Tris(2-ethylhexyl)phosphate as an extractant for trivalent gallium, indium and thallium

A systematic study of solvent extraction behaviour of gallium(III), indium(III) and thallium(III) with tris(2-ethylhexyl)phosphate from salicylate media has been undertaken and a scheme for their separation is proposed. The optimum extraction conditions are evaluated and described. The method is applicable to the analysis of standard aluminium and aluminium alloys samples. The results obtained are reproducible and accurate.     

Complexometric determination of thallium(III) in pure solution,alloys, and complexes using semicarbazide hydrochloride as a releasing agent

A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions     

Photochemical Synthesis of the Bioactive Fragment of Salbutamol and Derivatives in a Self-Optimizing Flow Chemistry Platform

The implementation of self-optimizing flow reactors has been mostly limited to model reactions or known synthesis routes. In this work, a self-optimizing flow photochemistry platform is used to develop an original synthesis of the bioactive fragment of Salbutamol and derivatives. The key photochemical steps for the construction of the aryl vicinyl amino alcohol moiety consist of a C−C bond forming reaction followed by an unprecedented, high yielding (>80 %), benzylic oxidative cyclization.     

Thermal studies of furosemide–caffeine binary system that forms a cocrystal

Thermal techniques, differential scanning calorimetry (DSC), and hot stage microscopy (HSM) have been used to study the interactions between furosemide and caffeine that are known to form a 1:1 cocrystal. This system has been used as an example to study the probable mechanism of cocrystal formation when the individual components, which are polymorphic, are heated. The study indicates that the phase transition of the low temperature stable polymorph of furosemide initiates cocrystal formation. This result suggests increased mass transfer rate can trigger cocrystal formation. The binary phase diagram (composition–temperature plots) of furosemide–cocrystal–caffeine system was determined from the DSC curves. The results imply that the cocrystal forms eutectic with caffeine but not with furosemide. This study has thus exemplified the use of DSC in understanding binary phase system where the two components form a cocrystal.     

Relevance of ICRP metabolic model of Th in bio-assay monitoring

This paper compares the urinary excretion levels of Th obtained in bio-assay monitoring using the neutron activation technique with those predicted by applying the ICRP metabolic model to the measured Th activity in chest and total body of a group of Thorium plant workers. The results indicated much lower urinary Th excretion as compared to what was expected on the basis of the ICRP model. Lower urinary excretion in occupational subjects is explained in terms of negligible contribution of skeleton and soft tissue to the activity excreted in urine. It is suggested that the existing model should be modified to enable it to be applicable to the bio-assay monitoring of occupational workers.     

A new ion-selective electrode for nitrate determination

Summary A new ion-selective electrode which can be used for the nitrate determination in a concentration range of 10^–1 to 10^–4 mol/l is described. The polymer ion-exchanger membrane is formed by an epoxy resin, after Nitron nitrate having been introduced serving as an anchor group. The selectivity constants k _t-i have been determined for Cl^–, ClO ₄ ^– , HCO ₃ ^– , SO ₄ ^2– , HPO ₄ ^2– , MoO ₄ ^2– and WO ₄ ^2– .

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Neue ionenselektive Elektrode für die Nitratbestimmung

Zusammenfassung Es wird eine neue ionenselektive Elektrode beschrieben, die für Nitratbestimmungen im Konzentrationsbereich von 10^–1 bis 10^–4 mol/l verwendet werden kann. Die Ionenaustauschermembran besteht aus Epoxidharz, in das Nitronnitrat als Ankergruppe eingeführt wurde. Die Selektivitätskonstanten K _T-I für Cl^–, ClO ₄ ^– , HCO ₃ ^– , SO ₄ ^2– , HPO ₄ ^2– , MoO ₄ ^2– und WO ₄ ^2– wurden bestimmt.

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Dedicated to Prof. Dr. H. Monien on the occasion of his 60th birthday     

Conformationally Locked Cyclo[2]Dipyrrins Linked with Anthracene Subunits: Synthesis and Chiroptical Properties

Herein, we report the synthesis of anthracene-containing twisted cyclo[2]dipyrrin 1 by utilizing a non-planar building block, 1,5-dipyrrylanthracene (1,5-DPA). The non-planar nature of the macrocycle enhanced the solubility and helped in structural characterization. Macrocycle 1 adopts a twisted ‘figure of eight’ conformation stabilized by strong intramolecular H-bonding interactions and exists as a pair of helical enantiomers, as revealed by X-ray crystallographic analysis. More importantly, the sterically locked structure enabled facile optical resolution using chiral HPLC. The (P,P) and (M,M) enantiomers show moderate chiroptical properties, such as absorption dissymmetry factors |g_abs| in the order of 10⁻³, and luminescence dissymmetry factors |g_lum| of 3.8×10⁻³ and 2.9×10⁻³ at 702 nm, respectively.     

Structural characterization of alpha-helices of implicitly solvated poly-alanine

The structural characteristics of alpha-helices in poly-alanine-based peptides have been investigated via molecular dynamics simulation with the goal of understanding the basic features of peptide simulations within the context of a model system, classical molecular dynamics with generalized Born (GB) solvation, and to shed insight into the formation and stabilization of alpha-helices in short peptides. The effects of peptide length, terminal charges, proline substitution, and temperature on the alpha-helical secondary structure have been studied. The simulations have shown that distinct secondary structure begins to develop in peptides with lengths approaching 10 residues while ambiguous structures occur in shorter peptides. The helical content of peptides with lengths > or =10 amino acids is observed to be nearly constant up to (Ala)(40). Interestingly, terminal charges and proline in the second position from the N-terminus alter the secondary structure locally with little effect on the overall alpha-helical content of the peptide. The free energy profile of helix formation was also investigated. A large increase in free energy accompanying the formation of helices with more than two consecutive hydrogen bonds in the (i, i + 4) pattern was observed while the free energy increases linearly with additional hydrogen bonds. Values for the change in enthalpy and entropy of helix nucleation and propagation are reported. Additionally the results obtained from the GB model are compared to explicit solvent simulations of two synthetic alanine-based peptides.     

Radioimmunoassay for individual lactate dehydrogenase isoenzymes 1 and 2

Radioimmunoassays (RIA) for the determination of the individual lactate dehydrogenase (LDH) isoenzymes, LDH-1 and LDH-2 have been developed. LDH-1 can be measured in the range of 5–100 ng and LDH-2 in the range of 5–80 ng, if there is no significant cross reactivity. Immunization of several rabbits with LDH-1 and LDH-2 isoenzymes reveals that some animals do not produce antisera to LDH-2 while those injected with LDH-1 generated antiserum in each case. The results of the binding studies suggest that a 50% binding that is recommended for RIA can be achieved with a titer value of 12000 dilution of the antisera. Cross reactivity studies indicate that LDH-1 cross reacts with the antisera to LDH-2 if its concentration is higher than 30 ng/ml of the RIA mixture while LDH-2 cross reacts with the antisera to LDH-1 only if its concentration exceeds 80 ng/ml.     

The kinetics of olation of some hydroxoaquotetrammine-cobalt(III) complexes in the solid state

The solid-state kinetics for the olation reactions of [Co(NH₃₄(OH)(H₂O)]X₂ (where X  Cl^?, Br^?, or $\text{1}\text{2}$SO^2?₄ were determined by several different methods using dynamic and isothermal thermogravimetric data. For the reduced-time plot method, E values were 20, 43, and 25 kcal mol^?1 for the chloride-bromide, and sulfate complexes, respectively. For the Jacobs and Kureishy method, E values of 21, 37, and 17 kcal mol^?1, were obtained for the above three complexes, respectively. A possible reaction pathway is suggested for the olation reaction.