AgNP-decorated SBA-15 for MWCNT Paste Modified Electrode: A Sensor for Simultaneous Voltammetric Determination of Paracetamol and Sulfamethoxazole

A new electrochemical sensor based on a carbon nanotube paste electrode modified with a Santa Barbara Amorphous material (SBA-15) decorated with silver nanoparticles, namely CNT/SBA/Ag-PE, was developed. It was successfully applied for individual and simultaneous determination of both paracetamol (PC) and sulfamethoxazole (SMZ) medicines. The electrode exhibited a linear dynamic range of 0.12–110 μmol L⁻¹ for paracetamol and 0.06–70 μmol L⁻¹ for sulfamethoxazole, and detection limits of 38 and 19 nmol L⁻¹, respectively. The proposed sensor offered high sensitivity, fast response time and the potential for detecting both drugs simultaneously. The CNT/SBA/Ag-PE enabled the simultaneous determination of PC and SMZ in urine samples with high recovery rates.     

Use of combined mass spectrometry methods for the characterization of a new variant of human hemoglobin: The double mutant hemoglobin villeparisis β77(EF1) His → Tyr, β 80 (EF4) Asn → Ser

Hemoglobin Villeparisis was found during a systematic measurement of glycated hemoglobin. Electrospray mass spectra of the globin indicate an apparently unchanged molecular weight within the error range (0.01%). The tryptic digest of the β chain shows a chromatographically abnormal βT-9 peptide. The mass-to-charge ratio value of its [M+H]⁺ ion, as measured by liquid secondary ionization mass spectrometry, is one mass unit lower than that of the normal βT-9. However, the electrospray mass spectrum of this peptide exhibits mainly a doubly charged ion, whereas the normal βT-9 gives a triply charged ion. None of the allowed single amino acid substitutions for a 1-u shift down (Glu → Gln, Asp → Asn, or Asn → Ile) can explain the suppression of one protonation site. This can be due only to the replacement of the internal histidine by a nonbasic residue. Thus at least two amino acid exchanges occur within the same peptide: one involves the internal histidine, and the sum of the mass shifts is ?1 u. Consideration of the βT-9 sequence and taking account for the genetic code rules, the only possibility was ¹¹His → Tyr (+26 mass shift) associated with ¹⁴Asn → Ser (?27 mass shift). This conclusion was consistent with the tandem mass spectrum of the [M+H]⁺ ion and was further confirmed by chemical microsequencing.     

The application of radiochronometry during the 4th collaborative materials exercise of the nuclear forensics international technical working group (ITWG)

Journal of Radioanalytical and Nuclear Chemistry - In a recent international exercise, 10 international nuclear forensics laboratories successfully performed radiochronometry on three low enriched...     

Solution and latex properties of model alkali‐soluble rheology modifiers,synthesized via the reversible addition–fragmentation chain transfer process,and the effects of the ethylene oxide chain length on the rheological properties

Model alkali‐soluble rheology modifiers were synthesized through the reversible addition–fragmentation chain transfer polymerization of methyl methacrylate, methacrylic acid, and three different associative macromonomers containing 20, 50, and 100 ethylene oxide spacer units, respectively. The synthesized polymers showed well‐controlled molar masses and narrow molar mass distributions. The rheological properties of the model alkali‐soluble rheology modifiers were measured in alkali solutions and in the presence of a well‐characterized core–shell emulsion. The steady‐shear viscosity data for the emulsion solutions, thickened with the associative rheology modifiers, were described by the Carreau model. The rheology modifiers containing the macromonomers with the longest ethylene oxide spacer units produced the highest viscosity in the latex systems but the lowest viscosity in alkali solutions. The highest viscosities in alkali solutions were obtained for the rheology modifiers containing macromonomers with 50 ethylene oxide spacer units. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2502–2512, 2004     

Total synthesis of (+)-arteanniun M using the tandem oxy-Cope/ene reaction

[see reaction]. The first total synthesis of (+)-arteannuin M was accomplished using the tandem oxy-Cope/transannular ene reaction as the key step to construct the bicyclic core of the natural product. The tandem reaction proceeded with high diastereo- and enantiomeric excess.     

Quantized double-layer charging of highly monodisperse metal nanoparticles

We describe unprecedented resolution of electrochemically observed quantized double layer (QDL) charging, attained with use of reduced solution temperatures and with an annealing procedure that produces hexanethiolate monolayer protected gold clusters (C6 MPCs) with a high level of monodispersity in charging capacitance, C(CLU). The spacing DeltaV = e/C(CLU) on the electrochemical potential axis between one electron changes in the electronic charge of nanoscopic metal particles is determined by their effective capacitance C(CLU). The high monodispersity of the C6 MPCs with Au(140) cores facilitates (a) detailed rotated disk and cyclic voltammetric measurements, (b) simulation of QDL waveshapes based on assumed reversible, multivalent redox-like behavior, (c) determination of nanoparticle diffusion rates, and (d) observation of as many as 13 changes in the MPC charge state, from MPC(6-) to MPC(7+). The single electron QDL charging peaks are quite evenly spaced (DeltaV constant) at potentials near the MPC potential of zero charge, but are irregularly spaced at more positive and negative potentials. The irregular spacing is difficult to rationalize with classical double layer capacitance ideas and is proposed to arise from a correspondingly structured (e.g., not smooth) density of electronic states of the nanoparticle core, resulting from its small HOMO/LUMO gap and incipiently molecule-like behavior.     

Styrene‐ethylene co‐oligomerization with bis‐(diphenylphosphino)‐amine/chromium catalysts and the use of the co‐oligomerization products in copolymerization reactions with metallocenes

Ethylene‐styrene (or 4‐methylstyrene) co‐oligomerization using various bis(diphenylphoshino)amine ligands in combination with chromium is discussed. GC analysis of the reaction mixture shows that various phenyl‐hexene and phenyl‐octene isomers are formed either through cotrimerization or cotetramerization. It seems that the more bulky ligands display lower selectivity to co‐oligomerization and favor ethylene homo‐oligomerization. Subsequent copolymerization of the oligomerization reaction mixture using a metallocene polymerization catalyst results in a copolymer with a branched structure as indicated by Crystaf and ¹³C NMR analysis. Assignments of the ¹³C NMR spectrum are proposed from an APT NMR experiment combined with calculated NMR chemical shift data using additivity rules. An indication of the ability of the different co‐oligomerization products to copolymerize into the polyethylene chain could be established from these assignments. Unreacted styrene and the more bulky isomers, 3‐phenyl‐1‐hexene and 3‐phenyl‐1‐octene, are not readily incorporated while branches resulting from the other isomers present in the co‐oligomerization reaction mixture are detected in the NMR spectrum. © 2008 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 1488–1501, 2008     

Surface properties of porous carbon obtained from polystyrene sulfonic acid-based organic salts

Pyrolysis ofpolysterene sulfonic acid-co-maleic acid salts at 800 degrees C resulted in formation of new materials consisting of porous carbon and metal species dispersed on the surface. After hydrochloric acid treatment, the metal oxides/salts were removed. Obtained materials were characterized using adsorption of nitrogen, thermogravimetric analysis, Raman spectroscopy, and scanning electron microscopy with energy dispersive analysis of X-rays. The results showed highly developed porous structures in the range of micro- and mesopores. The porous features of new materials resemble those characteristics for carbon foams. The differences in the porous structure are linked to the type of transition metal used for the modification of the initial polymer and the chelation process. Macro- and mesopores are spherical/cylindrical in shape, and they are likely formed when release of pyrolysis gases, such as CO2, NO2, SO2, H2S, and CxHy, occurs. Moreover, reduction of metal, its migration to the surface, and agglomeration contribute to development of porosity. Depending on the reactivity of the metal used for cation exchange (Fe, Co, or Ni) either sulfides (nickel and cobalt) or oxides (cobalt and iron) are formed on the carbon surface.