Search results for "SAMPLE"

An effective negative pressure cavitation-microwave assisted extraction for determination of phenolic compounds in P. calliantha H. Andr.

2013

A novel negative pressure and microwave assisted extraction technique (NMAE) was first proposed and applied for extraction of phenolic compounds from pyrola. [C₄MIM]BF₄ aqueous solution was selected as extraction solvent. Optimal extraction conditions were microwave power 700 W, negative pressure -0.07 MPa, temperature 40 °C, liquid-solid ratio 20 : 1, ionic liquid (IL) concentration 0.5 M, extraction time 15 min. The predominance of NMAE was investigated by comparing with microwave-assisted extraction (MAE) and negative pressure cavitation extraction (NPCE) using a first-order kinetics equation. The C∞ values of the target compounds by NMAE were from 0.406 to 5.977 mg g⁻¹ higher than these…

Rapid analysis of effluents generated by the dairy industry for fat determination by preconcentration in nylon membranes and attenuated total reflect…

2014

Abstract This paper describes a new approach for the determination of fat in the effluents generated by the dairy industry which is based on the retention of fat in nylon membranes and measurement of the absorbances on the membrane surface by ATR-IR spectroscopy. Different options have been evaluated for retaining fat in the membranes using milk samples of different origin and fat content. Based on the results obtained, a method is proposed for the determination of fat in effluents which involves the filtration of 1 mL of the samples through 0.45 µm nylon membranes of 13 mm diameter. The fat content is then determined by measuring the absorbance of band at 1745 cm −1 . The proposed method c…

On-line extraction coupled to liquid chromatographic analysis of hydrophobic organic compounds from complex solid samples-Application to the analysis…

2019

This work investigates the applicability of on-line extraction (OLE) directly coupled to liquid chromatography (LC) for the dynamic extraction of hydrophobic organic compounds from complex solid samples. The method operates within the existing apparatus of the LC by replacing the valve loop with an extraction vessel comprised of an empty guard column loaded with the sample. In this manner, extraction is accomplished by the mobile phase as it flows through the extraction vessel under high pressure without the need for additional apparatus other than those comprising the LC system or additional sample pretreatment steps. The experimental parameters affecting the extraction efficiency of the m…

Limited Usefulness of Capture Procedure and Capture Percentage for Evaluating Reproducibility in Psychological Science

2018

In psychological science, there is an increasing concern regarding the reproducibility of scientific findings. For instance, Replication Project: Psychology (Open Science Collaboration, 2015) found that the proportion of successful replication in psychology was 41%. This proportion was calculated based on Cumming and Maillardet’s (2006) widely employed capture procedure (CPro) and capture percentage (CPer). Despite the popularity of CPro and CPer, we believe that using them may lead to an incorrect conclusion of (a) successful replication when the population effect sizes in the original and replicated studies are different; and (b) unsuccessful replication when the population effect sizes i…

Reliability results of straylight measurements using the C-Quant

2008

Purpose Assessment of repeatability and reproducibility of straylight measures with the C-Quant straylightmeter (Oculus AG, Germany), effect of age on reliability measures and correlation of measures determined with new methods of scatter determination. Methods Results from different studies will be presented. For repeatability assessment, 20 eyes (age 26.9±2.7 years) were examined with the C-Quant, taking 10 consecutive readings. 5 subjects were also examined on 5 consecutive days to assess reproducibility. Repeated measures from 84 subjects, age range 19-86 years, were analysed to assess the effect of patient’s age. Software was developed to quantify scatter from centroid patterns obtaine…

Screen media time usage of 12-16 year-old Spanish school adolescents: Effects of personal and socioeconomic factors, season and type of day.

2007

Abstract This study examined screen media time usage (SMTU) and its association with personal and socioeconomic factors, as well as the effect of season and type of day, in a Spanish sample of 12–16 year-old school adolescents (N = 323). The research design was a cross-sectional survey, in which an interviewer-administered recall questionnaire was used. Statistical analyses included repeated measures analyses of variance, analysis of covariance and structural equation models. Results showed an average of 2.52 h per day of total SMTU and partial times of 1.73 h per day in TV viewing, 0.27 h per day in computer/videogames, and 0.52 h per day in mobile use. Four significant predictors of SMTU …

On the Difference between a-priori and observed statistical power - A comment on "statistical power and sample size calculations: A primer for pediat…

2019

Exploring the Coherence of Student Reasoning when Responding to Questionnaires on Thermally Activated Phenomena

2021

Many research results show that students often highlight “mixed-type” reasoning when tackling problematic situations and problems. This reasoning is based on the simultaneous use of common-sense and mere descriptions of facts, perceived as sufficient to build an “explanation” of observed or proposed situations and problems. This fact can be interpreted as a lack of coherence. In this paper, we study the coherence of responses that a sample of undergraduate chemical engineering student give when they are asked to face real-life situations, to create explanations, and to use models in different contexts. We administered open-ended questionnaires before and after a twenty-hour Inquiry-Based wo…

Rugged Large Volume Injection for Sensitive Capillary LC-MS Environmental Monitoring

2017

A rugged and high throughput capillary column (cLC) LC-MS switching platform using large volume injection and on-line automatic filtration and filter back-flush (AFFL) solid phase extraction (SPE) for analysis of environmental water samples with minimal sample preparation is presented. Although narrow columns and on-line sample preparation are used in the platform, high ruggedness is achieved e.g. injection of 100 non-filtrated water samples would did not result in a pressure rise/clogging of the SPE/capillary columns (inner diameter 300 µm). In addition, satisfactory retention time stability and chromatographic resolution were also features of the system. The potential of the platform for …

Trace analysis by ion mobility spectrometry: From conventional to smart sample preconcentration methods. A review.

2018

Ion mobility spectrometry (IMS) is a rapid and high sensitive technique widely used in security and forensic areas. However, a lack of selectivity is usually observed in the analysis of complex samples due to the scarce resolution of the technique. The literature concerning the use of conventional and novel smart materials in the pretreatment and preconcentration of samples previous to IMS determinations has been critically reviewed. The most relevant strategies to enhance selectivity and sensitivity of IMS determinations have been widely discussed, based in the use of smart materials, as immunosorbents, aptamers, molecularly imprinted polymers (MIPs), ionic liquids (ILs) and nanomaterial. …