Chemical process to separate iron oxides particles in pottery sample for EPR dating

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

The Variable Sample Size (X)over-bar Chart with Estimated Parameters

The VSS X chart, dedicated to the detection of small to moderate mean shifts in the process, has been investigated by several researchers under the assumption of known process parameters. In practice, the process parameters are rarely known and are usually estimated from an in-control Phase I data set. In this paper, we evaluate the (run length) performances of the VSS chart when the process parameters are estimated, we compare them in the case where the process parameters are assumed known and we propose specific optimal control chart parameters taking the number of Phase I samples into account.

X̄ charts with variable sample size

The usual practice in using a control chart to monitor a process is to take samples of size n from the process every h hours. This article considers the properties of the X̄ chart when the size of each sample depends on what is observed in the preceding sample. The idea is that the sample should be large if the sample point of the preceding sample is close to but not actually outside the control limits and small if the sample point is close to the target. The properties of the variable sample size (VSS) X̄ chart are obtained using Markov chains. The VSS X̄ chart is substantially quicker than the traditional X̄ chart in detecting moderate shifts in the process.

X̄ chart with variable sample size and sampling intervals

Recent theoretical studies have shown that the X̄ chart with variable sampling intervals (VSI) and the X̄ chart with variable sample size (VSS) are quicker than the traditional X̄ chart in detecting shifts in the process. This article considers the X̄ chart with variable sample size and sampling intervals (VSSI). It is assumed that the amount of time the process remains in control has exponential distribution. The properties of the VSSI X̄ chart are obtained using Markov chains. The VSSI X̄ chart is even quicker than the VSI or VSS X̄ charts in detecting moderate shifts in the process.

Joint X̄ and R Charts with Variable Sample Sizes and Sampling Intervals

Recent studies have shown that the X̄ chart with variable sampling intervals (VSI) and/or with variable sample sizes (VSS) detects process shifts faster than the traditional X̄ chart. This article extends these studies for processes that are monitored by both the X̄ and R charts. A Markov chain model is used to determine the properties of the joint X and R charts with variable sample sizes and sampling intervals (VSSI). The VSSI scheme improves the joint X̄ and R control chart performance in terms of the speed with which shifts in the process mean and/or variance are detected.

Determination of vanadium in urine by electrothermal atomic absorption spectrometry using hot injection and preconcentration into the graphite tube

In this work it was developed a procedure for the determination of vanadium in urine samples by electrothermal atomic absorption spectrometry using successive injections for preconcentration into a preheated graphite tube. Three 60 μL volumes were sequentially injected into the atomizer preheated to a temperature of 110°C. Drying and pyrolysis steps were carried out after each injection. A chemical modifier, barium difluoride (100 mg L-1), and a surfactant, Triton X-100 (0.3% v v-1), were added to the urine sample. When injecting into a hot graphite tube, the sample flow-rate was 0.5 μL s-1. The limits of detection and quantification were 0.54 and 1.82 without preconcentration, and 0.11 and 0.37 μg L-1 with preconcentration, respectively. The accuracy of the procedure was evaluated by an addition-recovery experiment employing urine samples. Recoveries varied from 96.0 to 103% for additions ranging from 0.8 to 3.5 μg L-1 V. The developed procedure allows the determination of vanadium in urine without any sample pretreatment and with minimal dilution of the sample.

Rapid determination of zinc in foods by flow injection analysis with flame AAS using gradient calibration method

A calibration method was developed using flow injection analysis (FI) with a Gradient Calibration Method (GCM). The method allows the rapid determination of zinc In foods (approximately 30 min) after treatment with concentrated sulphuric acid and 30% hydrogen peroxide, and analysis with flame atomic absorption spectrometry (FAAS). The method provides analytical results with a relative standard deviation of about 2% and requires less time than by conventional FI calibration. The electronic selection of different segments along the gradient and monitoring of the technique covers wide concentration ranges while maintaining the inherent high precision of flow injection analysis. Concentrations, flow rates, and flow times of the reagents were optimized in order to obtain best accuracy and precision. Flow rates of 10 mL/min were selected for zinc. In addition, the system enables electronic dilution and calibration where a multipoint curve can be constructed using a single sample injection.

Use of the internal standardization for difficult sampling by graphite furnace atomic absorption spectrometry

This work shows the potentiality of As as internal standard to compensate errors from sampling of sparkling drinking water samples in the determination of selenium by graphite furnace atomic absorption spectrometry. The mixture Pd(NO 3) 2/Mg(NO 3) 2 was used as chemical modifier. All samples and reference solutions were automatically spiked with 500 μg l -1 As and 0.2% (v/v) HNO 3 by the autosampler, eliminating the need for manual dilutions. For 10 μl dispensed sample into the graphite tube, a good correlation (r=0.9996) was obtained between the ratio of analyte absorbance by the internal standard absorbance and the analyte concentrations. The relative standard deviations (R.S.D.) of measurements varied from 0.05 to 2% and from 1.9 to 5% (n=12) with and without internal standardization, respectively. The limit of detection (LD) based on integrated absorbance was 3.0 μg l -1 Se. Recoveries in the 94-109% range for Se spiked samples were obtained. Internal standardization (IS) improved the repeatability of measurements and increased the lifetime of the graphite tube in ca. 15%. © 2004 Elsevier B.V. All rights reserved.

Simultaneous effects of total solids content, milk base, heat treatment temperature and sample temperature on the rheological properties of plain stirred yogurt

Response surface methodology was used to establish a relationship between total solids content, milk base, heat treatment temperature, and sample temperature, and consistency index, flow behaviour index, and apparent viscosity of plain stirred yogurts. Statistical treatments resulted in developments of mathematical models. All samples presented shear thinning fluid behaviour. The increase of the content of total solids (9.3-22.7 %) and milk base heat treatment temperature (81.6-98.4°C) resulted in a significant increase in consistency index and a decrease in flow behaviour index. Increase in the sample temperature (1.6-18.4°C) caused a decrease in consistency index and increase in flow behaviour index. Apparent viscosity was directly related to the content of total solids. Rheological properties of yogurt were highly dependent on the content of total solids in milk.

Comparative studies of the sample decomposition of green and roasted coffee for determination of nutrients and data exploratory analysis

The contents of some nutrients in 35 Brazilian green and roasted coffee samples were determined by flame atomic absorption spectrometry (Ca, Mg, Fe, Cu, Mn, and Zn), flame atomic emission photometry (Na and K) and Kjeldahl (N) after preparing the samples by wet digestion procedures using i) a digester heating block and ii) a conventional microwave oven system with pressure and temperature control. The accuracy of the procedures was checked using three standard reference materials (National Institute of Standards and Technology, SRM 1573a Tomato Leaves, SRM 1547 Peach Leaves, SRM 1570a Trace Elements in Spinach). Analysis of data after application of t-test showed that results obtained by microwave-assisted digestion were more accurate than those obtained by block digester at 95% confidence level. Additionally to better accuracy, other favorable characteristics found were lower analytical blanks, lower reagent consumption, and shorter digestion time. Exploratory analysis of results using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that Na, K, Ca, Cu, Mg, and Fe were the principal elements to discriminate between green and roasted coffee samples. ©2007 Sociedade Brasileira de Química.

Slurry sample injection for determination of ferrite nanocolloids chemical composition by ICP spectrometry

This work proposes a new method to determine the chemical composition of magnetic ferrite nanoparticles by the slurry injection technique using the inductively coupled plasma optical emission spectroscopy. In this way, experimental conditions such as aerosol gas flow rate and colloidal stability were optimized in order to use aqueous calibration curves in the slurry nebulization and to determine the chemical composition of a series of sols containing chemically synthesized size-tailored NiFe 2O 4 nanograms. Then, the results of direct sampling and those of conventional aqueous introduction analysis are compared, showing the efficiency of the proposed method.

Análise morfológica dos folículos primordiais de ovários de ovino criopreservados em EG, DMSO e sua associaçã o

Objective: Compare the cryoprotectants Dimethyl Sulphoxide (DMSO), Ethylene Glycol (EG) and their association for cryopreservation of sheep ovarian cortex. Methodology: Fragments collected from ovaries were divided into 3 parts. 1. One part from sample was destined for analysis of fresh material. 2. The second part was incubated with solution of freezing having 1,5M EG or 1,5M DMSO or 1,5MEG + 1,5M DMSO and washed for dilution of the cryoprotectants. 3. The third part was submitted to cryopreservation using the same cryoprotectans (EG 1,5M; DMSO 1,5M and EG + DMSO 1,5M) and cryopreserved. In all groups, one part of sample was submitted to pre-antral follicles isolation and the remainder was destined to ultra-structural analysis. Results: After isolation of fresh primordial follicles (control), the percentage of viable follicles was 78,9%. The percentage of viable follicles only exposed to cryoprotectants 1,5M EG, 1,5M DMSO and 1,5M EG + 1,5M DMSO was 77,1%, 68,4% and 60,7% respectively. After cryopreservation were 75%, 60% and 55,6% respectively. Ultra-structural analysis of the primordial follicles derived from fresh ovarian fragments or from fragments just exposed to the cryoprotectants showed similar morphology. However, in frozen samples, alterations of mitochondria were observed in all groups. Despite this, the integrity of the remained organelles was preserved in follicles cryopreserved with EG, while that in others groups (DMSO and association) an excess of vacuolizaton in cytoplasm of oocytes and swelling of nuclear membrane was observed indicating degeneration. Conclusion: The Ehilene Glycol seems to be the cryoprotector more adequated for cryopreservation of sheep ovarian tissue.

Childhood trauma in substance use disorder and depression: An analysis by gender among a Brazilian clinical sample

Objective: In this study, we compared the frequency and intensity of childhood traumas in alcohol- or other drug-dependent patients, in patients with depression, and in a control group without psychiatric diagnoses. Methods: The study had a retrospective design of a clinical sample of men and women from the groups listed above. They were evaluated by the same standardized instrument: the Childhood Trauma Questionnaire.. Results: A higher frequency and intensity of emotional, physical, and sexual abuse were found in alcohol- and other drug-dependent patients than in patients with depression, who, in turn, presented significantly higher proportions than the control group. In all of the cases, the frequency was higher among women than men. Conclusion: Because of the high frequency and intensity of childhood traumas among alcohol- or other drug-dependent patients and depressed patients, the assessment of problems due to childhood traumas among these patients is essential to a better understanding of the etiology of those disorders and to their treatment. © 2010 Elsevier Ltd. All rights reserved.

Sperm motility of Prochilodus lineatus in relation to dilution rate and temperature of the activating medium

The objective of this study was to assess the effects of an activating solution on the sperm motility duration (SMD) of 'curimbatá', Prochilodus lineatus through of the definition of qualitative and quantitative parameters of the semen pool used in the experiment; evaluation of the effects of different ratios of semen dilution corresponding to 1-:-1, 1-:-2, 1-:-20, 1-:-200, 1-:-2000, 1-:-20-000 and 1-:-100-000 semen:dilute solution on the SMD and, assessment of the effects of different temperatures of the activating solution (5, 10, 15, 20, 25, 30, 35, 40, 45 and 50°C) on the SMD. The results of SMD were directly proportional to the dilution (P<0.05), starting from the dilution of 1-:-2 (semen:water), with 23.04-s. Were used three replicates of the semen pool for each test. Two-year-old brookstock were maintained in ponds culture conditions. In November-December 2006, twelve mature males broodfish were selected (mean weight and length of 405.8±134.2-g and 25.6±3.1-cm, respectively). The males released that semen under slight pressure of the urogenital papilla were selected for the experiment. The SMD increased proportionally to the increase in dilution, until it reached a maximum of 28.83-s for the ratio 1-:-100-000 semen: dilute solution. The results of SMD in relation to the temperature of the activating solution exhibited a quadratic behavior (P<0.05) with a maximum theoretical performance in terms of sperm motility duration of 21.36-s at a temperature of 17.3°C. Thus, for the species considered, the increase in the dilution ratio proved favorable for the rise in motility duration until the maximum value studied of 1-:-100-000 semen:dilute solution. As for the temperature of the activating solution, the best results of SMD were obtained at the temperature of 17.3°C. At higher temperatures used in the experiment (25, 30, 35, 40, 45 and 50°C), a decrease in motility duration. © 2010 Blackwell Verlag, Berlin.

Simple electroanalytical method for determination of guanosine in biological sample

A poly glutamic acid film modified electrode exhibited a catalytic response toguanosine oxidation potential and higher peak current value. Linear concentration curve was obtained in the concentration interval of 1.0 a 10.0 μmol L-1 in 0.04 mol L-1 B-R buffer pH 2.0 with a detection limit of 0.198 μmol L-1. The electrode was used for the determination of guanosine in the potential of +1.1 V (vs. Ag/AgCl) using differential pulse voltammetry (DPV) at urine sample with good recovery. © 2010 by CEE.