Use of 1,3-diaminepropane-3-propyl grafted onto a silica gel as a sorbent for flow-injection spectrophotometric determination of copper (II) in digests of biological materials and natural waters

The 1,3-diaminepropane-3-propyl-anchored silica gel (DAPPS) was successfully employed as a sorbent in a spectrophotometric flow system for the preconcentration of Cu(2+) in digests of biological materials (maize powder, soybean, citrus leaves, corn stalks) as well as water samples (river, stream, streamlet, springwater and well). The system presented a minicolumn packed with DAPPS, where the sample solution was passed through it for a period of time, and subsequently, an eluent solution, stripped-out the retained analyte which was further determined with DDTC at 460 nm. The better preconcentration conditions utilized were: 120s loading, 60s elution, 30s regeneration of the column, loading flow rate 6.5 ml min(-1), buffer solution for the preconcentration and regeneration of the column-borate buffer pH 8.5, elution flow rate 2.3 ml min(-1), time of elution 60s, eluent composition, 0.4 mol l(-1) HNO(3). Under these conditions, the preconcentration factor obtained was 36, and the detection limit achieved was 8.4 ng ml(-1) in water samples and 0.84 microg g(-1) in biological material. The maximum adsorption capacity of DAPPS to Cu(2+) was 0.49 mmol g(-1) (31.1 mg g(-1)) obtained in a batch system. The recovery of copper in the water samples ranged from 96.9 to 102.4% and in the biological materials ranged from 97.0 to 102.6%.     

Modeling cassava starch saccharification with amyloglucosidase

Applied Biochemistry and Biotechnology - A solution of α-amylase liquefied cassava starch, 30% (w/v), was saccharified with amyloglucosidase at 45°C, pH 4.5, in a batch reactor in the...     

An isocratic HPLC method for the quantitation of eicosanoids in human platelets

We describe here a modified protocol for the simultaneous quantification of specific eicosanoids formed during stimulation of human platelets in vitro with adenosine diphosphate. The eicosanoids thromboxane B(2) (TXB(2)), arachidonic acid (AA), 12-R-hydroxyeicosatetraenoic acid (12-R-HETE), 12-S-hydroxyheptadecatrienoic acid (12-S-HHTrE) and the internal standard prostaglandin B(1) (PGB(1)) were extracted from human platelets by liquid-liquid extraction using ethyl acetate. This was followed by derivatization and fluorescent detection prior to analysis by reversed phase liquid chromatography. The high-performance liquid chromatographic method consisted of ODS reversed-phase column (3 microm) and a mobile phase of acetonitrile-water (85:15). TXB(2) and AA plasma calibration curves were linear between 6.25 and 125 ng mL(-1) (r(2) > 0.997), whereas for 12-R-HETE and 12-S-HHTrE the curves were linear between 5.0 and 40 ng mL(-1) (r(2) > 0.998). All calibration curve standards had <15% CV (coefficient of variation) and between-run precision, and the percentage relative deviation for replicate (n = 6) quality controls was less than 5.5%. The method was adapted to allow the screening of drugs that may affect either one or both of the lipoxygenase and cyclo-oxygenase pathways.     

Far infrared laser lines and assignments of CH3OH: a review

Methyl alcohol is the most important lasing molecule in the Far-Infrared (FIR) spectral region, and the most widely used for investigation and for applications. Since the last critical review of 1984, over seventy papers have been published dealing with the FIR laser lines and the infrared spectroscopy of CH₃OH. In 1984 we could list about 330 FIR laser lines, 98 of which were measured in frequency and 105 assigned. Since then more than 70 papers were published increasing the number of the known laser lines to 575 (103 measured in frequency). Also the FIR and IR spectroscopy was largely improved thanks to the analysis of high resolution FT spectra, and the number of the correctly assigned laser lines has been increased to 224. The wavenumbers of the assigned lines can now be predicted with an accuracy of about 0.001 cm^–1 or better, thus approaching the accuracy of the experimental frequency measurements.     

Elastic, inelastic scattering and fusion of the 14N +59Co system at energies close to the coulomb barrier

Elastic and inelastic scattering differential cross sections were measured in the energy range 30 MeV ≤ E _lab ≤ 55 MeV, for the ¹⁴N +⁵⁹Co system. Ambiguities of the optical potential derived from the analysis of the elastic scattering data were removed by performing calculations at the radius of sensitivity and by comparison with the available fusion cross section data. A simultaneous analysis of the three mechanisms was performed by coupled channel calculations, and a unique energy independent nuclear potential was found to be able to fit the data. Discussions and comparisons concerning the optical model, the threshold anomaly, full and approximated coupled channel calculations are presented. Received: 6 February 1997 / Revised version: 1 August 1997     

Structure and magnetism of electrodeposited ZnSe–Co granular films

ZnSe–Co granular films have been electrodeposited under potentiostatic condition on polished stainless steel substrates. X-ray diffraction and transmission electron microscopy measurements indicate the formation of polycrystalline granular films with Co particles dispersed in an ZnSe matrix without evidence of intermediate compound formation. Magnetic measurements reveal low values of coercive field and remanence, indicating that the overall magnetic response of the deposited films is determined by multidomain nanosized particles.     

A review of optically pumped far-infrared laser lines from methanol isotopes

The technique of optical pumping in polar molecules is the most efficient for Far-Infrared (FIR) laser generation, providing also a versatile and powerful tool for molecular spectroscopy in this spectral region. Methanol (CH₃OH) and its isotopic varieties are the best media for optically pumped FIR laser, with over thousand lines observed, and the most widely used for investigations and applications. In this sense, it is important organize and make available catalogues of FIR laser lines as complete as possible. Since the last critical reviews of 1984 [1] on methanol and its isotopic varieties [2,3,4], over hundred papers have been published dealing with hundreds of new FIR laser lines. In 1992 a review of FIR laser lines from CH₃OH was presented [5]. In this communication we extend this work to the other methanol isotopes, namely CH₃OD, CD₃OH, CD₃OD,¹³CH₃OH,¹³CD₃OH,¹³CD₃OD, CH₃ ¹⁸OH, CH₂DOH, CHD₂OH and CH₂DOD.     

Optically pumped 13CD3OH: far infrared laserlines and assignment

Fourier transform and IR optoacoustic absorption data of ¹³ CD₃OH were used to search for new FIR laser lines. We have used a waveguide CO₂ laser of 300 MHz tunability as the optical pumping source. We report the observation and characterization of 13 new lines. Three of these lines are associated with absorbing transitions appertaining to the weak ¹³CD₃ asymmetric bending mode     

Determination of 21-hydroxydeflazacort in human plasma by high-performance liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry. Application to bioequivalence study

A liquid chromatographic atmospheric pressure chemical ionization tandem mass spectrometric method is described for the determination of 21-hydroxydeflazacort in human plasma using dexamethasone 21-acetate as an internal standard. The procedure requires a single diethyl ether extraction. After evaporation of the solvent under a nitrogen flow, the analytes are reconstituted in the mobile phase, chromatographed on a C18 reversed-phase column and analyzed by mass spectrometry via a heated nebulizer interface where they are detected by multiple reaction monitoring. The method has a chromatographic run time of less than 5 min and a linear calibration curve with a range of 1-400 ng ml(-1) (r>0.999). The between-run precision, based on the relative standard deviation for replicate quality controls, was < or =5.5% (10 ng ml(-1)), 1.0% (50 ng ml(-1)) and 2.7% (200 ng ml(-1)). The between-run accuracy was +/-7.1, 3.8 and 4.8% for the above concentrations, respectively. This method was employed in a bioequivalence study of two DFZ tablet formulations (Denacen from Marjan Industria e Comercio, Brazil, as a test formulation, and Calcort from Merrell Lepetit, Brazil, as a reference formulation) in 24 healthy volunteers of both sexes who received a single 30 mg dose of each formulation. The study was conducted using an open, randomized, two-period crossover design with a 7-day washout interval. The 90% confidence interval (CI) of the individual geometric mean ratio for Denacen/Calcort was 89.8-109.5% for area under the curve AUC(0-24 h) and 80.7-98.5% for Cmax. Since both the 90% CI for AUC(0-24 h) and Cmax were included in the 80-125% interval proposed by the US Food and Drug Administration, Denacen was considered bioequivalent to Calcort according to both the rate and extent of absorption.