有良好的输送效果,同时证实,羧酸输送RE~(3+)离子是通过三个H~+离子与一个RE~(3+)离子的交换,而当载体皂化时,皂化的载体直接与接收相H~+离子发生交换,从而降低了羧酸对RE~(3+)离子的输送和分离效果。 在大块液膜研究的基础上,建立了一个以无皂化的环烷酸为载体的乳状液膜体系,从模拟离子矿的硫酸铵浸出液中萃取希土,通过正交试验确定了最优的液膜萃取条件,希土萃取率达96％以上,富集度30～40倍。     

Characterization of the ion beam inside the skimmer cone of an inductively coupled plasma mass spectrometer by laser excited atomic and ionic fluorescence

Laser-induced atomic and ionic fluorescence have been used to characterize the material extracted from an inductively coupled plasma through a differentially pumped interface of the type used in inductively coupled plasma mass spectrometry. Measurements were made in the 8 mm downstream from the tip of the skimmer cone. Reference measurements were also made outside the interface at the tip of the sampling cone. Sc and Ba ions and Pb atoms were used as test analytes. Sc⁺ densities drop more rapidly than either Ba⁺ or Pb densities. The transmission efficiencies of both Sc⁺ and Ba⁺ are suppressed by the addition of either Mg or Pb to the analyte solution. The effects of the two matrix additions are approximately the same. Based on the magnitude of the fluorescence signal for Ba⁺, a lower limit of 0.3% for the transmission of Ba⁺ from the plasma into the second vacuum stage has been calculated.     

Determination of trace rare earth elements by inductively coupled plasma atomic emission spectrometry after preconcentration with multiwalled carbon nanotubes

A new method has been developed for the determination of trace rare earth elements (REEs) in water samples based on preconcentration with a microcolumn packed with multiwalled carbon nanotubes (MWNTs) prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The optimum experimental parameters for preconcentration of REEs, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been investigated. The studied REEs ions can be quantitatively retained by MWNTs when the pH exceed 3.0, and then eluted completely with 1.0 mol L⁻¹ HNO₃. The detection limits of this method for REEs was between 3 and 57 ng L⁻¹, and the relative standard deviations (RSDs) for the determination of REEs at 10 ng mL⁻¹ level were found to be less than 6% when processing 100 mL sample solution. The method was validated using a certified reference material, and has been successfully applied for the determination of trace rare earth elements in lake water and synthetic seawater with satisfactory results.     

Simultaneous electrothermal vaporization and nebulizer sample introduction system for inductively coupled plasma mass spectrometry

The novel analytical application of the combination of an inline electrothermal vaporization (ETV) and nebulization source for inductively coupled plasma mass spectrometry (ICP-MS) has been studied. Wet plasma conditions are sustained during ETV introduction by 200 mL/min gas flow through the nebulizer, which is merged with the ETV transport line at the torch. The use of a wet plasma with ETV introduction avoided the need to change power settings and torch positions that normally accompany a change from wet to dry plasma operating conditions. This inline-ETV source is shown to have good detection limits for a variety of elements in both HNO₃ and HCl matrices. Using the inline-ETV source, improved limits of detection (LOD) were obtained for elements typically suppressed by polyatomic interferences using a nebulizer. Specifically, improved LODs for ⁵¹V and ⁵³Cr suffering from Cl interferences (⁵¹ClO⁺ and ⁵³ClO⁺ respectively) in a 1% HCl matrix were obtained using the inline-ETV source. LODs were improved by factors of 65 and 22 for ⁵¹V and ⁵³Cr, respectively, using the inline-ETV source compared to a conventional concentric glass nebulizer. For elements without polyatomic interferences, LODs from the inline-ETV were comparable to conventional dry plasma ETV-ICP time-of-flight mass spectrometry results. Lastly, the inline-ETV source offers a simple means of changing from nebulizer introduction to inline-ETV introduction without extinguishing the plasma. This permits, for example, the use of the time-resolved ETV-ICP-MS signals to distinguish between an analyte ion and polyatomic isobar.     

Visible and near-IR luminescence via energy transfer in rare earth doped mesoporous titania thin films with nanocrystalline walls

Selected photoluminescence in the wavelength range of 600-1540 nm is generated by energy transfer from a light-gathering mesostructured host lattice to an appropriate rare earth ion. The mesoporous titania thin films, which have a well-ordered pore structure and two-phase walls made of amorphous titania and TiO₂ nanocrystallites, were doped with up to 8 mol% lanthanide ions, and the ordered structure of the material was preserved. Exciting the titania in its band gap results in energy transfer and it is possible to observe photoluminescence from the crystal field states of the rare earth ions. This process is successful for certain rare earth ions (Sm³⁺, Eu³⁺, Yb³⁺, Nd³⁺, Er³⁺) and not for others (Tb³⁺, Tm³⁺). A mechanism has been proposed to explain this phenomenon, which involves energy transfer through surface states on titania nanocrystals to matching electronic states on the rare earth ions.     

Gas-phase reactions of Sc+, Y+, and Lu+ with alcohols. Effects of the class and chain length of alcohols on the nature of primary products

The primary gas-phase reactions between methanol, ethanol, propan-1-ol, propan-2-ol, and 2-methyipropan-2-ol and the isovalent rare earth metal ions Sc⁺, Y⁺, and Lu⁺ generated by laser desorption-ionization of metal targets have been investigated by using a Fourier transform ion cyclotron resonance mass spectrometer. The three metal ions react exothermically with all the alcohols. The overall reactivity is controlled by the high oxophilicity of these metals, and the primary metallated ions obtained are principally oxygenated species. However, the number and the nature of these primary products depends on the electronic configuration of the metal ions as well as on the class and the principal chain length of alcohols. The order of reactivity is Y⁺ > Sc⁺ > Lu⁺. The Y⁺ and Sc⁺ ions principally react via C—O and O—H insertions, whereas Lu+ reacts by direct abstraction or via various five-center electrocyclic mechanisms as a function of the class and the alcohol chain length.     

Protein phosphorylation stoichiometry by simultaneous ICP-QMS determination of phosphorus and sulfur oxide ions: A multivariate optimization of plasma operating conditions

Molecular mass spectrometry (MS) analysis of protein phosphorylation is partially limited by the molecular specie specificity of the analytical responses that might impair both qualitative and quantitative performances. Elemental MS, such as inductively coupled plasma mass spectrometry (ICP-MS) can overcome these drawbacks; in fact, analytical performance is theoretically independent of the molecular structure of a target analyte naturally containing the elements of interest. Nevertheless, isobaric interferences derived from sample matrix and laboratory environment can hinder the quantitative determination of both phosphorus (P) and sulfur (S) as ³¹P⁺ and ³²S⁺ by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) under standard plasma conditions. These interferences may be overcome by quantifying P and S as oxide ions ³¹P¹⁶O⁺ and ³²S¹⁶O⁺, respectively.In this study, we present a systematic investigation on the effect of plasma instrumental conditions on the oxide ion responses by a design of experiment approach for the simultaneous ICP-QMS determination of P and S (³¹P¹⁶O⁺ and ³²S¹⁶O⁺, respectively) in protein samples without the use of dynamic reaction, collision reaction cells or pre-addition of oxygen as reactant gas in the torch. The proposed method was evaluated in terms of limit of detection, limit of quantification, linearity, repeatability, and trueness. Moreover, detection and quantification capabilities of the optimized method were compared to the standard plasma mode for determination of ³¹P⁺ and ³⁴S⁺. Spectral and non-spectral interferences affecting the quantification of ³¹P⁺, ³¹P¹⁶O⁺ and ³²S¹⁶O⁺ were also studied. The suitability of inorganic elemental standards for P and S quantification in proteins was assessed. The method was applied to quantify the phosphorylation stoichiometry of commercially available caseins (bovine β-casein, native and dephosphorylated α-casein) and results were confirmed by Matrix Assisted Laser Desorption Ionization Time of Flight MS analysis.We demonstrate that ICP-QMS, by quantifying P and S as oxide ions, was able to accurately calculate the degree of phosphorylation of β-casein and α-casein and to detect specific partial enzymatic dephosphorylation. The collected results might lead to further development of ICP-QMS interfaces optimized for protein phosphorylation studies and for proteomics investigations.     

Liquid Membrane Transport of Heavier Rare Earth Metal Ions Based on CPC Results with Di(2-Ethylhexyl) Phosphoric Acid

Abstract

The behaviors of heavier rare earth metal ions in bulk liquid membrane transport systems were examined for Gd³⁺, Tb³⁺, Dy³, Ho³⁺, Er³⁺, Tm³, Yb³⁺ and Lu³⁺ ions. The liquid membrane transport system was constructed by aq. HCl/CHCl₃ containing Di (2-ethylhexyl) phosphoric acid/aq. HCl. The optimum concentration of HCl in the aqueous phase with respect to the rate of transport for these ions increased with the atomic number of the rare earth elements. This trend of transport behaviors was on the same line observed for lighter rare earth ions in the preceding work. Difference in the rate of transport can be used for selective liquid membrane transport of several sets of combination with these ions.     

Inductively coupled plasma mass spectrometry with an enlarged sampling orifice and offset ion lens. II. Polyatomic Ion interferences and matrix effects

A new inductively coupled plasma mass spectrometer with an enlarged sampling orifice (1.31-mm dia.) and an offset ion lens yields very low levels of many troublesome polyatomic ions such as ArO⁺, ArN⁺, Ar₂ ⁺, ClO⁺, and ArCl⁺. The signals from refractory metal oxide ions are ≈ 1% of the corresponding metal ion signals, which is typical of most ICP-MS devices. Grounding the first electrode of the ion lens greatly reduces the severity of matrix effects to <- 20% loss in signal for Co⁺, Y⁺, or Cs⁺ in the presence of 10 mM Sr, Tm, or Pb. This latter lens setting causes only a modest loss (30%) in sensitivity for analyte elements compared to the best sensitivity obtainable by biasing the first lens. Alternatively, matrix effects can also be mitigated by readjusting the voltage applied to the first lens with the matrix present.     

UV photochemical vapor generation-atomic fluorescence spectrometric determination of conventional hydride generation elements

A systematic investigation of UV photochemical vapor generation (photo-CVG) and its potential application for seven typical hydride-forming elements (As, Sb, Bi, Te, Sn, Pb and Cd) when combined with atomic fluorescence spectrometry (AFS) detection is presented. These analyte ions were converted to volatile species following UV irradiation of their aqueous solution to which low molecular weight organic acids (such as formic, acetic or propionic acid) had been added, and introduced to an atomic fluorescence spectrometer for subsequent analytical measurements. The experimental conditions for photo-CVG and the interferences arising from concomitant elements were carefully investigated. Limits of detection as low as 0.08, 0.1, 0.2 and 0.5 ng mL^− 1 were obtained for Te, Bi, Sb and As, respectively, comparable to those by hydride generation-AFS. The RSDs obtained with the proposed method for these elements were better than 5% at 50 ng mL^− 1. It is noteworthy that the presence of TiO₂ nanoparticles combined with UV irradiation remarkably enhances the CVG efficiencies of Se(VI) and Te(VI), which cannot form hydrides with KBH₄/NaBH₄. Moreover, photo-CVG has a greater tolerance toward interferences arising from transition elements than hydride generation, and this facilitates its application to the analysis of complicated sample matrices.     

The effect of pre-evaporation on ion distributions in inductively coupled plasma mass spectrometry

The connecting tube (2 or 5-mm i. d., 11-cm long) between the spray chamber and the torch was heated (to 400 °C) to investigate the effect of pre-evaporation on the distribution of ions in inductively coupled plasma mass spectrometry (ICP-MS). Axial and radial profiles of analyte ions (Al⁺, V⁺, Cr⁺, Ni⁺, Zn⁺, Mn⁺, Zn⁺, As⁺, Se⁺, Mo⁺, Cd⁺, Sb⁺, La⁺, Pb⁺) in 1% HNO₃ as well as some polyatomic ions (LaO⁺, ArO⁺, ArN⁺, CO₂⁺) were simultaneously obtained on a time-of-flight ICP-MS instrument. Upon heating the connecting tube, the optimal axial position of all elements shifted closer to the load coil. Without the heated tube, 3.5 mm was the compromise axial position for multielemental analysis, which was optimal for 6 analytes. With the heated tube, this position became 1.5 mm, which was then optimal for 9 of the 14 analytes. Furthermore, the radial profiles, which were wide with a plateau in their middle without heating, became significantly narrower and Gaussian-like with a heated tube. This narrowing, which was most important for the 5-mm tube, slightly (by a factor of two at the most) yet significantly (at the 95% confidence level) improved the sensitivity of all elements but Mn upon optimisation of the axial position for compromise multi-element analysis. Furthermore, a concurrent decrease in the standard deviation of the blank was significant at the 95% confidence level for 9 of the 14 analytes. For most of the analytes, this translated into a two-fold to up to an order of magnitude improvement in detection limit, which is commensurate with a reduction of noise resulting from the smaller droplets entering the plasma after traversing the pre-evaporation tube.     

Synthesis,crystal structures and competitive complexation property of a family of calix-crown hybrid molecules and their application in extraction of potassium from bittern

A family of calix-crown hybrid molecules containing calix[4]arene and crown-5/6, either at lower rim or at both upper and lower rims, have been synthesised, characterised and their competitive complexation property towards alkali and alkaline earth metal ions in aqueous media have been investigated. The competitive metal ion extraction study, carried out with equimolar mixture of Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺ and Sr²⁺ in aqueous media, revealed that the amount of K⁺ extracted is remarkably high compared to other metal ions. Complexation with K⁺ has been investigated by ¹H NMR, association constants and thermodynamic parameters have been determined by isothermal calorimetric study. The molecular structures of one of the receptors and two of the K⁺ complexes have been established by single crystal X-ray study. One of the receptors formed bimetallic complex and it exhibited interesting polymeric network structure with bridged picrate anion. These receptors have been applied for extraction of metal ions from bittern.     

Determination of gallium originated from a gallium-based anticancer drug in human urine using ICP-MS

Urine analysis gives an insight into the excretion of the administered drug which is related to its reactivity and toxicity. In this work, the capability of inductively coupled plasma mass spectrometry (ICP-MS) to measure ultratrace metal levels was utilized for rapid assaying of gallium originating from the novel gallium anticancer drug, tris(8-quinolinolato)gallium(III) (GaQ₃), in human urine. Sample dilution with 1% (v/v) HNO₃ as the only required pre-treatment was shown to prevent contamination of the sample introduction system and to reduce polyatomic interferences from sample components. The origin of the blank signal at masses of gallium isotopes, 71 and 69, was investigated using high-resolution ICP-MS and attributed, respectively, to the formation of ³⁶Ar³⁵Cl⁺ and ⁴⁰Ar³¹P⁺ ions and, tentatively, to a triplet of doubly charged ions of Ba, La, and Ce. The accuracy and precision performance was tested by evaluating a set of parameters for analytical method validation. The developed assay has been applied for the determination of gallium in urine samples spiked with GaQ₃. The achieved recoveries (95–102%) and quantification limit of 0.2 μg L⁻¹ emphasize the practical applicability of the presented analytical approach to monitor renal elimination of GaQ₃ at all dose levels in clinical trials that are currently in progress.