Classical Gravimetric Method Research Articles

Evaluation of cut alfalfa moisture content and operative conditions by hyperspectral imaging combined with chemometric tools: In-field application

High quality of hay or silage can be obtained by monitoring the moisture level at mowing or harvest time to reduce the losses of yield and nutrients and preserve feeds in the long term. Mechanical conditioning is one of the most common ways to increase the rate of water loss from forage during drying. Near Infrared (NIR) spectroscopy is a good alternative to the classical gravimetric method to timely provide information on forage moisture content. The aim of this work was to evaluate the potential of in-field Vis/NIR hyperspectral imaging combined with chemometric tools to monitor alfalfa parameters after conditioning. Partial LeastSquares Discriminant Analysis (PLSDA) models were developed to discriminate samples according to several operative conditions (level of conditioning, field type, time after conditioning, and time of day) and yielded good discrimination power (mean sensitivity = 87%, mean probability = 89%). Moisture content was estimated by Partial LeastSquares (PLS) models obtaining determination coefficient (R 2 ) = 0.86 and Root Mean Square Error (RMSE) = 2.00% (external validation). The number of spectral bands was reduced by using the Variable Importance in Projection (VIP) method, passing from 272 to 74 bands. Further PLS models were built considering the reduced variable numbers and achieved comparable results to those obtained with the full spectra, demonstrating that reduction of the number of variables did not affect the goodness of the models. Finally, the best PLS model was applied to each pixel of the hyperspectral images to obtain false colour images. Pixels having similar colours were characterized by comparable moisture content. The models developed may be useful to determine moisture content of alfalfa remotely and in real-time during mowing or harvest procedures. • Quality of alfalfa after cutting was evaluated. • In-field Vis/NIR hyperspectral imaging was used. • Regression models to predict moisture content were developed. • The samples were discriminated according to several operative parameters. • The models could be used remotely or in real-time during mowing or harvest procedures.

Leveraging Lyophilization Modeling for Reliable Development, Scale-up and Technology Transfer.

Modeling of the lyophilization process, based on the steady-state heat and mass transfer, is a useful tool in understanding and optimizing of the process, developing an operating design space following the quality-by-design principle, and justifying occasional process deviations during routine manufacturing. The steady-state model relies on two critical parameters, namely, the vial heat transfer coefficient, Kv, and the cake resistance, Rp. The classical gravimetric method used to measure Kv is tedious, time- and resource-consuming, and can be challenging and costly for commercial scale dryers. This study proposes a new approach to extract both Kv and Rp directly from an experimental run (e.g., temperature and Pirani profiles). The new methodology is demonstrated using 5% w/v mannitol model system. The values of Kv obtained using this method are comparable to those measured using the classic gravimetric method. Application of the proposed approach to process scale-up and technology transfer is illustrated using a case study. The new approach makes the steady-state model a simple and reliable tool for model parameterization, thus maximizes its capability and is particularly beneficial for transfer products from lab/pilot to commercial manufacturing.

Determination of ash content of milk-based powders by Energy Dispersive X-ray Fluorescence

A simple and rapid method for the determination of ash content by Energy Dispersive X-Ray Fluorescence (ED-XRF) was established and validated for milk-based powders. ED-XRF determination can interestingly replace classical gravimetric methods by reducing the analytical time from several hours to three minutes only. Indeed the results obtained show that ED-XRF gives statistically comparable results to classical methods (furnace and thermo-gravimetric analyzer). The relative expanded uncertainty of the ED-XRF method was found to be <10%, which is acceptable.Using ED-XRF technique for ash content determination on top of elemental determination analyses allows to reduce delays and costs.

Non-invasive in vitro and in vivo monitoring of degradation of fluorescently labeled hyaluronan hydrogels for tissue engineering applications

Tracking of degradation of hydrogels-based biomaterials in vivo is very important for rational design of tissue engineering scaffolds that act as delivery carriers for bioactive factors. During the process of tissue development, an ideal scaffold should remodel at a rate matching with scaffold degradation. To reduce amount of animals sacrificed, non-invasive in vivo imaging of biomaterials is required which relies on using of biocompatible and in situ gel forming compounds carrying suitable imaging agents. In this study we developed a method of in situ fabrication of fluorescently labeled and injectable hyaluronan (HA) hydrogel based on one pot sequential use of Michael addition and thiol-disulfide exchange reactions for the macromolecules labeling and cross-linking respectively. Hydrogels with different content of HA were prepared and their enzymatic degradation was followed in vitro and in vivo using fluorescence multispectral imaging. First, we confirmed that the absorbance of the matrix-linked near-IR fluorescent IRDye® 800CW agent released due to the matrix enzymatic degradation in vitro matched the amount of the degraded hydrogel measured by classical gravimetric method. Secondly, the rate of degradation was inversely proportional to the hydrogel concentration and this structure–degradation relationship was similar for both in vitro and in vivo studies. It implies that the degradation of this disulfide cross-linked hyaluronan hydrogel in vivo can be predicted basing on the results of its in vitro degradation studies. The compliance of in vitro and in vivo methods is also promising for the future development of predictive in vitro tissue engineering models. Statement of significanceThe need for engineered hydrogel scaffolds that deliver bioactive factors to endogenous progenitor cells in vivo via gradual matrix resorption and thus facilitate tissue regeneration is increasing with the aging population. Importantly, scaffold should degrade at a modest rate that will not be too fast to support tissue growth nor too slow to provide space for tissue development. The present work is devoted to longitudinal tracking of a hydrogel material in vivo from the time of its implantation to the time of complete resorption without sacrificing animals. The method demonstrates correlation of resorption rates in vivo and in vitro for hydrogels with varied structural parameters. It opens the possibility to develop predictive in vitro models for tissue engineered scaffolds and reduce animal studies.

On the water-sorption properties of pectin

In this work we investigate the water-sorption isotherms of three types of pectins (from apple, citrus and sunflower) at 25 °C, 35 °C and 45 °C through the classical gravimetric method. The experimental data are treated with BET and GAB model equations for finding the monolayer moisture content X w , a , BET and Guggenheim constants. The investigated pectins were characterized by their X-ray and infrared spectra and an attempt was made to correlate between their water-sorption properties and their molecular structure and crystal organization.

Concentrations of Particulate Matter in Schools in Southwest Germany

During the winter season 2005/2006, measurements of small particulate matter were taken in 22 schools in southwest Germany. PM2.5 was measured gravimetrically. Laser particle counter (LPC) and condensation particle counter (CPC) were used to determine different particle fractions. The investigation included measurements inside (in classrooms) and outside of school buildings. During the whole investigation period continuous reference measurements were taken near the State Health Office in the city of Stuttgart. Information on building-specific data and traffic near the schools was collected via questionnaire. Although distances between the different schools and the location of the State Health Office building in Stuttgart in some cases exceeded 100 km, the concentration levels of particles > 0.3 μm measured by LPC near the different schools were similar to those measured in Stuttgart. The differences between the measurements in Stuttgart and at the other locations were smaller than the variation in time. In the winter season, the impaction of particulate matter was strongly influenced by specific weather conditions. Time resolution of measurements in classrooms showed variation in particle concentration depending on the type of building and indoor activities like cleaning or moving during breaks. Concentrations of very small particles in buildings and in ambient air measured by CPC were influenced by traffic emissions. The observed data give reason to assume that the influence of high traffic emissions to indoor particle concentration may have been overestimated. Furthermore, there is an urgent need for standardization of measurement protocols, sampling, and determination of indoor particulate matter. The classical gravimetric methods are less appropriate since they do not allow for a time resolution of measurements.

Transport and dielectric properties of poly(ethylene terephthalate) as determined via electrochemical techniques

AbstractThe electrochemical impedance spectroscopy (EIS) technique was used to evaluate the water transport (diffusion and equilibrium water uptake) and the dielectric properties of free‐standing poly(ethylene terephthalate) (PET) membranes at 40°C. Permeability and diffusion coefficients were also obtained using the Payne cup method and the MacBain quartz spring balance to assess the reliability of the EIS method when compared to other techniques. In addition, an electromigration (dc) technique was used to estimate the NaCl diffusion coefficient across PET films. Results obtained indicate that PET is highly permeable to water and much less permeable to salt. The water diffusion coefficient, D, varies from 2.11× 10−9 to 9.97× 10−9 cm2s−1 for thicknesses between 22 and 205μm, whereas the equilibrium water uptake, W, varies from 0.54 to 0.95 wt % for the same given range of thicknesses. The average calculated dielectric constant of the free‐standing PET films is 3.6. An estimate of the NaCl diffusion coefficient, Ds, is 9.34× 10−14 cm2s−1. Transport properties results obtained via the electrochemical technique are in reasonable agreement with those obtained with the classical gravimetric method. © 1993 John Wiley &amp; Sons, Inc.

Evaporation rates of solvent blends measured by gas chromatography

A gas chromatographic method that enables the measurement of individual and total evaporation rates from solvent blends has been developed; the composition of the remaining liquid can also be determined. The method offers definite advantages over the classical gravimetric methods. Isothermal vapour—liquid equilibrium data can also be obtained.

The copolymerization of vinyl chloride with 1-olefins. I. A new method of investigation of the kinetics of homopolymerization and copolymerization of vinyl chloride

The indirect volumetric method following the amount of monomers in the heterogeneous liquid reaction mixture in a constant volume of samples periodically withdrawn by means of gas chromatography. This new method utilizes periodic sampling of the heterogeneous reaction mixture from the reactor during the reaction and gas chromatographic determination of the unreacted monomers contained in the sample. Its suitability and reliability were verified for the suspension homopolymerization of vinyl chloride. The reproducibility of sampling and the accuracy of determination of the degree of conversion and of the initial reaction rate were investigated. The conversion curves obtained by this method are compared with those obtained by the classical gravimetric method.

Determination of tungsten in ores, concentrates and plant process materials using internal standard X‐ray fluorescence spectrophotometry

AbstractA method is described for the X‐ray fluorescence determination of tungsten in non‐metallic samples over the range 0–100%. The sample is fused with (65% sodium, 35% lithium) tetraborate, barium nitrate and tantalum pentoxide, the internal standard, at 1200°C and the melt cast into a platinum/5% gold mould. After cooling the cast bead, the tungsten and tantalum Lα intensities are determined by X‐ray fluorescence. The tungsten content of the sample is found by comparing the measured intensity ratio with intensity ratios obtained from standards prepared using pure tungsten trioxide.A wide range of ores, concentrates and plant process materials are analysed for tungsten by this method. The accuracy and precision of the method, which is quicker and requires less skill from the analyst, are found to be superior to those of the classical gravimetric method.

Barium and strontium in silicates: A study on the development of analytical methods

Barium and strontium in silicates have been determined by a number of methods, and their contents in several standard samples are reported. Instrumental techniques evaluated include isotope dilution mass spectrometry, flame emission and absorption spectrometry, emission spectrography and spectrometry. X-ray fluorescence spectrography, and neutron activation analysis. Classical gravimetric methods are reported. Two X-ray fluorescence procedures were used; one involves fusion with lithium metaborate and yields only strontium values. The other uses a direct dilution technique and gives results for both barium and strontium. In practice, this method requires a suite of analyzed standards, which should be generally similar in composition to the unknown. Strontium can be satisfactorily determined by atomic absorption spectrometry in whole-rock solutions, but there are difficulties in determining barium in this way. Emission spectrometry, with a spark-solution technique and automated equipment, gives rapid and accurate results for both barium and strontium. Flame emission spectrometry, neutron activation analysis, and classical gravimetric methods are not satisfactory as practicable routine methods for barium and strontium in silicate rocks. Conslusions are that barium and strontium may be satisfactorily determined by several methods, and that refinement of these methods is possible to the point where sampling error, rather than analytical error, may often determine variance in the results.

Ultraviolet Determination of Elemental Sulfur in Ore

In a method for the determination of elemental sulfur in ores reported in 1964 by a Japanese worker, sulfur was extracted from the ore into carbon disulfide and determined by using the absorption edge of the sulfur band. Although the procedure is an improvement over the classical gravimetric method, it is not entirely satisfactory as a general procedure because the measurement is made on the steep slope of the curve. Other investigations have reported spectra and determination of free sulfur in a variety of solvents.

Determination of calcium and magnesium in magnesite by a complexometric method employing co-precipitation of calcium with strontium sulphate

In the classical gravimetric method calcium is precipitated as phosphate along with the magnesium and recovered by adding sulphuric acid and alcohol, then Ca2+ and Mg2+ are determined separately by the usual method [1]. In the proposed method calcium is co-precipitated with strontium sulphate and in the filtrate magnesium ions are determined by EDTA. Then calcium is calculated by difference after estimating combined Ca2+ and Mg2+ ions [2].

Comparison of gravimetric and chromic oxide methods for measuring percentage utilization and consumption of food by phytophagous insects

An indirect method using chromic oxide (Cr 2O 3) for measuring percentage utilization and consumption of dry matter in diets by two species of phytophagous insects is described and results are compared with those of the classical gravimetric method. Fifth-instar larvae of the two-striped grasshopper, Melanoplus bivittatus Say, and fifth-instar larvae of the pale western cutworm, Agrotis orthogonia Morr., were fed individually. Diets were prepared from lyophilized tissues of the wheat plant to which about 4 per cent of the inert index compound, chromic oxide, was added. Three diets varying widely in nutritive value were compared for both utilization and consumption. When residual food and excreta could be quantitatively recovered, measurements by the two methods generally agreed. However, the chromic oxide procedure for measuring utilization gives more reliable results than did the gravimetric method, is convenient, and can be used even when quantitative recovery of excreta is not possible.

Determination of Lead in Leaded Free Cutting Steels by the Chelatometric Titration Method

A simple chelatometric titration method for the determination of Lead in Leaded free cutting steel has been developed. The samples are dissolved in HCl, HNO3 and HClO4 and Iron (III) is extracted into Methyl Isobutyl Ketone from 6 N HCl solution. Chromium (VI), Molybdenum (VI), Vanadium (V), are also extracted. In the aqueous solution, Aluminum, Copper, Nickel, Cobalt and Manganese ions are masked with Triethanolamine and Potassium Cyanide. Lead is titrated at pH 10 to pH 11 using Thymolphthalein complexone as an indicator. The proposed has the advantage of speed, yet has the same accuracy as the classical gravimetric method.

Détermination du sodium par spectrophotométrie de flamme dans l'oxyde d'aluminium

Flamephotometric methods enable accurate and time-saving analyses for sodium. The determination of sodium in aluminium oxide (mainly consisting of refractory α Al 2O 3) however, requires a complete attack on the sample. This was obtained by a fusion method, using a mixture of Li 2CO 3 and B 2O 3 ( x : y) at a temperature of exactly 1200°C. No volatilization losses of sodium could be established under these conditions. The cako is dissolved in hydrochloric acid. The resulting solution contained chlorides and borates of Li, Al, Ca, Fe and obviously sodium with small amounts of Ti and Si and the influence of these components on the sodium emission had to be investigated. influence of the following components separately as well as in combination will be considered: hydrochloric acid, aluminium, lithium, calcium and boric acid. Under average conditions the combined influence can easily be taken into account while the buffering action of lithium is of advantage. After extensive tests the method has been applied to carry out control analyses of the Bayer process, using the Beckmann DU apparatus with flame attachment. Total time of analysis was three and a half hours. The method compares favourably with classical gravimetric methods.

La détermination rapide du calcium et du magnésium dans l'eau de mer

A rapid method is described for the determination of calcium and magnesium in sea. water. The classical gravimetric methods are very lengthy and are susceptible to errors if used for sea-water. The two alkaline earths are determined by complexometric titration using complexen III (disodium ethylenediaminetetra-acetate) as reagent and two indicators (murexide and ériochrome black T) for the determination of calcium and for the sum of Ca +2 and Mg +2 ions. The quantity of magnesium is obtained by difference. While the classical gravimetric methods take at least 24 hours, these two determinations can be effected in 1 hour, giving satisfactory accuracy.

Le dosage par voie complexométrique du calcium et du magnésium dans les milieux trés riches en chlorures (sel marin brut et saumures)

A rapid method is described for the determination of calcium and magnesium in natural sea salts and in brine. The classical gravimetric methods are very lengthy and are susceptible to errors if used in media rich in chlorides. The two alkaline earths are determined by complexometric titration using Complexen III (disodium ethylenediaminctetra-acetate) as reagent and two indicators (Murexide and Eriochrome Black T) for the determination of calcium and for the sum of Ca+2 and Mg+2 ions. The quantity of magnésium is obtained by difference. While the classical gravimetric methods take at least 24 hours, these two determinations can be effected in 1 hour, giving satisfactory accuracy.