Α-hydroxyisobutyric Acid Research Articles

Thorium Complexation with Aliphatic and Aromatic Hydroxycarboxylates: A Combined Experimental and Theoretical Study.

Hydroxycarboxylic acids, viz., α-hydroxyisobutyric acid (HIBA) and mandelic acid (MA), have been widely employed as eluents for inner transition metal separation studies. Both extractants have identical functional groups (OH and COOH) with different side-chains. Despite their similarities in binding motifs, they show different retention behaviors for thorium and uranium in liquid chromatography. To understand the mechanism behind the trend, a detailed study on the aqueous phase interaction of thorium with both extractants is carried out by speciation, spectroscopy, and density functional theory-based calculations. Potentiometric titration experiments are carried out to reveal the stability and species formed. Electrospray ionization mass spectrometry is performed to identify the formation of different species by Th with both HIBA and MA. It is seen that for Th-HIBA and Th-MA, the dominating species are ML3 and ML4, respectively. A similar pattern observed in potentiometric speciation analysis supports the tendency of Th to form higher stoichiometric species with MA than with HIBA. The difference in the dominating species thus helps in explaining the reversal in the retention behavior of uranium and thorium in the reverse-phase liquid chromatographic separation. The results obtained are corroborated with extended X-ray absorption fine structure spectroscopic measurements and density functional theory (DFT) calculations.

Reverse phase liquid chromatographic method for the measurement of uranium in process stream solutions from uranium extraction facility

Abstract The present paper describes a simple method for the determination of uranium in uranium process stream solutions by reversed-phase liquid chromatographic method using C18 column, mixture of α-hydroxy isobutyric acid and methanol as eluent and flow-through spectrophotometer detector. This method has an advantage that interfering elements like rare-earth elements do not retain on the column and elute near the solvent peak thereby not interfering with uranium elution peak. Different eluents and parameters like pH, concentration of eluent are studied for the purpose. The spiking standard recovery was found to be more than 90 %. The developed method has been compared with other techniques and found to be in agreement.

High Separation Factor, High Molar Activity, and Inexpensive Purification Method for the Production of Pure 165Er.

Introduction: Auger electron-emitting radionuclides with low (0.001-1 keV) energy, short-range (2-500 nm), and high linear energy transfer (4-26 keV/μm) can play an important role in the targeted radionuclide therapy (TRT) of cancer. 165Er is a pure Auger electron-emitting radionuclide, making it a useful tool for the fundamental studies of the biological effects of Auger electrons. This work develops a simple, inexpensive, high separation factor, and high molar activity radiochemical isolation process for the production of 165Er (t1/2 10.36 h) suitable for TRT in vitro and in vivo studies using irradiated natHo solid targets. Methods: Small medical cyclotron proton-irradiation of natHo targets produced 165Er in GBq scale quantities. 165Er was isolated using cation exchange chromatographic resin (AG 50W-X8, 200-400 mesh, 20 mL, under atmospheric pressure) using α-hydroxyisobutyric acid (70 mM, pH 4.75) followed by extraction using TK212, TK211, and TK221 extraction chromatographic columns. Radio nuclidic and chemical purity of the final 165Er were confirmed using HPGe Gamma spectrometry and induction coupled plasma-mass spectrometry analysis, respectively. The purified 165Er was radiolabeled with two radiometal chelators (DOTA and Crown) and used to produce a new Auger electron-emitting radiopharmaceutical, [165Er]Er-Crown-TATE. Results: Irradiation of 200 mg natHo targets with 20-30 μA of 12.8 MeV protons produced 165Er at 25 ± 5 MBq·μA-1·h-1. The 4.5 ± 0.5 h radiochemical isolation yielded GBq scale of 165Er in 0.05 M HCl (2 mL) with a radiochemical yield of 78.0 ± 5.6% decay corrected to the end of bombardment (EoB) and a Ho/165Er separation factor of (1.14 ± 0.25) × 106. The product showed high radio nuclidic purity and chemical purity. Concentration-dependent radiolabeling experiments with Crown and DOTA were performed resulting in the successful labeling of 165Er with high (>90%) radiochemical yield. Radiolabeling experiments with Crown-TATE were performed 8 h after EoB and synthesized [165Er]Er-Crown-TATE at molar activities of 202.4 MBq·nmol-1 at the end of synthesis (EoS). Conclusions: A 3 h cyclotron irradiation and 4.5 h radiochemical separation produced GBq-scale 165Er suitable for producing radiopharmaceuticals at molar activities satisfactory for investigations of targeted radionuclide therapeutic effects of Auger electron emissions. This will enable future fundamental radiation biology experiments of pure Auger electron-emitting therapeutic radiopharmaceuticals, such as [165Er]Er-Crown-TATE, which will be used to understand the impact of Auger electrons in TRT.

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.

Paeonol reduces microbial metabolite α-hydroxyisobutyric acid to alleviate the ROS/TXNIP/NLRP3 pathway-mediated endothelial inflammation in atherosclerosis mice.

Gut microbiota dysbiosis is an avenue for the promotion of atherosclerosis (AS) and this effect is mediated partly via the circulating microbial metabolites. More microbial metabolites related to AS vascular inflammation, and the mechanisms involved need to be clarified urgently. Paeonol (Pae) is an active compound isolated from Paeonia suffruticoas Andr. with anti-AS inflammation effect. However, considering the low oral bioavailability of Pae, it is worth exploring the mechanism by which Pae reduces the harmful metabolites of the gut microbiota to alleviate AS. In this study, ApoE-/- mice were fed a high-fat diet (HFD) to establish an AS model. AS mice were administrated with Pae (200 or 400 mg·kg-1) by oral gavage and fecal microbiota transplantation (FMT) was conducted. 16S rDNA sequencing was performed to investigate the composition of the gut microbiota, while metabolomics analysis was used to identify the metabolites in serum and cecal contents. The results indicated that Pae significantly improved AS by regulating gut microbiota composition and microbiota metabolic profile in AS mice. We also identified α-hydroxyisobutyric acid (HIBA) as a harmful microbial metabolite reduced by Pae. HIBA supplementation in drinking water promoted AS inflammation in AS mice. Furthermore, vascular endothelial cells (VECs) were cultured and stimulated by HIBA. We verified that HIBA stimulation increased intracellular ROS levels, thereby inducing VEC inflammation via the TXNIP/NLRP3 pathway. In sum, Pae reduces the production of the microbial metabolite HIBA, thus alleviating the ROS/TXNIP/NLRP3 pathway-mediated endothelial inflammation in AS. Our study innovatively confirms the mechanism by which Pae reduces the harmful metabolites of gut microbiota to alleviate AS and proposes HIBA as a potential biomarker for AS clinical judgment.

Structural Speciation of Ti(IV)-(α-Hydroxycarboxylic Acid) Complexes in Metabolism-Related (Patho)Physiology-In Vitro Approaches to (Pre)Adipocyte Differentiation and Mineralization.

The prospect of developing soluble and bioavailable Ti(IV) complex forms with physiological substrates, capable of influencing (patho)physiological aberrations, emerges as a challenge in the case of metabolism-related pathologies (e.g., diabetes mellitus 1 and 2). To that end, pH-specific synthetic efforts on binary Ti(IV)-(α-hydroxycarboxylic acid) systems, involving natural physiological chelator ligands (α-hydroxy isobutyric acid, D-quinic acid, 2-ethyl-2-hydroxybutyric acid) in aqueous media, led to the successful isolation of binary crystalline Ti(IV)-containing products. The new materials were physicochemically characterized by elemental analysis, FT-IR, TGA, and X-ray crystallography, revealing in all cases the presence of mononuclear Ti(IV) complexes bearing a TiO6 core, with three bound ligands of variable deprotonation state. Solution studies through electrospray ionization mass spectrometry (ESI-MS) revealed the nature of species arising upon dissolution of the title compounds in water, thereby formulating a solid-state-solution correlation profile necessary for further employment in biological experiments. The ensuing cytotoxicity profile (pre-adipocytes and osteoblasts) of the new materials supported their use in cell differentiation experiments, thereby unraveling their structure-specific favorable effect toward adipogenesis and mineralization through an arsenal of in vitro biological assays. Collectively, well-defined atoxic binary Ti(IV)-hydroxycaboxylato complexes, bearing bound physiological substrates, emerge as competent inducers of cell differentiation, intimately associated with cell maturation, thereby (a) associating the adipogenic (insulin mimetic properties) and osteogenic potential (mineralization) of titanium and (b) justifying further investigation into the development of a new class of multipotent titanodrugs.

Impact of the degradation leachate of the polyacrylonitrile-based material UP2W on the retention of Ni(II), Eu(III) and Pu(IV) by cement.

The uptake of 63Ni(II), 152Eu(III) and 242Pu(IV) by hardened cement paste (HCP, CEM I) in the degradation stage II (pH ≈ 12.5, [Ca] ≈ 0.02 M) was investigated in the presence of a degradation leachate of UP2W, a polyacrylonitrile-based (PAN) material used as a filter aid in nuclear power plants. The degradation leachate with a concentration of dissolved organic carbon of ∼40 ppm was obtained from the degradation of UP2W in portlandite-buffered solutions for ca. 1100 days. Redox conditions in the Pu systems were buffered with hydroquinone, which defines mildly reducing conditions (pe + pH ≈ 10) where Pu(IV) is the predominant oxidation state. The degradation leachate investigated in this work is moderately sorbed by cement, with distribution ratios (Rd) of (0.35 ± 0.15) m3 kg-1. These values are 30 to 100 times greater than distribution ratios previously reported for proxy ligands of PAN degradation products, i.e., glutaric acid, α-hydroxyisobutyric acid and 3-hydroxybutyric acid. The presence of the degradation leachate induces a moderate decrease in the uptake of 63Ni(II), 152Eu(III) and 242Pu(IV) by cement, as compared to the sorption in the presence of the proxy ligands. Nevertheless, retention in the presence of the degradation leachate remains high for all investigated radionuclides, with Rd(63Ni(II)) ≈ 2 m3 kg-1, Rd(152Eu(III)) ≈ 100 m3 kg-1 and Rd(242Pu(IV)) ≈ 30 m3 kg-1. These observations possibly reflect that the multiple functionalities (-COOH, -OH, amide groups) expected in the macromolecules (10-15 kDa) present in the degradation leachate, can offer further binding/chelating capabilities compared to the small organic proxy ligands with at most bidentate binding.

Uptake of selected organic ligands by hardened cement paste: Studies on proxy ligands for the degradation of polyacrylonitrile and general considerations on the role of different functionalities in the uptake process

The uptake of α-hydroxyisobutyric acid (HIBA), 3-hydroxybutyric acid (HBA) and glutaric acid (GTA) by hardened cement paste (HCP) in the degradation stage II was investigated at various ligand concentrations (10−7 M ≤ [L]tot ≤ 0.1 M) and solid-to-liquid ratios (0.2 g⋅dm−3 ≤ S:L ≤ 50 g⋅dm−3). These organic ligands were previously identified as representative of the main degradation products of UP2W, a polyacrylonitrile-based material used as filter aid in nuclear power plants, under repository conditions. Sorption experiments were conducted with inactive (HIBA, HBA, GTA) and active (14C-labelled GTA) organic ligands. Sorption experiments show a weak uptake of HIBA and HBA by HCP, with distribution coefficients determined as Rd (HIBA) = (2.2 ± 1.3)⋅10−3 m3⋅kg−1 and Rd (HBA) = (1.6 ± 0.8)⋅10−3 m3⋅kg−1. A stronger uptake is observed for GTA, i.e. Rd (GTA) = (1.3 ± 0.5)⋅10−2 m3⋅kg−1, likely reflecting the contribution from the ligand’s second carboxylate group. GTA follows a linear sorption behaviour within 10−7 M ≤ [GTA]tot ≤ 0.1 M, which was successfully modelled with a one-site Langmuir isotherm. The adsorption capacity determined for the uptake of GTA by HCP is slightly higher but in line with the capacity previously reported for isosaccharinic acid (ISA), whereas the affinity constant derived for GTA is significantly lower than values reported for stronger binding sites in HCP for the uptake of ISA. HIBA and HBA have a minor impact on the surface charge of HCP up to [L]tot ≈ 0.1 M. On the contrary, GTA induces a clear decrease in the surface charge above [GTA]tot ≈ 10−3 M resulting in an isoelectric point at [GTA]tot ≈ 6⋅10−2 M. Comparison of sorption data obtained in this work and reported in the literature for organic ligands containing the functional groups -COOH and -OH underlines the key role of multiple functionalities as a factor strengthening the interaction with the HCP surface. The participation of alcohol groups is particularly strong when present in their deprotonated state. These results provide information to quantitatively assess the uptake by HCP of organic ligands relevant in the context of nuclear waste disposal, and to understand their impact on the surface properties of cement.

A High-Fat High-Fructose Diet Dysregulates the Homeostatic Crosstalk Between Gut Microbiome, Metabolome, and Immunity in an Experimental Model of Obesity.

Ample evidence supports the prominent role of gut-liver axis in perpetuating pathological networks of high-fat high-fructose (HFF) diet induced metabolic disorders, however, the molecular mechanisms are still not fully understood. Herein, this study aims to present a holistic delineation and scientific explanation for the crosstalk between the gut and liver, including the potential mediators involved in orchestrating the metabolic and immune systems. An experimental obesity-associated metaflammation rat model is induced with a HFF diet. An integrative multi-omics analysis is then performed. Following the clues illustrated by the multi-omics discoveries, putative pathways are subsequently validated by RT-qPCR and Western blotting. HFF diet leads to obese phenotypes in rats, as well as histopathological changes. Integrated omics analysis shows that there exists a strong interdependence among gut microbiota composition, intestinal metabolites, and innate immunity regulation in the liver. Some carboxylic acids may contribute to gut-liver communication. Moreover, activation of the hepatic LPS-TLR4 pathway in obesity is confirmed. HFF-intake disturbs gut flora homeostasis. Crosstalk between gut microbiota and innate immune system mediates hepatic metaflammation in obese rats, associated with LPS-TLR4 signaling pathway activation. Moreover, α-hydroxyisobutyric acid and some other organic acids may play a role as messengers in the liver-gut axis.

Transcriptomics and metabolomics analyses provide insights into postharvest ripening and senescence of tomato fruit under low temperature

Tomato is one of the most important vegetable crops in the world and is a model plant used to study the ripening of climacteric fleshy fruit. During the ripening process of tomato fruit, flavor and aroma metabolites, color, texture and plant hormones undergo significant changes. However, low temperatures delayed the ripening process of tomato fruit, inhibiting flavor compounds and ethylene production. Metabolomics and transcriptomics analyses of tomato fruit stored under low temperature (LT, 5 °C) and room temperature (RT, 25 °C) were carried out to investigate the effects of storage temperature on the physiological changes in tomato fruit after harvest. The results of transcriptomics changes revealed that the differentially expressed genes (DEGs) involved in tomato fruit ripening, including several kinds of transcription factors (TFs) (TCP, WRKY, MYB and bZIP), enzymes involved in cell wall metabolism [beta-galactosidase (β-GAL), pectinesterase (PE) and pectate lyase (PL), cellulose and cellulose synthase (CESA)], enzymes associated with fruit flavor and aroma [acetyltransferase (AT), malic enzyme (ME), lipoxygenase(LOX), aldehyde dehydrogenase (ALDH), alcohol dehydrogenase (ADH) and hexokinase (HK)], genes associated with heat stress protein 70 and genes involved in the production of plant hormones such as Ethylene responsive factor 1 (ERF1), Auxin/indoleacetic acids protein (AUX/IAA), gibberellin regulated protein. Based on the above results, we constructed a regulatory network model of the effects of different temperatures during the fruit ripening process. According to the analysis of the metabolomics results, it was found that the contents of many metabolites in tomato fruit were greatly affected by storage temperature, including, organic acids (L-tartaric acid, a-hydroxyisobutyric acid and 4-acetamidobutyric acid), sugars (melezitose, beta-D-lactose, D-sedoheptulose 7-phosphate, 2-deoxyribose 1-phosphate and raffinose) and phenols (coniferin, curcumin and feruloylputrescine). This study revealed the effects of storage temperature on postharvest tomato fruit and provided a basis for further understanding of the molecular biology and biochemistry of fruit ripening.

Dual column HPLC method for determination of lanthanides in zirconium matrix

A high performance liquid chromatography (HPLC) method is developed for the determination of lanthanides present in zirconium matrix. α-Hydroxyisobutyric acid (α-HIBA) is used as an eluent for the removal of bulk of zirconium and pre-concentration of lanthanides. Later the pre-concentrated lanthanides are individually separated by dynamic ion exchange method. The method offers linearity in the concentration range of lanthanides from 2 to 100 ppb. The developed methodology is validated by analyzing simulated zirconium sample containing known amounts of lanthanides. The method is then used for quantitative recovery and determination of lanthanides in ZrO2 matrix with Zr/Ln amount ratios up to 250,000.

Distribution Coefficients of the REEs, Sr, Y, Ba, Th, and U between α-HIBA and AG50W-X8 Resin

Rare-earth elements (REEs) are known for their similar behaviors, which make their purification through chromatographic techniques particularly challenging. The use of α-hydroxyisobutyric acid (α-H...

Americium pertraction across supported liquid membranes containing multiple diglycolamide ligands: Role of alkyl substitution and spacer length in carrier ligands

Liquid–liquid extraction and subsequent supported liquid membrane (SLM) transport studies involving Am3+ ion were carried out from nitric acid feed solutions using three N-pivot tripodal diglycolamide (DGA) ligands with varying substituent at the inner carboxamide N atom and spacer length. The ligand with an isopropyl substituent and with C2 spacer is termed as iPr3-TREN-DGA, while the one without alkyl substituent is termed as TREN-DGA. The third ligand with no substituent but a C3 spacer is termed as TRPN-DGA. The trend of metal ion extraction was iPr3-TREN-DGA > TRPN-DGA > TREN-DGA when solutions of ca. 1.0×10−3 M ligand in 95% n-dodecane+5% isodecanol were used. Stripping studies were carried out using 0.01M HNO3, 0.01M EDTA (at pH 3.0) and 1M α-HIBA (α-hydroxyisobutyric acid) The extraction and stripping kinetics studies suggested attainment of equilibrium in about 30minutes. The SLM studies were carried out in a two-compartment cell with 20mL feed as well as receiver phase volumes and PTFE (polytetrafluoroethylene) flat sheets as the solid support. The transport rates followed the same trend as that of the metal ion extraction study, suggesting comparable diffusion coefficients of the complexes (obtained by the lag-time method). Membrane stability studies indicated the best stability for the TRPN-DGA ligand.

Influence of competitive eluting agents on REEs recovery from silica gel adsorbent with immobilized aminodiphosphonic acid

It was demonstrated that traces of rare earth elements (REEs) can be quantitatively preconcentrated from contaminated water with pH ≥ 3 on a silica-based adsorbent with covalently immobilized amino-di(methylenephosphonic) acid (SiO2-AdPA). However, recovery of REEs from the adsorbent required utilization of a strong mineral acid. In order to reduce environmental impact and increase the reusability of the adsorbent, a ligand-exchange approach that includes treatment of the adsorbent with strong complexing ligands was used. The eluting potential of several ligands was investigated, namely EDTA, 5-sulfosalicylic acid (SSA), citric acid (CiA), aminosulfonic acid (AmSA), α-hydroxyisobutyric acid (HBA), oxalic acid (OxA) and ascorbic acid (AsA). The results were compared to those obtained by acidic treatment (HCl or HNO3). It was demonstrated that the complete desorption of all REEs can be achieved by using 10−2 mol L-1 EDTA solution with pH = 8.0, while acidic treatment requires 1.0 mol L-1 HNO3. Reusability tests demonstrated complete stability of the adsorbent for at least five consecutive adsorption/desorption cycles with no decrease in its adsorption characteristics.

Preconcentration mechanism of trivalent lanthanum on eQCM electrodes in the presence of α-hydroxy isobutyric acid

Electroprecipitation can be used to preconcentrate lanthanum on carbon electrode surfaces. The use of complexing ligands is expected to improve the electroprecipitation of lanthanum by protecting La ions in solution from the alkaline region near the electrode surface. However, the electroprecipitation mechanism of La in the presence of a complexing ligand is not known. The goal of this work is to 1) determine the effect of the complexing ligand, α-hydroxy isobutyric acid (HIBA), on the electroprecipitation of La onto the gold electrodes, and 2) identify the changes in the mechanism of accumulation when preconcentrating in the presence of HIBA. We used an electrochemical quartz crystal microbalance (eQCM) and needle type pH microelectrodes to determine pH near the electrode surface in combination with cyclic voltammetry to understand the electroprecipitation mechanism. We used the bi-dentate ligand HIBA as a ligand and found that lanthanum electroprecipitation is hindered in the presence of HIBA. The presence of HIBA also delayed the onset of film formation during a cyclic voltammetric experiment by ~100 mV compared to experiments performed without HIBA. The shift in onset potential is attributed to the buffering action of HIBA (pKa = 3.7) since the shift is not present in subsequent scans. The precipitated film was characterized by scanning electron microscopy, X-ray photoelectron spectrometry, and Auger nanoprobe spectrometry. While we found that La(OH)3 was the predominant chemical state of the film on electrodes in the absence of HIBA, La2O3 was found for films created in the presence of HIBA. Our finding demonstrates that La(OH)3 can be electrodeposited at room temperature.

Evaluation of three novel benzene-centered tripodal diglycolamide ligands for the pertraction of americium(III) through flat sheet membranes for nuclear waste remediation applications

Three benzene-centered tripodal diglycolamide (Bz-T-DGA) ligands were evaluated for the pertraction of Am3+ across PTFE flat sheet membranes. The feed phase contained a tracer spiked nitric acid solution (3 M), while the receiver phase contained 1 M α-hydroxyisobutyric acid (AHIBA). The transport of Am3+ was quantitative with ligand LI, with ethyl groups appended to the benzene ring at the 1,3,5-positions and two spacer atoms between the ring and the DGA group. Ligand LIII, with a butoxy tether between the ring and the DGA unit, displayed a much better transport efficiency than ligand LII having an ethylamide linkage, although in both cases the transport rates are lower than that of LI. The transport efficiency of the actinide ions was Am3+ > Pu4+ ≫ UO22+ suggesting that Am and Pu can be easily decontaminated from U in a mixture. The membrane stability was reasonably good with LI, while it was poor for the other two ligands.

Design and optimization of a fused-silica microfluidic device for separation of trivalent lanthanides by isotachophoresis.

Elemental analysis of rare earth elements is essential in a variety of fields including environmental monitoring and nuclear safeguards; however, current techniques are often labor intensive, time consuming, and/or costly to perform. The difficulty arises in preparing samples, which requires separating the chemically and physically similar lanthanides. However, by transitioning these separations to the microscale, the speed, cost, and simplicity of sample preparation can be drastically improved. Here, all fourteen non-radioactive lanthanides (lanthanum through lutetium minus promethium) are separated by ITP for the first time in a serpentine fused-silica microchannel (70µm wide×70µm tall×33cm long) in <10min at voltages ≤8kV with limits of detection on the order of picomoles. This time includes the 2min electrokinetic injection time at 2kV to load sample into the microchannel. The final leading electrolyte consisted of 10mM ammonium acetate, 7mM α-hydroxyisobutyric acid, 1% polyvinylpyrrolidone, and the final terminating electrolyte consisted of 10mM acetic acid, 7mM α-hydroxyisobutyric acid, and 1% polyvinylpyrrolidone. Electrophoretic electrodes are embedded in the microchip reservoirs so that voltages can be quickly applied and switched during operation. The limits of detection are quantified using a commercial capacitively coupled contactless conductivity detector (C4 D) to calculate ITP zone lengths in combination with ITP theory. Optimization of experimental procedures and reproducibility based on statistical analysis of subsequent experimental results are addressed. Percent error values in band length and conductivity are ≤8.1 and 0.37%, respectively.

Separation, Analysis and Validation of Metal Ions in Aqueous Samples Using Capillary Electrophoresis

Capillary electrophoresis (CE) has been developed as one of the powerful separation techniques for the analysis of inorganic and organic ions in complex matrices in the recent past. In aqueous samples, most of the inorganic ions are having weak absorption profiles in the UV-Vis region of the spectrum. These low absorption profile ionic species are commonly detected by indirect UV absorbance with the addition of an absorbing co-ion (chromophore) into the electrolyte. The inorganic cations oftenly require an additional complexing agent to selectively alter their similar mobilities and proper separation. The indirect detection at 214 nm was performed with α-hydroxyisobutyric acid (α-HIBA)-4-aminopyridine background electrolyte (BGE) that has a characteristic absorbance at 214 nm. The BGE was applied for the separation, analysis, and validation of metal ions in water samples. The metal ions such as K+, Na+, Ca2+, Mg2+, Mn2+, Fe2+, Cd2+, Pb2+, Ni2+ and Zn2+ were separated successfully in this study. Also, the effect of electrolyte pH, applied voltage and injection time for the separation of cations was investigated.

Reversed-Phase High-Performance Liquid Chromatography for the Determination of 15 Rare Earth Elements in Surface Water Sample Collected in a Mining Area from Lavras do Sul/RS, Brazil

A methodology was developed to assay 15 rare earth elements (REE) (La to Lu and Y) in a surface water sample from a mining area. The samples were collected in the mining area of Lavras do Sul, RS, Brazil. Reversed phase high-performance liquid chromatography employing α-hydroxyisobutyric acid (HIBA), sodium dodecyl sulfate as the ion interaction reagent, and acetonitrile as the organic modifier was used. Analytical detection was performed by spectrophotometry after post-column derivatization with 4-(2-pyridylazo)-resorcinol (PAR). Different chromatographic parameters such as ionic interaction reagent, HIBA concentration, pH, and PAR reagent concentration were studied to achieve the best conditions for the individual separation of REE. The method was validated in terms of the main analytical characteristics (linearity, limits of detection and quantification, precision, interferences, and accuracy). A method for sample cleanup was discussed. Under optimized conditions, it was possible to separate 15 REE (La to Lu and Y) in less than 15 min, with resolution of peaks Y and Dy. The cleanup procedure ensured the selectivity required to determine REE in natural water samples. The accuracy was assessed by regression analysis against measurements by ICP-MS. The calculated quantification limits ranged from 0.07 to 0.48 µg mL−1, for the most sensitive (Dy) to least sensitive (La), respectively.

Mechanism of Ligand-Assisted Electrodeposition of La2O3 on Gold Electrochemical Quartz Crystal Microbalance Electrodes

The rapid preconcentration of lanthanides in aqueous solution is of interest to enable follow-on analysis of nuclear fallout samples. The large negative overpotential of La reduction along with its instability in aqueous solutions has limited electrode-assisted preconcentration efforts to Hg amalgam and carbon paste electrodes. Previous work has shown that lanthanum films can be deposited on the electrochemical quartz crystal microbalance (eQCM). The frequency response of the eQCM tracked the formation of a La film during the cathodic sweep of cyclic voltammograms that resulted in the hydrogen reduction reaction. Recent findings determined that the lanthanum film associated with potentials beyond the cathodic stability limit of water are directly related to the increase in surface pH due to water hydrolysis. Additionally, x-ray photoelectron spectrometry and auger nanoprobe spectrometry results confirm that the films produced in this manner are La(OH)3. The formation of lanthanum film is likely to follow an electroprecipitation mechanism due to the basic environment on the electrode surface during the hydrogen reduction reaction. Surprisingly, the addition of the ligand α-hydroxyisobutyric acid resulted in films of the form La2O3 rather than La(OH)3. The mechanism of ligand-assisted La2O3 formation is being investigated. These findings will aid in miniaturizing the electrochemical preconcentration of lanthanides on microelectrodes.