Laser Ablation Saturated Absorption Spectroscopy (LA-SAS) for In Situ Detection of Neodymium Isotopes.

This study introduces a novel optical system integrating laser ablation with saturated absorption spectroscopy (LA-SAS) for the detection of neodymium isotopes, crucial for the characterization process in nuclear forensics. Conventional methods for isotope analysis have encountered challenges, such as the inability to perform on-site detection or difficulty in distinguishing minor isotope differences. The LA-SAS system overcomes these limitations by combining pulsed laser for ablation and counter-propagated diode laser for saturated absorption, enabling preparation-free detection with enhanced spectral resolution. The analytical capability was demonstrated through the successful detection of seven neodymium isotopes (142Nd, 143Nd, 144Nd, 145Nd, 146Nd, 148Nd, and 150Nd) with a line width narrowed to 0.1 pm, significantly improving upon the resolution limit of conventional LA-based methods. In addition, quantitative analysis of isotope abundance was facilitated by evaluating the signals from saturated absorption spectra. Special attention was given to the hyperfine structure of odd isotopes, which was resolved by multiple fitting in spectra, thereby refining the accuracy of isotope quantification up to an average bias of 0.45%. The established LA-SAS system offers on-site detection capability based on LA, and also the high resolution from SAS, making it a promising method for in situ nuclear forensics. Consequently, the study enhances the academic understanding of neodymium isotopes and underscores the potential of LA-SAS in fields requiring detailed isotopic information.

Compensating isotope effect on molecular emission of hydroxyl and imidogen isotopologues in laser-induced plasma.

BACKGROUND: The molecular isotopologues in laser-induced plasma exhibit riddling emission behaviors in terms of wavelength, intensity, and temporal evolution of spectra due to the isotope effect. Although this phenomenon introduces uncertainty to isotope analyses based on molecular spectra, its underlying mechanism remains undisclosed. RESULTS: In this study, laser-induced breakdown spectroscopy (LIBS) is employed to identify the emission behavior of hydrogen, oxygen, and nitrogen isotopologues in a plasma plume. The goal is to discern the details of the isotope effect and mitigate resulting uncertainty. The molecular emissions of hydroxyl (OH) and imidogen (NH) were measured from plasma ablated on isotopically enriched water samples. Time-resolved detection clearly reveals distinct isotopic disparities in intensity variation and optimum gate delay, which were attributed to plasma thermo-hydrodynamics. Lighter isotopologues exhibit earlier and faster associations than their heavier counterparts due to their fast reaction rates and expansion velocities. The extent of the isotope effect hinged on plasma characteristics governed by measurement conditions. Consequently, comparing spectral intensity between molecular isotopologues cannot directly indicate the nominal isotope abundance of the sample. To address it, a compensation strategy has been devised, quantifying isotope effects through parameters like the slope and optimum delay of time-resolved detection. The approach successfully predicts nominal isotope abundance using compensated intensity ratios, with an absolute bias of less than 3 %. SIGNIFICANCE: This study not only offered fundamental insights into the isotope effect in laser-induced plasma but also proposed an alternative method for isotope quantification that circumvents complicated calibration processes.

Thermodynamic, Spectroscopic, and Structural Study on a Sodium Uranyl Tri-2-Methoxybenzoate Dodecahydrate Coordination Compound with Considerably Low Solubility in Acidic Conditions.

A spontaneous crystallization of an uranium(VI)-organic coordination compound with sodium and 2-methoxybenzoate (2-mba) was observed in acidic solutions, and the solubility product, molecular vibrations, crystal structure, thermal stability, and emission properties of the atypically low-soluble U(VI) complex (Na[UO2(2-mba)3]·12H2O(s)) were fully investigated for the first time. A long-term solubility experiment and speciation modeling gave a solubility product of log Ks,0 = -12.18 ± 0.02 (T = 25 °C and I = 0.1 M NaClO4), and vibrational analyses confirmed the overall molecular structure of complex and the frequencies of characteristic stretching motions of uranyl moiety as well. The crystal quality of Na[UO2(2-mba)3]·12H2O(s) was improved by a digestion method, and X-ray diffraction analysis of the single crystalline specimen verified that the newly studied uranyl-organic compound contains one-dimensional channels with a diameter of 20 Å along the [001] direction; the sodium and water molecules are arranged in the channel structures. In the coordination environment around uranyl, three aromatic carboxylates are symmetrically bound in the equatorial plane of uranyl coplanarily, and the unit [UO2(2-mba)3]- complexes are further extended along the plane to form the layered-morphologies. The three-dimensional packing of [UO2(2-mba)3]- anions is driven by the parallel-displaced π-stacking of aromatic rings with a centroid-centroid distance of 3.7 Å. Additional thermogravimetric analysis confirmed that the Na[UO2(2-mba)3]·12H2O(s) is stable up to 250 °C, and dehydration and release of the organic ligand were subsequently observed beyond that temperature. Photoluminescence spectrum of the Na[UO2(2-mba)3]·12H2O(s) clearly displayed the characteristic U(VI) emission, and a band spacing between the ground electronic states of U(VI) uranyl was evaluated to be 831 ± 14 cm-1. Such detailed characterization of the unique Na[UO2(2-mba)3]·12H2O(s) is advancing upon a systematic understanding of the structural effects of the aromatic model ligands on U(VI) complexation, with relevance to the environmental chemistry of U(VI) and crystal engineering for development of diverse uranyl-organic frameworks.

Spectroscopic Study on Aqueous Uranyl(VI) Complexes with Methoxy- and Methylbenzoates: Electronic and Steric Effects of the Substituents.

Aqueous complexation of uranyl(VI) ions with methoxy- and methylbenzoates in 0.1 M NaClO4 solutions was studied by means of UV-vis absorption and Raman spectroscopy. The predominance of 1:1 complexation (uranyl to ligand) was verified for all uranyl carboxylates under acidic conditions (-log [H+] < 3.2), and absorption spectra, stability constants, and symmetric stretching frequencies of the uranyl group of the complexes were determined for the first time. For meta- and para-substituted benzoates, a linear free energy relationship (LFER) was observed between the equilibrium constants for the protonation (log ßP) and uranyl complexation (log ßU) reactions, and the electronic effects of the substituents were successfully described by the Hammett equation. In the case of ortho-substituted benzoates, the stability constant of uranyl 2-methoxybenzoate is slightly lower than the LFER trend, which is generally explained by the destabilization of cross-conjugation in the uranyl complex due to the steric hindrance between the reaction center and adjacent methoxy group. On the contrary, the stability constant of uranyl 2-methylbenzoate is comparable to the LFER trend, implying that the steric effect is relatively insignificant for the smaller methyl group. The utility of such thermodynamic correlations between the uranyl-substituted benzoates is useful for the molecular understanding and predictive modeling of chemical interactions between actinyl(VI) ions and various organic carboxyl groups.

Visible-NIR absorption spectroscopy study of the formation of ternary plutonyl(VI) carbonate complexes.

We present the first experimental evidence for the ternary complexation of calcium and magnesium ions with plutonyl(vi)tricarbonate species in carbonate-containing aqueous solutions using visible-NIR spectrophotometric titration. Prior to studying the ternary plutonyl(vi) carbonate complexation, visible-NIR absorption spectral information of PuO2(CO3)22- and PuO2(CO3)34- was successfully obtained. PuO2(CO3)22- has a prominent peak at 853 nm and its molar absorptivity was determined to be ε853, PuO2(CO3)22- = 49.0 ± 4.2 M-1·cm-1. The spectrophotometric titration results by adding calcium or magnesium to the plutonyl(vi) carbonate system consisting of PuO2(CO3)22- and PuO2(CO3)34- indicate the formation of CaPuO2(CO3)32- and MgPuO2(CO3)32- complexes and provide the formation constants at 0.1 M H/NaClO4 for MPuO2(CO3)32- from PuO2(CO3)34-, log K = 4.33 ± 0.50 and 2.58 ± 0.18 for M = Ca2+ and Mg2+, respectively. In addition, the formation constants of CaPuO2(CO3)32- and MgPuO2(CO3)32- from PuO2(CO3)34- at infinite dilution (log K°) were proposed to be 6.05 ± 0.50 and 4.29 ± 0.18, respectively, based on the correction of ionic strength using the Davies equation. The absorption spectrum of the ternary plutonyl(vi) complexes of CaPuO2(CO3)32- is similar to that of PuO2(CO3)34- with the exception of a characteristic absorption peak at 808 nm (ε808, CaPuO2(CO3)32- = 42.9 ± 1.6 M-1·cm-1). According to the calculated aqueous plutonyl(vi) speciation including the ternary plutonyl(vi) complexes, CaPuO2(CO3)32- is considered the dominant Pu(vi) species under environmental conditions, and plutonyl(vi) may be more mobile than expected in previous assessments.

Efficient removal of iodide anion from aqueous solution with recyclable core-shell magnetic Fe3O4@Mg/Al layered double hydroxide (LDH).

Magnetic Mg/Al layered double hydroxides (LDH) with three cationic ratios (Mg/Al = 2:1, 3:1, and 4:1) were successfully synthesized and utilized for the first time in an iodide adsorption study. The effects of the Mg/Al ratio of LDH on iodide adsorption were investigated, and physicochemical properties of synthetic LDHs depending on Mg/Al ratio were confirmed by XRD, TEM, ICP-OES, VSM, Zeta-potential, and BET analyses. The ferrimagnetic property was well preserved even after a coating of LDH on magnetite irrespective of the Mg/Al ratio. Among the three Mg/Al ratios, the calcined Fe3O4@4:1 Mg/Al LDH exhibited excellent performance for iodide removal with 105.04 mg/g of the maximum iodide adsorption capacity due to its wide interlayer spacing and largest BET surface area. In the presence of competing carbonate anions, the Fe3O4@4:1 LDH showed removal rate of >80% at a dosage of over 3 g/L solid to liquid ratio. The recyclability test of Fe3O4@4:1 LDH showed that the removal performance for iodide is maintained at >80% even during the first to the fourth cycles. These results demonstrated that the magnetic Mg/Al LDH adsorbent can be effectively utilized for remediation of radioactive iodide anions with high efficiency and economics.

Complexation of UO2(CO3)34- with Mg2+ at varying temperatures and its effect on U(vi) speciation in groundwater and seawater.

The ternary alkaline earth metal uranyl tricarbonate complexes, MnUO2(CO3)32n-4 (M = Mg and Ca), have been considered to be the major U(vi) species contributing to uranium mobility in natural water. Although MgUO2(CO3)32- can account for a substantial portion of U(vi) in a Mg2+-rich aqueous system and most processes regarding uranium are subjected to variable temperatures, chemical thermodynamic data for the prediction of the formation of MgUO2(CO3)32- at variable temperatures are still unknown. To fill the knowledge gap in the current chemical thermodynamic database, ultraviolet/visible (UV/Vis) absorption spectroscopy was employed to determine the formation constants (log K') of MgUO2(CO3)32- at varying temperatures of 10-85 °C in 0.5 mol kg-1 NaCl. The formation constants at infinite dilution, log K°, were obtained with specific ion interaction theory (SIT), and an increasing tendency of log K° with temperature was observed. Using calorimetric titration, the endothermic molar enthalpy of reaction (ΔrHm) of Mg2+ complexation with UO2(CO3)34- was determined at 25 °C. According to the chemical thermodynamic data obtained in this work, approximation models for the prediction of the temperature-dependent formation constant at a given temperature were examined and the constant enthalpy approximation with modification to the isoelectric reaction showed a satisfactory agreement with our experimental results. Finally, the effects of temperature on U(vi) speciation in Mg2+-rich groundwater and U(vi) extraction from seawater by amidoxime derivatives were examined. For the first time, this work provides important chemical thermodynamic data of MgUO2(CO3)32n-4 to assess the impact of temperature on U(vi) behaviour in groundwater and seawater.

Formation of CaUO2(CO3)32- and Ca2UO2(CO3)3(aq) complexes at variable temperatures (10-70 °C).

The ternary complexation of calcium uranyl tricarbonate species, CaUO2(CO3)32- and Ca2UO2(CO3)3(aq), which are the predominant U(vi) complexes in groundwater and seawater, was investigated at variable temperatures from 10 to 70 °C. Time-resolved laser fluorescence spectroscopy (TRLFS), calcium ion-selective electrode potentiometry, and ultraviolet/visible (UV/Vis) absorption spectroscopy were complementarily employed to determine the formation constants (log Kx13, x = 1 and 2 for mono- and dicalcium complexes, respectively). at infinite dilution (zero ionic strength) was determined by correction using specific ion interaction theory (SIT), and an increasing tendency of with temperature was observed. In addition, the molar enthalpy of complexation (ΔrHm) was measured by calorimetry at 25 °C. Based on thermodynamic data obtained in this work, the approximation models were examined for the prediction of the temperature effect on the complexation, and the constant enthalpy approximation with the chemical complexation reaction modified to an isoelectric reaction showed a satisfactory prediction of in the temperature range of 10-70 °C. Finally, the results of U(vi) speciation in groundwater indicated that the dominance of calcium uranyl tricarbonate complexes would be weakened at elevated temperatures by the strongly enhanced hydrolysis of U(vi).

Immobilization of radioactive corrosion products by cold sintering of pure hydroxyapatite.

An efficient method for the consolidation of cobalt (Co(II)) adsorbed calcium hydroxyapatite was investigated to develop a simplified route for decontamination of the coolant system of nuclear power plants and direct immobilization of as-spent adsorbent. Calcium hydroxyapatite nano-powder synthesized by a wet precipitation method was used as an adsorbent and 94% Co(II) surrogate removal from simulated water was measured. The as-spent adsorbent was sintered at 200 °C, a temperature significantly lower than conventional sintering temperatures (900-1300 °C) for hydroxyapatite, under a uniaxial pressure of 500 MPa for 10 min. The relative density after the cold sintering was >97% and sintered samples displayed good compressive strength (175 MPa). The normalized leaching rate of the Co(II) was measured as per ASTM-C1285 standard and found to be 2.5 × 10-5 g/m2/day. ANSI/ANS-16.1 test procedure was used to analyze the leachability of the sintered matrices and the measured leaching index value was 6.5. Thus, the use of pure calcium hydroxyapatite nano-powder as adsorbent and its cold sintering offers a mean by which radioactive waste form can be processed in an environment friendly manner.

Selective morphological analysis of cerium metal in electrodeposit recovered from molten LiCl-KCl eutectic by radiography and computed tomography.

This paper presents, for the first time, a study to analyze the surface morphology of metal extracted from a high temperature molten salt medium in the electrodeposit using x-ray radiography and computed tomography. Widely used methods such as scanning electron microscopy and inductively coupled plasma-optical emission spectrometry/mass spectrometry are destructive and the related processes are often subject to the air condition. The x-ray imaging can provide rich information of the target sample in a non-destructive way without invoking hydrolysis or oxidation of a hygroscopic sample. In this study, the x-ray imaging conditions were optimized as following: tube voltage at 100 kVp and the current exposure time product at 8.8 mAs in our in-house x-ray imaging system. LiCl-KCl and cerium metals used in this work produced substantially distinguishable contrasts in the radiography due to their distinctive attenuation characteristics, and this difference was well quantified in the histograms of brightness. Electrodeposits obtained by chronoamperometry and chronopotentiometry demonstrated a completely different behavior of electrodeposition even at the same applied charge. In particular, computed tomography and volumetric analysis clearly showed the structural and morphological dissimilarity. The structure of cerium metal in the electrodeposit was successfully separated from the chloride salt structure in the CT image by an image segmentation process.

Efficient immobilization of ionic corrosion products by a silica-hydroxyapatite composite via a cold sintering route.

We have successfully demonstrated a new method of radioactive waste immobilization by hosting a waste-bearing form in another waste matrix. A cold sintering route was used to consolidate a silica-incorporated hydroxyapatite (Si-HAp) composite at 200 °C by applying a uniaxial pressure of 500 MPa for a short holding time of 10 min. The higher relative sintered density of up to 98.0 ± 1.3% was achieved by 25 wt% Si loaded HAp. Results from high resolution X-ray diffraction, micro-hardness, and high resolution scanning electron microscopy confirmed the densification with good mechanical strength (micro-hardness = 2.9 ± 0.3 GPa). For practical applications, two kinds of wastes (25 wt% ionic corrosion product-sorbed EDTA functionalized mesoporous silica and 75 wt% ionic corrosion product-sorbed HAp) were mixed, consolidated and tested. The chemical stability of the solidified composite matrix was positively assessed for low leaching rates of 5.9 × 10-9 to 1.2 × 10-5 g per m2 per day using a standard product consistency test. The consolidated composite can bear compressive stress up to 358 MPa, which is orders of magnitude higher than the waste acceptance criteria of 3.5 MPa. The low process temperature can make this sintering process very powerful for the immobilization of radionuclides with volatility and low boiling point. Such a low temperature solidified matrix hosting various wastes may be a promising path for waste management because of its simplicity, reliability, scalability, cost effectiveness and environmental friendliness.

Uranium(VI) sorption complexes on silica in the presence of calcium and carbonate.

Uranium sorption on minerals and related solids depends to a large degree on its aqueous speciation. The present work attempts to understand the U(VI) sorption behavior on silica under environmentally relevant conditions, i.e. at neutral to weakly alkaline pH and in the presence of dissolved calcium and carbonate. Under these conditions, Ca(UO2)(CO3)32- and Ca2(UO2)(CO3)3(aq) complexes emerge as the dominant aqueous U(VI) species. The U(VI) sorption affinity was measured as a function of contact time, solution pH, and humic acid. The U(VI) sorption decreased with increase of pH and was not affected by the addition of 50 mg/L humic acid. On the other hand, nitric acid was more effective than EDTA and carbonate at desorbing U(VI). Generally, the U(VI) sorbed on silica at neutral pH was less readily desorbed than that sorbed at higher pH values. Therefore, the U(VI) complex favorably sorbed on silica at the neutral pH is more strongly bound to the silica surface than that sorbed at higher pH values. Time-resolved laser fluorescence spectroscopy confirmed the results of the batch sorption experiments and revealed the presence of two surface U(VI) complexes with fluorescence lifetimes 251 ± 8 µs and 807 ± 24 µs.

Decontamination of radionuclides by functionalized mesoporous silica under gamma irradiation.

Schiff base functionalized mesoporous silica (SA-SBA-15) was synthesized by the co-condensation method to remove the radioactive corrosion products from contaminated water coming from nuclear installations. SA-SBA-15 nanoparticles were first irradiated in a solid powder form and then applied to remove Cu(ii), Ni(ii), and Co(ii) from their aqueous mixture in the range from 0 to 1000 Gy of gamma irradiation. The FTIR, TGA, zeta potential, XRD, BET, TEM, and CHN analysis results revealed the stability of a ligand support material, mesopore ordering and the functional groups. The structural and functional group endurance under our studied gamma irradiation makes SA-SBA-15 a potential adsorbent for routine decontamination and decommissioning activities as well as in radioactively contaminated emergency scenarios. Furthermore, the adsorbent-metal complexation followed the Irving-Williams order (Cu(ii) > Ni(ii) > Co(ii)) and showed a higher selectivity for Cu(ii) with removal capacity up to 99.76 ± 0.01%, thus suggesting its applicability to separate Cu(ii) from other metal ions.

Formation of ternary CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) complexes under neutral to weakly alkaline conditions.

The chemical behavior of ternary Ca-UO2-CO3 complexes was investigated by using time-resolved laser fluorescence spectroscopy (TRLFS) in combination with EDTA complexation at pH 7-9. A novel TRLFS revealed two distinct fluorescence lifetimes of 12.7 ± 0.2 ns and 29.2 ± 0.4 ns for uranyl complexes which were formed increasingly dependent upon the calcium ion concentration, even though nearly indistinguishable fluorescence peak shapes and positions were measured for both Ca-UO2-CO3 complexes. For identifying the stoichiometric number of complexed calcium ions, slope analysis in terms of relative fluorescence intensity versus calcium concentration was employed in a combination with the complexation reaction of CaEDTA(2-) by adding EDTA. The formation of CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) was identified under given conditions and their formation constants were determined at I = 0.1 M Na/HClO4 medium, and extrapolated to infinitely dilute solution using specific ion interaction theory (SIT). As a result, the formation constants for CaUO2(CO3)3(2-) and Ca2UO2(CO3)3(aq) were found to be log ß113(0) = 27.27 ± 0.14 and log ß213(0) = 29.81 ± 0.19, respectively, providing that the ternary Ca-UO2-CO3 complexes were predominant uranium(vi) species at neutral to weakly alkaline pH in the presence of Ca(2+) and CO3(2-) ions.

Highly sensitive analysis of boron and lithium in aqueous solution using dual-pulse laser-induced breakdown spectroscopy.

We have applied a dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) to sensitively detect concentrations of boron and lithium in aqueous solution. Sequential laser pulses from two separate Q-switched Nd:YAG lasers at 532 nm wavelength have been employed to generate laser-induced plasma on a water jet. For achieving sensitive elemental detection, the optimal timing between two laser pulses was investigated. The optimum time delay between two laser pulses for the B atomic emission lines was found to be less than 3 µs and approximately 10 µs for the Li atomic emission line. Under these optimized conditions, the detection limit was attained in the range of 0.8 ppm for boron and 0.8 ppb for lithium. In particular, the sensitivity for detecting boron by excitation of laminar liquid jet was found to be excellent by nearly 2 orders of magnitude compared with 80 ppm reported in the literature. These sensitivities of laser-induced breakdown spectroscopy are very practical for the online elemental analysis of boric acid and lithium hydroxide serving as neutron absorber and pH controller in the primary coolant water of pressurized water reactors, respectively.

Age estimation of Korean adults by occlusal tooth wear.

The aim of the present study was to evaluate the validity of the modified Kim's scoring system as a practical method of recording occlusal tooth wear and estimating age. For this purpose, 1092 pairs of maxillary and mandibular full-arch casts were randomly selected, scored, and analyzed. The results showed that the modified Kim's scoring system had excellent reliability, and that occlusal tooth wear had a positive correlation with age. Tooth wear scores of all teeth except the two lower central incisors were higher in males than in females. Calculating tables for age estimation were designed by multiple linear regression analysis. Estimated ages were within +/-5 years of actual ages in 63.5% of male subjects, and 64.0% of female subjects. The accuracy of age estimation was increased when the subjects were divided into two age groups and data were re-analyzed. Collectively, it was shown that the modified Kim's scoring system is a reliable and accurate method for age estimation, and that the data from these 1092 individuals can be used as a standard for age estimation of Korean adults.

Formation of aquatic Th(IV) colloids and stabilization by interaction with Cm(III)/Eu(III).

The present investigation is to ascertain under what conditions actinide ions undergo aggregation via oxo-bridging to form stable colloidal species. Eu and Th are taken for this purpose as trivalent and tetravalent actinide homologue ions, respectively. For verification of the effects of impurities in chemicals on the actinide colloid generation, pH is adjusted either by a conventional acid-base titration or by coulometry without addition of NaOH. The colloid generation is monitored by highly sensitive laser-induced breakdown detection in varying pH from 3 to 7, first in dilute Eu and Th solutions separately and then in a mixture of both, all in 0.5 M HCl/NaCl. The formation of stable colloids is observed particularly in a mixed solution of Eu and Th, suggesting that aggregation via mutual oxo-bridging of trivalent and tetravalent metal ions results in surface polarization, leading to stable hydrophilic particles of 20-30 nm in diameter. When Eu is replaced by Cm in the mixed solution in favor of the high fluorescence intensity of the latter, the chemical speciation is determined on colloid-borne Cm by time-resolved laser fluorescence spectroscopy. Two different colloid-borne Cm species, oxo-bridged with Th, are identified: a minor amount at 598.0 nm (denoted as Cm-Th(1)) and a major amount at 604.8 nm (Cm-Th(2)). The former is found as a transitional state, which converts to the latter with increasing pH and prevails at pH > 5.5. Both colloid-borne species (Cm-Th) are distinctively different from hydrolyzed Cm or its carbonate complexes with respect to their fluorescence peak positions and lifetimes. In conclusion, a mixed oxo-bridging of trivalent and tetravalent actinides elicits the generation of stable colloids, whereas individual ions in their pure state form colloids under oversaturation at near neutral pH only as a transitional state for precipitation.

Laser-induced breakdown detection combined with asymmetrical flow field-flow fractionation: application to iron oxi/hydroxide colloid characterization.

The combination of asymmetrical flow field-flow fractionation (AsFlFFF) with the laser-induced breakdown detection (LIBD) is presented as a powerful tool for the determination of colloid size distribution at trace particle concentrations. Detection limits (D1) of 1, 4, and 20 microg/L have been determined for a mixture of polystyrene reference particles with 20, 50, and 100 nm in size, respectively. This corresponds to injected masses of 1, 4, and 20 pg, which is lower than found in a previous study with the symmetrical FlFFF (SyFlFFF). The improvement is mainly due to the lower colloid background discharged from the AsFlFFF channel. The combined method of AsFlFFF-LIBD is then applied to the analysis of iron oxi/hydroxide colloids being considered as potential carriers for the radionuclide migration from a nuclear waste repository. Our LIBD arrangement is less sensitive for iron colloid detection as compared to reference polystyrene particles which results in a detection limit of approximately 240 microg/L FeOOH for the AsFlFFF-LIBD analysis. This is superior to the detection via UV-Vis absorbance and comparable to ICP-MS detection. Size information (mean size 11-18 nm) for different iron oxi/hydroxide colloids supplied by the present method is comparable to that obtained by sequential ultrafiltration and dynamic light scattering. A combined on-line ICP-MS detection is used to gain insight into the colloid-borne main and trace elements.