Pesticide residue analysis by off-line SPE and on-line reversed-phase LC-GC using the through-oven-transfer adsorption/desorption interface

A new method to determine pesticide residue in water is presented. The described method includes using off-line solid-phase extraction (SPE) and on-line reversed-phase liquid chromatography-gas chromatography (RPLC-GC). An interface, based on a modified programmed temperature vaporizer (PTV) injector, packed with a suitable trapping material, is used for on-line RPLC-GC. The changes made in the PTV injector affect the pneumatic system, sample introduction, and solvent elimination. The new interface is easily capable of automation. Methanol/wate (70/30) is used as the eluent in the LC preseparation step. The LC column flow during elution is different from the flow during the transfer step. The transferred volumes range from 500 to 1400 microL (volume of the fractions of interest). Solvent elimination is almost 100% before the sample reaches the GC column. The described system does not show any variation of the peak retention times. The detection limit for real samples ranges from 0.04 to 1.5 ng/L, using NP detection.     

Nutritional and microbiological profile of soybean sausages available in Costa Rica

The nutritional and microbiological quality of 80 soybean sausage samples (50% frankfurter and 50% sausage mortadela) was studied. On average, the protein content was 17.5 g/100 g in sausage mortadela and 20 g/100 g in frankfurter. The mean total fat content was 5.5 g/100 g for both products. However when products of different manufacture industries were compared, a highly significant difference (p = 0.0000) in the fatty acids speciation between both groups and between samples of the same product were found. Bigger differences were found in the content of palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2). Cholesterol was not detected in samples analyzed. On average the atherogenicity index was 0.55 for sausage mortadela and 0.59 for frankfurter. A consumption of 25 grams of of soybean protein from these sausages can bring an intake of saturated fatty acids between 20-90% of the daily recommendation. Likewise, they can supply between 12-70% of the recommended daily polyunsaturated fatty acids. These variations are owing to the big difference in fatty acids speciation in each sausage brand. Around 20% of soybean sausages studied showed total coliform levels above 10(4)/g, being more frequent in sausage mortadela. Also 60% of this product and 10% of frankfurters showed psychrotroph levels of 10(6)/g. Clostridium perfringens, in levels above 10(2)/g was evidenciated in 5% of samples, Escherichia coli was not isolated from them. The findings of this study suggest the urgent need for implementing a quality control system for soybean sausages, before national health authorities consider to support nutritional campainings that promote their consumption.     

Uptake of cations under two different water regimes in a boreal scots pine forest

There is still much to find out about how trees react to changing nutrient conditions. In this cation uptake study, 134Cs and 22Na were injected between the humus and the mineral soil, and into a 20-cm depth in the mineral soil, respectively. Half of the experimental site was subjected to desiccation in 1995 and 1996, while the other half was subjected to irrigation in 1995, and desiccation in 1996. One month after the injections, the concentration of 134Cs in the xylem sap was higher in the irrigated plots (ID) than in the desiccated plots (DD). In August 1995, the difference in the 134Cs concentration in the xylem sap was even higher between the treatments. In 1995, 22Na was also higher in the xylem sap on the ID plots than on the DD plots, but not significantly. Exponential relationships were found between the amount of 134Cs and 22Na in the xylem sap; the relative water uptake from humus and 0-10-cm mineral soil (134Cs); and 10-25-cm mineral soil (22Na) in July 1995, when the tracers had not yet reached the top of the boles. The relative uptake of injected 22Na was larger than that of injected 134Cs, probably due to low exchangeability of Cs in the soil. One year after the injection (1996), more 134Cs was found in the wood, bark, needles and cones on the plots irrigated in 1995 than on the desiccated plots. The content of 134Cs in the stem wood and stump amounted to nearly 80% of the total uptake in the trees. The Cs distribution 1 year after the Chernobyl accident was dominated by Cs on/in needles and bark. After 10 years of redistribution, the Chernobyl Cs content of the different parts of the trees approached that of K.     

Influence of Avicel PH-301 on the compressibility of alpha-methyldopa and phenobarbitone in direct compression

The aim of this work was to investigate the compressibility behavior of alpha-methyldopa and phenobarbitone using a Korsch EK0 instrumented eccentric tablet machine, with force-time and force-displacement curves constructed and applied to calculate different compressional values to study the compressional behavior. The results of this work revealed a difference in compressibility behavior between the two drugs during the compressional process. alpha-Methyldopa gave an abnormal compressional curve with high friction in the pre- and postcompressional phases. A residual force could be seen on the lower punch. Furthermore, capping and sticking were observed visually during tablet pressing, indicating poor compressibility behavior. In the case of phenobarbitone, no friction was observed in the precompressional phase, but there was higher friction in the postcompressional phase, especially in the ejection phase. The compressibility of the drugs was improved by the addition of Avicel PH-301 and magnesium stearate.     

The influence of chemical treatment and suture on the elastic behavior of calf pericardium utilized in the construction of cardiac bioprostheses

Poor mechanical properties of biological tissue are known to cause wear, leading to the failure of cardiac bioprostheses made of calf pericardium. Different chemical agents such as sodium dodecyl sulfate (SDS) are presently being tested as possible inhibitors of the calcification process. The objective of this report was to determine the mechanical behavior of calf pericardium treated with SDS for 24 h and the influence of the suture on the mechanical properties of the tissue. Forty-eight samples were tested: 24 subjected to a standard treatment with glutaraldehyde (12 sewn with 4/0 silk suture thread) and 24 incubated with SDS for 24 h (12 sewn with the same suture thread). Each sutured and non-sutured sample was cut into two strips to yield paired samples. All were subjected to tensile stress to breaking point. The mean stress at breaking point in the non-sutured series treated with glutaraldehyde alone was 16.42 and 13.85 MPa depending on the region of the pericardium, while in the sutured samples subjected to glutaraldehyde the mean stress was 7.50 and 7.63 MPa, respectively, differences which were statistically significant (p = 0.03 and p = 0.003, respectively) when the means for non-sutured samples from equivalent regions treated with glutaraldehyde were compared. The stress at breaking point was lower in the SDS-treated series, ranging between 2.60 and 3.56 MPa. The mathematical functions that govern the stress/strain or deformation were obtained. In the series of pericardium treated with SDS, deformations of 10% were produced with stresses of under 0.4 MPa, an outcome that is intolerable from the constructive point of view. We established a regression model that enabled us to determine the mechanical behavior of a sutured sample by testing a contiguous piece of tissue, with a high correlation coefficient (r > 0.99). We consider this finding to be of interest in the selection of pericardium for use in the construction of leaflets for cardiac bioprostheses.     

Immunolocalization of the cellular prion protein in normal brain

We examined the localization of PrP(c) in normal brain using free-floating section immunohistochemistry and monclonal antibody 3F4. In the mature hamster and baboon brain, PrP(c) is localized to the neuropil with a synaptic distribution and the PrP(c) immunoreactivity is denser in regions known for ongoing plasticity. Cell bodies and major fiber tracts have little or no PrP(c) immunoreactivity. At the electron microscopic level, PrP(c) immunoreactivity decorates synaptic profiles, both pre- and postsynaptically. Results obtained with two additional antibodies, 3B5 and Pri-304, showed similar patterns of PrP(c) bands on Western blots, although Pri-304 was less sensitive. On sections through the adult hamster hippocampus, 3B5 and Pri-304 both stained the synaptic neuropil while cell bodies in the pyramidal and dentate granule cell layers were not immunoreactive. Pri-304 differentiated between synaptic layers in the hippocampus and closely resembled the pattern of staining obtained with 3F4. Preliminary results of developing brain showed that PrP(c) is initially localized along fiber tracts in the neonate brain. These results show that PrP(c) has a synaptic distribution in the adult brain and suggest that there are important changes in its distribution during brain development. These results also characterize two additional reagents for studies of PrP(c) localization.     

Adaptive systems in speckle-pattern interferometry

The concept of adaptivity in television holography is discussed, and various realizations of adaptivity are presented. In one possible variation, functions of the components of the optical arrangement may be changed to adapt them to measurement conditions. An additional peculiarity of the technique is that reference waves are produced by holographically reconstructed virtual images. A method, believed to be new, is introduced for synthesizing the phase front of the master object beam that is produced by a simple holographic optical element and is used as a smooth or a speckled reference beam in the electronic speckle-pattern interferometer. An adaptive interferometer is presented as a measuring device for various measuring tasks. Selected applications are shown, demonstrating different aspects of adaptivity.     

Effect of local microroughness on the gloss uniformity of printed paper surfaces

A critical factor that affects the appearance of printed paper surfaces is gloss uniformity, which is usually assessed visually. To relate gloss uniformity to nonvisual quantities, we first visually identified areas of either high or low gloss on the same sample for two different types of paper. We then measured the roughness and the reflectance of these areas. Microroughness was measured with an atomic-force microscope, and roughness was measured over a larger area with a confocal laser scanning microscope. The local reflectance of the high-gloss and the low-gloss areas was obtained from images taken with a gloss-imaging instrument and compared with the roughness of each area. This correlation is nonlinear, and roughness is insufficient to predict the local reflectance. Light-scattering measurements were made in the specular direction to map the gloss uniformity over larger areas than was possible with the gloss-imaging instrument. These maps were used to show the possibility of using both the spatial frequency and the fan filters, which together form a set of cortex filters, to analyze the variation of the gloss about the mean value and its spatial distribution on the surface in terms of spatial frequency and azimuthal orientation.     

Laboratory facilities and recommendations for the characterization of biological ultraviolet dosimeters

A laboratory facility for characterizing biological dosimeters for the measurement of UV radiation has been built and tested. The facility is based on a solar simulator, stabilized by photofeedback, and monitored by a spectroradiometer, with a versatile filter arrangement. This enables the following characteristics of the dosimeters to be ascertained: spectral response, linearity, and reciprocity; angular acceptance and response; calibration in simulated sunlight. The system has been tested on a variety of dosimeters and has the potential to be used with other radiometers, subject currently to the size of their active surface.