LC-MS<Superscript><Emphasis Type="BoldItalic">n</Emphasis></Superscript> Analysis of Isomeric Chondroitin Sulfate Oligosaccharides Using a Chemical Derivatization Strategy

Improved methods for structural analyses of glycosaminoglycans (GAGs) are required to understand their functional roles in various biological processes. Major challenges in structural characterization of complex GAG oligosaccharides using liquid chromatography-mass spectrometry (LC-MS) include the accurate determination of the patterns of sulfation due to gas-phase losses of the sulfate groups upon collisional activation and inefficient on-line separation of positional sulfation isomers prior to MS/MS analyses. Here, a sequential chemical derivatization procedure including permethylation, desulfation, and acetylation was demonstrated to enable both on-line LC separation of isomeric mixtures of chondroitin sulfate (CS) oligosaccharides and accurate determination of sites of sulfation by MS ⁿ . The derivatized oligosaccharides have sulfate groups replaced with acetyl groups, which are sufficiently stable to survive MS ⁿ fragmentation and reflect the original sulfation patterns. A standard reversed-phase LC-MS system with a capillary C18 column was used for separation, and MS ⁿ experiments using collision-induced dissociation (CID) were performed. Our results indicate that the combination of this derivatization strategy and MS ⁿ methodology enables accurate identification of the sulfation isomers of CS hexasaccharides with either saturated or unsaturated nonreducing ends. Moreover, derivatized CS hexasaccharide isomer mixtures become separable by LC-MS method due to different positions of acetyl modifications.     

Quantitative MALDI-MS<Superscript><Emphasis Type="Italic">n</Emphasis></Superscript> analysis of cocaine in the autopsied brain of a human cocaine user employing a wide isolation window and internal standards

Detection of drugs in tissue typically requires extensive sample preparation in which the tissue is first homogenized, followed by drug extraction, before the extracts are finally analyzed by LC/MS. Directly analyzing drugs in intact tissue would eliminate any complications introduced by sample pretreatment. A matrix-assisted laser desorption/ionization tandem mass spectrometry (MALDI-MS ⁿ ) method as been developed for the quantification of cocaine present in postmortem brain tissue of a chronic human cocaine user. It is shown that tandem mass spectrometry (MS² and MS³) increase selectivity, which is critical for differentiating analyte ions from background ions such as matrix clusters and endogenous compounds found in brain tissue. It is also shown that the use of internal standards corrects for signal variability during quantitative MALDI, which can be caused by inhomogeneous crystal formation, inconsistent sample preparation, and laser shot-to-shot variability. The MALDI-MS ⁿ method developed allows for a single MS³ experiment that uses a wide isolation window to isolate both analyte and internal standard target ions. This method is shown to provide improved precision [∼10–20 times reduction in percent relative standard deviation (%RSD)] for quantitative analysis compared to using two alternating MS³ experiments that separately isolate the target analyte and internal standard ions.     

Scalar-relativistic 5f-in-core pseudopotentials and core-polarization potentials for trivalent actinides: calibration calculations for Ac<Superscript>3+</Superscript>, Cm<Superscript>3+</Superscript> and Lr<Superscript>3+</Superscript> complexes

The performance of recently proposed 5f-in-core pseudopotentials for the trivalent actinides was investigated in calculations for model complexes An³⁺L ⁿ⁻ for three selected actinides (An³⁺ = Ac³⁺, Cm³⁺, Lr³⁺) and eight simple ligands with atoms from the first three periods of the table of elements (L ⁿ⁻ = F⁻, Cl⁻, OH⁻, SH⁻, CO, NH₂⁻, H₂O, H₂S, NH₃). Results of Hartree-Fock and Coupled Cluster with singles, doubles and perturbative triples calculations using basis sets of quadruple-zeta quality are compared to corresponding reference data obtained with scalar-relativistic energy-adjusted 5f-in-valence small-core pseudopotentials. The inclusion of core-polarization potentials in the 5f-in-core pseudopotential calculations and corrections of the basis set superposition error by the counterpoise correction leads to very good agreement between the 5f-in-valence and 5f-in-core pseudopotential results for bond lengths, bond angles and binding energies. Results from 5f-in-core pseudopotential calculations using different density functionals also show reasonable agreement with the more rigorous Coupled Cluster results. It is argued that the An 5f rather than the An f population is a useful criterion for the applicability of a specific An 5f-in-core pseudopotential.     

Production of <Superscript>122</Superscript>Sb for the study of environmental pollution

This article presents, ¹²²Sb (T _1/2 = 2.723 days, I _β- = 97.59%) was produced via the ^natSn(p,xn) nuclear process at the AMIRS (Cyclone-30, IBA, Belgium). The electrodeposition experiments were carried out by potassium stannate trihydrate (K₂Sn(OH)₆) and potassium hydroxide. The optimum conditions of the electrodeposition of tin were as follows: 40 g/L ^natSn, 20 g/L KOH, 115 g/L K₂Sn(OH)₆, DC current density of 5 A/dm² with a bath temperature of 75 °C. The electroplated Tin-target was irradiated with 26.5 MeV protons at current of 180 μA for 20 min. Solvent extraction of no-carrier-added ¹²²Sb from irradiated Tin-natural target hydrochloric solution was investigated using di-n-butyl ether (C₈H₁₈O). Yields of about 3.61 MBq/μAh were experimentally obtained.     

Development of <Superscript>177</Superscript>Lu-DOTA-anti-CD20 for radioimmunotherapy

Rituximab was successively labeled with ¹⁷⁷Lu-lutetium chloride. ¹⁷⁷Lu chloride was obtained by thermal neutron flux (4 × 10¹³ n cm⁻² s⁻¹) of natural Lu₂O₃ sample with a specific activity of 2.6–3 GBq/mg. The macrocyclic bifunctional chelating agent, N-succinimidyl-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA-NHS) was prepared at 25 °C using DOTA, N-hydroxy succinimide (NHS) in CH₂Cl₂. DOTA-rituximab was obtained by the addition of 1 mL of a rituximab pharmaceutical solution (5 mg/mL, in phosphate buffer, pH 7.8) to a glass tube pre-coated with DOTA-NHS (0.01–0.1 mg) at 25 °C with continuous mild stirring for 15 h. Radiolabeling was performed at 37 °C in 24 h. Radio-thin layer chromatography showed an overall radiochemical purity of >98% at optimized conditions (specific activity = 444 MBq/mg, labeling efficacy; 82%). The final isotonic ¹⁷⁷Lu-DOTA-rituximab complex was checked by gel electrophoresis for structure integrity control. Radio-TLC was performed to ensure that only one species was present after filtration through a 0.22 μm filter. Preliminary biodistribution studies in normal rats were carried out to determine complex distribution of the radioimmunoconjugate up to 168 h. The biodistribution data were in accordance with other antiCD20 radioimmunoconjugates already reported.     

Determination of jasmonic acid in <Emphasis Type="Italic">Lemna minor</Emphasis> (L.) by liquid chromatography with fluorescence detection

A new method is described for the determination of endogenous jasmonic acid (JA) in Lemna minor plant extracts using liquid chromatography (LC) with fluorescence detection. Plant tissues were extracted and derivatised using 9-anthryldiazomethane (ADAM reagent) prepared in situ. Accuracy and precision were improved by using the internal standard dihydrojasmonic acid (dh-JA) for the correction of JA losses during sample preparation steps. Liquid chromatography–mass spectrometry (LC/MS) analysis of ADAM derivatives of JA and dh-JA confirmed that a single molecule of JA and dh-JA was coupled with one molecule of reagent. Derivatives of JA and dh-JA were separated with gradient elution on a C₁₈ reversed-phase column using acetonitrile/water as a mobile phase and detected by a fluorescence detector at excitation and emission wavelengths of 254 and 412 nm, respectively. The detection limits of JA and dh-JA were 2.9 ng mL⁻¹ and 3.7 ng mL⁻¹ per 50-μL injection. The method is reproducible and selective and yields single peaks for each compound regardless of isomer. The specificity and accuracy of the proposed LC/FD method was confirmed by liquid chromatography–TurboIon Spray tandem mass spectrometric (LC/MS/MS) analysis of free JA in Lemna minor samples under multiple reaction monitoring conditions.     

Determination of <Superscript>151</Superscript>Sm and <Superscript>147</Superscript>Pm using liquid scintillation tracer methods

The long-lived rare earth isotopes ¹⁵¹Sm (90 years, β _max = 76.3 keV) and ¹⁴⁷Pm (2.62 years, β _max = 224.6 keV) are low-yield fission products that generally require lengthy separation procedures to isolate and count by their beta emissions. We will describe novel liquid scintillation counting techniques using radioactive tracers to determine radiochemical yields from an environmental matrix. The recovery of ¹⁵¹Sm is determined from the alpha decay (2.25 MeV) of ¹⁴⁷Sm in the natural Sm carrier and is in excellent agreement with the gravimetric recovery. The ¹⁴⁷Pm recovery is determined by the use of ¹⁴⁵Pm (17.7 years, EC) tracer, custom-produced at LANL using an isotopically enriched target of ¹⁴⁴Sm. We have determined the ¹⁴⁵Pm recovery both from the 37.4 keV k_α1 X-ray, and the electron-capture emissions by LSC. A comparison of these recovery methods is presented.     

Photochemical substitution of benzene in the iron cyclohexadienyl complex [(η<Superscript>5</Superscript>-C<Subscript>6</Subscript>H<Subscript>7</Subscript>)Fe(η-C<Subscript>6</Subscript>H<Subscript>6</Subscript>)]<Superscript>+</Superscript>

The visible light irradiation of the [(η⁵-C₆H₇)Fe(η-C₆H₆)]⁺ cation (1) in acetonitrile resulted in the substitution of the benzene ligand to form the labile acetonitrile species [(η⁵-C₆H₇)Fe(MeCN)₃]⁺ (2). The reaction of 1 with Bu^tNC in MeCN produced the stable isonitrile complex [(η⁵-C₆H₇)Fe(Bu^tNC)₃]⁺ (3). The photochemical reaction of cation 1 with pentaphosphaferrocene Cp*Fe(η-cyclo-P₅) afforded the triple-decker cation with the bridging pentaphospholyl ligand, [(η⁵-C₆H₇)Fe(μ-η:η-cyclo-P₅)FeCp*]⁺ (4). The latter complex was also synthesized by the reaction of cation 2 with Cp*Fe(η-cyclo-P₅). The structure of the complex [3]PF₆ was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 2007.     

Synthesis of <Emphasis Type="Italic">N</Emphasis><Superscript>2</Superscript>-Arylisocytidines and <Emphasis Type="Italic">N</Emphasis><Superscript>2</Superscript>-Aryl-2′-deoxyisocytidines

Summary. 2-(Arylamino)pyrimidin-4-ones were synthesized, silylated, and condensed with l,2,3,5-tetra-O-acetyl-β- d-ribofuranoside to afford the corresponding N ²-aryl protected isocytidines. Deprotection of the acetylated isocytidines using saturated NH₃ in MeOH solution gave 1-(β-d-ribofuranosyl)-2-(arylamino)-4-pyrimidinones. Methyl 2-deoxy-3,5-di-O-toluyl-α/β-d-ribofuranoside was prepared and condensed with the previously silylated bases to afford the anomeric mixture of protected nucleosides. The pure β-anomers were synthesized with better yield by treating the sodium salts of N ²-arylisocytosine derivatives with 2-deoxy-3,5-di-O-toluyl-α-d-ribofuranosyl chloride. Deprotection of the latter anomers afforded the corresponding free hydroxyl derivatives. The synthesized free nucleosides are under antiviral and oligonucleotide investigations.     

Data-dependent neutral gain MS<Superscript>3</Superscript>: Toward automated identification of the N-Oxide functional group in drug metabolites

We report here an automated method for the identification of N-oxide functional groups in drug metabolites by using the combination of liquid chromatography/tandem mass spectrometry (LC/MS ⁿ ) based on ion-molecule reactions and collision-activated dissociation (CAD). Data-dependent acquisition, which has been readily utilized for metabolite characterization using CAD-based methods, is adapted for use with ion-molecule reaction-based tandem mass spectrometry by careful choice of select experimental parameters. Two different experiments utilizing ion-molecule reactions are demonstrated, data-dependent neutral gain MS³ and data-dependent neutral gain pseudo-MS³, both of which generate functional group selective mass spectral data in a single experiment and facilitate increased throughput in structural elucidation of unknown mixture components. Initial results have been generated by using an LC/MS ⁿ method based on ion-molecule reactions developed earlier for the identification of the N-oxide functional group in pharmaceutical samples, a notoriously difficult functional group to identify via CAD alone. Since commercial software and straightforward, external instrument modification are used, these experiments are readily adaptable to the industrial pharmaceutical laboratory.     

Determination of HEPES in <Superscript>68</Superscript>Ga-labeled peptide solutions

A practical and reliable HPLC method was used for the determination of 2-[4-N-(2-hydroxyethyl)-1-piperazinyl]-N′-ethanesulfonic acid (HEPES) content in the ⁶⁸Ga-labeled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-Nal3-octreotide (DOTANOC). Linearity of this method was observed in a concentration range of 0.01–10 mg mL⁻¹ and the quantitative limit (signal to noise = 11) was determined as 10 μg mL⁻¹. The HEPES concentration in the final products of ⁶⁸Ga-DOTANOC was typically lower than the detection limit. Pure water and HEPES buffer as reaction medium were investigated using various activities of gallium-68. It was demonstrated that the presence of HEPES buffer consistently furnished very high radiochemical purity of ⁶⁸Ga-DOTANOC, which remained stable for several hours post-labeling. Evidence is provided that in addition to its role as a buffer, HEPES also functions as a radioprotectant agent.     

An Isotope (<Superscript>18</Superscript>O, <Superscript>15</Superscript>N,and <Superscript>2</Superscript>H) Technique to Investigate the Metal Ion Interactions Between the Phosphoryl Group and Amino Acid Side Chains by Electrospray Ionization Mass Spectrometry

Cationic metal ion-coordinated N-diisopropyloxyphosphoryl dipeptides (DIPP-dipeptides) were analyzed by electrospray ionization multistage tandem mass spectrometry (ESI-MS ⁿ ). Two novel rearrangement reactions with hydroxyl oxygen or carbonyl oxygen migrations were observed in ESI-MS/MS of the metallic adducts of DIPP-dipeptides, but not for the corresponding protonated DIPP-dipeptides. The possible oxygen migration mechanisms were elucidated through a combination of MS/MS experiments, isotope (¹⁸O, ¹⁵N, and ²H) labeling, accurate mass measurements, and density functional theory (DFT) calculations at the B3LYP/6-31 G(d) level. It was found that lithium and sodium cations catalyze the carbonyl oxygen migration more efficiently than does potassium and participation through a cyclic phosphoryl intermediate. In addition, dipeptides having a C-terminal hydroxyl or aromatic amino acid residue show a more favorable rearrangement through carbonyl oxygen migration, which may be due to metal cation stabilization by the donation of lone pair of the hydroxyl oxygen or aromatic π-electrons of the C-terminal amino acid residue, respectively. It was further shown that the metal ions, namely lithium, sodium, and potassium cations, could play a novel directing role for the migration of hydroxyl or carbonyl oxygen in the gas phase. This discovery suggests that interactions between phosphorylated biomolecules and proteins might involve the assistance of metal ions to coordinate the phosphoryl oxygen and protein side chains to achieve molecular recognition.     

Cyclotron production of <Superscript>169</Superscript>Yb: a potential radiolanthanide for brachytherapy

In the present study, ytterbium-169 was produced via the ¹⁶⁹Tm(p, n)¹⁶⁹Yb nuclear process at the AMIRS (Cyclone-30, IBA, Belgium) cyclotron, irradiating Tm₂O₃ with proton particles of 15 MeV primary energy and 20 μA current for 20 min. Deposition of Tm₂O₃ on Cu substrate was carried out via by the sedimentation method. The 543 mg of thulium(III)oxide with 108 mg of ethyl cellulose and 8 mL of acetone were used to prepare a Tm₂O₃ layer of 11.69 cm². Yields of about 0.643 MBq ¹⁶⁹Yb per μAh were experimentally obtained. ¹⁶⁹Yb was separated in 80 ± 5% radiochemical yield using liquid–liquid extraction. Solvent extraction of no-carrier-added ¹⁶⁹Yb from irradiated thulium(III)oxide target hydrochloric solution was investigated using di-(2-ethylhexyl)phosphoric acid (HDEHP).     

The use of acetone as a substitute for acetonitrile in analysis of peptides by liquid chromatography/electrospray ionization mass spectrometry

The recent worldwide shortage of acetonitrile has prompted interest in alternative solvents for liquid chromatography/mass spectrometry (LC/MS). In this work, acetone was substituted for acetonitrile in the separation of a peptide mixture by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and in the positive electrospray ionization mass spectrometry (ESI‐MS) of individual peptides. On both C12 and C18 stationary phases, the substitution of acetone for acetonitrile as the organic component of the mobile phase did not alter the gradient elution order of a five‐peptide retention standard, but did increase peak width, shorten retention times, and increase peak tailing. Positive ESI mass spectra were obtained for angiotensin I, bradykinin, [Leu⁵]‐enkephalin, and somatostatin 14 dissolved in both acetonitrile/water/formic acid (25%/75%/0.1%) and acetone/water/formic acid (25%/75%/0.1%). Under optimized ESI‐MS conditions, the mass spectral response of [Leu⁵]‐enkephalin was increased two‐fold when the solvent contained acetone. The substitution of acetone for acetonitrile resulted in only slight changes in the responses of the remaining peptides. A higher capillary voltage was required for optimum response when acetone was used. Compared with acetonitrile/water/formic acid (50/50/0.1%), more interfering species below m/z = 140 were found in the ESI‐MS spectra of acetone/water/formic acid (50/50/0.1%). Copyright © 2009 John Wiley & Sons, Ltd.     

Comparative study of Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, and I<Superscript>−</Superscript> ion adsorption from N-methylformamide at Ga-, (In-Ga)-, and (Tl-Ga)-electrodes

Adsorption of Cl⁻, Br⁻, and I⁻ (Hal⁻) ions from their 0.1 M solutions in N-methylformamide, a solvent with the highest permittivity (182.4 at 25°C), at liquid Ga-, (In-Ga)-, and (Tl-Ga)-electrodes with refreshable surface was studied by the measuring of differential capacitance and by using an open-circuit jet electrode. It is shown that the adsorption parameters and the surface activity series depend significantly on the metal nature. For the (In-Ga)- and (Tl-Ga)-electrodes, like for Hg-electrode, the halogenide-ion surface activity increases in the following series: Cl⁻ < Br⁻ < I⁻; for the Ga-electrode, it varies in the opposite sequence: I⁻ < Br⁻ < Cl⁻. By example of the Ga-electrode in N-methylformamide, it is shown for the first time that the phenomenon of the surface activity series reversal can be observed not only in aprotic solvents but also in protonic ones. The data obtained in N-methylformamide is compared with that obtained in dimethyl formamide and acetonitrile. The halogenide-ion adsorption at the Ga-, (In-Ga)-, and (Tl-Ga)-electrodes decreases in the series N-methylformamide < dimethyl formamide < acetonitrile. The results in aggregate are explained in terms of the Andersen-Bockris model. The data obtained in N-methylformamide, dimethyl formamide, and acetonitrile evidence the increase of ΔG _M-Hal ⁻in the series (Tl-Ga) < (In-Ga) < Ga, that is, with the increasing of the metal work function. This points out the donor-acceptor nature of the metal-halogenide-ion interaction, in which the halogenide-ions are donors of electron pair with respect to the metals.     

Determination of activity ratios of <Superscript>238,239+240,241</Superscript>Pu, <Superscript>241</Superscript>Am, <Superscript>134,137</Superscript>Cs,and <Superscript>90</Superscript>Sr in Bulgarian soils

The origins of different artificial radionuclides found in soils from Northern and Southern Bulgaria was determined by measurements of their actual concentrations and respective ratios. On the basis of the measured mobility and concentrations of the investigated radionuclides in soils, it was estimated that after the Chernobyl accident the mean depositions of fresh ¹³⁷Cs were 3.0 ± 2.5 kBq/m² for Northern Bulgaria and 15 ± 7 kBq/m² for Southern Bulgaria. As a result of global fallout following atmospheric nuclear weapon tests in the 1950s, mean depositions (corrected to 1965) were calculated for Northern and Southern Bulgaria as follows: for ⁹⁰Sr—1.0 ± 0.5 and 2.3 ± 1.3 kBq/m², ²³⁸Pu—1.3 ± 0.8 and 2.8 ± 1.6 Bq/m², ^239+240Pu—15 ± 14 and 47 ± 38 Bq/m², and ²⁴¹Pu—520 ± 200 and 760 ± 260 Bq/m².     

Second Dissociation Constant of H<Subscript>2</Subscript>Te and the Absorption Spectra of HTe<Superscript>–</Superscript>, Te<Superscript>2–</Superscript> and Te<Subscript>2</Subscript><Superscript>2–</Superscript> in Aqueous Solution

We have measured the second acid dissociation constant, K _2a , at several ionic strengths for hydrogen telluride (H₂Te) using the Charge Transfer to Solvent (CTTS) uv spectra of its anions HTe⁻ and Te²⁻. Since it is produced in our solutions, we have also determined the spectra of Te₂ ²⁻ both in the uv and in the visible regions. At 25 ^∘C, K _2a = (1.28 ± 0.02) × 10⁻¹² by extrapolation to zero ionic strength. Its value at an ionic strength equal to 0.5 mol.dm^-3 was estimated to be (8.7 ± 0.2) × 10⁻¹². The solution thermodynamics of these species are also discussed and comparisons are made to related acids.     

Targetry and specification of <Superscript>167</Superscript>Tm production parameters by different reactions

In recent years, there has been a rapid expansion in the use of radio nuclides for therapeutic purposes. Thulium–167 is an important radionuclide (T _1/2 = 9.25 d) due to it could be used for tumor and bone studies in nuclear medicine. ¹⁶⁷Tm complexed with hydroxy ethylene diamine tetra-acetic acid (HEDTA) could be used with the aim of bone imaging. ¹⁶⁷Tm emits a prominent γ ray of 208 keV energy and low energy electrons. This study describes calculations on the excitation functions of ¹⁶⁵Ho(α,2n)¹⁶⁷Tm, ¹⁶⁷Er(p,n)¹⁶⁷Tm, ^natEr(d,xn)¹⁶⁷Tm and ^natEr(p,xn)¹⁶⁷Tm reactions by ALICE/ASH (hybrid and GDH models) and TALYS-1.0 codes. In addition, calculated data by codes were compared to experimental data that earlier were published and TENDL-2010 database. Moreover, optimal thickness of the targets and physical yield were obtained by SRIM (stopping and range of ions in matter) code for each reaction. According to the results, the ¹⁶⁷Er(p,n)¹⁶⁷Tm and ¹⁶⁵Ho(α,2n)¹⁶⁷Tm reactions are suggested as the best method to produce ¹⁶⁷Tm owing to minimum impurities. The TALYS-1.0 code, predict the maximum cross-section of about 382 mb at 11 MeV and 849 mb at 26 MeV for ¹⁶⁷Er(p,n)¹⁶⁷Tm and ¹⁶⁵Ho(α,2n)¹⁶⁷Tm reactions, respectively. Finally, deposition of ^natEr₂O₃ on Cu substrate was carried out via the sedimentation method. The 516 mg of erbium(III)oxide with 103.2 mg of ethyl cellulose and 8 mL of acetone were used to prepare a ^natEr₂O₃ layer of 11.69 cm². ¹⁶⁷Tm was produced via the ^natEr(p,n)¹⁶⁷Tm nuclear process at 20 μA current and 15 → 7 MeV protons beam (1 h). Yield of about 3.2 MBq ¹⁶⁷Tm per μA h were experimentally obtained.     

Investigation of radionuclide <Superscript>63</Superscript>Ni(II) sorption on ZSM-5 zeolite

The sorption of ⁶³Ni(II) from aqueous solution using ZSM-5 zeolite was investigated by batch technique under ambient conditions. ZSM-5 zeolite was characterized by point of zero net proton charge (PZNPC) titration. The sorption was investigated as a function of shaking time, pH, ionic strength, foreign ions, humic acid (HA), fulvic acid (FA) and temperature. The results indicate that the sorption of ⁶³Ni(II) on ZSM-5 zeolite is strongly dependent on pH. The sorption is dependent on ionic strength at low pH, but independent of ionic strength at high pH values. The presence of HA/FA enhances ⁶³Ni(II) sorption at low pH values, whereas reduces ⁶³Ni(II) sorption at high pH values. The sorption isotherms are simulated by Langmuir model very well. The thermodynamic parameters (i.e., ∆H ⁰, ∆S ⁰ and ∆G ⁰) for the sorption of ⁶³Ni(II) are determined from the temperature dependent sorption isotherms at 293.15, 313.15 and 333.15 K, respectively, and the results indicate that the sorption process of ⁶³Ni(II) on ZSM-5 zeolite is spontaneous and endothermic.     

Determination of <Superscript>241</Superscript>Am/<Superscript>243</Superscript>Am ratios

Determination of ²⁴¹Am/²⁴³Am ratios is required for vanous purposes including assay of Am by isotope dilution techniques. Alpha-spectrometry on electrodeposited sources is a preferred technique for this determination. However, there is an inherent problem of tail contribution which necessitates the use of suitable algorithms to account for the same. Recently, in the frame of a Coordinated Research Program (CRP) of the International Atomic Energy Agency (IAEA), WinALPHA software has been developed which is a combination of an asymmetrical Gaussian for the main part of the peak and a low energy function. Therefore, it was of interest to compare the use of this algorithm with the routinely used method, in our laboratory, based on geometric progression (G. P.) decrease. Since, there are no reference materials available commercially for ²⁴¹Am/²⁴³Am ratios, synthetic mixtures covening a wide range (0.3 to 2.0) of ²⁴¹Am/²⁴³Am α-activity ratios were used and un-ignited electrodeposited sources were prepared for α-spectrometry. The α-spectra obtained using PIPS detector, were evaluated using the two algonthms The ²⁴¹Am/²⁴³Am α-activity ratios obtained were also compared with those determined by thermal ionization mass spectrometry (TIMS). An agreement of about 1% was obtained in the ²⁴¹Am/²⁴³Am ratios determined by the two methods and also by using the two algorithms for α-spectrum evaluation.