Validation of a confirmatory method for the determination of sulphonamides in muscle according to the European Union regulation 2002/657/EC

A simple multiresidue method is described for assaying 10 sulphonamides (SAs) (sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfachlorpyridazine, sulfamethoxazole, sulfaquinoxaline and sulfadimethoxine) in muscle samples. Samples were prepared by homogenizing the tissue, extracting with ethyl acetate and cleaning up with a cation-exchange solid-phase extraction (SPE) column. The detection of analytes was achieved by HPLC-diode array detection (DAD) at 270 nm. The procedure was validated according to the European Union regulation 2002/657/EC determining specificity, decision limit, detection capability, trueness and precision. The results of validation process demonstrate that the method is suitable for application in European Union statutory veterinary drug residue surveillance programmes.     

Copolymers of vinyl chloride with the vinyl esters and acrylates of low molecular weight polyesters of hydroxyacids

Vinyl esters and acrylates of polyesters derived from C₁₀?C₁₈ hydroxyacids have been synthesized and copolymerized with vinyl chloride with the hope of achieving an internally plasticized poly(vinyl chloride). Copolymers containing 10–30% polyester are film-forming materials, and the films cast from THF solutions are generally flexible. A number of these vinyl chloride copolymers with polyesters at approximately 15 and 25% level have been tested for various properties. The internal plasticization is not extensive.     

Perfluoroalkyl-substituted triazapentadienes and their metal complexes

Triazapentadienides, C(3)F(7)-C(=NR)-N=C(NHR)-C(3)F(7), result from the reaction of primary amines RNH(2) with the fluorinated imine C(3)F(7)-CF=N-C(4)F(9). The aniline derivative (R = Ph) is a weak monoprotic acid in dmso. Its conjugate base exhibits an extensive coordination chemistry. It acts as a bidentate ligand toward the molecular fragments Pd(C(3)H(5)), Rh(c-C(8)H(12)), Ir(c-C(8)H(12)), and Rh(CO)(2). The chelates [C(3)F(7)-C(NPh)-N-C(NPh)-C(3)F(7)](2)M, M = Mg, Mn, Fe, Co, Ni, Cu, Zn, and Pd, were prepared. In the crystallographically characterized Co complex, the metal is 3d(7), S = (3)/(2) and tetrahedrally coordinated. Spin densities at carbon in the C(6)H(5) and C(3)F(7) groups were estimated from the (1)H and (19)F contact shifts. Spin delocalization onto phenyl sp(2) carbons is approximately 10 times greater than onto the fluorinated sp(3) carbons.     

PHOTODYNAMIC THERAPY OF B16 PIGMENTED MELANOMA WITH LIPOSOME-DELIVERED Si(IV)-NAPHTHALOCYANINE

The possibility of extending photodynamic therapy to the treatment of highly pigmented neoplastic lesions was tested by using Si(IV)-naphthalocyanine (SiNc) as a tumor-localizing agent. Si(IV)-naphthalocyanine displays intense absorbance at 776 nm (ɛ= 5 × 10⁵ M⁻¹ cm⁻¹), where melanin absorption becomes weaker. As an experimental model we selected B16 pigmented melanoma subcutaneously transplanted to C57BL mice. Upon injection of 0.5 or 1 mg kg⁻¹ of liposome-incorporated SiNc, maximal accumulation of the photosensitizer in the tumor was observed at 24 h with recoveries of 0.35 and 0.57 μg g⁻¹, respectively. However, the tumor targeting by SiNc shows essentially no selectivity, since the photosensitizer concentrations in the skin (peritumoral tissue) were very similar to those found in the tumor at all postinjection times examined by us. Irradiation of SiNc-loaded melanoma with 776 nm light from a diode laser at 24 h postinjection induces tumor necrosis and delay of tumor growth. The effect appears to be of purely photochemical nature at dose rates up to 260 mW cm⁻²; at higher dose rates, thermal effects are likely to become important.     

Mesomeric dipole moments. Part 12

The dipole moments of para-substituted azoxybenzenes (1, a-e) and phenylazoxycyanides (2, a-e) were analyzed in terms of bond moments and additional contributions expressing electron delocalization. The results are compatible with a significant participation of the polar mesomeric formula B (25% or 34% for1 and2, respectively), the N-O bond acquiring considerable double-bond character. Comparison of known x-ray structures reveals that this bond is significantly shortened, whereas the N=N bond is extended only very slightly. Hence we can consider the possibility that the N1 atom allocates somewhat more than eight valence electrons, similarly to nitro compounds. In all respects the properties of the azoxy group are between those of the nitro and imino-N-oxide groups.Part 11 appears in Exner, O.J. Phys. Org. Chem. 1990,3, 190.     

Consecutive processes in the photolysis of dimethyl-s-tetrazine molecules in the vapor phase

Experimental studies of the variation of the fluorescence yield and photochemical product yield are presented for dimethyl-s-tetrazine (DMT) at 0.6 Torr and 300 K. Results are also reported for the variation of these yields upon adding argon buffer gas. The fluorescence yield decreases with increasing excitation energy (0 to 4200 cm^?1 vibrational energy excess in the first excited singlet state) but the decrease is insufficient to account for the corresponding increase in product yield. Added gas (600 Torr argon) quenches the photochemistry but not the fluorescence. The results imply that the photo-dissociation involves a bottleneck (B) in the non-radiative singlet decay. The molecules in B can be relaxed by collisions, relax to photostable DMT molecules without collisions, or undergo photodissociation.     

Computational transport phenomena in bioprocessing with the approach of the optimized source term in the governing equations

Progress in the modeling of bio and food industry processes can be achieved by developing robust and efficient codes. Even complex configurations can be tackled, featuring multiphysics mechanisms that are interdependent or even competing with each other. In this paper the use of optimized “source terms” of the governing partial differential equations are discussed, reporting on simulation results. The related framework is addressed, as well as the potential of the adopted approach.     

A new terpyridine tethered polythiophene: Electrosynthesis and characterization

A novel polythiophene bearing a pendant terpyridine moiety has been synthesized by electrochemical polymerization of a new thiophene monomer, namely 4′‐(2,2′:5′,2″‐terthien‐3′‐ethynyl)‐2,2′:6′,2″‐terpyridine (TAT). The insertion of a conjugated ethynyl spacer between the terthiophene and the terpyridine fragments provides for an effective extension of the delocalization of electrons within the structural unit and the polymer as a whole. The synthesis and characterization of the relevant monomer, the electrosynthesis of the corresponding polymer and its electrochemical, UV–visible spectroelectrochemical and IR characterization are described. Finally, a comparison between the electrochemical, spectroscopic, and spectroelectrochemical properties of PTAT and the analogue, saturated‐spacer PTTT (TTT = 4′‐[(2,2′:5′,2″‐terthien‐3′‐yl)methoxy]‐2,2′:6′,2″‐terpyridine) polymer is discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011