Pure Reagents Research Articles

Chiral Analysis of Amphetamine and Methamphetamine in Urine by Liquid Chromatography-Tandem Mass Spectrometry Applying Mosher Derivatization

Methamphetamine (MA) and amphetamine (AM) are central nervous system doping agents, listed in the WADA Prohibited List, which in the past years showed the highest prevalence among all stimulants. Specifically, concerning these stimulants, it is essential to distinguish between d and l-isomers of AM and MA due to their distinction in illicit or legal nonprescription use. The main separation methods used for the urinary determination of MA and AM enantiomers are based on chromatographic procedures, such as gas chromatography after chiral derivatization or liquid chromatography (LC) applying chiral columns, followed by the mass spectrometer (MS) detection. The use of the optically pure reagent R-(-)-α-methoxy-α-(trifluoromethyl) phenylacetic acid chloride (R-MTPA-Cl – Mosher’s Reagent) allows the isomeric separation by both chromatographic procedures while preserving the isomeric composition of the substances. Therefore, in the present work, an LC-MS2 approach has been developed for AM and MA detection in urine after Mosher derivatization. The method was validated and can be used for the enantioselective confirmation of AM and MA for doping control purposes and forensic analysis in general, being useful for the distinction between the medicinal and illicit use of both stimulants.

Evaluation of Internal Distribution and Extracellular Action of the Cell via TOF-SIMS.

Cisplatin is one of the most popular and traditional platinum-based anti-cancer drugs. Additionally, it is known for its effect on different types of cancers. To clarify the reaction mechanism of anti-cancer drugs in a cell, the visualization of drugs in a single cell is required. In this study, we investigated a secondary ion species obtained from cisplatin, which was bounded to the nucleus in a cell and its intensity. PtCl2- was mainly detected via SIMS during an analysis of pure cisplatin reagent. In contrast, a high-intensity signal for PtCN- was detected from cultured cells that were administered cisplatin. However, this signal was not detected from cisplatin in the reagent state. Chlorine in the cisplatin structure is replaced with water when it is combined with the cell nucleus. Therefore, PtCN- was mainly detected from the intracellular region because the structure was changed by cisplatin binding to the nucleus and which exhibits anti-cancer activity. The results showed that the cisplatin selectively combined with the nucleus. Through TOF-SIMS, we achieved a visual distribution of the cisplatin intracellular nucleus.

An Improved Protocol for the Synthesis and Purification of Yariv Reagents.

Yariv reagents are glycoconjugate tris-azo dyes widely used in plant biology. These reagents are synthesized by diazo coupling between phloroglucinol and a para-diazophenyl glycoside. Despite their synthetic accessibility, well-defined protocols for obtaining pure Yariv reagents, and their complete compound characterization data, have not been reported. We report here optimized protocols used to synthesize, purify, and characterize a panel of six Yariv reagents and suggest approaches that could be valuable for the purification and characterization of other glycoconjugates as well.

A review on fabricating functional materials by heavy metal-containing sludges.

With the development of industry, sustainable use of natural resources has become a worldwide hot topic. Heavy metal-containing sludge (HMS) is a hazardous waste after wastewater treatment. At present, HMS is still treated by landfill or landfill after incineration. Considering the components, HMS usually contains various heavy metals and organic compounds, which is potentially used as a raw resource for catalyst production. This review thus concludes recent reports and developments in this field. First, basic technologies are summarized as component regulation, precursor formation, and structure transformations. Second, prepared materials are applied in various catalytic fields, such as gas purification, photocatalysis, electrocatalysis, and Fenton catalysis. During these processes, key factors are multi-metallic components, metal doping, temperature, and pH. They not only influence the formation of HMS-derived catalyst but also the catalytic activity. Furthermore, catalytic activities of HMS-derived catalysts are compared with those synthesized by pure reagents. An assessment and accounting are also supplied if raw resources are substituted by HMS. Finally, in order to apply HMS in a real application, more works must be devoted to the influence of trace metal doping on catalytic activities and stabilities. Besides, more pilot experiments are urgently necessary.

Granular crystallization using CFBC ash for phosphorus removal via hydroxyapatite

Abstract To prevent eutrophication and remove phosphorus, circulating fluidized bed combustion (CFBC) ash was utilized to elute Ca2＋ and OH − for hydroxyapatite (HAP) crystallization. CFBC ash was compared with the gypsum byproduct of a domestic waste incineration plant and pure CaO reagent. CFBC ash proved to be a suitable raw material to supply Ca2＋ and OH − for HAP crystallization. CFBC ash was reprocessed as a granular crystallization agent (GCA) to improve its applicability to non-point pollution source control. In addition, a manufacturing procedure for a GCA utilizing 4.8% blast furnace slag as a binder was developed based on durability and the ion elution rate in water. Column tests with sedimentation showed that 93% and 98% of T-P and PO4-P were removed after 12 h of settling, respectively. In on-site filtration trench tests, filtration following crystallization with a 4 h retention time achieved a 63.5% and 52.8% removal efficiency with respect to T-P and PO4-P, respectively. After operation for 13 d, an increase in porosity with pore distribution on the surface of the GCA was observed. Through their long-term on-site operation, crystallization–filtration trenches using GCA provide an effective alternative process for the management of agricultural non-point source pollution.

Artemisia cina 30 CH homeopathic treatment against Haemonchus contortus

The anthelmintic resistance problem is widely recognized in sheep production. Therefore, new methods of control against gastrointestinal nematodes (GIN) need to be integrated. The aim of this work was to assess the toxicity of A. cina 30 CH as a homeopathic product against Haemonchus contortus in in vitro and in vivo assays. A. cina 30 CH was obtained from a commercial laboratory, and confirmation of artemisinin as a key ingredient was performed with mass spectrophotometry. The A. cina 30 CH and the artemisinin pure reagent were used for the inhibition of egg hatching (IEH) and for the inhibition of larval migration of H. contortus L3 (ILM). In addition, three groups of 10 naturally infected lambs with GIN were treated with A. cina 30 CH and albendazole, and 10 were used as control. The parasitic infection was monitored at 0, 7, 14 and 28 d postreatment (PT) to determine the number of eggs per gram (epg) and FAMACHA index. The in vitro data showed 100 % IEH and 64.7 % ILM by A. cina 30 CH, and nonlethal activity was observed with the artemisinin pure reagent. The toxicity of A. cina 30 CH against H. contortus in infected lambs was observed after 7 d of infection. Administration of the A. cina 30 CH yielded a 69 % reduction in the epg at 28 d PT, similar to the albendazole (P<0.05). In conclusion, A. cina 30 CH had the ability to IEH and ILM of H. contortus in in vitro assays and reduced the number of eggs of H. contortus, which is the primary parasitic nematode in grazing lambs, thereby reducing infection.

A Review on Chiral Columns/Stationary Phases for HPLC

The chiral separation of pharmaceutical molecules and their precursors is one of the important areas of application of HPLC in pharmaceutical analysis for obtaining enantiomerically pure drug. The latter procedures include the use of so-called chiral selectors to enantio-selectively recognise and isolate the enantiomer. The direct approaches, i.e. those which do not derivate the compound of interest before separation, are addressed in detail, since they are now the most common approaches. The role of stereochemistry in medicinal products is being given greater emphasis to medical practice. For physicians to make conscious choice about the use of single-enantiomered medicinal products, basic knowledge is required. For few treatments single-enantiomer formulations can provide more selectivity than a combination of enantiomers in their biological purposes, enhanced therapeutic indexes and/or better pharmacokinetics. This highlights the possible biological and pharmacological variations between the two drug enantiomers and underlines the clinical experience of individual enantiomers. Particular emphases have been put on chiral separation by HPLC on chiral stationary phases (CSPs). Chiral derivatization reagents (CDRs) are optically pure reagent on reaction with drugs forms a pair of diastereoisomers that can be separated on conventional achiral phase. In Chiral mobile phase additive (CMPA) method, the stationary phase is achiral and the chiral selector is dissolved during the mobile phase. Interaction with the analyte’s enantiomer leads to the formation of transient diastereomeric complexes that are separated by their affinity towards mobile/stationary phase. Separation mechanisms and method development for chiral molecules using these phases are discussed in this review.

Lithium silicates synthetized from iron and steel slags as high temperature CO2 adsorbent materials

The use of solid wastes and industrial by-products to prepare CO2 adsorbents is an alternative to conventional reagent grade raw materials that has recently gained interest. Among waste materials, slag has a high content of silica and calcium and is the largest solid by-product from iron and steel industry, thus its use can reduce the production costs of CO2 adsorbent materials, such as lithium silicates, which are applied in capture processes at high temperatures. Li4SiO4 has potential applications in post-combustion CO2 capture as well as in H2 production by sorption enhanced steam reforming process. In this study, Li4SiO4 was prepared using solid-state reaction and two iron and steel slags as SiO2 sources to evaluate their characteristics and CO2 capture capacities. The slag-derived lithium silicates (S1-Li4SiO4 and S2-Li4SiO4) were characterized by XRD, adsorption-desorption N2 and SEM. Different capture tests at CO2 partial pressures ( $$P_{{{\text{CO}}_{2} }}$$ ) of 0.05, 0.10, 0.15 and 0.20 were performed using thermogravimetric (TG) and temperature programmed (TPC-TPDC) techniques. The kinetic parameters of the CO2 capture process were obtained by fitting the experimental results to the Avrami–Erofeev model. Finally, the cyclic behavior of S1-Li4SiO4 and S2-Li4SiO4 was analyzed in $$P_{{{\text{CO}}_{2} }}$$ of 0.2 and 0.05. XRD patterns showed that Li4SiO4 was the main crystal phase (60 wt%) present in S1-Li4SiO4 and S2-Li4SiO4 in addition to calcium phases such as Li2CaSiO4, Ca3SiO5 and CaO. According to the TG and TPC-TPDC tests, the derived lithium silicates showed CO2 uptake three times greater than the values recorded for Li4SiO4 (134 mgCO2/g sorbent for S1-Li4SiO4) produced from pure reagents, at $$P_{{{\text{CO}}_{2} }}$$ between 0.2 and 0.05 and 650 °C. Furthermore, these materials had kinetic constants at least one order of magnitude higher than those reported for Li4SiO4, at the aforementioned operating conditions. Both materials exhibited an excellent stability during 20 cycles of CO2 adsorption/desorption. These results showed that slags can be used as silica source to produced adsorbents with better performance and stability in the CO2 capture process at high temperature than the one of Li4SiO4 produced from pure reagents, at $$P_{{{\text{CO}}_{2} }}$$ of 0.2–0.05.

Optimization of α-Hydroxyketone and Pyrazine Syntheses Employing Preliminary Reactions of Glucose and Buffer Solutions

Summary Glucose and selected phosphate buffers have been reacted employing systematic variations in reaction temperature and time (150–160 °C for 60–90 min) to optimize the yield of acetol. This mixture was reacted further with NH4OH, systematically varying reaction conditions and reagent ratios to optimize pyrazine yield. The highest yield of pyrazine was obtained when 1 g of glucose was reacted with 25 mL of buffer at 150–160 °C for 60 min, which in turn was reacted with 1 mL of concentrated aqueous NH4OH at 120–130 °C for 17–18 h. Higher temperatures and higher concentrations of glucose caused a decrease in the yield of pyrazines. The addition of hydrolyzed tobacco-derived F1 protein as a secondary source of nitrogen increased the yield of pyrazines by 2–10% depending on F1 protein concentration. Furthermore, the addition of any α-hydroxyketone, similar in structure to acetol, as a pure reagent to the reaction mixture not only increased the yields of pyrazine by ranging from 25–100 % depending on the reagent concentration, but also significantly altered the qualitative and quantitative distribution of the pyrazines. With all of the reaction parameters examined (reaction time, temperature, reagent ratios, etc.) the most significant impacts on both pyrazine yield and distribution were noted when: 1) glucose was pre-reacted with buffer, 2) hydrolyzed F1 protein was added as a second nitrogen source, and 3) when pure α-hydroxyketones were employed as co-reagents. Use of these reaction parameters was found to dramatically shift the pyrazine distribution toward higher molecular weight resulting in a pyrazine array having more desirable physical and sensory attributes.

Simultaneous ultraviolet spectrophotometric determination of sodium benzoate and potassium sorbate by BP-neural network algorithm and partial least squares

In this study, we proposed a reliable method to quickly and simultaneously determine the content of sodium benzoate and potassium sorbate simultaneously by ultraviolet (UV) spectrophotometry with BP-neural network algorithm(BP-ANN) and partial least squares regression(PLS). The pure reagents were used to prepare a series of sodium benzoate and potassium sorbate solutions and used deionized water as a reference solution. The calibration models were constructed by using 36 reference samples according to the orthogonal design and the prediction model set consisted of 9 sets of randomly configured mixed solutions. The results used BP-ANN and PLS showed that the root mean square error prediction (RMSEP) of sodium benzoate and potassium sorbate were 0.129, 0.09 and 0.155, 0.089, and the correlation coefficient (R2) were 0.9997, 0.9994 and 0.9998, 0.9995, respectively. The recovery of the actual samples by both methods was over 97%.

Asymmetric Difluoromethylthiolation of Carbon Nucleophiles with Optically Pure Difluoromethylthiolating Reagents Derived from Camphorsultam

Summary of main observation and conclusionThe invention of a family of optically pure electrophilic difluoromethylthiolating reagents 9a–c based on the camphorsultam skeleton was described. These reagents reacted with a variety of soft carbon nucleophiles such as oxazolone, oxindole, benzolactone and β‐ketoester in good to excellent enantioselectivities.

Chlorogenic acid attenuates cadmium-induced intestinal injury in Sprague–Dawley rats

Chronic exposure to cadmium (Cd) causes remarkable damage to the liver and gastrointestinal tract. Previous studies have revealed that chlorogenic acid (CGA) could improve the intestinal barrier integrity for weaned rats. Hence, this study sought to investigate the protective effects of CGA from pure reagent and sunflower seed extract (SSE) on growth performance, antioxidant indicators, inflammatory biomarkers and intestinal barrier function in Cd treated rats. A total of 32 Sprague–Dawley female rats with similar weights were randomly allotted to four treatments: control, CdCl2 (6 mg/kg BW), co-treatment of Cd (6 mg/kg BW) and pure CGA (50 mg/kg BW), and co-treatment of Cd (6 mg/kg BW) and SSE (50 mg/kg BW) for 14 days. The data indicated that, CGA or SSE with Cd sequestration and good antioxidative ability decreased Cd absorption and accumulation in the jejunum and increased fecal Cd levels in Cd-exposed rats. Compared with the Cd group, co-treatment with CGA or SSE also alleviated inflammation, ameliorated the villus damage, reversed the disruption of tight junctions, and recovered weight gain of rats. These results suggest that CGA or SSE can protect the intestinal barrier, which is related to the alleviation of Cd-induced oxidative stress and growth decrease.

Effect of gangue composition on assimilation characteristic of iron ore in the sintering process

ABSTRACT A new method for determining the timing of assimilation reaction by measuring the change of electrical conductivity of assimilation reaction contact surface was proposed. Experimental study of lowest assimilation temperature (LAT) of 15 iron ores were conducted, and pure reagents simulating tests of LAT were also carried out for purpose of achieving the influence of gangue composition on LAT. The results show that for pure reagents, the increase of Al2O3 and MgO promoted the LAT, low SiO2 (≤3.0 wt%) was good to the LAT, but high SiO2 (>3.0 wt%) was bad, LOI was favorable for LAT. For iron ores, the influence of gangue composition on LAT is basically the same as that of pure reagents, but the linear correlation coefficient is not obvious. It is better to study the effect of synergy of SiO2, Al2O3 and MgO content in iron ore on LAT than that of single factor.

Comparison of Lewis Acidity between Al-MCM-41 Pure Chemicals and Al-MCM-41 Synthesized from Bentonite

This study focused on the Lewis acidity of Al-MCM-41 prepared from bentonite (Al-MCM-bentonite) as silica and aluminum source simultaneously. This acidity was compared with Al-MCM-41 synthesized from pure chemicals reagents (Al-MCM-standard). Structural analysis showed that the substitution of the silicon atom by the aluminum atom decreases the structural order of Al-MCM-standard, whereas Al-MCM-bentonite has a better structural organization. The Lewis acidity of the Al-MCM-bentonite was evaluated in allylation reaction of benzaldehyde with allyltrimethylsilane and pyridine adsorption experiments. The results showed that the difference in acidity between Al-MCM-standard and Al-MCM-bentonite is due to the amount of aluminum incorporated into the framework of our mesoporous materials. According to the EDX analysis, the incorporation of aluminum in Al-MCM-standard (Si/Al = 13.47) is more important than in Al-MCM-bentonite (Si/Al = 43.64). This explains the low acidity of Al-MCM-bentonite, and the moderate yields in the allylation reactions of benzaldehyde with allyltrimethylsilane.

Advantages of bimetallic nitric oxide reduction catalysts consisting of heavy metals rich in hazardous wastes

Abstract High-value-added recycling of hazardous waste is a key problem in environmental science and engineering. In previous reports, a hazardous-waste-derived catalyst showed better activity than a catalyst synthesised from pure reagents for the reduction of nitric oxide. The multimetallic nature of hazardous waste was speculated to increase the catalytic activity. In this work, a further investigation was conducted to confirm this speculation. It was found that bimetallic catalysts showed better activity than monometallic ones at 50–200 °C. A bimetallic catalyst removed 75.05% of nitric oxide (990 ppm) at 150 °C, whereas monometallic ones removed only 19.50%. Moreover, the bimetallic catalyst removed 11.46 mmol/g of nitric oxide after 1200 min at 300 °C, which was a much higher concentration than that removed by the monometallic catalyst (2.72 mmol/g). Experimental and simulated Raman spectroscopy revealed that enhanced activity was accompanied by a larger blue shift of the metal band (indicating catalytic centre activity) and a smaller blue shift of the carbon band (indicating reductant stability). In a theoretical calculation, a second metal changed the electron density difference of the catalytic centre and activated the distant reductant, increasing both the low-temperature activity and activity stability. The main result of this study explained the reason bimetallic catalysts outperformed the monometallic ones. Because hazardous waste usually contains bimetallic species, it can be used as a suitable resource for producing effective catalysts.

Understanding of the high hydrothermal stability of a catalyst prepared from Mn slag for low-temperature selective catalytic reduction of NO

Manganese slag is a hazardous waste, which lacks proper treatment. For the first time, an effective catalyst for selective catalytic reduction of nitric oxide was synthesized from manganese slag by a sol-gel method. The obtained catalyst had an excellent low-temperature activity and high hydrothermal stability. It removed 46.3% of nitric oxide (990 ppm) at a temperature as low as 100 °C; its removal increased to 100% at 220 °C, which lasted for more than 2000 min. Moreover, hydrothermal treatment at 400 °C showed little influence on its activity. Even after hydrothermal treatment at 900 °C, the catalyst still removed 39.7% of NO at 220 °C, 22.7% higher than another catalyst synthesized from pure reagents. The hydrothermal stability was attributed to an amorphous layer of MnSixOy. This layer covered the catalyst surface, protected active metal species, pore size and pore volume from steam attacking. Manganese slag thus realized the high-value-added utilization by synthesizing a catalyst with the high hydrothermal stability.

Highly wear-resistant UV-curing antibacterial coatings via nanoparticle self-migration to the top surface

It is highly desirable that surface coatings such as kitchen furniture coatings, hospital wall, furniture coatings and many other coatings used in public areas possess antibacterial properties. Although many antibacterial coatings have already been developed and are now commercially available for some time, effective antibacterial properties often require the addition of antibacterial agents in large amount which deteriorate the mechanical properties of the coatings and hence limit their wide-spread uses. Herein we show the fabrication of a robust and wear-resistant polyurethane-based coatings via addition of fluoro-containing quaternary ammonium compounds (QACF) modified silica nanoparticles. The nanoparticles are obtained from a classical Stöber process with a thin layer of thiol groups on the particle surface and the QACF is then further linked to particle surface through double bond and thiol group reaction. QACF and its modified silica nanoparticles both show high levels of antibacterial properties toward Gram positive and Gram negative bacteria. Addition of the nanoparticles in as less as 10 wt% in the formulation recipe would be enough to produce an antibacterial coating with excellent anti-wear resistance due to the self-migration of the modified silica nanoparticles to the surface layer of the coating. We have used XPS and confocal microscopy to show the particle migration to the top of the coatings enables us to clarify the mechanism. Compared to coatings with added pure antibacterial reagents, our coating shows enhanced anti-wear property at relatively low particle additions.

Synthesis of In37P20(O2CR)51 Clusters and Their Conversion to InP Quantum Dots.

This text presents a method for the synthesis of In37P20(O2C14H27)51 clusters and their conversion to indium phosphide quantum dots. The In37P20(O2CR)51 clusters have been observed as intermediates in the synthesis of InP quantum dots from molecular precursors (In(O2CR)3, HO2CR, and P(SiMe3)3) and may be isolated as a pure reagent for subsequent study and use as a single-source precursor. These clusters readily convert to crystalline and relatively monodisperse samples of quasi-spherical InP quantum dots when subjected to thermolysis conditions in the absence of additional precursors above 200 °C. The optical properties, morphology, and structure of both the clusters and quantum dots are confirmed using UV-Vis spectroscopy, photoluminescence spectroscopy, transmission electron microscopy, and powder X-ray diffraction. The molecular symmetry of the clusters is additionally confirmed by solution-phase 31P NMR spectroscopy. This protocol demonstrates the preparation and isolation of atomically-precise InP clusters, and their reliable and scalable conversion to InP QDs.

СОВЕРШЕНСТВОВАНИЕ ТЕХНОЛОГИИ ПЕРЕРАБОТКИ СУНГУЛИТ-ВЕРМИКУЛИТОВЫХ КОНГЛОМЕРАТОВ

Актуальность. Усовершенствованная энерго- и ресурсосберегающая технология, реализуемая в новых технологических комплексах с предварительным «холодным» дообогащением, позволяет вернуть в промышленный оборот ценные сырьевые ресурсы и получить вермикулитовые и сунгулитовые концентраты из горнопромышленных отходов, накопленных на Ковдорском флогопит-вермикулитовом месторождении. В связи с этим данная работа посвящена вопросам совершенствования технологии переработки сунгулит-вермикулитовых конгломератов. Цель: анализ возможности совершенствования технологии получения термоактивированного сунгулита и вспученного вермикулита из горно-промышленных отходов Ковдорского флогопит-вермикулитового месторождения и повышение ее энергоэффективности. Объект: технологическое оборудование по переработке сунгулит-вермикулитовых конгломератов, реализующее энерго- и ресурсосберегающую технологию получения активированного сунгулита и вермикулитового концентрата. Методы исследования базируются на экспериментальных данных и анализе процессов аэродинамического отделения вермикулита и сунгулита от оливин-пироксеновой породы и повышения доли сунгулита в сунгулит-вермикулитовом концентрате. Результаты подтверждают достижение цели исследования. На их основе можно создать усовершенствованную технологию получения вермикулита, в том числе вспученного и магнезиально-силикатного реагента (термоактивированный сунгулит) из горно-промышленных отходов с экономией энергии до 182 кДж/кг, что уменьшает энергоемкость их переработки на 28 % по сравнению с предшествующей технологией. Кроме того, дополнительные технологические операции позволяют получить 350 кг вермикулита-сырца, 68 кг чистого магнезиально-силикатного реагента с размерами зерен 2,4…3,5 мм и 158 кг сунгулитового концентрата в термоактивированном виде с зернами 1,3…2,4 мм при почти 86 процентной концентрации. В целом можно сделать вывод о перспективности продолжения работ в области развития и совершенствования технологий переработки сунгулит-вермикулитовых конгломератов.

Synthesis of hard magnetic NdFeB composite particles by recycling the waste using microwave assisted auto-combustion and reduction method

The present work provides a facile and energy-saving approach to recycle Nd-Fe-B wastes. Employing the severely oxidized and contaminated sintered Nd-Fe-B scraps as the raw materials, sub-micro sized Nd-Fe-B/α-Fe composite magnetic powders were successfully synthesized by microwave assisted auto-combustion method followed by a reduction diffusion process. In details, the waste magnets were dissolved in HNO3 solution and both the rare earth oxides and iron oxide were obtained by auto-combustion approach with the help of microwave heating. These oxides were then reduced to achieve Nd-Fe-B alloys with the reducing agent CaH2. To modify the composition of the final product, Nd(NO3)3·6H2O and H3BO3 were added during dissolving and consequently three compositions of the final products were obtained. TEM results demonstrate that the sizes of α-Fe and Nd2Fe14B grains are below 10 nm and 20 nm, respectively. The magnetic properties of the composite powders obtained from the wastes in this study are comparable to those obtained by other methods using pure reagents. The room temperature coercivity of as-synthesized Nd15Fe77B8 is higher than 400 kA/m. In addition, an appropriate mass ratio of CaH2 to Nd-Fe-B oxides is required in order to obtain good magnetic properties.