Analysis of Steroids using Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry-Mass Spectrometry (SPME-GC-MS-MS)

Direct immersion SPME-GC-MS-MS was used for the analysis of steroids in water at part-per-trillion(ppt) and lower concentrations. The method was validated and extended to real sample analysis. The method were linear from 0.01 to 5 ng/ml with precision less than 10% relative standard deviation for a steroid mixture at 1 ng/ml. Limit of quantitation and limit of detection was found to be 200- 1200 pg/L and 30-200 pg/L respectively and recoveries ranged from 88-103 %. To understand the extraction efficiency of the fiber, a depletion study was performed. The fiber/ sample partition coefficients for the steroids were determined to be 1.0 x 104 to 1.5 x 104 . The extraction was performed without derivatization or the use of an internal standard. SPMEGC-MS-MS effectively demonstrated ultra-trace level detection of steroids in water.

Peptídeos cíclicos hepatotóxicos: MALDI-TOF como uma ferramenta analítica

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

Isotope analysis (δ 13c) of pulpy whole apple juice

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

Development and validation of an LC-MS/MS method for quantitative analysis of mirtazapine in human plasma

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

Feasibility of internal standardization in the direct and simultaneous determination of As, Cu and Pb in sugar-cane spirits by graphite furnace atomic absorption spectrometry

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

Internal standardization combined with dilute-and-shoot preparation of distilled alcoholic beverages for Cu determination by high-resolution continuum source flame atomic absorption spectrometry

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

Evaluation of Philips and Ziegler-Natta high-density polyethylene degradation during processing in an internal mixer using the chain scission and branching distribution function analysis

The oxidative and thermo-mechanical degradation of HDPE was studied during processing in an internal mixer under two conditions: totally and partially filled chambers, which provides lower and higher concentrations of oxygen, respectively. Two types of HDPEs, Phillips and Ziegler-Natta, having different levels of terminal vinyl unsaturations were analyzed. Materials were processed at 160, 200, and 240 degrees C. Standard rheograrns using a partially filled chamber showed that the torque is much more unstable in comparison to a totally filled chamber which provides an environment depleted of oxygen. Carbonyl and transvinylene group concentrations increased, whereas vinyl group concentration decreased with temperature and oxygen availability. Average number of chain scission and branching (n(s)) was calculated from MWD curves and its plotting versus functional groups' concentration showed that chain scission or branching takes place depending upon oxygen content and vinyl groups' consumption. Chain scission and branching distribution function (CSBDF) values showed that longer chains undergo chain scission easier than shorter ones due to their higher probability of entanglements. This yields macroradicals that react with the vinyl terminal unsaturations of other chains producing chain branching. Shorter chains are more mobile, not suffering scission but instead are used for grafting the macroradicals, increasing the molecular weight. Increase in the oxygen concentration, temperature, and vinyl end groups' content facilitates the thermo-mechanical degradation reducing the amount of both, longer chains via chain scission and shorter chains via chain branching, narrowing the polydispersity. Phillips HDPE produces a higher level of chain branching than the Ziegler-Natta's type at the same processing condition. (c) 2006 Elsevier Ltd. All rights reserved.

The influence of cervical finish line, internal relief, and cement type on the cervical adaptation of metal crowns

Objective: the aim of this investigation was to evaluate the cervical adaptation of metal crowns under several conditions, namely (1) variations in the cervical finish line of the preparation, (2) application of internal relief inside the crowns, and (3) cementation using different luting materials. Method and Materials: One hundred eighty stainless-steel master dies were prepared simulating full crown preparations: 60 in chamfer (CH), 60 in 135-degree shoulder (OB), and 60 in rounded shoulder (OR). The finish lines were machined at approximate dimensions of a molar tooth preparation (height: 5.5 mm; cervical diameter: 8 mm; occlusal diameter: 6.4 mm; taper degree: 6; and cervical finish line width: 0.8 mm). One hundred eighty corresponding copings with the same finish lines were fabricated. A 30-mu m internal relief was machined 0.5 mm above the cervical finish line in 90 of these copings. The fit of the die and the coping was measured from all specimens (L0) prior to cementation using an optical microscope. After manipulation of the 3 types of cements (zinc phosphate, glass-ionomer, and resin cement), the coping was luted on the corresponding standard master die under 5-kgf loading for 4 minutes. Vertical discrepancy was again measured (L1), and the difference between L1 and L0 indicated the cervical adaptation. Results: Significant influence of the finish line, cement type, and internal relief was observed on the cervical adaptation (P < .001). The CH type of cervical finish line resulted in the best cervical adaptation of the metal crowns regardless of the cement type either with or without internal relief (36.6 +/- 3 to 100.8 +/- 4 mu m) (3-way analysis of variance and Tukey's test, alpha = .05). The use of glass-ionomer cement resulted in the least cervical discrepancy (36.6 +/- 3 to 115 +/- 4 mu m) than those of other cements (45.2 +/- 4 to 130.3 +/- 2 mu m) in all conditions. Conclusion: the best cervical adaptation was achieved with the chamfer type of finish line. The internal relief improved the marginal adaptation significantly, and the glass-ionomer cement led to the best cervical adaptation, followed by zinc phosphate and resin cement.

The thermal stability of fission tracks in the 612 nist glass standard at room temperature

Two wafers of the NIST (formerly NBS) glass standard SRM 612 recently irradiated have been compared to the pre-irradiated wafers RT3 and RT4 of glass SRM 962-7, stored for 9 years at 5°C, and SRM 962, stored for 20 years at room temperature. Track area densities on internal surfaces of the glass as well as track size measurements suggest that (1) the old SRM 962 and the more recent SRM 962a calibrations are consistent and (2) annealing of the fission tracks in the pre-irradiated wafers is negligible. This last experimental result enables a direct comparison of contemporary and previous fission track age calibrations. © 1995.

Marginal fit of nickel-chromium copings before and after internal adjustments with duplicated stone dies and disclosing agent.

STATEMENT OF PROBLEM: Despite careful procedures, master stone dies may be damaged during laboratory procedures. The dentist routinely adjusts castings because the marginal fit of casting is not as accurate as on the dies. PURPOSE: This study evaluated the technique of internal adjustment of castings with use of duplicated stone dies and a disclosing agent to improve marginal fit discrepancy. MATERIAL AND METHODS: Thirty-two nickel-chromium copings were fabricated and simulated standard clinical and laboratory procedures with 2 variables: tooth preparation convergence angles of 6 and 18 degrees, with or without internal relief. Master stone dies and their duplicates were selected for coping construction and internal adjustment, respectively. A specimen positioning device was coupled with a Toolmakers microscope to allow reproducibility of measurements. Each coping was evaluated at 8 locations of its marginal perimeter, before and after internal adjustment. RESULTS: Marginal fit discrepancy of copings were significantly reduced with an internal adjustment technique (mean > 52%) for all experimental groups. Tooth preparations with greater convergence and internally relieved castings recorded a better marginal fit. CONCLUSION: The casting internal adjustment technique with use of duplicated stone dies and a disclosing agent substantially reduced marginal fit discrepancy.

Biomechanical Study in Polyurethane Mandibles of Different Metal Plates and Internal Fixation Techniques, Employed in Mandibular Angle Fractures

The aim of this study was to perform a physicochemical and morphological characterization and compare the mechanical behavior of an experimental Ti-Mo alloy to the analogous metallic Ti-based fixation system, for mandibular angle fractures. Twenty-eight polyurethane mandibles were uniformly sectioned on the left angle. These were divided into 4 groups: group Eng 1P, one 2.0-mm plate and 4 screws 6 mm long; group Eng 2P, two 2.0-mm plates, the first fixed with 4 screws 6 mm long and the second with 4 screws 12 mm long. The same groups were created for the Ti-15Mo alloy. Each group was subjected to linear vertical loading at the first molar on the plated side in a mechanical testing unit. Means and standard deviations were compared with respect to statistical significance using ANOVA. The chemical composition of the Ti-15Mo alloy was close to the nominal value. The mapping of Mo and Ti showed a homogeneous distribution. SEM of the screw revealed machining debris. For the plates, only the cpTi plate undergoes a surface treatment. The metallographic analysis reveals granular microstructure, from the thermomechanical trials. A statistically significant difference was found (P < 0.05) when the comparison between both internal fixation techniques was performed. The 2P technique showed better mechanical behavior than 1P.

Axial loads on implant-supported partial fixed prostheses for external and internal hex connections and machined and plastic copings: strain gauge analysis

The aim of this in vitro study was to use strain gauge (SG) analysis to compare the effects of the implant-abutment joint, the coping, and the location of load on strain distribution in the bone around implants supporting 3-unit fixed partial prostheses. Three external hexagon (EH) implants and 3 internal hexagon (IH) implants were inserted into 2 polyurethane blocks. Microunit abutments were screwed onto their respective implant groups. Machined cobalt-chromium copings and plastic copings were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in a cobalt-chromium alloy (n = 5): group 1 = EH/machined. group 2 = EH/plastic, group 3 = IH/machined, and group 4 = IH/plastic. Four SGs were bonded onto the surface of the block tangentially to the implants. Each metallic structure was screwed onto the abutments and an axial load of 30 kg was applied at 5 predetermined points. The magnitude of microstrain on each SG was recorded in units of microstrain (mu epsilon). The data were analyzed using 3-factor repeated measures analysis of variance and a Tukey test (alpha = 0.05). The results showed statistically significant differences for the type of implant-abutment joint, loading point, and interaction at the implant-abutment joint/loading point. The IH connection showed higher microstrain values than the EH connection. It was concluded that the type of coping did not interfere in the magnitude of microstrain, but the implant/abutment joint and axial loading location influenced this magnitude.

ITScan: a web-based analysis tool for Internal Transcribed Spacer (ITS) sequences

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