Carbon‐based Nanosensors for Salicylate Determination in Pharmaceutical Preparations

Thiourea derivative‐based carbon paste electrode (TUD1‐CPE) was constructed as a potentiometric sensor for the determination of salicylate anion in pharmaceutical formulations, Aspocid® and Aspirin®. The optimized CPE contained 45.5 % graphite, 0.5 % reduced graphene oxide (rGO), 46.0 % nitrophenyl octyl ether (NPOE) plasticizer, 5.0 % TUD1 ionophore, and 3.0 % tridodecylmethyl ammonium chloride as additive. The incorporation of NPOE of high dielectric constant, and rGO in electrode caused better performance of the sensor; Nernstian response of 59.0 mV decade^?1 in the concentration range of 10^?1–10^?5 mole L^?1, a detection limit of 1×10^?5 mole L^?1 in a very short response time of 6 seconds. The prepared sensor showed high selectivity against similar anions (i. e. , benzoate, I^?, SCN^?). Selectivity was confirmed by calculating the formation constant (K_β) using sandwich membrane method, where K_β for TUD1‐salicylate is 10^0.43. Theoretical calculations at DFT‐B3LY/6‐31G** level of theory were performed to find interaction mechanism, Energies of HOMO and LUMO orbitals, non‐linear optical (NLO) properties (the electronic dipole moment (μ), first‐order hyperpolarizability (β), the hyper‐Rayleigh scattering (β_HRS) and the depolarization ratio (DR)), and other global properties; these calculations showed lower values of β and DR, higher value of β_HRS, and the shortest lengths of the four N?H bonds between TUD1 and salicylate which confirm their strong complexation and salicylate‐selectivity. Also, all the studied anion‐TUD1 exhibited relatively high NLO properties, and these results were considered as a preliminary study for investigating new types of NLO bearing materials. The sensors were applied successfully for the determination of salicylate anion in Aspocid® and Aspirin®.     

Separation of strontium from simulated waste in K2SO4/Nitrate medium containing Sr2+, Eu3+, Ce3+, Pd2+, Rh3+, Ru3+, UO 2 2+ , Fe3+, Cr3+, Ni2+, Al3+, Ca2+ and Cs+, by strongly basic anion exchanger

In this work Strontium was separated selectively form, Pd²⁺, Ni²⁺ and Ca³⁺ using anionic resins of Amberlite type IRA-900 and IRA-410 from nitrate medium. The Separation of strontium by strongly basic anion exchangers IRA-410 and IRA-900 from simulated waste containing, Sr²⁺, Eu³⁺, Ce³⁺, Pd²⁺, Rh³⁺, Ru³⁺, VO₂ ²⁺, Fe³⁺, Cr³⁺, Ni²⁺, Al³⁺, Ca²⁺, and Cs⁺, in K₂SO₄/nitrate medium which adsorbed as strontium sulphate complex was achieved through ligand- ligan exchange. The elution of strontium carried out via “loading” the column with a solution of 0.03N EDTA in presence of 0.1N NaNO₃ at pH7 where Sr²⁺ has low K_d value. An inductively Coubled Plasma — Optical Emission Spectrometry (ICP — OES) of ARL type model 3520, was used for elemental analysis.     

The acid-base properties of solochrome violet R. S.

Summary The acid base properties of solochrome violet R.S. has been studied with the object of testing its use as an acid base indicator or as a colorimetric reagent. The pk values of 4.35, 7.4, and 9.45 corresponding to the three steps of ionisation of the free acid were evaluated by the aid of the relation between log (acid)/(salt) and ph values obtained during the course of the potentiometric titration of the free acid with a free base. The dye has proved to be a suitable indicator in titrating some mineral and organic acids as well as a colorimetric reagent for the microdetermination of vanadium.     

Enhancement of the catalytic activity of [Cu2(TS)(OH)2(OAc)] using superconductor cuprate sample

A superconducting sample (Nd_0.1Y_0.9Ba₂Cu₃O_7-δ) has been tried as a catalyst for H₂O₂ decomposition. All parameters affecting the reaction rate (concentration of H₂O₂, weight of catalyst, temperature and pH) were studied and the optimum conditions were evaluated. A mixture of the superconducting cuprate with [Cu₂(TS)(OH)(OAc)] using different percentages of the sample has been prepared and tried kinetically under the same mentioned conditions. An attempt was made to increase the activity of the complex. The data show that the cuprate sample alone was found to be almost inactive when compared with that of the mixture. The catalytic mechanism in the absence and presence of the complex was suggested.     

De novo enantioselective syntheses of galacto-sugars and deoxy sugars via the iterative dihydroxylation of dienoate

An efficient route to various sugar lactones has been developed. Key to the overall transformation is the sequential osmium-catalyzed dihydroxylation of 2,4-dienoates. The simplest (one-step/racemic) example of this reaction occurs when the dihydroxylation is performed with aqueous NMO in MeOH. When the first dihydroxylation is performed using the AD-mix procedure, an enantioselective variant results. When a matched AD-mix procedure is used for the second dihydroxylation, an exceedingly diastereo- and enantioselective synthesis of galacto-1,4-lactone results. [Reaction: see text]     

New many fold 1,2,3‐selenadiazole aromatic derivatives

The many fold aromatic ketones 2a‐d are versatile compounds for the synthesis of the many fold 1,2,3‐selenadiazole aromatic derivatives 5a‐d . The preparation starts with the reaction between the many fold bromomethylene benzene derivatives 1a‐d and 4‐hydroxyacetophenone, which are transformed through the reaction with semicarbazide hydrochloride or ethylhydrazine carboxylate into the corresponding semicarbazones derivatives 3a‐d or hydrazones 4a‐d . The reaction with selenium dioxide leads to regiospecific ring closure of semicarbazones or hydrazones to give the many fold 1,2,3‐selenadiazole aromatic derivatives in high yield.     

Coordination compounds of hydrazine derivatives with transition metals,part XVIII. Cobalt(II) and cobalt(III) chelates with schiff bases derived from hydrazine-S-methyldithiocarboxylate and thiosemicarbazide

Summary The reactions of aldehydic and ketonic Schiff bases derived from hydrazine-S-methyl dithiocarboxylate and thiosemicar-bazide with cobalt(II) acetate were investigated. Octahedral tris ligand cobalt(III) chelates were formed with aldehydic Schiff bases whereas tetrahedral bis ligand cobalt (II) chelates were isolated with ketonic Schiff bases.N-isopropylidene hydrazine-S-methyldithiocarboxylate, however, gave both octahedral tris cobalt(III) and tetrahedral bis cobalt(II) chelates. These results are interpreted in terms of the steric requirements of the Schiff base used.     

Synergic effect of triphenylphosphine oxide (TPPO) on the extraction of Hg(II), Se(IV), Co(II) and Mn(II) with fluorinated pyrazolone (HPMTFP)

Extraction of Hg(II), Se(IV), Mn(II) and Co(II) has been carried out with 1-phenyl-3-methyl-4-trifluoroacetyl-2-pyrazolin-5-one (HPMTFP) and triphenylphosphine oxide (TPPO) into chloroform from pH 1–10. Quantitative extraction of Hg(II), Mn(II) and Co(II) at pH 4 with equimolar 0.05M (PMTFP+TPPO) in chloroform was observed. Se(IV) remains unextracted at this pH range. The stoichiometric composition of the extracted complexes M(PMTFP)₂·nH₂O (M=Mn, Hg), M(PMTFP)₂·2TPPO (M=Mn and Co) and Co(PMTFP)₂·TPPO·H₂O at less than 0.1M TPPO has been established. The formation constantsK _m,0 andK _m,n and stability constants _m,n have been computed. The analytical method developed was applied to the IAEA standard reference material (SRM) potato fluor V-4 for the determination of these elements using NAA technique.     

Fused quinoline heterocycles VI: Synthesis of 5H‐1‐thia‐3,5,6‐triazaaceanthrylenes and 5H‐1‐thia‐3,4,5,6‐tetraazaaceanthrylenes

Ethyl 3‐amino‐4‐chlorothieno[3,2‐c]quinoline‐2‐carboxylate ( 4 ) is a versatile synthon, prepared by reacting an equimolar amount of 2,4‐dichloroquinoline‐3‐carbonitrile ( 1 ) with ethyl mercaptoacetate ( 2 ). Ethyl 5‐alkyl‐5H‐1‐thia‐3,5,6‐triazaaceanfhrylene‐2‐carboxylates 9a‐c , novel perianellated tetracyclic heteroaro‐matics, were prepared by refluxing 4 with excess of primary amines 7a‐c to yield the corresponding amino‐thieno[3,2‐c]quinolines 8a‐c . Subsequent reaction with an excess of triethyl orthoformate (TEO) furnished 9a‐c . Reaction of 4 with TEO in Ac₂O at reflux, gave the simple acetylated compounds, thieno[3,2‐c]‐quinolines 12 and 13 . Refluxing 4 with benzylamine ( 7d ) gave 10 , and subsequent treatment with TEO gave the tetracyclic compound 11 . Refluxing 13 with an excess of alkylamines 7a‐d gave the fhieno[3,2‐c]quino‐lines 15 . Refluxing the aminothienoquinolines 8b with an excess of triethyl orthoacetate gave thieno[3,2‐c]quinoline 17 , while heating with Ac₂O gave 18 and 19 , with small amounts of 16 . Reaction of 8a,b with ethyl chloroformate and phenylisothiocyanate generated the new 1‐thia‐3,5,6‐triazaaceanthrylenes 20a,b and 21a,b , respectively. Diazotization of 8a‐c afforded the novel tetracyclic ethyl 5‐alkyl‐5H‐1‐fhia‐3,4,5,6‐tetraazaaceanthrylene‐2‐carboxylates 22a‐c in good yields.     

Highly sensitive catalytic determination of molybdenum

A novel, highly sensitive, selective, and simple kinetic method was developed for the determination of Mo(VI) based on its catalytic effect on the oxidation of 1-amino-2-naphthol-4-sulfonic acid (ANSA) with H₂O₂. The reaction was followed spectrophotometrically by tracing the oxidized product at 465 nm after 30 min of mixing the reagents. The optimum reaction conditions were: 10 mmol l⁻¹ ANSA, 50 mmol l⁻¹ H₂O₂, 100 mmol l⁻¹ acetate buffer of pH 5.0 ± 0.05 and at 40 °C. Addition of 200 μg ml⁻¹ diethylenetriaminepentaacetic acid (DTPA) conferred high selectivity for the proposed method. Following the recommended procedure, Mo(VI) could be determined with a linear calibration graph up to 2.5 ng ml⁻¹ and a detection limit, based on the 3S_b-criterion, of 0.027 ng ml⁻¹. The unique sensitivity and selectivity of the implemented method allowed its direct application to the determination of Mo(VI) in natural and industrial waste water. The method was validated by comparison with the standard ETAAS method. Moreover, published catalytic-spectrophotometric methods for the determination of molybdenum were reviewed.