Tetraphenylborate Ion Research Articles

Tetraphenylborate enhanced enzymatic production of γ-cyclodextrin: System construction and its mechanism

γ-Cyclodextrin (γ-CD) is an attractive material among the natural cyclodextrins owing to its excellent properties. γ-CD is primarily produced from starch by γ-cyclodextrin glycosyltransferase (γ-CGTase) in a controlled system. However, difficulty in separation and low conversion rate leads to high production costs for γ-CD. In this study, γ-CGTase from Bacillus sp. G-825-6 STB17 was used in γ-CD production from cassava starch. With the introduction of sodium tetraphenylborate (NaBPh4), the total conversion rate was promoted from an initial 18.07 % to 50.49 % and the γ-CD ratio reached 78.81 % with a yield of 39.79 g/L. Furthermore, the mechanism was conducted via the determination of binding constant, which indicated that γ-CD exhibited much stronger binding strength with NaBPh4 than β-CD. The reformation of water molecules and the chaotropic effect might be the main driving forces for the interaction. Additionally, the conformations of CD complexes were depicted by NMR and molecular docking. The results further verified different binding patterns between CDs and tetraphenylborate ions, which might be the primary reason for the specific binding. This system not only guides γ-CD production with an efficient and easy-to-remove production aid but also offers a new perspective on the selection of complexing agents in CD production.

Monitoring of the prohibited 2-phenethylamine in dietary supplements using a t-Butyl calix[8]arene/Ag/CuO composite-based potentiometric sensor

2-phenethylamine (PEA) is a prohibited trace amine, that possesses amphetamine-like effect and toxicity. However, it is still present in many weight loss dietary supplements on which the quantities of PEA are not always listed. Therefore, monitoring of this toxic compound in these hypothetically safe products is essential. Herein, PEA was assayed using ion-selective potentiometric membrane sensors. A novel combination of silver doped copper oxide (Ag/CuO) nanoparticles with 4-tert-butylcalix[8]arene (BCX8) was investigated as a new ion-to-electron transducer layer used with solid contact glassy carbon electrodes. To study the effect of this novel combination, three sensors were proposed based on the incorporation of plain sodium tetraphenylborate (TPB) ion exchanger (sensor 1), TPB with BCX8 only (sensor 2) and TPB with Ag/CuO nanoparticles and BCX8 (sensor 3). The doped metal oxide nanoparticles were prepared using a simple wet co-precipitation synthesis procedure and were characterized for particle shape and size, elemental composition, and optical band gap energy. Near Nernstian responses were achieved with slope values of 52.28 ± 0.45, 54.64 ± 0.98 and 55.34 ± 0.35 mV/concentration decade and LOD of 9.88 × 10−5, 7.18 × 10−5, and 9.77 × 10−6 M for sensors 1, 2 and 3; respectively. Sensor 3 showed linearity range 1 × 10−5 to 1 × 10−2 M and response time of 10 s. The Ag/CuO nanoparticles incorporated within BCX8 network provided improved electron transfer kinetics, and was found to provide the best sensitivity, widest linearity range and the most stable and fastest response among the compared sensors. The proposed sensors showed excellent percent recoveries when applied for the analysis of PEA in its multi-ingredient formulation and showed no statistical difference with the reported method.

The Magnesium Dication and Water Synergistically Promote the Protonolysis of Two of the B-C Bonds in the Tetraphenylborate Anion.

Analytes are sampled from both solution phase and gas-phase environments during the ESI process, and thus, the mass spectrum that is measured can reflect both solution and gas-phase conditions. In the gas-phase regime, ion-molecule reactions can influence the types of ions that are observed. Herein, the synergistic effects of a Lewis acid (Mg2+) and background water are shown to lead to protonolysis of two of the B-C bonds of the tetraphenylborate ion in the gas phase, giving rise to different ions at different reaction times in ESI-MS/MS experiments in a linear ion trap mass spectrometer. At short reaction times (1 ms), the expected adduct [Mg(BPh4)]+ is observed. At 10 ms, [(HO)Mg(BPh3)]+ and [(HO)2Mg(BPh2)]+ are observed. At 100 ms, the water adducts [(HO)2Mg(BPh2)(H2O)]+ and [(HO)2Mg(BPh2)(H2O)2]+ appear, and these become the dominant ions at longer reaction times. DFT calculations provide a plausible explanation as to why only [(HO)Mg(BPh3)]+ and [(HO)2Mg(BPh2)]+ but not [(HO)3Mg(BPh)]+ are observed.

Charge transfer across the ionic liquid/oil interface: Facilitated ion transfer and electron transfer

Facilitated ion transfer (FIT) and electron transfer (ET) across the ionic liquid (IL)/oil (O) interface between ethylamine nitrate (EAN) and 1,4-dichlorobutane (DCB) have been electrochemically studied. Cyclic voltammograms (CVs) for the FIT of Li+ cation in IL by dicyclohexano-18-crown-6 (DCH18C6) across the IL/O interface formed at a micropipette tip show that the onset of the FIT current is significantly shifted due to the facilitation beyond the potential window limit and that the current is proportional to the concentration of DCH18C6 in O limited by the diffusion of DCH18C6 inside the micropipette. CVs for the ET from supporting electrolyte anions in O to NO3−, the IL anion of EAN, across the IL/O interface studied using a closed-bipolar cell show that NO3− in EAN has an ability to oxidize tetraphenylborate ions in O but not tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ions, the latter of which have more oxidation resistance.

Development of a potentiometric sensor for the determination of carbamazepine and its application in pharmaceutical formulations

AbstractBACKGROUNDEpilepsy is a neurological disorder and its treatment is carried out with anti–epileptic drugs. Carbamazepine has been in use since 1965, as a safe and effective anti–epileptic agent. In this paper, a poly(vinyl chloride) (PVC) membrane carbamazepine selective potentiometric sensor was developed for the determination of carbamazepine in pharmaceutical formulations. Carbamazepine–tetraphenylborate (CBZ–TPB) ion−pair was synthesized as an electroactive component and PVC membrane sensors were prepared with different CBZ–TPB ratios. The membrane with the best analytical properties was determined as the one with 2.0% CBZ–TPB ion–pair, 33.0% PVC and 65.0% o–nitrophenyl octyl ether (o–NPOE).RESULTSThe proposed sensor exhibited linear responses over the concentration range 1.0 × 10−5 – 1.0 × 10−2 mol L−1 (R2 = 0.999). The limit of detection was 9.60 × 10−6 mol L−1. The developed sensor showed high selectivity against carbamazepine over some ionic species investigated and also over other anti–epileptic drugs. The potentiometric response of the sensor was not affected by pH in the wide pH range of 4.0–9.0 and the response was fast, at ≈10s.CONCLUSIONThe fabricated carbamazepine–selective sensor was applied for the determination of carbamazepine contents of some pharmaceutical formulations. The potentiometric measurement results for the pharmaceutical formulations gave results with good agreement with data obtained using UV–visible spectroscopy. As a result, the developed carbamazepine selective potentiometric sensor can be considered as an alternative to other analytical methods for the determination of carbamazepine in pharmaceutical samples. © 2022 Society of Chemical Industry (SCI).

Effect of Tetraphenylborate on Physicochemical Properties of Bovine Serum Albumin.

The binding interactions of bovine serum albumin (BSA) with tetraphenylborate ions ([B(Ph)4]−) have been investigated by a set of experimental methods (isothermal titration calorimetry, steady-state fluorescence spectroscopy, differential scanning calorimetry and circular dichroism spectroscopy) and molecular dynamics-based computational approaches. Two sets of structurally distinctive binding sites in BSA were found under the experimental conditions (10 mM cacodylate buffer, pH 7, 298.15 K). The obtained results, supported by the competitive interactions experiments of SDS with [B(Ph)4]− for BSA, enabled us to find the potential binding sites in BSA. The first site is located in the subdomain I A of the protein and binds two [B(Ph)4]− ions (logK(ITC)1 = 7.09 ± 0.10; ΔG(ITC)1 = −9.67 ± 0.14 kcal mol−1; ΔH(ITC)1 = −3.14 ± 0.12 kcal mol−1; TΔS(ITC)1 = −6.53 kcal mol−1), whereas the second site is localized in the subdomain III A and binds five ions (logK(ITC)2 = 5.39 ± 0.06; ΔG(ITC)2 = −7.35 ± 0.09 kcal mol−1; ΔH(ITC)2 = 4.00 ± 0.14 kcal mol−1; TΔS(ITC)2 = 11.3 kcal mol−1). The formation of the {[B(Ph)4]−}–BSA complex results in an increase in the thermal stability of the alfa-helical content, correlating with the saturation of the particular BSA binding sites, thus hindering its thermal unfolding.

Ion-Transfer Voltammetry at Fluorous Ether | Water Interfaces.

This paper describes that fluorous ethers, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, can be used for a non-aqueous medium in electrochemistry at a liquid | liquid interface. These solvents dissolved a high concentration of tetraalkylammonium salts with highly-fluorinated anions, such as bis(nonafluorobutanesulfonyl)imide and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate ions, and the solution had a high conductivity. The fluorous ether | water interfaces exhibited a substantial polarizable potential window, and various ions, including tetraphenylarsonium and tetraphenylborate ions, gave a reversible voltammetric wave due to their ion transfer across the interfaces. Using the tetraphenylarsonium-tetraphenylborate assumption, the formal potentials for the ion transfer and the formal Gibbs energies of ion transfer from the ethers to water were estimated. The Gibbs energies were close to those from a previously reported fluorous solvent, 1,1,1,2,3,4,4,5,5,5-decafluoropentane; the fluorous ethers also exhibited a higher affinity for fluorinated ions. Because of a lower volatility, the fluorous ethers would be more advantageously used in two-phase electrochemistry, particularly concerning analytical purposes.

A validated potentiometric method for determination of alfuzosin hydrochloride in pharmaceutical and biological fluid samples

Recently, graphene nanosheet has attracted the most attention for the potential applications in various electrochemical sensing fields to biomedical diagnosis and therapy due to its large theoretical specific surface area, unique physical and electrical properties. In this paper, a newly sensitive and selective modified carbon paste electrodes (MCPEs) were developed for the determination of alfuzosin hydrochloride (ALF.HCl) in pharmaceutical preparation and biological fluid samples. The paste of these sensors was prepared by mixing alfuzosin phosphomolybdate (ALF-PMA) and alfuzosin tetraphenylborate (ALF-TPB) ion pairs as recognition reagents with different supporting matrices including graphite powder alone or different ratios of graphite to graphene powders and plasticizer of a relatively high dielectric constant. The sensor prepared based on graphite alone as a supporting matrix gave Nernstian slope values of 56.7 ± 0.75 and 51.1 ± 1.11 mV decade−1 for electrode modified with ALF-PMA and ALF-TPB ion pairs, respectively, in the concentration range from 1.0 × 10−5 to 1.0 × 10−2 mol L−1 at 25 °C, and the response of the electrode was found to be independent on pH in the range of 2.0–5.0. The Nernstian slope for ALF-TPB modified carbon paste electrode was improved to be 55.8 ± 1.07 mV decade−1 upon mixing graphene with graphite in the paste and showed pH independence in the range of 2.0–6.0. The proposed sensors were successfully applied for the determination of ALF.HCl in pure, biological fluid samples and pharmaceutical preparation using the direct potentiometric and standard addition methods. Finally, the results obtained using the proposed sensors were compared with those from the official method.

Ion-Solvation and Ion-Association Behavior of Tetraphenylphosphonium Chloride, Sodium Tetraphenylborate and Sodium Chloride in Polyethylene Glycol + Water Mixtures at 298.15 K

Electrical conductances of solutions of tetraphenylphosphonium chloride, sodium tetraphenylborate, and sodium chloride in polyethylene glycol (PEG) + water mixed solvent systems having 0.200, 0.400, and 0.600 mass fractions of PEG are reported at 298.15 K. In this study three different average molar masses of PEG, e.g., 300 (designated as PEG 300), 400 (designated as PEG 400), and 600 (designated as PEG 600) g·mol−1 were employed. The conductance data have been analyzed using the 1978 Fuoss conductance–concentration equation in terms of the limiting molar conductance, the association constant and the association diameter of the electrolytes. The ionic contributions to the limiting molar conductances have been estimated using tetraphenylphosphonium tetraphenylborate as the “reference electrolyte”, considering the similarity of the sizes and chemical characters of the tetraphenylphosphonium and tetraphenylborate ions possessing a quasi-spherical surface of the phenyl rings. Analyses of the results provided important information as to the ion-association and solvation behavior of the electrolytes/ions investigated in PEG + water mixed solvent media.

Communication: Inside the water wheel: Intrinsic differences between hydrated tetraphenylphosphonium and tetraphenylborate ions.

Tetraphenylphosphonium tetraphenylborate (TPTB) is a common reference electrolyte in physical chemistry of solutions allowing for a convenient partitioning of thermodynamic properties into single-ion contributions. Here, we compute on the basis of ab initio molecular dynamics simulations the infrared (IR) spectra for hydrated constituent ions of the TPTB assumption. Using spectral decomposition techniques, we extract important information pertaining to the state of the hydration water from the IR spectra. Within their physical radii, the ions manage to capture about a dozen H2O molecules, several of which penetrate deep into the grooves between the tetrahedrally oriented "sails" of the rotating ions. In accordance with previous IR and Raman experiments, we find a considerable blue shift of the ν OH stretching band of liquid water by 240 cm-1 for TB, due to the extensive O-H⋯π hydrogen bonding, which is much weaker for TP. On the other hand, both ions show a second prominent band in the ν OH vibration range, only mildly blue shifted with respect to bulk water and attributable to the general distortion of the hydrogen bond network of the neighboring solvent. Finally, spatially resolved IR spectra allow us to pinpoint the exact location around the solutes, from which different IR resonances of the solvent originate.

Electrogenerated chemiluminescence at a 9,10-diphenylanthracene/polyvinyl butyral film modified electrode with a tetraphenylborate coreactant.

A new, efficient electrochemiluminescent (ECL) system based on a 9,10-diphenylanthracene/polyvinyl butyral film modified glassy carbon electrode and a tetraphenylborate anion coreactant is described. The system demonstrates strong dependence of its response on the potential scan rate. In pulsed excitation mode, the system allows for tetraphenylborate detection at a level down to 5 nM with a broad range of linear responses. The anodic cyclic voltammetry response of the system shows 2 distinct ECL waves. It was found that the first of them is due to the reaction of an oxidized fluorophore with tetraphenylborate while the second one is due to the oxidation of tetraphenylborate only. The presented results demonstrate the high potential of the tetraphenylborate coreactant for exciting pulsed ECL in fluorescent species/labels immobilized on the electrode surface, which has application potential for a number of existing ECL assay systems. Due to the ability of tetraphenylborate ions to interact with a number of cations and inorganic oxidants, the developed ECL system can also be applied for quantification based on ECL quenching that was demonstrated on the examples of hydrogen peroxide and hypochlorite.

Disposable gold nanoparticle functionalized and bare screen-printed electrodes for potentiometric determination of trazodone hydrochloride in pure form and pharmaceutical preparations.

In the present study, screen-printed electrodes unmodified and chemically modified with gold nanoparticles were used as sensitive electrochemical sensors for the determination of trazodone hydrochloride. The sensors were based on the use of a tetraphenylborate ion association complex as an electroactive material in screen-printed electrodes with dioctyl phthalate (DOP) as a solvent mediator modified with gold nanoparticles which improve the electrode conductivity and enhance the surface area. The sensors displayed a stable response for 5, 6 and 7 months with a reproducible potential and linear response over the concentration range 1 × 10−5–1 × 10−2 mol L−1 at 25 ± 1 °C with Nernstian slopes of 57.50 ± 0.66, 58.30 ± 0.45 and 59.05 ± 0.58 mV per decade and detection limits of 7.9 × 10−6, 7.6 × 10−6 and 6.8 × 10−6 mol L−1 for sensor 1, 2 and 3 respectively. The analytical performance of the screen printed electrodes in terms of selectivity coefficients for trazodone hydrochloride relative to the number of potentially interfering substances was investigated. The proposed method has been applied successfully for the analysis of the drug in its pure and dosage forms and there is no interference from any common pharmaceutical additives.

Solvation state of sodium tetraphenylborate in 3-methylpyridine and its aqueous solutions

The solvation states of the sodium ion (Na+) and the tetraphenylborate ion (BPh4−) in 3-methylpyridine (3MP) and its mixture with deuterium oxide (D2O) were investigated by Raman spectroscopy and DFT calculations. Raman spectra observed for the 3MP solutions systematically varied with increase in the amount of NaBPh4; the Raman band at 633cm−1 weakened and that at 639cm−1 strengthened with increase in the salt concentration. According to DFT calculations, the former was assigned to the 3MP molecule in the bulk and the latter to that bound to the Na+ ion. The number of 3MP molecules bound to Na+, n, was estimated to be 6.1, that is, a [Na(3MP)6]+ complex was formed in the 3MP/NaBPh4 solution. On the other hand, n was estimated to be 1.6 in the D2O/3MP/NaBPh4 mixtures with χ3MP=0.50, where χ3MP denotes the mole fraction of 3MP in the D2O/3MP mixtures. Furthermore, both integrated intensities at 633cm−1 (free 3MP) and 640cm−1 (hydrated 3MP by D2O) were almost independent of the salt concentration in the case of D2O/3MP mixtures with χ3MP=0.09. Additionally, the position of the other Raman bands at 609, 616, 626, and 672cm−1, arising from BPh4−, were almost independent of χ3MP between 1 and 0.09. These results suggest that Na+ is preferentially solvated with D2O, whereas BPh4− is preferentially solvated with 3MP in such mixtures.

Efficient Catalytic Electrode for CO2 Reduction Realized by Physisorbing Ni(cyclam) Molecules with Hydrophobicity Based on Hansen's Theory.

An electrochemical electrode physisorbed with Ni(cyclam) complex molecules containing tetraphenylborate ions (BPh4(-)) as counteranions shows catalytic activity for the reduction reaction of CO2 to CO in an aqueous electrolyte, superior to that of an electrode physisorbed with conventional [Ni(cyclam)]Cl2 complex molecules. The BPh4(-)-containing Ni(cyclam) is inferred as having high hydrophobicity based on its Hansen solubility parameter (HSP), with an interaction sphere excluding HSPs of water in a three-dimensional vector space. The high hydrophobicity of BPh4(-)-containing Ni(cyclam) molecules inhibits their dissolution into aqueous electrolyte and retains their immobilization onto the electrode surface, which we believe to result in the improved catalytic activity of the electrode physisorbed with them. HSP analysis also provides an optimized mixing ratio of solvents dissolving BPh4(-)-containing Ni(cyclam) molecules.

N,N,N′,N′,N′′-Pentamethyl-N′′-[2-(trimethylazaniumyl)ethyl]guanidinium bis(tetraphenylborate) acetone monosolvate

The asymmetric unit of the title solvated salt, C11H28N42+·2C24H20B−·C3H6O, comprises two cations, four tetraphenylborate anions and two acetone molecules. One cation shows an orientational disorder at the CN3moiety and two sets of N-atom positions were found related by a 60° rotation, with a refined occupancy ratio of 0.935 (1):0.065 (1). The respective nitrogen-bonded –CH2and –CH3groups are included in the disorder model. The C—N bond lengths in the central CN3units of both guanidinium ions range between 1.3329 (17) and 1.364 (16) Å, indicating a degree of double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and one positive charge is delocalized in the CN3plane. The C—N bond lengths in the terminal trimethylammonium groups have values close to a typical single bond, and the second positive charge is localized there. In the crystal, the guanidinium ions are connected by C—H...O hydrogen bonds with the acetone molecules. C—H...π interactions are present between the guanidinium and acetone hydrogen atoms and the phenyl rings of the tetraphenylborate ions, leading to the formation of a two-dimensional supramolecular pattern along thebcplane.

N,N,N′,N′-Tetramethyl-N′′-[2-(trimethylazaniumyl)ethyl]guanidinium bis(tetraphenylborate) acetone disolvate

The asymmetric unit of the title solvated salt, C10H26N42+·2C24H20B−·2C3H6O, comprises one cation, two tetraphenylborate ions and two acetone solvent molecules. The N and methyl C atoms of the terminal trimethylammonium group are disordered over two sets of sites, with a refined occupancy ratio of 0.846 (3):0.154 (3). The C—N bond lengths in the central C3N unit of the guanidinium ion range between 1.3308 (16) and 1.3508 (16) Å, indicating a degree of double-bond character. The central C atom is bonded to the three N atoms in a nearly ideal trigonal–planar geometry and the positive charge is delocalized in the CN3plane. The C—N bond lengths in the terminal trimethylammonium group have values close to that of a typical single bond, and the second positive charge is localized there. In the crystal, the guanidinium ion is connected by N—H...O and C—H...O hydrogen bonds with the acetone molecules. C—H...π interactions are present between the guanidinium H atoms and the phenyl rings of the tetraphenylborate ions, leading to the formation of a two-dimensional supramolecular pattern along thebcplane.

N,N,N′,N′,N′′,N′′,N′′′,N′′′-Octamethyl(but-2-yne)bisamidinium bis(tetraphenylborate)

The asymmetric unit of the title salt, C12H24N42+.2C24H20B−, comprises half a cation and one tetraphenylborate ion. An inversion centre is situated at the mid-point of the triple C[triple-bond]C bond in the cation. The bisamidinium C—N bonds [1.3249 (11) and 1.3267 (11) Å] have double-bond character and both positive charges are delocalized between the dimethylamino groups. The bonds between the N atoms and the terminal C-methyl groups all have values characteristic for a typical single bond [1.4656 (12)–1.4687 (12) Å]. The acetylenic bond length [1.1889 (18) Å] is consistent with a triple C[triple-bond]C bond and the butyne carbon chain is almost linear. C—H...π interactions between the bisamidinium methyl H atoms and the phenyl C atoms of the tetraphenylborate ions are present. The phenyl rings form aromatic pockets, in which the cations are embedded. This leads to the formation of a two-dimensional supramolecular pattern in theabplane.

2-Dimethylamino-1-(2-ethoxy-2-oxoethyl)-3-methyl-4,5-dihydroimidazolium tetraphenylborate

In the crystal structure of the title salt, C10H20N3O2+·C24H20B−, the C—N bond lengths in the cation are 1.327 (3), 1.339 (3) and 1.342 (3) Å, indicating partial double-bond character. The central C atom is bonded to the three N atoms, indicating only a slight deviation from a trigonal–planar geometry. The positive charge is delocalized in the CN3plane. The ethoxy group is disordered over two orientations, with an occupancy ratio of 0.60 (1):0.40 (1). C—H...π interactions are present between the guanidinium H atoms and the phenyl C atoms of the tetraphenylborate ions. The phenyl rings form aromatic pockets, in which the cations are embedded. This leads to the formation of a two-dimensional supramolecular pattern along theacplane.

Crystal structure of N-[3-(di-methyl-amino)-prop-yl]-N',N',N'',N''-tetra-methyl-N-(N,N,N',N'-tetra-methyl-form-amid-in-ium-yl)guanidinium bis-(tetra-phenyl-borate).

In the title salt, C15H36N6 2+·2C24H20B−, the three N—C bond lengths in the central C3N unit of the bis­amidinium ion range between 1.388 (3) and 1.506 (3) Å, indicating single- and double-bond character. Furthermore, four C—N bonds have double-bond character. Here, the bond lengths range from 1.319 (3) to 1.333 (3) Å. Delocalization of the positive charges occurs in the N/C/N and C/N/C planes. The dihedral angle between both N/C/N planes is 70.5 (2)°. In the crystal, C—H⋯π inter­actions between H atoms of the cation and the benzene rings of both tetra­phenyl­borate ions are present. The benzene rings form aromatic pockets, in which the bis­amidinium ion is embedded. This leads to the formation of a two-dimensional supra­molecular pattern along the ab plane.

Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples

In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values.