Hydrolysis of post-consume poly(ethylene terephthalate) with sulfuric acid and product characterization by WAXD, C NMR and DSC

Post-consume PET was hydrolysed with commercial sulfuric acid (96%) with varying reaction times (5-120 min). The structure of the material obtained was analysed by ¹³C NMR, DSC, and WAXD and the results were correlated with reaction time. ¹³C NMR shows a decrease in chain size with reaction time and an increase in the number of carboxyl groups at the end of the chains. The correlation of DSC and WAXD data indicates the presence of structures of different sizes and an increase in crystallinity with reaction time. The structure of the samples hydrolysed for 5-60 min is less ordered than those of the samples hydrolysed for 60-120 min because the amorphous phase is predominantly quickly dissolved. Dissolution of the crystalline phase is favoured by the increase in reaction time. In this process, the crystalline memory retained in the dissolution of the crystalline phase behaves as nucleation sites which form smaller and more ordered structures compared to those obtained with shorter reaction times.     

Extracts of the unripe fruit of Ilex paraguariensis as a potential chemical control against the golden apple snail Pomacea canaliculata (Gastropoda,Ampullariidae)

Plant extracts can provide a viable alternative to controlling many crop pests. This study sought to assess the efficacy of vegetable extracts of the unripe fruits of Ilex paraguariensis (yerba maté) for chemical control of the channeled apple snail (Pomacea canaliculata) and of non-target species as the South American catfish (Rhamdia quelen) under laboratory conditions. In P. canaliculata, the LC₅₀ of the decoction extract was 31.39 mg.L^?1 and the LT₅₀ was over 26 h. The LC₅₀ of the butanol extract was 24.75 mg.L^?1 and the LT₅₀ was in the range of 28 to 32 h. In juvenile R. quelen, the LC₅₀ of the decoction was 17.98 mg.L^?1 and the LT₅₀ was in the range of 10–12 h. These extracts are particularly attractive considering the source of compounds and their effectiveness as molluscicides.     

Solid-phase microextraction method for the quantitative analysis of styrene in water

A headspace solid-phase microextraction (HS-SPME) method is developed for the determination of styrene in drinking water. Gas chromatography (GC)-mass spectrometry is utilized for qualitative analysis. A manual SPME holder with 85-microm polyacrylate coating is used to extract the styrene from water, which is determined to have good linearity (correlation coefficient r = 0.9999 for 1.00-100.00 microg/L range), a relative standard deviation of 1.9%, and a detection limit of 0.30 microg/L. This method is compared with a classical headspace GC method.     

Polarographic determination of cyanide as nickelcyano complex in blood plasma after selective extraction in a methylene blue impregnated polyethylene column

A method for the determination of cyanide in blood plasma by differential pulse polarography (DPP) is described without a drastic acidification of the sample. Cyanide was determined as tetracyanonickelate(II)-anion complex after a microwave-acid assisted cleanup and a selective complex extraction in a polyethylene methylene blue (PE-MB) impregnated column. The cyano complex was eluted from the column with water/acetonitrile and determined by pulse-polarography at –380 mV (Ag/AgCl). The linear range of calibration was obtained from 1.2 to 9.6 μg of cyanide with r = 0.99 and RSD = 9% of 1.2 μg of cyanide. A detection limit of 40 μg L^–1 was calculated and the recoveries of cyanide from spiked samples were about 80%. This method was compared with the classical pyridine-pyrazolone method.     

Simultaneous determination of reduced and oxidized glutathione in freshly isolated rat hepatocytes and cardiomyocytes by HPLC with electrochemical detection

Glutathione and glutathione disulphide constitute an essential thiol redox system present in the cell. The balance in favour of the latter is an indication of oxidative stress. Glutathione and glutathione disulphide quantification in isolated cells may therefore be essential for the evaluation of mechanistic and comparative studies of toxic xenobiotics. In this study, a rapid and sensitive isocratic reverse-phase high-performance liquid chromatographic method using coulometric detection was implemented for the simultaneous detection of glutathione and glutathione disulphide, in freshly isolated hepatocytes and cardiomyocytes of the rat. The method implemented proved to be effective for the measurement of glutathione and glutathione disulphide in control conditions and for the detection of variations in this redox system, induced by tert-butylhydroperoxide. tert-Butylhydroperoxide is an organic peroxide, which has been used as a model molecule for inducing oxidative stress in isolated cells. A comparative study with a previously published HPLC-electrochemical detection method was performed.     

Development of novel pillared clays for the encapsulation of inorganic complexes

Several pillared clays were prepared by using a polyalcohol (ethylene glycol or poly(vinyl alcohol)) or a poly(ethylene oxide) surfactant as an interlayer gallery template and an aluminum oligomer species as the pillaring agent. The use of polyalcohols or nonionic surfactants, such as Tergitol, gave materials which, in general, presented larger basal spacing than those found for the solids prepared by a similar procedure but without additives. The initial positive effect in the expansion of the clay interlayers was not totally retained after calcination of the materials; most probably, at the end, the basal spacing is still ruled by the intercalating aluminum species. The pillared clay with the largest basal spacing and specific surface area was used to encapsulate copper(II) complexes with pentadentate N3O2 Schiff base ligands derived from copper(II) acetylacetonate by in situ synthesis. The characterization made (X-ray diffraction, X-ray photoelectron spectroscopy, FTIR spectroscopy, chemical analysis, and low-temperature N2 adsorption) provided evidence that copper(II) complexes with pentadentate N3O2 Schiff base ligands were efficiently entrapped within the lower dimension pores of the pillared clay and that they interact strongly with the pillared clay matrix.     

Optimation of PGNAA instrument design for cement raw materials using the MCNP code

A simulation study of a PGNAA measuring arrangement with a²⁵²Cf neutron source for the characterization of cement raw materials was carried out using the MCNP code to investigate the effect on the system response of varying the bulk density and the water contentv _w of samples of fixed dry composition. The source is placed at the centre of a lead cylinder of extemal radiusR _Pb. This cylinder is enclosed in a coaxial cylinder of polyethylene moderator of extermal radiusR _in. The sample material is confined to the space between an outer cylindrical surface of radiusR _out and the moderator cylinder. The first series of simulation runs was carried out for different sets of values ofR _in,R _out and , and constantv _w. The system specific responseS (count rate per wt%) shows a broad maximum aroundT _M=R _in-R _Pb=4 cm andT _S=R _out-R _in=8.5 cm and a dependence on that is almost linear in the region of the maximum. In a second series of runs the dependence ofS onv _w was studied for a geometry corresponding to a real experiment described elsewhere and for a geometry for which the density saturation effect is already apparent. It is shown that when the sensitivity of the system is optimized both andv _w must be used as calibration parameters while in the low-sensitivity design regionv _w can be used as the only calibration parameter.     

Determination of lamotrigine simultaneously with carbamazepine,carbamazepine epoxide,phenytoin, phenobarbital,and primidone in human plasma by SPME-GC-TSD

A simple and rapid analytical method is presented for the determination of lamotrigine simultaneously with primidone, carbamazepine, carbamazepine epoxide, phenobarbital, and phenytoin in human plasma using solid-phase microextraction (SPME) and gas chromatography with thermionic specific detection. The best conditions for the SPME procedure is established as following: direct extraction on a 65-microm Carbowax-divinylbenzene fiber; 1.0 mL of a sample plasma matrix modified with 15% NaCl and 3 mL of a potassium phosphate buffer (pH 7.0); extraction temperature at 30 degrees C; and stirring at a rate of 2500 rpm for 15 min. The method shows good linearity between 0.05 and 40.0 microg/mL with regression coefficients ranging between 0.9965 and 0.9995 and a coefficient of variation of the points of the calibration curve lower than 10%. The lowest limit of quantitation for the plasma-investigated drugs varies from 0.05 to 0.20 microg/mL, according to the drug. The proposed method is sensitive enough to work into subtherapeutic and therapeutic concentrations, being that it is applied in pharmacokinetic studies and patient routine therapeutic drug monitoring.     

An MP2 and DFT study of heterocyclic hydrogen complexes CnHmY-HX with n=2, m=4 or 5, Y=O, S or N and X=F or Cl

We present a theoretical study through MP2 ab initio molecular orbital calculations and B3LYP density functional theory with the 6-311++G(d,p) basis set of the heterocyclic hydrogen complexes, CnHmY-HX, where CnHmY = C2H4O, C2H5N and C2H4S, and X=F or Cl. This study aided in the elucidation the main changes in the structural, electronic and the vibrational properties in isolated species, due the hydrogen complexes formation, CnHmY-HX, revealing systematic tendencies in these chemical systems studied. The complexes has CS symmetry, with the HX subunit lying in the plane perpendicular to that of CYC nuclei of heterocyclic and acting as proton donor in forming a hydrogen bond to the heteroatom, Y. A weak secondary interaction between the CH2 groups of heterocyclics and the X atoms in HX causes a significant nonlinearity of the primary hydrogen bond. The hydrogen bond linearity deviations in these complexes due to secondary interactions are represented by theta angle. The MP2 intermolecular distances of complexes C2H5N-HF, C2H4O-HF and C2H4S-HF correspond the 1.652, 1.671 and 2.164 A, respectively, these results are in excellent agreement with experimental results of 1.700 and 2.193 A found for the last two complexes. In the same way, the MP2 values to theta angle, 14.7, 19.1 and 16.8 degrees, has a better reproduction in the experimental results of 16.5, 21.0 and 16.8 degrees, get to the C2H4O-HCl, C2H4S-HCl and C2H4S-HF complexes, respectively.     

Determination of mono- and disaccharides by capillary electrophoresis with contactless conductivity detection

The separation and detection of common mono- and disaccharides by capillary electrophoresis (CE) with contactless conductivity detection (CCD) is presented. At high values of pH, the sugars are converted to anionic species that can be separated by CE and indirectly detected by CCD. The main anionic species present in the running electrolytes are hydroxide and phosphate, which have greater mobility than the ionized sugars, and, thus, the indirect detection is possible. The method was applied to analysis of glucose, fructose, and sucrose in soft drinks, isotonic beverages, fruit juice, and sugarcane spirits. Galactose was used as internal standard in all cases. Plate numbers range from ca. 70,700 to 168,200 and the limits of detection from 13 to 31 microM.