Cationic flotation of quartz from an artificial mixture with hematite using hexylamine

The cationic flotation of quartz was carried out from an artificial mixture (1:1 by weight) of fine grained ( − 10 μm) quartz and hematite, using hexylamine acetate (HAA) and dodecylamine acetate (DAA) as collectors. Selective flotation of quartz was possible in the pH range 9–10 using HAA. The adsorption densities of DAA and HAA on quartz and hematite were measured at pH 9.8 and the relationship between the flotation behavior of both minerals and the surface coverage of collectors was established. Complete flotation of quartz and hematite required a surface coverage (θ) of DAA of about 100% at pH 9.8, while complete flotation of quartz took place at θ ⋍ 10% with HAA. The flotation behavior with DAA was explained by considering the adsorption of undissociated free amine. Zeta potential measurements were incorporated to interpret the difference in the adsorption behavior of both collectors on quartz and hematite.     

Full Characterization of Colloidal Solutions of Long‐Alkyl‐Chain‐Amine‐Stabilized ZnO Nanoparticles by NMR Spectroscopy: Surface State,Equilibria, and Affinity

Full NMR characterization of ZnO nanoparticles (NPs) stabilized by various amines (hexadecylamine, dodecylamine, and octylamine) in C₇D₈ demonstrated that the surface of this apparently simple system was very complex. Using different NMR spectroscopic techniques (¹H, PGSE‐NMR, diffusion‐filtered ¹H NMR, NOESY, ROESY), we observed at least three different modes of interaction of the amines at the surface of the NPs, in thermodynamic equilibrium with the free amines, the relative populations of which varied with their concentration. The first mode corresponded to a strong interaction between a small amount of amine and the ZnO NPs (k_desorp≈13 s^?1). The second mode corresponded to a weak interaction between the amines and the surface of the ZnO NPs (k_off(2)≈50–60 s^?1). The third, and weakest, mode of interaction corresponded to the formation of a second ligand shell by the amine around the NPs that was held together through van der Waals interactions (k_off(1)≈25×10⁵ s^?1). The second and third modes were in fast exchange on the NMR timescales with the free amines. The strongly interacting amines at the NPs surface (first mode) were in slow exchange with the other modes. A complex hydrogen‐bonding network at the NPs surface was also observed, which did not only involve the coordinated amine but also THF and water molecules that remained from the synthesis.     

Evaluation of Chromatographic Methods for the Determination of Isocyanates in Air

Abstract

Chromatographic methods for the determination of toluene diisocyanates (TDI) in air, at concentrations of 20–40μg/m³, were evaluated. Test atmospheres were generated by a gas-phase permeation principle. The GC method was based on sampling in impingers containing an acidic aqueous solution (0.4 M HC1), where the isocyanates are hydrolysed into the corresponding amines. The pentafiuoropropionic acid derivatives of the amines were analysed using glass capillary GC with thermionic detection. The HPLC methods were based on reaction with the amine reagents 9-(N-methylaminomethyl)-anthracene (1 × 10^?4M in toluene) and 1-(2-methoxyphenyl)-piperazine (2 × 10^?4M in toluene). The urea derivatives were determined using UV detection. The sampling efficiency for gaseous TDI with toluene as absorbing solution was 97%. Sampling efficiencies in various acidic aqueous solutions were 83–88%. The relative standard deviation for the various methods was ca. 6%. No sampling losses for TDI, due to influences of interfering substances (diethylamine, dimethylethylamine, N-methylmorpholine, DABCO, aniline, ethanol, phenol) using acidic aqueous 0.4 M HC1 were obtained. Diethylamine, N-methylmorpholine and DABCO affected the analytical results when toluene solutions of the amine reagents MAMA and MPP were used.     

Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na₂S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na₂S and Na₂SiO₃, and OPA 1214 outdid the others in saving the usage of both the Na₂S and Na₂SiO₃. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation.     

Liquid Chromatography–Single-Quadrupole Mass Spectrometry as a Responsive Tool for Determination of Biogenic Amines in Ready-to-Eat Baby Foods

Baby food has never been the object of biogenic amine profiling. The aim of this study was to develop a highly sensitive method for analysis of biogenic amines in ready-to-eat baby foods. The principle of the developed method involves high-performance liquid chromatography coupled to single-quadrupole mass spectrometry (HPLC–APCI–MS) of dansyl derivatives, presented also in comparison with common diode array and fluorescence detection systems. The confirmation of correct identification of derivatives was performed by in-source fragmentation of the product ion at 170 m/z, performed only in one MS analyzer. The method was used to identify the amine profile and quantify the putrescine, cadaverine, histamine, tyramine, spermidine, and spermine content in 68 ready-to-eat baby foods. The limits of detection and quantification were in the range of 0.07–1.67 and 0.2–5.0 ng mL^??1. The method enabled quantification of amines at ng/g level in almost all analyzed samples, without any preconcentration step. Amine recoveries of 86.0–105.2% were obtained with RSD?≤?9.7%. The developed method could be used for quantification of the most frequently occurring BAs in foods including vegetables, fish, meat, or fruit at previously undetectable concentration levels, making the method multimatrix applicable and highly-sensitive.     

Full characterization of colloidal solutions of long-alkyl-chain-amine-stabilized ZnO nanoparticles by NMR spectroscopy: surface state, equilibria, and affinity

Full NMR characterization of ZnO nanoparticles (NPs) stabilized by various amines (hexadecylamine, dodecylamine, and octylamine) in C(7)D(8) demonstrated that the surface of this apparently simple system was very complex. Using different NMR spectroscopic techniques ((1)H, PGSE-NMR, diffusion-filtered (1)H NMR, NOESY, ROESY), we observed at least three different modes of interaction of the amines at the surface of the NPs, in thermodynamic equilibrium with the free amines, the relative populations of which varied with their concentration. The first mode corresponded to a strong interaction between a small amount of amine and the ZnO NPs (k(desorp)≈13 s(-1)). The second mode corresponded to a weak interaction between the amines and the surface of the ZnO NPs (k(off(2))≈50-60 s(-1)). The third, and weakest, mode of interaction corresponded to the formation of a second ligand shell by the amine around the NPs that was held together through van der Waals interactions (k(off(1))≈25×10(5) s(-1)). The second and third modes were in fast exchange on the NMR timescales with the free amines. The strongly interacting amines at the NPs surface (first mode) were in slow exchange with the other modes. A complex hydrogen-bonding network at the NPs surface was also observed, which did not only involve the coordinated amine but also THF and water molecules that remained from the synthesis.     

Analysis of Aromatic Amines in Surface Waters Receiving Wastewater from a Textile Industry by Liquid Chromatographic with Electrochemical Detection

Abstract

A high performance liquid chromatography (HPLC) method with electrochemical detection (ED) was developed for the determination of benzidine, 3,3‐dimethylbenzidine, o‐toluidine and 3,3‐dichlorobenzidine in the wastewater of the textile industry. The aromatic amines were eluted on a reversed phase column Shimadzu Shimpack C₁₈ using acetonitrile+ammonium acetate (1×10^?4 mol L^?1) at a ratio 46:54 v/v as mobile phase, pumped at a flow rate of 1.0 mL min^?1. The electrochemical oxidation of the aromatic amines exhibits well‐defined peaks at a potential range of +0.45 to +0.78 V on a glassy carbon electrode. Optimum working potentials for amperometric detection were from 0.70 V to +1.0 V vs. Ag/AgCl. Analytical curves for all the aromatic amines studied using the best experimental conditions present linear relationship from 1×10^?8 mol L^?1 to 1.5×10^?5 mol L^?1, r=0.99965, n=15. Detection limits of 4.5 nM (benzidine), 1.94 nM (o‐toluidine), 7.69 nM (3,3‐dimethylbenzidine), and 5.15 nM (3,3‐dichlorobenzidine) were achieved, respectively. The detection limits were around 10 times lower than that verified for HPLC with ultra violet detection. The applicability of the method was demonstrated by the determination of benzidine in wastewater from the textile industry dealing with an azo dye processing plant.     

C_（60）与含烯丙基胺聚合物加成物的荧光行为

Ｃ_（６０）与含烯丙基胺聚合物加成物的荧光行为田慧洁，陈立桅，姚光庆，金朝霞，李福绵（北京大学化学系北京１００８７１）关键词脂肪胺，Ｃ_（６０），聚烯丙基胺，荧光Ｃ６０是一高度对称的笼状碳簇分子，室温下难以观察到荧光现象［１］，但我们发现它与聚烯丙基胺...     

Facile cellulose nanofibrils amidation using a ‘<Emphasis Type="Italic">one</Emphasis>-<Emphasis Type="Italic">pot</Emphasis>’ approach

We report a ‘one-pot’ synthetic approach for TEMPO (2,2,6,6-tetramethyl-piperidin-1-oxyl) oxidized cellulose nanofibrils (TOCN) surface amidation by coupling up to 70% of superficial carboxylic units in TOCN with long alkyl chain primary amines (dodecylamine and octadecylamine) using TBTU [O-(1H-benzotriazol-1-yl)-N,N,N’,N’-tetramethyluronium tetrafluoroborate] uronium salt as coupling agent. Raw TOCNs were produced from commercial microcrystalline cellulose and have an elongated highly tangled morphology with nanometric diameters and lengths up to several micrometers with a crystallinity of 62%. TOCN´s degree of oxidation was 1.25 mmol –COOH groups/g cellulose. The TOCN-amidated products named TOCN-AMDC12 and TOCN-AMDC18 depending upon to the primary amine used for the synthesis (dodecylamine –C12– for the former and octadecylamine –C18– for the latter), were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy with attenuated total reflectance and X-ray diffraction. After amidation the hydrated gel-like TOCNs become a cream-colored gel insoluble in water and soluble in toluene. IR data indicates formation of an amide bond after the reaction, and FESEM images suggest a slight increase in fibril width as a result of the long-chain amide derivatives grafted onto the TOCN’s surface. Thermal stability and hydrophobicity of the products were determined using thermogravimetrical analysis and contact angle (CA) measurements. The TOCN-amidated products showed improved thermal properties with maximum decomposition temperatures of 347 and 358 °C, for TOCN-AMDC12 and TOCN-AMDC18 respectively, when compared to the raw TOCN (T_d 340 °C); and high hydrophobicity with CA of 61° and 67°, respectively. Finally, the proposed method for TOCN amidation has advantages over current amidation approaches in that it is performed in aqueous media, does not require heating and occurs rapidly (2 h).     

Understanding the role of ion interactions in soluble salt flotation with alkylammonium and alkylsulfate collectors

There is anecdotal evidence for the significant effects of salt ions on the flotation separation of minerals using process water of high salt content. Examples include flotation of soluble salt minerals such as potash, trona and borax in brine solutions using alkylammonium and alkylsulfate collectors such as dodecylamine hydrochloride and sodium dodecylsulfate. Although some of the effects are expected, some do not seem to be encompassed by classical theories of colloid science. Several experimental and modeling techniques for determining solution viscosity, surface tension, bubble-particle attachment time, contact angle, and molecular dynamics simulation have been used to provide further information on air–solution and solid–solution interfacial phenomena, especially with respect to the interfacial water structure due to the presence of dissolved ions. In addition atomic force microscopy, and sum frequency generation vibrational spectroscopy have been used to provide further information on surface states. These studies indicate that the ion specificity effect is the most significant factor influencing flotation in brine solutions.     

Discrimination of Primary Amines from Other Fluorescent Compounds in Biological Fluids

Abstract

Experimental condition and parameters involved in HPLC distinction of primary amines from non-primary amine compounds with native fluorescence were investigated. The discrimination conditions were designed to enable utilization of the sensitive reagent fluorescamine as a means of monitoring primary amines in physiologic fluids.     

Strong Room-Temperature Photoluminescence from the Novel Adduct of C_(60) with Aliphatic Amines

Fullerene C,, is a good electron-accepting molecule. It has been shown that it can formthe charge~transfer complexes (CTC) with ammes as the electron-donorly. Based on theweak CT interactions of C,, with various ammes, the fiuorescence emission spectra forboth of C,. and its CTC (including the derivatives of C,,) frequently appear at relativelylonger wavelengths more than 700 urn2-4. Whereas the fluorescence emission at relativieshorter wavelengths are often neglected and have not been re…     

云母表面吸附烷基伯胺对其疏水性的影响

矿物表面的疏水性受吸附在其表面的表面活性剂的影响,进而影响矿物的浮选行为.本文通过表面接触角测量、原子力显微镜(AFM)观测以及密度泛函理论(DFT)和分子动力学(MD)模拟计算,研究了吸附在云母表面的烷基伯胺的链长对其疏水性的影响.通过比较氧密度和氢键数量分布,发现每个水分子在碳氢链尾端和水相接触的界面上相对于在体相中形成氢键的能力有所降低,而吸附烷基伯胺的云母由亲水性转化为疏水性.研究结果还表明,在单分子层吸附状态下,吸附十八胺的云母的疏水性比吸附十二胺的云母的疏水性要强,且由于十八胺的临界半胶束浓度(HMC)要远低于十二胺,十八胺更易在云母表面形成多层吸附,证明烷基伯胺的碳链越长,其对云母表面疏水性改善的能力越强.实验结果与理论计算结果吻合良好.     

Determination of Atenolol in Human Plasma by Pseudo Reversed Phase Liquid Chromatography-Tandem Mass Spectrometry

Previous HPLC determination of atenolol on reversed-phase packings has often required a mobile phase containing three components: organic modifier, buffer and ion-pairing reagent or organic amine. In addition to the complexity of the eluents employed, alkyl sulphonates and organic amines in the mobile phase can reduce the life of silica-based bonded columns. A new simple, rapid and sensitive method—pseudo reversed-phase liquid chromatography/tandem mass spectrometry has been developed for the analysis of atenolol in human plasma using bare silica as the stationary phase coupled with a simple mobile phase consisted of 5% acetonitrile and 95% formate buffer. The optimization of separation is fast and easy. The assay was validated for the concentration range 1–100 ng mL^?1 with a detection limit of 1 ng mL^?1. Moreover, the silica column was durable with the mainly aqueous eluents. No obvious loss in performance was observed for 30,000 column volumes of eluent.     

1,2,3-苯三氧基三乙酸的浮选抑制性能

抑制剂;1;2;3-苯三氧基三乙酸的浮选抑制性能     

Spectrophotometric determination of aromatic primary amines and nitrite by flow injection analysis

Aromatic primary amines are determined by injection into dilute hydrochloric acid carrier which merges sequentially with 4-N-methylaminophenol and dichromate. The purple-red color formed by oxidative coupling of amines with 4-N-methylaminophenol is measured at 530 nm. In contrast to the manual procedure, the flow-injection procedure avoided errors arising from the instability of the coupling intermediate, oxidation of the amine, and too great an excess of the oxidant. The method improves the selectivity for certain amines in the presence of those which are sterically hindered or have an electron-deficient aromatic nucleus. Nitrite is determined by diazotization of sulfanilamide and quantifying the residual sulfanilamide by oxidative coupling. The sample thourghout for the assay of amines (0.05–20 μg ml^?1 NH₂-N) and nitrite (1–10 μg ml^?1 NO₂^--N) was 120 h^?1. A system for the consecutive determination of aromatic primary amines and nitrite is decribed.     

Gas-chromatographic determination of aliphatic amines in natural surface water and wastewater

A procedure was developed for the gas-chromatographic determination of aliphatic amines C₇–C₂₀ with prederivatization by N-methyl-bis(trifluoroacetamide), in the concentration range of natural surface water, to 10^?4-1 mg/L, and wastewater, to 10^?3-1 mg/L. The conditions were optimized for the extraction preconcentration of aliphatic amines with toluene from natural surface water and wastewater. The detection limit for aliphatic amines at a signal-to-noise ratio of 3: 1 was 50 ng/L.     

Determination of Biogenic Amines in Digesta by High Performance Liquid Chromatography with Precolumn Dansylation

A rapid high-performance liquid chromatographic method for the determination of nine biogenic amines in digesta sample from pig cecum and colon was developed using a simple direct derivatization with dansyl chloride. After precipitation with trichloroacetic acid and extraction by n-hexane, the amines were separated on a C₁₈ column using a water–acetonitrile gradient elution program. The calibration curve for each amine was linear over the range of 50 to 250 µmol/L, and the relative standard deviation for intra-assay precision was below 0.5%. The recovery ranged from 86.79% to 117.62% while the limit of detection was 0.1 µmol/L for the amines except for spermine with a value of 0.03 µmol/L. This procedure was successfully applied to identify and quantify biogenic amines in the hindgut digesta of the pig.     

Validated Stability-Indicating Chromatographic Method for the Assay of Erlotinib Active Pharmaceutical Ingredient

Abstract

A simple stability-indicating high-performance liquid-chromatographic (HPLC) method for the assay of erlotinib in the presence of its degradation products was developed on a C18 column using a mobile phase of 0.01 M ammonium formate–acetonitrile–containing formic acid with a flow rate of 1.0 mL min^?1. The method was validated. Selectivity was validated by subjecting the stock solution of erlotinib to acidic, basic, photolysis, oxidative, and thermal degradation. The linearity range and values for limits of detection (LOD) and quantification (LOQ) were found to be 1–198, 0.33, and 1.1 µg mL^?1, respectively. The analysis of the tablets containing erlotinib was quite precise (relative standard deviation <1%).     

Analysis of six aromatic amines stability in workplace measurement

For aromatic amine determination in workplaces, stabilities of six types of carcinogenic aromatic amines (2,4-diaminotoluene, 4,4'-diamino-3,3'-dimethyldiphenylmethane, o-tolidine, 3,3'-dichlorobenzidine, 4,4'-methylenebis(2-chloroaniline), and o-dianisidine) were evaluated with air or argon gas bubbling for 45 min in aqueous solution under light irradiation (desk lamp) and heating conditions. Gas chromatography–mass spectrometry (GC–MS) was used to identify and quantify the aromatic amines. The following conditions were selected: temperature program 70°C (1 min), 7 grad/min up to 120°C (1 min), 10 grad/min up to 300°C (5 min), carrier gas flow rate 1.0 mL/min. 3,3'-Dichlorobenzidine concentration decreased by approximately 10% after irradiation with a desk lamp for 45 min in distilled water, and a monochloro compound was detected by GC–MS. The other aromatic amines were rarely different from the 0-min concentration. The shielding prevented the decomposition of 3,3'-dichlorobenzidine in distilled water.