Direct removal of trace ionic iodide from acetic acid via porous carbon spheres

The main purpose of this paper is to report the direct removal of trace ionic iodide (I(-)) from acetic acid through porous carbon spheres (PCS) derived from the carbonization of poly(vinylidene chloride). The surface morphology and pore size distribution of the PCS are distinct from activated carbon (AC); thus they possess the peculiar performance of removing ionic iodide from acetic acid. The easy reach of micropores in the PCS was different from that of AC, but similar to that of activated carbon fiber (ACF). The iodide removal process has a strong relation with temperature, which is a typical feature of physical adsorption. The ionic iodide content in acetic acid used in the adsorption experiment was at the parts per billion level, and the factors influencing the adsorption are discussed in detail.     

Preconcentration of trace cadmium ion using magnetic graphene nanoparticles as an efficient adsorbent

Graphene-based magnetic nanoparticles (G-Fe₃O₄) were prepared and used as an effective adsorbent for the solid-phase extraction of trace quantities of cadmium from water and vegetable samples. The method avoids some of the time-consuming steps associated with traditional solid phase extraction. The excellent sorption property of the G-Fe₃O₄ system is attributed to π - π stacking interaction and hydrophobic interactions between graphene and the Cd-PAN complex. The effects of pH, the amount of G–Fe₃O₄, extraction time, type and volume of eluent, desorption time and interfering ions on the extraction efficiency were optimized. The preconcentration factor is 200. Cd(II) was then quantified by flame atomic absorption spectrometry with a detection limit of 0.32 ng mL^?1. The relative standard deviation (at 50 ng mL^?1; for n?=?10) is 2.45 %. The method has a linear analytical range from 1.1 to 150 ng mL^?1, and the recoveries in case of real samples are in the range between 93.1 % and 102.3 %.

离子色谱安培检测法测定醋酸中的痕量碘离子

目前较为先进的醋酸生产工艺是甲醇羰基合成工艺,在生产醋酸的过程中加入碘甲烷作助催化剂。然而,碘离子的存在对不锈钢材料具有腐蚀性,所以在合成醋酸的过程中必须严格监测醋酸中碘离子的含量。研究表明[1],测定工业醋酸中痕量碘离子的有效方法是高效阴离子交换色谱(IC)与脉冲     

高效阴离子交换色谱-脉冲安培检测器测定工业醋酸中痕量碘离子的方法

用一次性银电极高效阴离子交换色谱-脉冲安培检测器(HPAEC-PAD)研究了36%HAc中痕量碘离子的测定方法。用5 mL分析纯HAc(36%,不含碘离子)配制碘离子的标准工作溶液,然后加入一定体积的质量分数为25%NaOH溶液中和HAc,待溶液冷却至室温后用Milli-Q水定容至10 mL,最后用高效阴离子交换色谱-脉冲安培检测器分离测定,得到碘离子的标准工作曲线。工业醋酸样品经同样处理步骤。方法的检出限为0.06μg/L(3倍基线噪音),定量限为0.2μg/L(10倍基线噪音)。10μg/L碘离子的加标回收率为105%,5次连续测定的相对标准偏差为3.4%。     

Supported Au nanoparticles as efficient catalysts for aerobic homocoupling of phenylboronic acid

Au nanoparticles with small sizes (1-4 nm) were effectively formed on Mg-Al mixed oxides (Au/MAO), which showed superior catalytic performances and good recyclability in aerobic homocoupling of phenylboronic acid.     

Ag nanoparticles from the mechanochemical decomposition of Ag oxalate

The present work focuses on the chemical reactivity of Ag oxalate powders under mechanical processing conditions. The powders were submitted to mechanical loads in the presence of an aqueous solution containing a polymeric surfactant. A gradual decrease of the total mass of powders was observed, ascribable to the occurrence of a decomposition process. X-ray diffraction and UV-vis spectrophotometric analyses indicated that the Ag oxalate decomposes into metallic Ag and gaseous carbon dioxide. Transmission electron microscopy showed that metallic Ag exists in the form of particles with average size of about 5 nm. The formation of nanometer-sized Ag particles can be related to the plastic deformation and attrition processes taking place at the points of contacts between neighboring particles during the mechanical loading at collision.     

A novel and selective synthesis of di- and trimethylpiperazinium acetic acid iodide salts

A novel synthetic route has been developed for the preparation of 1-carboxymethyl-1,4,4-trimethylpiperazinium diiodide and 4-carboxymethyl-1,1-dimethylpiperazinium iodide salts. These quaternary piperazinium acids have potential, for example, in the development of novel water-soluble prodrugs or polymer derivatives.     

Kinetics of reaction between acetic acid and Ag2+ in nitric acid medium

The reaction kinetics between acetic acid and Ag²⁺ in nitric acid medium is studied by spectrophotometry. The effects of concentrations of acetic acid (HAc), H⁺, NO^?₃, and temperature on the reaction are investigated. The rate equation has been determined to be –dc(Ag²⁺)/dt = kc(Ag²⁺)c(HAc)c^?1(H⁺), where k = (610 ± 15) (mol/L)^?1 min^?1 with an activation energy of about (48. 8 ± 3.5) kJ mol^?1 when the reaction temperature is 25°C and the ionic strength is 4.0 mol L^?1. The reduction rate of Ag²⁺ increases with the increase in HAc concentration and/or temperature and the decrease in HNO₃ concentration. However, the effect of NO^?₃ concentrations within 0.5–2.5 mol L^?1 on the reaction rate is negligible. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: 47–51, 2013     

Supported gold nanoparticles as catalysts for organic reactions

This critical review is intended to attract the interest of organic chemists and researchers on green and sustainable chemistry on the catalytic activity of supported gold nanoparticles in organic transformations. In the general part of this critical review, emphasis is given to the different procedures to form supported gold nanoparticles and to the importance of the support cooperating in the catalysis. Also the convergence of homogeneous and heterogeneous catalysis in the study of gold nanoparticles has been discussed. The core part of this review is constituted by sections in which the reactions catalyzed by supported gold nanoparticles are described. Special emphasis is made on the unique ability of gold catalysts to promote additions to multiple C-C bonds, benzannulations and alcohol oxidation by oxygen (282 references).     

Determination of anionic trace impurities in acetic acid by two-dimensional capillary isotachophoresis

Potential impurities such as nitrate, sulfate, nitrite, fluoride, formate, phosphate and oxalate were detected up to an analyte-to-excess ratio (ATER) of 1:3 · 10⁵ using an online two-dimensional isotachophoretic system. With the developed electrolyte system, consisting of two different leading electrolytes, limits of detection (LOD) in the nmol/L range were realised by conductivity detection. These optimized conditions were applied to the determination of these anionic impurities in different types of acetic acid and acetate salts in order to evaluate and to verify their quality. Without sample preparation and or preconcentration, we were able to determine the above mentioned analytes in the range of 0.00032–0.001% within 20 min. The results were compared with those obtained by classical methods. Received: 10 October 1997 / Revised: 9 December 1997 / Accepted: 10 December 1997     

Determination of anionic trace impurities in acetic acid by two-dimensional capillary isotachophoresis

Potential impurities such as nitrate, sulfate, nitrite, fluoride, formate, phosphate and oxalate were detected up to an analyte-to-excess ratio (ATER) of 1:3 · 10⁵ using an online two-dimensional isotachophoretic system. With the developed electrolyte system, consisting of two different leading electrolytes, limits of detection (LOD) in the nmol/L range were realised by conductivity detection. These optimized conditions were applied to the determination of these anionic impurities in different types of acetic acid and acetate salts in order to evaluate and to verify their quality. Without sample preparation and or preconcentration, we were able to determine the above mentioned analytes in the range of 0.00032–0.001% within 20 min. The results were compared with those obtained by classical methods. Received: 10 October 1997 / Revised: 9 December 1997 / Accepted: 10 December 1997     

Interference from iodide in the determination of trace level selenium

The rate of the reaction between iodide and selenium(IV) at trace levels to form selenium and iodine has been determined in 1-6M hydrochloric acid. The reaction rate increases rapidly with acidity. When hydrochloric acid is added to reduce selenate to selenite prior to the determination of total selenium, some selenium may be lost by reduction to the element if iodide is present. A table of half-lives of the selenite-iodide reaction under various conditions is presented. A method for removal of iodide is suggested.     

Dodecylbenzene sulfonate-coated magnetite nanoparticles as a new adsorbent for solid phase extraction-spectrophotometric determination of ultra trace amounts of ammonium in water samples

A new method was proposed for the determination of ammonium based on the preconcentration with dodecylbenzene sulfonate modified magnetite nanoparticles. Ammonium was oxidized to nitrite by hypobromite and then the nitrite produced was determined spectrophotometrically, using sulfabenzamide and N-(1-naphthyl) ethylenediamine after solid phase extraction. The azo dye produced was desorbed by an appropriate small volume of sodium hydroxide prior to the absorbance measurement. The linear calibration graphs were obtained in the concentration range of 0.03-6.00 ng mL(-1) ammonium. The relative standard deviation and recovery percents were 1.0 and 99.0, respectively, for 1.0 ng mL(-1) ammonium, and the limit of detection was 3.2 ng L(-1) ammonium. The interfering effects of a large number of diverse ions on the determination of ammonium were studied. The method was applied to the determination of ammonium in various types of water resources. The results revealed a high efficiency for the recommended ammonium determination method.     

Focused-ion-beam-fabricated Au nanorods coupled with Ag nanoparticles used as surface-enhanced Raman scattering-active substrate for analyzing trace melamine constituents in solution

A well-ordered Au-nanorod array with a controlled tip ring diameter (Au_NRs_d) was fabricated using the focused ion beam method. Au_NRs_d was then coupled with Ag nanoparticles (Ag NPs) to bridge the gaps among Au nanorods. The effect of surface-enhanced Raman scattering (SERS) on Au_NRs_d and Ag NPs/Au_NRs_d was particularly verified using crystal violet (CV) as the molecular probe. Raman intensity obtained from a characteristic peak of CV on Au_NRs_d was estimated by an enhancement factor of ≈10⁷ in magnitude, which increased ≈10¹² in magnitude for that on Ag NPs/Au_NRs_d. A highly SERS-active Ag NPs/Au_NRs_d was furthermore applied for the detection of melamine (MEL) at very low concentrations. Raman-active peaks of MEL (10⁻³ to 10⁻¹² M) in water or milk solution upon Au_NRs_d or Ag NPs/Au_NRs_d were well distinguished. The peaks at 680 and 702 cm⁻¹ for MEL molecules were found suitable to be used as the index for sensing low-concentration MEL in a varied solution, while that at 1051 cm⁻¹ was practical to interpret MEL molecules in water or milk solution bonded with Au (i.e., Au_NRs_d) or Ag (i.e., Ag NPs/Au_NRs_d) surface. At the interface of Ag NPs/Au_NRs_d and MEL molecules in milk solution, a laser-induced electromagnetic field or hotspot effect was produced and competent to sense low-concentration MEL molecules interacting with Ag and Au surfaces. Accordingly, Ag NPs/Au_NRs_d is very promising to be used as a fast and sensitive tool for screening MEL in complex matrices such as adulteration in e.g., food and pharmaceutical products.     

Co-sensitized cells from Antarctic resources using Ag nanoparticles

In the present work, we explore in photoanodes of dye-sensitized solar cell (DSSC) the co-sensitization of the red protein phycoerythrin extracted from Antarctic algae with spherical silver nanoparticles between 10 and 200 nm and triangular nanoparticles of ~100 nm. We found that the order of addition of the sensitizers matters. Best results achieved for a sequential approach was phycoerythrin used as a dipping solution at the first step and nanoparticles at the second. We found that cell efficiency depends on the protein concentration, although no main differences detected with the nanoparticle shape or size. Our results show an average increase of 25% in the conversion efficiency values in the presence of nanoparticles.     

Trifluoromethyl sulphonic acid as a titrant in glacial acetic acid systems

Trifluoromethyl sulphonic acid in glacial acetic acid has been compared with perchloric acid in glacial acetic acid as a titrant in a limited number of cases. It does not appear that the reagent is likely to compete seriously with perchloric acid in non-aqueous titrimetry. Although comparable to perchloric acid in acid strength in acetic acid as well as in instrument response, it is unlikely that the considerably higher cost can be justified on the grounds of freedom from precipitate formation alone and no other advantageous feature has been observed which could justify this.

Abstract

Trifluoromethylsulfonsäure in Eisessig wurde mit Perchlorsäure in Eisessig als Titrationsmittel verglichen. Es scheint nicht wahrscheinlich, dass das Reagens ernsthaft mit Perchlorsäure als Titrationmittel in nichtwässrigem Medium konkurrieren kann. Das Reagens ist zwar mit Perchlorsäure vergleichbar, soweit es die Stärke (in Essigsäure) und das Ansprechen des Instrumentes betrifft; es ist aber unwahrscheinlich, dass sich die beträchtlich höheren Kosten lediglich wegen Nichtauftretens von Niederschlägen rechtfertigen lassen. Dies ist der einzige auffindbare Vorteil.     

The use of graphene-based magnetic nanoparticles as adsorbent for the extraction of triazole fungicides from environmental water

A graphene-based magnetic nanocomposite (graphene-ferriferrous oxide; G-Fe(3) O(4) ) was synthesized and used as an effective adsorbent for the preconcentration of some triazole fungicides (myclobutanil, tebuconazole, and hexaconazole) in environmental water samples prior to high-performance liquid chromatography-ultraviolet detection. The method, which takes the advantages of both nanoparticle adsorption and magnetic phase separation from the sample solution, could avoid the time-consuming experimental procedures commonly involved in the traditional solid phase extraction such as centrifugation and filtrations. Various experimental parameters affecting the extraction efficiencies such as the amount of the magnetic nanocomposite, extraction time, the pH values of the sample solution, salt concentration, and desorption conditions were investigated. Under the optimum conditions, the enrichment factors of the method for the three analytes were 5824, 3600, and 4761, respectively. A good linearity was observed in the range of 0.1-50 ng/mL for tebuconazole and 0.05-50 ng/mL for myclobutanil and hexaconazole, respectively, with the correlation coefficients ranging from 0.9992 to 0.9996. The limits of detection (S/N = 3) of the method were between 0.005 and 0.01 ng/mL. The results indicated that as a magnetic solid-phase extraction adsorbent, the graphene-ferriferrous oxide (G-Fe(3) O(4) ) has a great potential for the preconcentration of some compounds from liquid samples.