Schultz Method Research Articles

A comparative study of surface properties of Urtica dioica (nettle) leaves, roots, and seeds and examination of their ability to separate xylene isomers.

Urtica dioica (nettle) is a plant species of the Urticaceae family that grows in various parts of the world and exerts antioxidant, antibacterial, antiulcer, antiviral, and anti-inflammatory effects. Their leaves, roots, and seeds are used in various fields such as food, medicine, and cosmetics. Inverse gas chromatography (IGC) was used to evaluate the surface characteristics and separation ability of U. dioica leaves, roots, and seeds. Characterization of these biomasses was performed by Fourier transform infrared spectroscopy (FTIR) analyses. The surface properties of the biomasses including dispersive surface energy, adsorption enthalpy, Gibbs free energy, and acidity-basicity constants were determined at infinite dilution using various organic solvents. These properties were compared with each other. Dispersive surface energies were calculated using the Dorris-Gray, Donnet-Park, and Schultz methods. The accuracy of these methods and their applicability were evaluated. In the last stage of this study, the separation of xylene isomers was investigated by using U. dioica biomasses as stationary phases. The surface functional groups were determined by FTIR analysis. As a result of the IGC studies, it was found that the adsorption of polar solvents on biomasses occurred exothermically and spontaneously. Besides, it was found that the surfaces of biomasses were basic. From the retention diagrams and selectivity coefficients, it was determined that xylene isomers were effectively separated. IGC is a promising, low-cost, easy-to-apply, and high-accuracy technique for the investigation of the surface properties of biomasses and their ability to separate isomers.

Is a clavicle fracture a contraindication for swinging (Schultz's method) of a child born with asphyxiation?

The article is prompted by the report of one case by Heydrich from the Breslavl polyclinic, which was published in No. 7 1890 Centralbl. fr Gynaec.

Surface properties of ionic liquids: A study of different calculation methods in inverse gas chromatography

The surface properties of 1-alkyl-3-vinylimidazolium hexafluorophosphate ([CnVIM][PF6], n = 2,4,6,8) ionic liquids and 1-allyl-3-vinylimidazolium ([AVIM]+), ionic-based liquids with different anions (Cl−, Br−, [BF4]−, [Tf2N]−) were investigated at temperatures between 303.15 and 343.15 K on the basis of inverse gas chromatography (IGC). The Schultz method and Dorris-Gray methods were used to estimate the dispersive free energy based on the net retention volumes of homogeneous n-alkanes, and it was found that the discrepancy between the two methods increases with increasing temperature, with the Dorris-Gray method providing slightly higher values than the Schultz method at the same test temperature. The Lewis acid-base parameters, KA and KB, were likewise assessed by the method proposed by Schultz, Flour and Papirer, Brookman and Sawyer, respectively. Although the difference between the values of acid-base parameters were observed, the ratios of KB/KA obtained by three methods presented the same tendency and implied that the surface of all the tested ionic liquids exhibited the Lewis amphoteric and stronger basic character. In addition, the values of the enthalpies of adsorption between the probes and ionic liquids were also determined.

Surface characterization of 1-butyl-1-ethylpiperidinium bromide by inverse gas chromatography

This work addresses the surface characterization of an organic salt based on a piperidinium cation and a halide anion, similar to a first generation ionic liquid, using the Inverse Gas Chromatography (IGC) technique. IGC was employed in order to assess the dispersive surface energy and the acid/base character of 1-butyl-1-ethylpiperidinium bromide, [C2C4PIP]Br at a temperature range (313.15–343.15 K) well below its melting point, where the retention mechanism is governed by the surface adsorption of the probes. This type of characterization was possible due to the high melting point of [C2C4PIP]Br, namely 413.15 K. The dispersive component of the surface energy was estimated with the aid of the Schultz method and the Dorris-Gray method. Results obtained using the first method were higher than the ones obtained by the latter. The discrepancy between the two methods was found to increase with the increase of temperature. The acid/base characterization was implemented by using the Flour and Papirer approach as well as the Brookman and Sawyer method. The acidity and basicity constants of the surface of [C2C4PIP]Br revealed that it is amphoteric with a predominantly basic character.

Viscoplastic self-consistent polycrystal modeling of texture evolution of ultra-low carbon steel during cold rolling

The viscoplastic self-consistent (VPSC) polycrystal model, where each grain is regarded as an ellipsoidal inclusion interacting with a homogeneous effective medium represented by the polycrystal has long been successful in explaining the mechanical response and crystallographic texture development during plastic deformation. VPSC has especially been used to model low-symmetry materials such as Mg-alloys, uranium, etc, which could not be addressed by the conventional Taylor model. Although there are several reports on the modeling of steel that successfully reproduce its measured crystallographic texture at specific reductions, few studies have been carried out to reproduce the evolution of the intensity of texture fibers at various rolling reductions. In this study the texture evolution of body-centered-cubic ultra-low carbon steel during cold rolling was calculated using the VPSC model and compared with textures measured at 40%, 60%, 70%, 80% and 90% reduction. The deformation by cold rolling was accommodated by and slip systems interacting via a Voce hardening law. Addressing a wide range of rolling reductions poses a more severe test on the modeling. It is found that accounting for grain shape, grain interaction with the surroundings, and their evolution with strain, is critical for explaining the experimentally observed evolution of texture intensities. Specifically, the mechanisms of grain-neighbor co-rotation and the role played by the relative plastic stiffness of grain and surrounding medium were explored in this work. The predicted evolution of the main texture components, namely, α fiber (RD//) and γ fiber (ND//) was compared with experimental data measured by x-ray Schultz method, resulting in that the calculated texture evolution using the above models captures well the experimental results which show a gentle ODF intensity increase in the γ fiber and a strong ODF increase near components in the α fiber during cold rolling.

Schultz matrix iteration based method for stable solution of discrete ill-posed problems

In this paper, we propose an iterative method for solving discrete ill-posed problems based on matrix iterations generated by Schultz method and known to converge to the Moore–Penrose pseudoinverse of a matrix. Practically, letting the Schultz matrix iteration be Xk, we construct the vector xk=Xkb where b is a data vector. Hence, by construction, the iterates converge to the minimum 2-norm solution of a least squares problem with coefficient matrix A and data vector b. We derive theoretical properties of the sequence xk and show that it is quadratically convergent. In the case of corrupted data, we analyze the semi-convergence behavior of the iterates and conclude that the iteration must be truncated to control the propagation of the noise error. As a result, we derive an error estimate for the case where the truncation parameter is chosen by the discrepancy principle. In addition, combining a projected approach with the new method, we propose variants of the method that are well suited for large-scale problems. Several numerical results are presented to illustrate the effectiveness of the method on well known test problems.

Inverse Gas Chromatography Study on London Dispersive Surface Free Energy and Electron Acceptor–Donor of Fluconazole Drug

The inverse gas chromatography study on the fluconazole drug surface was performed, and the net retention volumes, polar probes, and VN of n-alkanes are determined at four temperatures over the range 318.15–333.15 K. The net retention values of n-alkanes were used to evaluate the London dispersive surface free energy γSL by three different methods, namely, the Donnet–Park, Dorris–Gray, and Schultz methods. The γSL values were found to increase from 318.15 to 323.15 K for all three methods and then decrease from 323.15 to 333.15 K. The γSL values were found to be slightly higher in the Schultz method when compared to the results of the Donnet–Park and Dorris–Gray methods. The specific free energy values ΔGaS and the specific enthalpy ΔHaS values have been calculated using the VN data of polar probes. The Guttmann Lewis acid–base parameters, Ka and Kb, were obtained using ΔHaS values and were found to be 0.217 and 1.518, respectively. The surface character (Kb/Ka) was found to be 7.0. The results revealed t...

An Attempt to Chromatographic Determination of Acceptor-Donor Properties of Liquid Crystals

In order to obtain the most valuable information the Gibbs free energies of adsorption or solution, ΔG, should have been estimated in three ways on the basis of the retention times of the centre of gravity of the elution peak of the substances with defined physico-chemical properties. The temperature dependent van der Waals component of the surface free energy, dW s ν γ , has been estimated by employing the Dorris-Gray method and the Schultz method. The suggested approach has also been employed for carbon adsorbents on the basis of various literature data.

Inverse gas chromatographic determination of the surface energy of PMMA and PMMA/organophilic montmorillonite nanocomposites

Poly(methyl methacrylate)/organo‐montmorillonite (PMMA/OMt) nanocomposites containing 2% and 5% OMt by mass were prepared using the solution blending method with sonication. X‐ray diffraction, thermal gravimetric analysis, transmission electron microscopy, and inverse gas chromatography (IGC) were used for characterization of the nanocomposites. IGC studies were operated at infinite dilution, in the temperature range of 40 to 70 °C. The dispersive component of surface free energies of PMMA and PMMA/OMt nanocomposite systems was calculated by using the Lavielle–Schultz method. Copyright © 2016 John Wiley & Sons, Ltd.

Surface thermodynamics of Efavirenz and a blend of Efavirenz with cellulose acetate propionate by inverse gas chromatography

The purpose of this paper is to study the effect of an excipient on the surface energetics of Efavirenz (EFV) drug. The net retention volumes, VN, for n-alkanes and polar solutes on the two columns, namely, EFV drug and a blend of EFV with cellulose acetate propionate have been measured by inverse gas chromatography. The dispersive surface free energy, , Lewis acid parameter, Ka, and Lewis base parameter, Kb, have been determined using VN values. The values are decreased linearly with increase of temperature for pure EFV as well as for the blend. Furthermore, the values of EFV are higher than in the blend, for example, values at T = 318.15 K for EFV, and for the blend are 28.09 ± 6.02 mJ/m2 and 28.30 ± 2.31 mJ/m2, respectively. The specific component of surface free energy has been obtained by the Schultz method as well as by the Dong et al. method. The values have been used to calculate Lewis acid-base parameters for the EFV as well as the blend. The Ka values for the EFV and the blend are almost similar, where as the Kb values are higher in EFV than in the blend. Similar trend in Ka and Kb has been observed in both methods studied. Copyright © 2015 John Wiley & Sons, Ltd.

Finite Dilution Inverse Gas Chromatography as a Versatile Tool To Determine the Surface Properties of Biofillers for Plastic Composite Applications.

An improved understanding of a filler’s surface properties is important for determining the most effective polymer reinforcement fillers. In this work, the surface characteristics of two biofillers, namely, clam shell modified by hydrochloric acid (AMF) and furfural (FMF), were investigated using inverse gas chromatography (IGC). The IGC results showed that the dispersive surface energy (γ(S)(D)) contributed the major part to the total surface energy for the biofillers. The values changed as a function of surface coverages, meaning that both samples were energetically fairly heterogeneous. The γ(S)(D) calculated with the Dorris–Gray method was larger than that calculated with the Schultz method, with a γ(S,Dorris–Gray)(D)/γ(S,Schultz)(D) ratio of 1.10. Compared to AMF, FMF possessed higher γ(S)(D) value; however, this difference was compensated by specific (acid–base) surface energy (γ(S)(AB)). Both samples predominantly interacted with ethanol and acetonitrile, implying an amphoteric nature of the material surfaces. Gutmann acid and base number profiles indicated that the surfaces of both samples were more basic in nature. The FMF showed a lower total work of cohesion (W(Coh)(total)) value compared to the AMF, which could lead to an increase in composite performance.

Surface Thermodynamics of Poly(caprolactone) Diol by Inverse Gas Chromatography

Inverse gas chromatography was applied to evaluate the surface thermodynamic properties of biodegradable poly(caprolactone) diol (PCLD) in the temperature range 313.15–333.15 K with steps of 5 K. The net retention volumes, VN, were determined for the n-alkanes and polar solute probes. Dispersive surface free energy, , was calculated using the Schultz and Dorris-Gray methods, and at T = 313.15 K the values were found to be 19.87 and 21.61 mJm−2 respectively. The dispersive free energy decreased with increase in temperature. Surface Lewis acid parameter, Ka, and Lewis base parameter, Kb, were calculated following Gutmann’s approach. The Ka and Kb values were found to be 0.212 and 0.593 respectively, which revealed the basic nature of PCLD. The three components of the Hansen solubility parameters were determined using for the PCLD surface, and their variation with temperature was studied.

Surface properties studies of bivalve shell waste by the IGC technique: Probing its significant potential application in the polymer industry

Bivalve shell waste has the potential to be used as a bio-filler. In this work, the dispersive component (γsd) of surface free energies of the surfaces of clam shell waste (CS) and commercial calcium carbonate (CC) were evaluated using inverse gas chromatography with both the Dorris–Gray method and the Schultz method. Their acid-base character was investigated as well. The mechanical properties of PP composites filled with CS and CC were then studied. The results showed that the γsd calculated with Dorris–Gray method was a bit smaller than that calculated with Schultz method, with a γs,Dorris-Graydγs,Schultzd ratio of 0.98. The surface energy of the CS was significantly heterogeneous and its calculated γsd decreased drastically with increasing surface coverage from 0.5% to 2%, then slightly increased with surface coverage larger than 2%. The Ka/Kb ratio was 7.65 for CS and 1.48 for CC, indicating a more acidic character for the surfaces of CS. The mechanical properties analysis showed that the inclusion of CS powder played mainly a toughening role in the filled PP.

Surface characterization of 2-hydroxypyrimidine sulphate by inverse gas chromatography

The net retention volumes, V N , of n-alkanes and polar probes on 2-hydroxypyrimidine sulphate (2-HPS) drug surface are determined at 323.15, 328.15 and 333.15 K using inverse gas chromatography. The dispersive surface free energy, \( \gamma_{S}^{d} \) of 2-HPS are evaluated by applying Schultz method as well as Dorris–Gray method and found that \( \gamma_{S}^{d} \) values are higher by 8 per cent in the latter method. The \( \gamma_{S}^{d} \) values are decreasing in both the methods with increase of temperature. The specific component of the free energy of adsorption, \( \Updelta G_{a}^{S} \), for polar probes are obtained by three methods proposed by Schultz et al., Saint Flour–Papirer and Sawyer–Brookman. The Lewis acid–base parameters, K a and K b , are calculated using \( \Updelta G_{a}^{S} \) values. The surface character value, S = (K b /K a ) according to the Schultz et al., is found to be 3.9 whereas the S value in the other two methods are found to be 6.2 and 5.6. The results demonstrate that the 2-HPS powder surface contain relatively more basic sites and can interact strongly in the acidic media.

Comparison of Dorris–Gray and Schultz methods for the calculation of surface dispersive free energy by inverse gas chromatography

Inverse gas chromatography (IGC) is an important technique for the characterization of surface properties of solid materials. A standard method of surface characterization is that the surface dispersive free energy of the solid stationary phase is firstly determined by using a series of linear alkane liquids as molecular probes, and then the acid–base parameters are calculated from the dispersive parameters. However, for the calculation of surface dispersive free energy, generally, two different methods are used, which are Dorris–Gray method and Schultz method. In this paper, the results calculated from Dorris–Gray method and Schultz method are compared through calculating their ratio with their basic equations and parameters. It can be concluded that the dispersive parameters calculated with Dorris–Gray method will always be larger than the data calculated with Schultz method. When the measuring temperature increases, the ratio increases large. Compared with the parameters in solvents handbook, it seems that the traditional surface free energy parameters of n-alkanes listed in the papers using Schultz method are not enough accurate, which can be proved with a published IGC experimental result.

Characterization of the surface tension and solubility parameter of epoxy resin by using inverse gas chromatography

Inverse gas chromatography (IGC) was used to measure the surface tension and solubility parameter of E51 epoxy resin in this work. By using the Schultz method, decane, nonane, octane and heptane were chosen as the neutral probes to calculate the dispersive surface tensions (gamma(D)). Based on the Good-van Oss equation, the specific surface tension (gamma(SP)) of E51 epoxy resin was calculated with the acidic probe of dichloromethane and the basic probe of toluene. The results showed that the gamma(D) and gamma(SP) of the E51 resin decreased linearly with the increase of temperature. According to the Flory-Huggins parameters (chi) between the resin and a series of probes, the solubility parameters (delta) of E51 resin at different temperatures were estimated using the method developed by DiPaola-Baranyi and Guillet. It was found that the values of delta of the E51 resin were 11.78, 11.57, 11.48 and 11.14 MPa1/2 at 30, 40, 50 and 60 degrees C, respectively. The dispersive component (delta(D)) and the specific component (delta(SP)) of solubility parameter at different temperatures of the E51 resin were investigated according to the relationships between surface tension, cohesion energy and solubility parameter. The results showed that the values of delta(D) were higher than those of delta(SP) for the epoxy resin, and both of them decreased with the increase of temperature.

Chromatographic characterisation of ordered mesoporous silicas: Part I. Surface free energy of adsorption

The ordered mesoporous siliceous materials: MCM41C16, MCM41C16-SH and MCM41C16-NH 2 (known as MCMs) having different surface functionalities were studied by inverse gas chromatography at infinite dilution of chromatographed substances to elucidate their adsorption and adhesive properties. The free energies of adsorption, Δ G a d s , were calculated in two ways on the basis of the primary chromatographic data. The van der Waals component of the surface free energy, γ S v d W , was calculated by employing the Dorris–Gray method and the Schultz method. The van der Waals, γ S v d W , and specific, I S P , components of the surface free energy were temperature dependent, and were expressed as the linear dependences. The suggested approach was also employed for non-ordered silica adsorbents on the basis of various literature data.

Growing-season rainfall, ear number and the water-limited potential yield of wheat in south-western Australia

Knowledge of the contribution of ear number per unit area, grains per ear, and kernel weight to grain yield is important in understanding the limits to the water-limited potential yield of wheat in rain-fed agricultural regions. This paper analyses the relationships between grain yield, yield components and growing-season rainfall using data from the low-, medium-, and high-rainfall zones of the cropping region of south-western Australia. The aim of the paper is to quantify the contribution of ear number, grains per ear and kernel weight to grain yield and define the yield components of wheat required to achieve its water-limited yield. The grain yield of wheat was closely related to the number of grains per unit area (r2 = 0.90) and ears/m2 (r2 = 0.75), but poorly correlated with kernel weight (r2 = 0.30) and grains/ear (r2 = 0.09). The number of grains per unit area was highly related (r2 = 0.75) to the number of ears per unit area across the rainfall zones of the cropping region, and strongly correlated (r2 = 0.88–0.94) to the spike dry weight at anthesis. The highest yields achieved in the field were close to the water-limited potential estimated using the French and Schultz method. To achieve this water-limited potential, wheat requires 1 ear per m2 for every mm of growing-season rainfall (r2 = 0.92). We conclude that the number of ears per unit area is the most important factor required in order to achieve high yields of up to a yield of 6 t/ha in wheat in rain-fed south-western Australia.

Inverse Gas Chromatographic Method for Measuring the Dispersive Surface Energy Distribution for Particulates

Inverse gas chromatography (IGC) is a widely used method for determining the dispersive component of the surface energy (gamma s (d)) of particulate and fibrous solids. Such measurements are normally conducted at very low solute concentrations (infinite dilution), and they result in a single numerical value of gamma s (d) for homogeneous materials which exhibit Henry's Law adsorption behavior. However, many real solid surfaces are heterogeneous and this may be demonstrated by the nonlinear isotherms obtained at low solute surface coverages resulting in reported gamma s (d) values which are not unique. This paper presents a new method for determining of gamma s (d) distributions as a function of the solute surface coverage using adsorption isosteres for an homologous series of hydrocarbon adsorbates. gamma s (d) distributions reported here were successfully determined using two different solid materials (glass beads and alumina particles) up to typical surface coverages of approximately 10% and clearly show significant variations in gamma s (d) with solute surface coverage. The effects of sample aging and pretreatment also exhibited clear differences in the gamma s (d) distributions obtained. gamma s (d) was determined using both the Dorris-Gray and Schultz methods, with the Dorris-Gray method exhibiting a much lower experimental error. It was established that the errors associated with this statistical measurement of surface energy were strongly dependent on the quality of the experimental data sets obtained. R (2) for the linearity of fit of the retention data to the Dorris-Gray gamma s (d) analysis was found to be a valid criterion for predicting the robustness of gamma s (d) distributions obtained. Detailed discussions of other critical experimental and analysis factors relevant to this methodology, as well as the reproducibility of gamma s (d) profiles are also presented. This paper establishes that IGC can be used for determining the gamma s (d) distributions of particulate solids and is demonstrated that this method is very useful way for studying the surface energy heterogeneity of complex particulate solids.

Sequential extraction for radionuclide fractionation in soil samples: a comparative study

Two sequential extraction procedures, Tessier's method (Anal. Chem. 51(7) (1979) 844), and a current version known as Schultz's method (J. Environ. Radioact. 40(2) (1998) 155), were compared. The two procedures were applied to a natural soil sample that presents high activity concentrations in natural radionuclides of the 238U series. Reproducibility studies of each method and a comparison between the two sets of results were performed for uranium, thorium, and radium. The results were different for each radionuclide. Analysis of the extracted fractions was carried out by alpha spectrometry.