Feasibility of using in situ fusion for the determination of Co, Cr and Mn in Portland cement by direct solid sampling graphite furnace atomic absorption spectrometry

In situ fusion on the boat-type graphite platform has been used as a sample pretreatment for the direct determination of Co, Cr and Mn in Portland cement by solid sampling graphite furnace atomic absorption spectrometry (SS-GF AAS). The 3-field Zeeman technique was adopted for background correction to decrease the sensitivity during measurements. This strategy allowed working with up to 200 mu g of sample. The in situ fusion was accomplished using 10 mu L of a flux mixture 4.0% m/v Na(2)CO(3) + 4.0% m/v ZnO + 0.1% m/v Triton (R) X-100 added over the cement sample and heated at 800 degrees C for 20 s. The resulting mould was completely dissolved with 10 mu L of 0.1% m/v HNO(3). Limits of detection were 0.11 mu g g(-1) for Co, 1.1 mu g g(-1) for Cr and 1.9 mu g g(-1) for Mn. The accuracy of the proposed method has been evaluated by the analysis of certified reference materials. The values found presented no statistically significant differences compared to the certified values (Student`s t-test, p<0.05). In general, the relative standard deviation was lower than 12% (n = 5). (C) 2009 Elsevier B.V. All rights reserved.

Determination of lead in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry using direct solid sampling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Application of bag sampling technique for particle size distribution measurements

Bag sampling techniques can be used to temporarily store an aerosol and therefore provide sufficient time to utilize sensitive but slow instrumental techniques for recording detailed particle size distributions. Laboratory based assessment of the method were conducted to examine size dependant deposition loss coefficients for aerosols held in VelostatTM bags conforming to a horizontal cylindrical geometry. Deposition losses of NaCl particles in the range of 10 nm to 160 nm were analysed in relation to the bag size, storage time, and sampling flow rate. Results of this study suggest that the bag sampling method is most useful for moderately short sampling periods of about 5 minutes.

A sampling technique for two-spotted mite in papaya

Two-spotted mite, Tetranychus urticae Koch, was until recently regarded as a minor and infrequent pest of papaya in Queensland through the dry late winter/early summer months. The situation has changed over the past 4-5 years, so that now some growers consider spider mites significant pests all year round. This altered pest status corresponded with a substantial increase in the use of fungicides to control black spot (Asperisporium caricae). A project was initiated in 1998 to examine the potential reasons for escalating mite problems in commercially-grown papaya, which included regular sampling over a 2 year period for mites, mite damage and beneficial arthropods on a number of farms on the wet tropical coast and drier Atherton Tableland. Differences in soil type, papaya variety, chemical use and some agronomic practices were included in this assessment. Monthly visits were made to each site where 20 randomly-selected plants from each of 2 papaya lines (yellow and red types) were surveyed. Three leaves were selected from each plant, one from each of the bottom, middle and top strata of leaves. The numbers of mobile predators were recorded, along with visual estimates of the percentage and age of mite damage on each leaf. Leaves were then sprayed with hairspray to fix the mites and immature predators to the leaf surface. Four leaf disks, 25 mm in diameter, were then punched from each leaf into a 50 ml storage container with a purpose-built disk-cutting tool. Disks from each leaf position were separated by tissue paper, within the container. On return to the laboratory, each leaf disk was scrutinised under a binocular microscope to determine the numbers of two-spotted mites and eggs, predatory mites and eggs, and the immature stages of predatory insects (mainly Stethorus, Halmus and lacewings). A total of 2160 leaf disks have been examined each month. All data have been entered into an Access database to facilitate comparisons between sites.

A novel non-intrusive sampling technique for CO2 laser on-line beam monitoring utilising a silicon mirror

The measurement of high speed laser beam parameters during processing is a topic that has seen growing attention over the last few years as quality assurance places greater demand on the monitoring of the manufacturing process. The targets for any monitoring system is to be non-intrusive, low cost, simple to operate, high speed and capable of operation in process. A new ISO compliant system is presented based on the integration of an imaging plate and camera located behind a proprietary mirror sampling device. The general layout of the device is presented along with the thermal and optical performance of the sampling optic. Diagnostic performance of the system is compared with industry standard devices, demonstrating the high quality high speed data which has been generated using this system.

High Resolution measurement and mapping of tungstate in waters, soils and sediments using the low-disturbance DGT sampling technique.

Increasing tungsten (W) use for industrial and military applications has resulted in greater W discharge into natural waters, soils and sediments. Risk modeling of W transport and fate in the environment relies on measurement of the release/mobilization flux of W in the bulk media and the interfaces between matrix compartments. Diffusive gradients in thin-films (DGT) is a promising passive sampling technique to acquire such information. DGT devices equipped with the newly developed high-resolution binding gels (precipitated zirconia, PZ, or ferrihydrite, PF, gels) or classic/conventional ferrihydrite slurry gel were comprehensively assessed for measuring W in waters. FerrihydriteDGT can measure W at various ionic strengths (0.001–0.5 mol L−1 NaNO3) and pH (4–8), while PZDGT can operate across slightly wider environmental conditions. The three DGT configurations gave comparable results for soil W measurement, showing that typically W resupply is relatively poorly sustained. 1D and 2D high-resolution W profiling across sediment—water and hotspot—bulk media interfaces from Lake Taihu were obtained using PZDGT coupled with laser ablation ICP–MS measurement, and the apparent diffusion fluxes across the interfaces were calculated using a numerical model.

Bio-inspired optimization & sampling technique for side-chain packing in MCCE

The prediction of proteins' conformation helps to understand their exhibited functions, allows for modeling and allows for the possible synthesis of the studied protein. Our research is focused on a sub-problem of protein folding known as side-chain packing. Its computational complexity has been proven to be NP-Hard. The motivation behind our study is to offer the scientific community a means to obtain faster conformation approximations for small to large proteins over currently available methods. As the size of proteins increases, current techniques become unusable due to the exponential nature of the problem. We investigated the capabilities of a hybrid genetic algorithm / simulated annealing technique to predict the low-energy conformational states of various sized proteins and to generate statistical distributions of the studied proteins' molecular ensemble for pKa predictions. Our algorithm produced errors to experimental results within .acceptable margins and offered considerable speed up depending on the protein and on the rotameric states' resolution used.

Direct determination of iron in sand using solid sampling graphite furnace atomic absorption spectrometry

A fast and reliable method for the direct determination of iron in sand by solid sampling graphite furnace atomic absorption spectrometry was developed. A Zeeman-effect 3-field background corrector was used to decrease the sensitivity of spectrometer measurements. This strategy allowed working with up to 200 mu g of samples, thus improving the representativity. Using samples with small particle sizes (1-50 mu m) and adding 5 mu g Pd as chemical modifier, it was possible to obtain suitable calibration curves with aqueous reference solutions. The pyrolysis and atomization temperatures for the optimized heating program were 1400 and 2500 degrees C, respectively. The characteristic mass, based on integrated absorbance, was 56 pg, and the detection limits, calculated considering the variability of 20 consecutive measurements of platform inserted without sample was 32 pg. The accuracy of the procedure was checked with the analysis of two reference materials (IPT 62 and 63). The determined concentrations were in agreement with the recommended values (95% confidence level). Five sand samples were analyzed, and a good agreement (95% confidence level) was observed using the proposed method and conventional flame atomic absorption spectrometry. The relative standard deviations were lower than 25% (n = 5). The tube and boat platform lifetimes were around 1000 and 250 heating cycles, respectively.

Application of solid sampling device for direct determination of chromium and nickel in lubricating oils by graphite furnace atomic absorption spectrometry

One method using a solid sampling device for the direct determination of Cr and Ni in fresh and used lubricating oils by graphite furnace atomic absorption spectrometry are proposed. The high organic content in the samples was minimized using a digestion step at 400 degrees C in combination with an oxidant mixture 1.0% (v v(-1)) HNO3+15% (v v(-1)) H2O2+0.1% (m v(-1)) Triton X-100 for the in situ digestion. The 3-field mode Zeeman-effect allowed the spectrometer calibration up to 5 ng of Cr and Ni. The quantification limits were 0.86 mu g g(-1) for Cr and 0.82 mg g(-1) for Ni, respectively. The analysis of reference materials showed no statistically significant difference between the recommended values and those obtained by the proposed methods.

Evaluation of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry for direct determination of chromium in medicinal plants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the standard sampling technique for suspended solids /

Mode of access: Internet.

Direct detection of additives and degradation products from polymers by liquid extraction surface analysis employing chip-based nanospray mass spectrometry

RATIONALE: Polymer-based surface coatings in outdoor applications experience accelerated degradation due to exposure to solar radiation, oxygen and atmospheric pollutants. These deleterious agents cause undesirable changes to the aesthetic and mechanical properties of the polymer, reducing its lifetime. The use of antioxidants such as hindered amine light stabilisers (HALS) retards these degradative processes; however, mechanisms for HALS action and polymer degradation are poorly understood. METHODS: Detection of the HALS TINUVINW123 (bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate) and the polymer degradation products directly from a polyester-based coil coating was achieved by liquid extraction surface analysis (LESA) coupled to a triple quadrupole QTRAPW 5500 mass spectrometer. The detection of TINUVINW123 and melamine was confirmed by the characteristic fragmentation pattern observed in LESA-MS/MS spectra that was identical to that reported for authentic samples. RESULTS: Analysis of an unstabilised coil coating by LESA-MS after exposure to 4 years of outdoor field testing revealed the presence of melamine (1,3,5-triazine-2,4,6-triamine) as a polymer degradation product at elevated levels. Changes to the physical appearance of the coil coating, including powder-like deposits on the coating's surface, were observed to coincide with melamine deposits and are indicative of the phenomenon known as polymer ' blooming'. CONCLUSIONS: For the first time, in situ detection of analytes from a thermoset polymer coating was accomplished without any sample preparation, providing advantages over traditional extraction-analysis approaches and some contemporary ambient MS methods. Detection of HALS and polymer degradation products such as melamine provides insight into the mechanisms by which degradation occurs and suggests LESA-MS is a powerful new tool for polymer analysis. Copyright (C) 2012 John Wiley & Sons, Ltd.

Desorption electrospray ionisation mass spectrometry reveals in situ modification of a hindered amine light stabiliser resulting from direct N–OR bond cleavage

Detection and characterisation of structural modifications of a hindered amine light stabiliser (HALS) directly from a polyester-based coil coating have been achieved by desorption electrospray ionisation mass spectrometry (DESI-MS) for the first time. In situ detection is made possible by exposing the coating to an acetone vapour atmosphere prior to analysis. This is a gentle and non-destructive treatment that allows diffusion of analyte to the surface without promoting lateral migration. Using this approach a major structural modification of the HALS TINUVIN®123 (bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate) was discovered where one N-ether piperidine moiety (N-OC8H17) is converted to a secondary piperidine (N–H). With the use of 2-dimensional DESI-MS imaging the modification was observed to arise during high curing temperatures (ca. 260 °C) and under simulated physiological conditions (80 °C, full solar spectrum). It is proposed that the secondary piperidine derivative is a result of a highly reactive aminyl radical intermediate produced by N–O homolytic bond cleavage. The nature of the bond cleavage is also suggested by ESR spin-trapping experiments employing α-phenyl-N-tert-butyl nitrone (PBN) in toluene at 80 °C. The presence of a secondary piperidine derivative in situ and the implication of N–OR competing with NO–R bond cleavage suggest an alternative pathway for generation of the nitroxyl radical—an essential requirement in anti-oxidant activity that has not previously been described for the N-ether sub-class of HALS.

Structural identification of hindered amine light stabilisers in coil coatings using electrospray ionisation tandem mass spectrometry

Hindered amine light stabilisers (HALS) are the most effective antioxidants currently available for polymer systems in post-production, in-service applications, yet the mechanism of their action is still not fully understood. Structural characterisation of HALS in polymer matrices, particularly the identification of structural modifications brought about by oxidative conditions, is critical to aid mechanistic understanding of the prophylactic effects of these molecules. In this work, electrospray ionisation tandem mass spectrometry (ESI-MS/MS) was applied to the analysis of a suite of commercially available 2,2,6,6-tetramethylpiperidine-based HALS. Fragmentation mechanisms for the \[M + H](+) ions are proposed, which provide a rationale for the product ions observed in the MS/MS and MS(3) mass spectra of N-H, N-CH(3), N-C(O)CH(3) and N-OR containing HALS (where R is an alkyl substituent). A common product ion at m/z 123 was identified for the group of antioxidants containing N-H, N-CH3 or N-C(0)CH3 functionality, and this product ion was employed in precursor ion scans on a triple quadrupole mass spectrometer to identify the HALS species present in a crude extract from of a polyester-based coil coating. Using MS/MS, two degradation products were unambiguously identified. This technique provides a simple and selective approach to monitoring HALS structures within complex matrices. Copyright (C) 2010 John Wiley & Sons, Ltd.

Sampling accuracy of reef resource inventory technique

A new technique called the reef resource inventory (RRI) was developed to map the distribution and abundance of benthos and substratum on reefs. The rapid field sampling technique uses divers to visually estimate the percentage cover of categories of benthos and substratum along 2x20 in plotless strip-transects positioned randomly over the tops, and systematically along the edge of reefs. The purpose of this study was to compare the relative sampling accuracy of the RRI against the line intercept transect technique (LIT), an international standard for sampling reef benthos and substratum. Analysis of paired sampling with LIT and RRI at 51 sites indicated sampling accuracy was not different (P > 0.05) for 8 of the 12 benthos and substratum categories used in the study. Significant differences were attributed to small-scale patchiness and cryptic coloration of some benthos; effects associated with sampling a sparsely distributed animal along a line versus an area; difficulties in discriminating some of the benthos and substratum categories; and differences due to visual acuity since LIT measurements were taken by divers close to the seabed whereas RRI measurements were taken by divers higher in the water column. The relative cost efficiency of the RRI technique was at least three times that of LIT for all benthos and substratum categories and as much as 10 times higher for two categories. These results suggest that the RRI can be used to obtain reliable and accurate estimates of relative abundance of broad categories of reef benthos and substratum.