The characteristics of a test liquid formulation for use in evaluating the performance of handling and metering systems

Injection metering systems are an important option for the development of pesticide application equipment, with advantages relating to minimising the need for disposal of unused pesticide, improving the ease of cleaning and optimising the accuracy of chemical application. For all injection systems, characteristics such as the steady-state accuracy of delivered dose, dose stability and the time response for dose step changes are related to the ability of the system to operate with different chemical formulations. A system designed to inject liquids should be able to accommodate changes in viscosity and density. The aim of this study was to develop a methodology for testing chemical injection systems using liquids with different viscosities. The experimental arrangement simulating applications with injection metering systems used dye and salt solutions as tracers. Tests were conducted to analyse the influence of salt on the characteristics of the water and a viscous solution. Results showed that the salt interfered with the dye stability in the water solution. In tests with a viscous test liquid, the salt was introduced at different steps during the mixing process, providing four different liquids to be analysed in terms of viscosity, density and pH. Some differences in liquid characteristics were found which could influence the performance of the injection systems.

Validation of an immunoassay method for the determination of traces of carbaryl in vegetable and fruit extracts by liquid chromatography with photodiode array and mass spectrometric detection

A competitive enzyme-linked immunosorbent assay (ELISA) method for carbaryl quantitation in crop extracts was validated by liquid chromatography (LC) with diode array detection (DAD). For this purpose, six crops (banana, carrot, green bean, orange, peach and potato) were chosen for recovery and reproducibility studies. The general sample preparation included extraction with methanol followed by liquid-liquid partitioning and clean-up on Celite-charcoal adsorbent column of the vegetable extracts. ELISA samples consisted of a diluted LC extract in assay phosphate buffer (pH 7.5). The potential effect of methanol in these samples was evaluated. It was observed that a maximum content of 10% methanol present in the assay buffer could be tolerated without expressive losses in the ELISA performance. Under these conditions, a IC50 similar to 1.48 mu g l(-1) was obtained. A minimum matrix effect with a 1:50 dilution of the methanolic extracts in assay buffer was noticed, except for green bean samples that inhibited completely the assay. For the vegetable extracts, the ELISA sensitivities varied from 3.9 to 5.7 mu g l(-1), and good recoveries (82-96%) with R.S.D.s ranging from 5.7 to 12.1% were found. An excellent correlation between the LC-DAD and ELISA techniques was obtained. The confirmation of the carbaryl in less concentrated samples was achieved by LC-mass spectrometry interfaced with atmospheric pressure chemical ionisation. The [M + H](+)= 202 and [M + H-57](+)=145 ions, equivalent to the protonated molecular and l-naphthol ions, respectively, were used to carbaryl identification in these samples. (C) 1998 Elsevier B.V. B.V. All rights reserved.

Determination of aldicarb, aldicarb sulfoxide and aldicarb sulfone in some fruits and vegetables using high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An analytical method for the determination of aldicarb, and its two major metabolites, aldicarb sulfoxide and aldicarb sulfone in fruits and vegetables is described. Briefly the method consisted of the use of a methanolic extraction, liquid-liquid extraction followed by solid-phase extraction clean-up. Afterwards, the final extract is analyzed by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). The specific fragment ion corresponding to [M-74](+) and the protonated molecular [M+K](+) ion were used for the unequivocal determination of aldicarb and its two major metabolites. The analytical performance of the proposed method and the results achieved were compared with those obtained using the common analytical method involving LC with post-column fluorescence detection (FL). The limits of detection varied between 0.2 and 1.3 ng but under LC-FL were slightly lower than when using LC-APCI-MS. However both methods permitted one to achieve the desired sensitivity for analyzing aldicarb and its metabolites in vegetables. The method developed in this work was applied to the trace determination of aldicarb and its metabolites in crop and orange extracts. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Application of a new reverse Monte Carlo algorithm to polyatomic molecular systems. I. Liquid water

Using a new reverse Monte Carlo algorithm, we present simulations that reproduce very well several structural and thermodynamic properties of liquid water. Both Monte Carlo, molecular dynamics simulations and experimental radial distribution functions used as input are accurately reproduced using a small number of molecules and no external constraints. Ad hoc energy and hydrogen bond analysis show the physical consistency and limitations of the generated RMC configurations. (C) 2001 American Institute of Physics.

Simultaneous determination of furanocoumarins in infusions and decoctions from Carapia (Dorstenia species) by high-performance liquid chromatography

The use of furanocoumarins, which are photosensitizing compounds, combined with exposure to UV-A radiation is a common treatment for vitiligo, psoriasis, and a number of other skin diseases. Although furanocoumarins plus UV-A treatment is highly effective, several studies have shown that exposure to high doses increases the risk to development of cutaneus carcinoma. Several Dorstenia species are used in folk medicine, mainly against skin diseases, because of the presence of biologically active compounds. We present here analysis of the chemical composition of furanocoumarins from infusion and decoction of Carapia (Dorstenia species), which is used in Brazil against several diseases. We have employed high-performance liquid chromatography (HPLC) procedures for the quantitative determination of psoralen, bergapten, and isopimpinellin. The contents of furanocoumarins revealed an insignificant difference between infusion and decoction. Dorstenia tubicina and D. asaroides contained psoralen and bergapten only in the rhizomes, whereas D. vitifolia shows solely isopimpinellin in both rhizomes and aerial parts.

Development of alpha-SiAlON-SiC ceramic composites by liquid phase sintering

In this work, in situ alpha-SiAlON-SiC ceramic composites were obtained,by, liquid phase sintering, using SiC as reinforcement. Different beta-SiC powder contents (0-20 wt.%), were added to Si3N4-AlN-RE2O3. powder mixtures, and compacted by cold isostatic pressing. The samples were sintered at 1950 degrees C for 1 h, in N-2 atmosphere. Sintered: samples were characterized by relative density, weight loss, X-ray diffraction and scanning electron microscopy. Furthermore, mechanical properties such as hardness and fracture toughness were determined by Vickers indentation method. Lattice parameters of the alpha' phase did not considerably change with increase of SiC content. However, morphology, average grain size and aspect ratio of the alpha' phase were considerably changed with increase of the SiC content. These behavior influences significantly the mechanical properties of this hard ceramic composite. (C) 2006 Elsevier Ltd. All rights reserved.

Determination of acetaldehyde in fuel ethanol by high-performance liquid chromatography with electrochemical detection

The cyclic voltammetric behavior of acetaldehyde and the derivatized product with 2,4-dinitrophenylhydrazine (DNPHi) has been studied at a glassy carbon electrode. This study was used to optimize the best experimental conditions for its determination by high-performance liquid chromatographic (HPLC) separation coupled with electrochemical detection. The acetaldehyde-2,4-dinitrophenyl.hydrazone (ADNPH) was eluted and separated by a reversed-phase column, C-18, under isocratic conditions with the mobile phase containing a binary mixture of methanol/LiCl(aq) at a concentration of 1.0 x 10(-3) M (80:20 v/v) and a flow rate of 1.0 mL min(-1). The optimum condition for the electrochemical detection of ADNPH was +1.0 V vs. Ag/AgCl as a reference electrode. The proposed method was simple, rapid (analysis time 7 min) and sensitive (detection limit 3.80 mu g L-1) at a signal-to-noise ratio of 3:1. It was also highly selective and reproducible [standard deviation 8.2% +/- 0.36 (n = 5)]. The analytical curve of ADNPH was linear over the range of 3-300 mg L-1 per injection (20 mu L), and the analytical recovery was > 99%.

Models of liquid storage tanks

We present the results of a comparative study on thermally stratified tanks for hot storage. A two-dimensional model is employed. A numerical solution was obtained using the control-volume technique due to Patankar. The two-dimensional model was simplified for the pure conduction case. Results from the two models were compared with each other and with available numerical and experimental results. (C) 1997 Elsevier B.V. Ltd.

Determination of rice herbicides, their transformation products and clofibric acid using on-line solid-phase extraction followed by liquid chromatography with diode array and atmospheric pressure chemical ionization mass spectrometric detection

A simultaneous method for the trace determination of acidic, neutral herbicides and their transformation products in estuarine waters has been developed through an on-line solid-phase extraction method followed by liquid chromatography with diode array and mass spectrometric detection. An atmospheric pressure chemical ionization (APCI) interface was used in the negative ionization mode after optimization of the main APCI parameters. Limits of detection ranged from 0.1 to 0.02 ng/ml for 50 mi of acidified estuarine waters preconcentrated into polymeric precolumns and using time-scheduled selected ion monitoring mode. Two degradation products of the acidic herbicides (4-chloro-2-methylphenol and 2,4-dichlorophenol) did not show good signal response using APCI-MS at the concentration studied due to the higher fragmentor voltage needed for their determination For molinate and the major degradation product of propanil, 3,4-dichloroaniline, positive ion mode was needed for APCI-MS detection. The proposed method was applied to the determination of herbicides in drainage waters from rice fields of the Delta del Ebro (Spain). During the S-month monitoring of the herbicides, 8-hydroxybentazone and 4-chloro-2-methylphenoxyacetic acid were successively found in those samples. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Determination of 2,4-dichlorophenoxyacetic acid and its major transformation product in soil samples by liquid chromatographic analysis

The 2,4-dichlorophenoxyacetic acid (2,4-D) is one of the most applied herbicides around the world to control broad leave herbs in many crops: In this study, a method was developed for simultaneous extraction and determination of 2,4D and its major transformation product, i.e., the 2,4-dichlorophenol (2,4-DCP), in soil samples. The herbicide and its degradation product were extracted twice from soil samples, after acidification, by dichloromethane on ultrasound system for 1 h. Both extracts were combined and filtrated in qualitative filter paper and Celitee. The total extract was concentrated in rotatory evaporator, dried under N-2 and finally dissolved in 1 ml of methanol. High Performance Liquid Chromatography with UV detection at 230 nm was used for analysis. Recoveries were obtained from soil samples fortified at 0.1, 1.0, 2.0, 3.0 and 4.0 mg kg(-1) levels and the results varied from 85 to 111% (for 2,4-D) and from 95 to 98% (for 2,4-DCP). For both compounds, the limits of quantification were 0.1 mg kg(-1), which were the loss level at which the accuracy and the precision were studied. Nevertheless, the limits of detection, calculated by considering the blank standard deviation and the minimum concentration level, were 0.03 and 0.02 mg kg for 2,4-D and 2,4-DCP, respectively. This proposed method was applied to soil samples of eucalyptus crops, which was previously treated with the herbicide. Despite that, neither 2,4-D nor its degradation product were detected 30 days after the herbicide application. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Temperature and concentration dependence of density of model liquid foods

Density of binary solutions and combinations of sucrose, glucose, fructose, citric acid, malic acid, pectin, and inorganic salts were measured with an oscillating tube density meter in the temperature range from 10degrees to 60degreesC, at varying concentrations. Density can be predicted with accuracy better than 5 x 10(-5) g cm(-3) using predictive equations obtained by fitting the experimental data. Available literature values agreed well with experimental data. Relations for the excess molar volume of these solutions were derived in terms of mole fraction and temperature. A thermodynamic model for the volumetric analysis of multicomponent aqueous solutions containing electrolyte and non-electrolyte compounds was also proposed. These models can be used for prediction of density of liquid food systems, specially fruit juices and beverages, based on composition and temperature, with high accuracy and without elaborate experimental work.

Competition between anchoring and reversible photo-induced alignment of a nematic liquid crystal

We investigated the alignment induced on a nematic liquid crystal (LC) by a photo-aligned polymer film with azo-dye side groups. The orientation of the LC molecules can be manipulated in a reversible manner by irradiating the film with polarized light. We analyzed the competition between the orientation induced by the main chain, through rubbing of the film and that induced by the photo-aligned polymer. Anchoring strength for the different processing conditions are reported. The changes in film morphology caused by rubbing or photo-alignment could be captured by atomic force microscopy. The reversibility of the photo-induced alignment and the competition between the two anchoring mechanisms may allow recording and erasing of information in a LC display.

Detection and quantification of antibodies to Newcastle disease virus in ostrich and rhea sera using a liquid phase blocking enzyme-linked immunosorbent assay

A liquid phase blocking ELISA (LPB-ELISA) was adapted for the detection and quantification of antibodies to Newcastle disease virus. Sera from vaccinated and unvaccinated commercial flocks of ostriches (Struthio camelus) and rheas (Rhea americana) were tested. The purified and nonpurified virus used as the antigen and the capture and detector antibodies were prepared and standardized for this purpose. The hemagglutination-inhibition (HI) test was regarded as the reference method, the cutoff point for the LPB-ELISA was determined by a two-graph receiver operating characteristic analysis. The LPB-ELISA titers regressed significantly (P < 0.0001) on the HI titers with a high correlation coefficient (r = 0.875). The two tests showed good agreement ( = 0.82; P < 0.0001), relative sensitivity (90.91%) and specificity (91.18%), and accuracy (91.02%), suggesting that they are interchangeable.

Highly swollen liquid crystals as new reactors for the synthesis of nanomaterials

Synthesis and self-assembly of nanomaterials can be controlled by the properties of soft matter. on one hand, dedicated nanoreactors such as reverse microemulsions or miniemulsions can be designed. on the other hand, direct shape control can be provided by the topology of liquid crystals that confine the reacting medium within a specific geometry. In the first case, the preparation of micro- or miniemulsions generally requires energetic mechanical stirring. The second approach uses thermodynamically stable systems, but it remains usually limited to binary (water + surfactant) systems. We report the preparation of different families of materials in highly ordered quaternary mediums that exhibit a liquid crystal structure with a high cell parameter. They were prepared with the proper ratios of salted water, nonpolar solvent, surfactant. and cosurfactants that form spontaneously swollen hexagonal phases. These swollen liquid crystals can be prepared from all classes of surfactants (cationic, anionic, and nonionic). They contain a regular network of parallel cylinders, whose diameters can be swollen with a nonpolar solvent, that are regularly spaced in a continuous aqueous salt solution. We demonstrate in the present report that both aqueous and organic phases can be used as nanoreactors for the preparation of materials. This property is illustrated by various examples such as the synthesis of platinum nanorods prepared in the aqueous phase or zirconia needles or the photo- or gamma-ray-induced polymerization of polydiacetylene in the organic phase. In all cases, materials can be easily extracted and their final shapes are directed by the structure-directing effect imposed by the liquid crystal.