Search results for "SAMPLE"
showing 10 items of 2270 documents
Laser-Induced Breakdown Spectroscopy for Rapid Elemental Analysis of Drillcore
2013
Abstract The elemental and mineralogical contents of rock drillcore can be analyzed using a variety of methods. For efficient exploration the characterization of the drillcore should be performed rapidly, so that the further drillings can be better planned and unnecessary costs can be reduced. In this paper, laser-induced breakdown spectroscopy (LIBS) is studied as a potential rapid on-line method for automated elemental analysis of drillcore. The method is based on a pulsed laser beam that transforms a small volume of the sample into plasma. Individual elements in the plasma have characteristic emission patterns detectable by a spectrometer. Based on the measured spectra the amount of diff…
Determination of dithiocarbamates and metabolites in plants by liquid chromatography–mass spectrometry
2004
Abstract A quantitative matrix solid-phase dispersion and liquid chromatography–atmospheric pressure chemical ionization mass spectrometry (LC–APCI–MS) method is outlined for the simultaneous analysis of dithiocarbamates (DTCs) and their degradation products in plants. Compounds analyzed are dazomet, disulfiram, thiram and the metabolites ethylenthiourea and propylenthiourea. The performance of two different sample preparation protocols, the proposed one and other based on solid-phase extraction, as well as, of both atmospheric pressure ionization sources, APCI and electrospray, were compared. The effect of several parameters on the extraction, separation and detection was studied. Dithioca…
Routine application using single quadrupole liquid chromatography-mass spectrometry to pesticides analysis in citrus fruits.
2005
Abstract A rapid and sensitive liquid chromatography–electrospray ionization–mass spectrometry method has been developed for the routine analysis of buprofezin, bupirimate, hexaflumuron, tebufenpyrad, fluvalinate and pyriproxyfen in citrus fruits. Extracts were obtained by matrix solid-phase dispersion (MSPD) using C 18 as dispersant and dichloromethane-methanol (80:20, v/v) as eluent. Matrix effects were tested for all matrices by addition of standard to sample blank extracts (samples containing no detectable residues). Mean recoveries obtained at fortification levels between 0.01 and 5 mg kg −1 were 57–97% with relative standard deviations (RSDs) from 5 to 19%. The limits of quantificatio…
Determination of macrolide antibiotics in meat and fish using pressurized liquid extraction and liquid chromatography–mass spectrometry
2008
We developed a method for determining the quantities of seven macrolide antibiotics in meat and fish by using pressurized liquid extraction (PLE) and liquid chromatography-mass spectrometry with electrospray ionization (LC-(ESI)MS). The PLE was optimized with regard to solvents, temperature, pressure, extraction time and number of cycles. The optimum conditions were: methanol as the extraction solvent; a temperature of 80 degrees C; a pressure of 1500psi; an extraction time of 15min; 2 cycles; a flush volume of 150% and a purge time of 300s. All recoveries for macrolide antibiotics were over 77% at 200mug/kg, except for erythromycin, which was 58%. The repeatability and reproducibility on d…
Direct infusion mass spectrometry as a fingerprint of protein-binding media used in works of art
2005
A direct infusion mass spectrometry method for the characterization of proteinaceous glues from binding media used in pictorial works of art prior to conservation or restoration treatment is proposed. Amino acids are released by acid hydrolysis and dissolved in a mixture of acidic water and ethanol. This mixture is directly infused into a mass spectrometer without any derivatization. The mass spectrometer is operated in positive ion electrospray mode (ESI-MS) to yield [M+H]+ ions for the amino acids. Relative amounts of each amino acid are calculated for each protein (beef and porcine gelatines, albumin, casein and egg). The analyzed proteins were satisfactorily distinguished. The method is…
Conditions of dust sampling in pneumatic conveying through the horizontal pipeline
2007
Abstract The paper presents the results of examinations on the reciprocal relation between the isokinetic coefficient H of sampling, the quantity of measured mass concentration and the measuring usefulness of a dust sample aspired from the stream of solgas conveyed pneumatically in the horizontal pipeline. In gravimetric measurements of two-phase flows, the conditions under which aspiration is carried out, are extremely important. Available theoretical considerations and practical experiments usually concern aspiration in the vertical channels, where the manner of making measurements is universally known and it does not express any reservations. However, it is often necessary to conduct tes…
Is dust a suitable material for retrospective personal dosimetry?
2010
This work investigates the feasibility of using silicates contained in dust for retrospective individual dosimetry in case of a radiation accident or a radiological attack involving people not wearing physical dosimeters. It is well known that minerals (silicates) can be used for dosimetry and dust already plays an important role in the field of food irradiation detection using luminescence techniques as described in the European Standards (EN 13751 and EN 1788). This paper explores the feasibility of conducting retrospective personal dosimetry on the basis of thermoluminescence analysis of silicates extracted from dust on objects that people usually wear (e.g. jewelry, watches, keys and co…
The Psychological Science Accelerator’s COVID-19 rapid-response dataset
2023
Funder: Amazon Web Services (AWS) Imagine Grant
A Comparison of Formulae for Calculating Cost-Efficient Sample Sizes of Case-Control Studies with an Internal Validation Scheme
2000
When a case-control study is planned to include an internal validation study, the sample size of the study and the proportion of validated observations has to be calculated. There are a variety of alternative methods to accomplish this. In this article some possible procedures will be compared in order to clarify whether considerable differences in the suggested optimal designs occur, dependent on the used method.
Estimating person parameters via item response model and simple sum score in small samples with few polytomous items: A simulation study
2018
Background The Item Response Theory (IRT) is becoming increasingly popular for item analysis. Theoretical considerations and simulation studies suggest that parameter estimates will become precise only by utilizing many items in large samples. Method A simulation study focusing on a single scale was performed on data with (a) n = 40, 60, 80, 120, 200, 300, 500, and 900 cases utilizing (b) 4, 8, 16, or 32 items. The items were (c) symmetrically distributed vs. skew (skewness 0, 1, and 2). Item loadings were (d) homogeneous vs. heterogeneous. Item loadings were (e) low vs. high. Half of the items had (f) a correlated error or not. The number of answering categories (g) was four vs. five. A to…