Effect Of Sample Mass Research Articles

Effect of sample mass on the thermal decomposition of 2,4-DNT under sealed condition

Effect of sample mass on the thermal decomposition of 2,4-DNT under sealed condition

Effects of sample mass and suspension salinity on particle size distribution in predominantly medium to heavy textured soils using the hydrometer method

AbstractBackgroundParticle size distribution (PSD) is a fundamental soil measurement that is crucial for agriculture, engineering, hydrological, and environmental applications as well as in basic research such as in developing water release curves in flow and transport modeling. The accurate determination of PSD, particularly clay content, is especially critical in ascertaining the magnitude and rates of many physical, chemical, and hydrological processes in soils. The accuracy of the hydrometer method for PSD, which relies on the settling velocity of soil particles in a soil suspension, could be affected by the density of the suspension, which in turn, depends on the initial sample mass, texture, and mineralogy of the soil.AimsWe hypothesized that (1) initial mass determines the concentration and the physical interaction of particles in a soil suspension and affects particle settlement, recovery, and the accuracy of the hydrometer method, and (2) the widely used initial air‐dry mass of 50 g underestimates the clay percentage of medium to heavy textured tropical soils. The objective of this study was to investigate the effect of mass and KCl on clay recovery in tropical soils with varying texture and mineralogy using the hydrometer method.MethodsThe experiment comprised seven soils, four soil masses (10, 20, 30, 50 g), and two KCl treatments in a 7 × 4 × 2 factorial design replicated three times.ResultsResults showed a general trend of increasing estimates of clay % as the soil mass decreased from 50 to 10 g and the KCl concentration increased from 0 to 0.0025 M. This implies that using an initial sample mass of 50 g in sedimentation methods, underestimates, and 10 g overestimates the clay % in predominantly medium to heavy textured tropical soils. Interestingly, there was a drastic change in texture for most of the soils as the sample mass decreased to 10 g.ConclusionsWe conclude that the initial air‐dry mass affects the clay recovery of medium to heavy textured humid tropical soils. Results suggest that the ideal initial mass for these soils lies between 20 and 30 g. Furthermore, the mechanistic pathway that drives the observed decrease in clay recovery as soil sample mass increase could be due to the flocculating tendency of KCl.

Optimization of headspace solid-phase microextraction of volatile organic compounds from dry soil samples by porous coatings using COMSOL Multiphysics

Headspace solid-phase microextraction (HSSPME) is one of the simplest and cost-efficient sample preparation approaches for determination of volatile organic compounds (VOCs) in soil. This study was aimed at the development of the model for numerical optimization of HSSPME of volatile organic compounds from dry soil samples by porous coatings using COMSOL Multiphysics (CMP). ‘Transport of Diluted Species in Porous Medium’ physics was used for modeling. Effect of sample mass, pressure, fiber-headspace and soil-headspace distribution constants on extraction profiles and time of 95% equilibrium has been studied using the developed model. Equilibrium extraction under atmospheric pressure (1 atm) can take up to 97 min, while under vacuum (0.0313 atm) – 2.3 min. Equilibration time under vacuum was 42-43 times lower than under 1 atm at all studied distribution constants and sample masses. The developed model was modified for optimization of pre-incubation time using ‘Transport of Diluted Species’ physics. According to the obtained plots, 95% equilibration time can reach 13.3 min and depends on both sample mass and soil-headspace distribution constant of the analyte. The developed model can be recommended for optimization of pressure, preincubation and extraction time when fiber-headspace and soil-headspace distribution constants, soil porosity and density are known.

Comparison of Different Extraction Methods for the Recovery of Olive Leaves Polyphenols

In the present study, advanced extraction techniques, microwave (MAE), ultrasound (UAE), and high pressure (HPAE)-assisted extraction, were applied to improve extraction efficiency of olive (Olea europaea L.) leaves polyphenols. The effect of sample mass (1.5 and 3 g), MAE—time (2, 8.5, and 15 min) and temperature (45 and 80 °C), UAE—time (7, 14, and 21 min) and amplitude (50 and 100%) and HPAE—time (1, 5.5, and 10 min) and pressure (300 and 500 MPa) on the concentration of each analyzed polyphenol compound was examined. Identified polyphenols were oleuropein, hydroxytyrosol, chlorogenic acid, caffeic acid, verbascoside, and rutin. All three advanced extraction techniques yielded higher content of total polyphenols when compared to the conventional heat-reflux extraction (CE) along with a significant reduction of extraction time from 60 (CE) to 2, 21, and 5.5 min in MAE, UAE, and HPAE, respectively. The most intensive values of tested parameters in each technique were the ones that promoted cell wall disruption, e.g., temperature of 80 °C in MAE, 100% amplitude in UAE and 500 MPa in HPAE. MAE and UAE were more efficient in total polyphenols’ recovery than HPAE.

Miniature radiocarbon measurements ( < 150 µg C) from sediments of Lake Żabińskie, Poland: effect of precision and dating density on age–depth models

Abstract. The recent development of the MIni CArbon DAting System (MICADAS) allows researchers to obtain radiocarbon (14C) ages from a variety of samples with miniature amounts of carbon (<150 µg C) by using a gas ion source input that bypasses the graphitization step used for conventional 14C dating with accelerator mass spectrometry (AMS). The ability to measure smaller samples, at reduced cost compared with graphitized samples, allows for greater dating density of sediments with low macrofossil concentrations. In this study, we use a section of varved sediments from Lake Żabińskie, NE Poland, as a case study to assess the usefulness of miniature samples from terrestrial plant macrofossils for dating lake sediments. Radiocarbon samples analyzed using gas-source techniques were measured from the same depths as larger graphitized samples to compare the reliability and precision of the two techniques directly. We find that the analytical precision of gas-source measurements decreases as sample mass decreases but is comparable with graphitized samples of a similar size (approximately 150 µg C). For samples larger than 40 µg C and younger than 6000 BP, the uncalibrated 1σ age uncertainty is consistently less than 150 years (±0.010 F14C). The reliability of 14C ages from both techniques is assessed via comparison with a best-age estimate for the sediment sequence, which is the result of an OxCal V sequence that integrates varve counts with 14C ages. No bias is evident in the ages produced by either gas-source input or graphitization. None of the 14C ages in our dataset are clear outliers; the 95 % confidence intervals of all 48 calibrated 14C ages overlap with the median best-age estimate. The effects of sample mass (which defines the expected analytical age uncertainty) and dating density on age–depth models are evaluated via simulated sets of 14C ages that are used as inputs for OxCal P-sequence age–depth models. Nine different sampling scenarios were simulated in which the mass of 14C samples and the number of samples were manipulated. The simulated age–depth models suggest that the lower analytical precision associated with miniature samples can be compensated for by increased dating density. The data presented in this paper can improve sampling strategies and can inform expectations of age uncertainty from miniature radiocarbon samples as well as age–depth model outcomes for lacustrine sediments.

Slow Pyrolysis Kinetics of Two Herbaceous Feedstock: Effect of Milling, Source, and Heating Rate

Kinetic models for pyrolysis of switchgrass and tall fescue were obtained using thermogravimetric analysis and a newly proposed parameter-extraction methodology. The optimization strategy demonstrates the use of the Akaike information criterion for the statistical identification of the number of distinct processes and a robust global search method. The effects of sample mass, heating rates, particle size, and crystallinity index on the kinetic parameters of each feedstock were considered. For whole biomass particles, the kinetic parameters of the cellulose component was found to be similar to that of pure microcrystalline cellulose. Further particle size reduction through extensive milling reduced the activation energy of cellulose by 48%. X-ray diffraction indicated that the cellulose fraction of highly milled whole biomass becomes largely amorphous and that the amorphization of the cellulose, not the particle size reduction, is likely responsible for the decrease in activation energy.

Kinetic analysis of the process of melamine pyrophosphate synthesis

This paper presents the results of investigations of the kinetics of the first degree of condensation of melamine orthophosphate to melamine pyrophosphate. The investigations were conducted under isothermal conditions and at constant rate of sample heating. The effects of sample mass and heating rate on the kinetic parameters of the process were determined. The activation energy of the process was determined using the approximate Kissinger method and the isoconversional Kissinger–Akahira–Sunose method. A complete analysis of the process was conducted to establish a kinetic model and to determine the activation energy and the value of the pre-exponential factor. It was found that in the initial period of the conversion (up to the value of ca. 0.20), the limiting stage of the process is chemical reaction (first-order reaction model—Mampel F1 equation). At conversion values α above 0.2, the reaction is described by Avrami–Erofeev A2 model.

Quantifying Dynamic Processes in Reactive Materials: An Extended Burn Tube Test

AbstractA common method for measuring the reactivity of rapidly deflagrating materials has been to loosely pack a desired mixture into an approx. 10 cm long×3 mm diameter acrylic tube, ignite the material on one end, and report the observed self‐propagating flame velocity through the material. While this method can yield qualitative information, linking this to quantitative intrinsic properties, such as particle burn time, has remained challenging. In this work, we significantly redesign the traditional burn tube experiment. Between 25 and 250 mg of nanocomposite aluminum/copper oxide (Al/CuO) thermite is loosely packed into the capped end of a 1.8 m long tube, and the remainder of the tube is left unfilled. The material is ignited using a hot wire, resulting in a steadily‐propagating luminous front, which extends part, or all, of the way down the length of the tube. We suggest the behavior is a result of “reactive entrainment”, which occurs when the reaction time scale becomes longer than the characteristic momentum relaxation time scale. When this criterion is met, and when there are significant pressure gradients present or produced during the reaction, material will be entrained by the gases before and/or during the reaction; a behavior very different from conventional thermites, which use larger particle sizes. The effect of sample mass and tube diameter on propagation velocity is investigated, and we find a linear scaling with mass and a power law scaling with tube radius (r−1.3) between 1.56 and 4.76 mm radii. For several conditions, we observe the reaction complete; defined by the distance where the propagation velocity decreases to a fixed fraction of its steady value. The ratio of quench distance to propagation velocity was found to approach a constant value of 3.29±0.70 ms, which we suggest is the burn time of the Material. For the range of masses studied in this work, the burn time was found to be independent of mass, implying that it is an intrinsic particle burn time. We expect other quantitative information can be deduced from this experiment, so long as the chosen sample mass and tube dimensions allow one to observe the full extent of reaction.

Effects of sample mass on gravity recoverable gold test results in low-grade ores

Gravity recoverable gold characterisation methodologies are the single- or three-stage tests, which generally use a standard feed sample mass. A case study of low-grade coarse gold-dominated mineralisation is presented that demonstrates the high variability of test results using different sample masses. Samples were processed using the single-stage test and subsequently entire development rounds were batched through a plant for comparison. Unsurprisingly the results indicate that the small (≤50 kg) test samples grossly understate plant gravity recoverable gold and display poor precision. Larger samples display improved precision, but still understate plant gravity recoverable gold. The small mass samples are unrepresentative as they do not contain the full gold particle size distribution. Poor representivity is enhanced by gold particle clustering. Small samples generally capture finer more abundant and disseminated gold particles, but rarely contain clustered gold. The use of standard GRG test sample masses is challenged. Test work should be based on spatially distributed representative field samples, that if required are split to representative sub-samples for testing. An early stage gold particle size characterisation programme is required to optimise sample mass and improve representivity.

Dielectric properties and temperature increase characteristics of zinc oxide dust from fuming furnace

Cavity perturbation method was used to determine the dielectric properties (ɛ′, ɛ″, and tan δ) of zinc oxide dust in different apparent densities. The process was conducted to study the microwave-absorption properties of zinc oxide dust and the feasibility of microwave roasting zinc oxide dust to remove fluorine and chlorine. The dielectric constant, dielectric loss, and loss tangent were proportional to the apparent density of zinc oxide dust. The effects of sample mass and microwave power on the temperature increase characteristics under the microwave field were also studied. The results show that the apparent heating rate of the zinc oxide dust increases with the increase in microwave roasting power and decreases with the increase in the sample mass. The temperature of the samples reaches approximately 800 °C after microwave treatment for 8 min, which indicates that the zinc oxide dust has strong microwave-absorption ability.

Focused microwave-induced combustion for digestion of botanical samples and metals determination by ICP OES and ICP-MS

The advantages and shortcomings of focused microwave-induced combustion (FMIC) for digestion of plant samples were studied. The effects of sample mass, absorbing solution, oxygen gas flow-rate, and time of reflux step on recoveries of major, minor and trace metals were systematically evaluated. Afterwards, Al, Ba, Ca, Co, Cr, Cu, Mg, Mn, Ni, Sr, V, and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP OES) and by inductively coupled plasma mass spectrometry (ICP-MS). The main advantages of FMIC when compared to microwave-assisted wet digestion (MAWD) and focused-microwave-assisted wet digestion (FMAWD) are the possibility to digest larger masses of samples (up to 3g) using shorter heating times and diluted nitric acid solution for absorbing all analytes. Using the selected experimental conditions for FMIC, residual carbon content was lower than 0.7% for all samples and relative standard deviation (RSD) varied from 1.5 to 14.1%. Certified reference materials (NIST 1515 apple leaves and NIST 1547 peach leaves) were used for checking accuracy and determined values for all metals were in agreement with certified values at a 95% confidence level. No statistical difference (ANOVA, 95% of confidence level) was observed for results obtained by FMIC, FMAWD, and MAWD. Limits of detection were lower when using FMIC in the range of 0.02–0.15μgg−1 for ICP OES and 0.001–0.01μgg−1 for ICP-MS, which were about 3 and 6 times lower than the values obtained by FMAWD and MAWD, respectively. It is important to point out that FMIC was a suitable sample preparation method for major, minor and trace metals by both determination techniques (ICP OES and ICP-MS). Additionally, since it allows lower LODs (because up to 3g of sample can be digested) and diluted acid solutions are used (without any further dilution), the use of ICP-MS is not mandatory.

Measurement of Heating Value of Rice Husk by Using Oxygen Bomb Calorimeter with Benzoic Acid as Combustion Adjuvant

Heating value is a primary parameter availed in the design process of thermochemical conversion apparatus of rice husk. The published data for rice husk are different due to the diversity of testing conditions and rice husk varieties. In this study, the higher heating value of rice husk was measured by using oxygen bomb calorimeter with benzoic acid as combustion adjuvant. The effects of sample mass, oxygen gauge pressure and mass ratio of rice husk and benzoic acid were discussed. The results indicate that the measured higher heating value of rice husk increases at first with the increase of oxygen gauge pressure and the mass ratio of benzoic acid and rice husk, and then decreases. When the rice husk sample mass is 0.6g, the oxygen gauge pressure is 3.0MPa, and the mass ratio of rice husk and benzoic acid is 1.2:1, the higher heating value of rice husk reaches maximal, i.e. 15944±55J/g that corresponds to complete combustion and appropriate testing conditions. The measured heating value in this paper is higher than that based on the testing conditions specified in British and Chinese testing standards respectively. The present study documents new higher heating value of one Chinese rice husk and formulates a useful method for the determination of testing conditions under which the heating value of rice husks is measured.

Supplement on “Effects of heat-flux features on the differential scanning calorimetry curve of a thermoelastic martensitic transformation”

The melting process of a high purity indium was examined with a heat-flux differential scanning calorimeter (DSC). The effects of sample mass and the scanning rate on the resulting peaks are presented. The peaks were evaluated by two methods. The first one is a commercial method while the modified method involves a correction for the endpoint of the process. The results are compared to each other.

The effect of sample mass and heating rate on DSC results when studying the fractional composition and oxidative stability of lube base oils

The method of dynamic microdistillation instrumented through DSC has been further elaborated and validated using distillate and residual base oils as model systems. The two major experimental factors of the method—sample mass and heating rate were varied to determine the optimal (standard) experimental conditions for better fraction resolution and thus more reliable quality assessment of petroleum products (lube oils). If these are increased, the fraction resolution ability of the method is reduced—the lighter fractions evaporate at temperatures close to those of the heavier ones, and generally all the fractions evaporate/oxidize at higher temperatures. Two major types of reactions in the heated sample were identified—the one occurring on the metal surface of the crucible leading to a polymer (lacquer) film formation and the other the oxidative cracking in the bulk of the sample leading to the formation of gaseous products. The extent of the lacquer film formation on the crucible metal surface can be reduced by increasing the heating rate and/or the sample mass, while their reduction results in better fraction resolution.

A statistical model for the optimization of dsc performance in the evaluation of drugs for preformulation studies

Differential scanning calorimetry (DSC) is a thermal analytical tool for preformulation studies. Extrapolated melting temperature (TP) and heat of fusion (ΔHf) can be used as parameters for optimizing the DSC performance. Two model pharmaceuticals acetaminophen and nicotinamide are used in this study. Using a factorial design for the experimental model and matrix analysis the results, the effect of sample mass, heating rate and the nitrogen flow rate were evaluated on the ΔHf values and TP values. Two levels for each of the procedural variables were used as a balanced experimental design with two sample sizes, two heating rates and two nitrogen flow rates. It was found that the change in the heating rate caused significant changes in the ΔHf values but not the Tp values for acetaminophen. However, no significant effect was found for the Tp value but ΔHf value was affected to a certain extent for nicotinamide.

Effects of sample mass and macrofossil type on radiocarbon dating of arctic and boreal lake sediments

Dating lake sediments by accelerator mass spectrometry (AMS) 14C analysis of terrestrial plant macrofossils overcomes one of the main problems associated with dating bulk sediment samples, i.e., the presence of old organic matter. Even so, many AMS dates from arctic and boreal sites appear to misrepresent the age of the sediment. To understand the nature of these apparent dating anomalies better, we conducted a series of 14C dating experiments using samples from Alaskan and Siberian lake-sediment cores. First, to test whether our analytical procedures introduced a sample-mass bias, we obtained 14C dates for different-sized pieces of single woody macrofossils. In these sample-mass experiments, statistically equivalent ages were found for samples as small as 0.05 mg C. Secondly, to assess whether macrofossil type influenced dating results, we conducted sample-type experiments in which 14C dates were obtained for different macrofossil types sieved from the same depth in the sediment. We dated materials from multiple levels in sediment cores from Upper Capsule Lake (North Slope, northern Alaska) and Grizzly Lake (Copper River Basin, southern Alaska) and from single depths in other records from northern Alaska. In several of the experiments there were significant discrepancies between dates for different plant tissues, and in most cases wood and charcoal were older than other macrofossil types, usually by several hundred years. This pattern suggests that 14C dates for woody macrofossils may misrepresent the age of the sediment by centuries, perhaps because of their longer terrestrial residence time and the potential in-built age of longlived plants. This study identifies why some 14C dates appear to be inconsistent with the overall age-depth trend of a lake-sediment record, and it may guide the selection of 14C samples in future studies.

Tooth Enamel EPR Dosimetry: Optimization of EPR Spectra Recording Parameters and Effect of Sample Mass on Spectral Sensitivity

In order to improve the accuracy of the tooth enamel EPR dosimetry method, EPR spectra recording conditions were optimized. The uncertainty of dose determination was obtained as the mean square deviation of doses, determined with the use of a spectra deconvolution program, from the nominal doses for ten enamel samples irradiated in the range from 0 to 500 mGy. The spectra were recorded at different microwave powers and accumulation times. It was shown that minimal uncertainty is achieved at the microwave power of about 2 mW for a used spectrometer JEOL JES-FA100. It was found that a limit of the accumulation time exists beyond which uncertainty reduction is ineffective. At an established total time of measurement, reduced uncertainty is obtained by averaging the experimental doses determined from recorded spectra following intermittent sample shaking and sample tube rotation, rather than from one spectrum recorded at longer accumulation time. The effect of sample mass on the spectrometer's sensitivity was investigated in order to find out how to make appropriate corrections.

Thermal hazard assessment of AN and AN-based explosives

Ammonium nitrate (AN) is an essential ingredient in most fertilizers. It is also widely used in the commercial explosives industry. In this latter application, it is mostly mixed with fuel oil to form the most popular commercial explosive: ANFO. In both the fertilizer and the explosive industry, aqueous AN solutions (ANS) of various concentrations are processed. These solutions also form the basis of ammonium nitrate emulsion explosives (also called ammonium nitrate emulsions or ANE), which are produced either in bulk or in packaged form. For all these AN-based products, quantities of the order of 20,000 kg are being manufactured, transported, stored, and processed at elevated temperatures and/or elevated pressures. Correspondingly, major accidents involving overheating of large quantities of these products have happened in several of these operations. In comparison, convenient laboratory quantities to investigate thermal decomposition properties are generally less than 1 kg. As a result, in order to provide information applicable to real-life situations, any laboratory study must use techniques that minimize heat losses from the samples to their environment. In the present study, two laboratory-scale calorimeters providing an adiabatic environment were used: an accelerating rate calorimeter (ARC) and an adiabatic Dewar calorimeter (ADC). Experiments were performed on pure AN, ANFO, various ANS systems, and typical bulk and packaged ANE systems. The effects of sample mass, atmosphere, and formulation on the resulting onset temperatures were studied. A comparison of the results from the two techniques is provided and a proposed method to extrapolate these results to large-scale inventories is examined.

The effect of sample mass on the crystallization supercooling in bismuth melt

The effect of a sample mass (decreasing from 100 g to 0.1 mg) on the crystallization supercooling (Δ T−) relative to the melting temperature TL has been studied for bismuth. The entire mass range can be divided into three regions: for massive samples (m=100−6 g), Δ− is about several kelvins; for medium masses (1 g to 1.0 mg), ΔT− amounts to 30±4 K and is virtually independent of m; below 0.1 mg, ΔT− exhibits a rapid growth.

Investigation of biomass pyrolysis by thermogravimetric analysis and differential scanning calorimetry

The influence of sample size on the pyrolysis of wheat straw and three types of cellulose has been investigated by simultaneous thermogravimetric analysis and differential scanning calorimetry. Samples between 2 and 20 mg were pyrolyzed to a maximum temperature of 600°C at a heating rate of 40°C min −1. It was found that sample size had a large effect on the pyrolysis of Avicel cellulose; the mass loss peak was shifted to higher temperatures at higher sample mass. However, the effect of sample mass on the pyrolysis of wheat straw was insignificant. In wheat straw samples washed in water to reduce the KCl content, the influence of sample size was between that of cellulose and straw, but closer to straw. A model for the TGA/DSC-system has been developed, which includes heat transfer by both convection and radiation to the two crucibles and the sample. Simulations with the model showed that the sample mass had a large influence on the pyrolysis at high heat of reaction and in agreement with data, the pyrolysis peak shifts to higher temperatures at higher sample mass. The recommendation found in the literature that samples should be no larger than 1 mg in TGA measurements must be limited to biomass samples with a high heat of reaction such as cellulose.