Determination of Iron and Copper in Edible Oils by Flame Atomic Absorption Spectrometry After Liquid–Liquid Extraction

In the present work, a novel and rapid extraction method for Fe(III) and Cu(II) from liquid edible oils is described. N,N′‐Bis(4‐methoxysalicylidene)‐1,2‐diamino ethane (MSE) was utilized for the extraction of metal ions and the determination was achieved by flame atomic absorption spectrometry (FAAS). In order to optimize the extraction conditions, a central composite design (CCD) technique was employed. The optimum conditions, the ratio of MSE solution volume to oil mass, stirring time and temperature, were determined as 1.2 and 1.1 mL g^?1; 24.0 and 31.8 min and 25.3 and 33.2 °C for Fe(III) and Cu(II) extraction, respectively. The feasibility of the improved method was tested with oil‐based metal standards affording 98.6 % recovery for both metals and 67.3 ng g^?1 for Fe(III) and 15.3 ng g^?1 for Cu(II) as limit of detection (LOD).     

Sensitive Colorimetric Detection of Explosive 2,6‐Bis(picrylamino)pyridine after Preconcentration by Dispersive Liquid‐Liquid Microextraction

An experimental investigation for sensitive spectrophotometric detection of explosive, 2,6‐bis(picrylamino)pyridine (BPAP) using dispersive liquid‐liquid microextraction was carried out. Based on this procedure, which is a dispersive‐solvent‐free technique, the extractant is dispersed in the aqueous sample solution using Aliquat 336 (acted as disperser agent and carrier to extraction solvent) and monitored with microvolume UV/Vis spectrophotometer. The effect of different variables such as pH, concentration of sodium hydroxide, type and volume of extraction solvent, concentration of Aliquat 336 solution and coexisting substances were systematically investigated and optimized. Interference tests showed that the developed method has a good selectivity and could be used conveniently for determination of explosive analyte. The proposed method is capable of determining BPAP over a range of 2.0–150.0 ng mL⁻¹ with a limit of detection 1.0 ng mL⁻¹. Relative standard deviations (RSD) for 20.0 and 80.0 ng mL⁻¹ of BPAP were 3.3 and 1.2 % (n=10), respectively. This colorimetric method was applied to determine BPAP in different water and soil samples.     

缝管捕集原子吸收光谱法测定镉和银的研究和应用

报道了采用石英缝管捕集原子吸收光谱法测定镉和银的最佳实验条件、灵敏度、检出极限,并通过实验验证了缝管的捕集作用.应用该方法测定水样中的微量镉和银,灵敏度可分别提高60.97、31.47倍,加标回收率在91.3%～104.8%,结果令人满意.     

浊点萃取-石墨炉原子吸收测定自来水样中的铁

建立了一种用于环境水样中痕量铁元素测定的方法。该方法通过浊点萃取对环境水样中痕量铁进行预富集分离,并与石墨炉原子吸收分光光度法联用进行检测,在最优化条件下,测定水中的痕量铁,RSD为2．06％,检测限为1．2×10^-2μg／L。     

石墨炉原子吸收分光光度法测定土壤中的镉-全消解法和微波消解法比对实验

用微波消解法与全消解法消解土壤标准样品,用石墨炉原子吸收光谱法测定消解液铅含量,比较两种消解方法的精密度和准确度。微波消解法的相对标准偏差为3.8%,全消解法为8.6%。与标准值的相对相差比较,微波消解法低于10%,电热板消解法高于19%。微波消解法的测出值均高于电热板消解法。     

微波消解火焰原子吸收光谱法测定溶剂型木器涂料中的Pb、Cd和Cr

采用微波消解火焰原子吸收光谱法测定溶剂性木器涂料中的Pb、Cd和Cr,与传统的湿法消解样品相比,该方法操作简便、快速、样品消解完全,空白值低,选择性好,准确度和精确度都能满足分析要求。运用该方法测定某涂料样品,其中铅的含量为84.32mg/kg,铬的含量为50.76mg/kg,均低于国家标准,而该涂料样品中镉的含量则为未检出。     

Determination of Ni and Zn in an Oil Matrix using Schiff Base‐Assisted Extraction Followed by a Flame Atomic Absorption Spectrometer: A Simple Strategy to Determine Ni and Zn

In the present work, a new and simple Schiff base‐assisted extraction strategy for Ni and Zn from an edible oil matrix with subsequent determination using a flame atomic absorption spectrometer was suggested. According to the green approach, laborious sample‐pretreatment procedures were eliminated via complexation of the analytes with N,N′‐bis(4‐methoxysalycylidene)‐2‐hydroxy‐1,3‐propanediamine (4MSHP) and transferred from the oil phase to the aqueous phase. The complexation properties of 4MSHP, Ni, and Zn were investigated using UV–vis spectrophotometry. The experimental conditions that affect the extraction efficiency were optimized using central composite design. The optimum conditions for the extraction of Ni and Zn were as follows: a volume to oil mass ratio of 0.83 to 1.31 mL g^?1 of 4MSHP solution; 62.3‐ and 50.6‐min, stirring time; 27.3 and 31.1 °C, temperature, respectively. The detection limits (3s_bm^?1) were 0.41 μg g^?1 for Ni and 0.16 μg g^?1 for Zn. Validation of the suggested work was performed by the analysis of organometallic standard‐doped n‐hexane solutions as certified reference materials under the optimum experimental conditions. The recovery percentages were warranted the accuracy and found as 98.2 ± 1.8% for Ni and 99.8 ± 1.2% for Zn. In addition, relative SD values were below 5% for both the analytes. The Student's t‐test showed that there was no significant difference between the found and doped amount of analytes at 95% confidence level. The features such as the detection technique, cheapness, eco‐friendly solvent usage, and practicality were better compared to the literature.     

Comparison of Liquid Chromatography with Fluorescence Detection and Gas Chromatography/Mass Spectrometry for the Determination of Polycyclic Aromatic Hydrocarbons in Environmental Samples

Liquid chromatography (LC) with fluorescence detection and gas chromatography/mass spectrometry (GC/MS) have been compared for the determination of polycyclic aromatic hydrocarbons (PAHs) in a variety of environmental samples. Three sets of data are presented in this paper in which LC/fluorescence and GC/MS were used for the analysis of the same samples. These three data sets include the comparison of results from: (1) certification measurements for three natural matrix Standard Reference Materials (SRM's), (2) an international round robin for the determination of PAHs in air and diesel particulate samples, and (3) the analysis of four marine sediment reference materials. The results from these studies indicate that the two techniques generally provide comparable results for the measurement of PAHs in environmental samples (in the range of 0.1 to 300 ng/g), with differences in the two techniques between 5–20%. However, at low levels, anthracene and perylene are best measured using LC/fluorescence because of their selective and sensitive fluorescence detection characteristics. In contrast, GC/MS provides more accurate results for the determination of benzo[ghi]perylene because of its low fluorescence sensitivity.     

Liquid‐bridge flow in the channel of helical string and its application to gas–liquid contacting process

To solve the problems of the traditional packings, such as high pressure drop, mal‐distribution and short liquid residence time, a helical flow structured packings was proposed. Two different flow patterns, liquid‐bridge flow and liquid‐drop flow were identified when the width of the channel of the helical string was adjusted. Moreover, the characteristics of the helical liquid‐bridge flow including maximum liquid loading, mean thickness of liquid film, mean residence time and effective specific surface area, were examined. And the separation efficiency was studied by the lab‐scale distillation column. In comparison, the effective specific surface area of the helical flow type packings is almost as large as the traditional B1‐350Y structured packings, but with thinner liquid film, longer liquid residence time and finally higher separation efficiency. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3360–3368, 2018     

Determination of ternary solutions concentration in liquid–liquid extraction by the use of attenuated total reflectance‐Fourier transform infrared spectroscopy and multivariate data analysis

A simple and rapid Fourier transform infrared‐attenuated total reflectance (FTIR‐ATR) spectroscopic chemometric method was developed to determine the concentration of solute and solvent in the raffinate layer in a liquid–liquid extraction (LLE) process using partial least squares (PLS) regression. Five type I extraction systems were used with different solute–solvent affinity. The developed model (correlation coefficient from 0.91 to 0.99) was validated with known concentration samples, and in all cases the difference was not larger than 0.5%w. The LLE for the five extraction systems was carried out in a three‐stage crosscurrent extraction process, quantifying the solute and solvent with the chemometric model developed. The results were used to calculate the stage and overall stage efficiencies for the five systems. This method showed to be fast and precise for the quantification of ternary systems in LLE.     

Parallel hydrogenation for the quantification of wetting efficiency and liquid–solid mass transfer in a trickle‐bed reactor

A novel method for the measurement of wetting efficiency in a trickle‐bed reactor under reaction conditions is introduced. The method exploits reaction rate differences of two first‐order liquid‐limited reactions occurring in parallel, to infer wetting efficiencies without any other knowledge of the reaction kinetics or external mass transfer characteristics. Using the hydrogenation of linear‐ and isooctenes, wetting efficiency is measured in a 50‐mm internal diameter, high‐pressure trickle‐bed reactor. Liquid–solid mass transfer coefficients are also estimated from the experimental conversion data. Measurements were performed for upflow operation and two literature‐defined boundaries of hydrodynamic multiplicity in trickle flow. Hydrodynamic multiplicity in trickle flow gave rise to as much as 10% variation in wetting efficiency, and 10–20% variation in the specific liquid–solid mass transfer coefficient. Conversions for upflow operation were significantly higher in trickle‐flow operation, because of complete wetting and better liquid–solid mass transfer characteristics. © 2010 American Institute of Chemical Engineers AIChE J, 2011.     

Synthesis and Characterization of Xylan Grafted with Polyethylene Glycol in Ionic Liquid and Their Use as Moisture‐Absorption/Retention Biomaterials

The objective of this study is to broaden the application of xylan as moisture‐absorption/retention biomaterials by grafting polyethylene glycol (PEG) on xylan backbone. Ionic liquid 1‐allyl‐3‐methylimidazolium chloride ([Amim]Cl) and 4,4‐diphenylmethane diisocyanate are used as reaction media and coupling reagent, respectively. FT‐IR, ¹H‐NMR, and gel permeation chromatography analyses indicate the successful occurrence of the grafting reaction. Thermogravimetric analysis/derivative thermogravimetry indicates that the thermal stability of xylan increases after the grafting of the PEG side chains. With an increase of the degree of substitution of xylan‐g‐PEG, the molecular weight (M_w) of PEG side chains (1000 and 5000 g mol^?1), and the relative humidity of environment, the moisture‐absorption/retention ratio of xylan‐g‐PEG increases. To evaluate the biodegradability/biocompatibility of this promising material, the ratio of biochemical oxygen demand to chemical oxygen demand of xylan‐g‐PEG and the cytotoxicity are tested on the samples. The results indicate that PEG‐modified xylan has great potential as moisture‐absorption/retention biomaterials.

     

Thermodynamic Modeling of Multi‐phase Solid–Liquid Equilibria in Industrial‐Grade Oils and Fats

Compositional thermodynamic phase separation is investigated for industrial‐grade vegetable oils with complex compositions. Solid–liquid equilibria have been calculated by utilizing the Margules 2‐suffix activity‐coefficient model in combination with minimization of the Gibb's free energy of the system. On the basis of quasi‐equilibrium solid‐fat content (SFC) measurements, a new approach to the estimation of the interaction parameters, needed for the activity‐coefficient model, has been developed. The parameters are fitted by matching the SFC of two oils at various degrees of dilution and isothermal temperatures. Subsequently, the parameters are successfully validated against three oils, rich in asymmetric and symmetric triacylglycerols (TAG), respectively. The new approach developed is shown to be very flexible, allowing incorporation of additional TAG and polymorphic states. It thereby provides a simple way to dealing with multi‐component, multi‐phase TAG mixtures without having the required binary interaction parameters at hand a priori. This ultimately provides a powerful, predictive tool which may serve as a starting point for laboratory screening and creation of tailor‐made products because many different oil mixtures can be evaluated quickly with respect to specific properties, prior to more time‐consuming experimental evaluation.     

A Modified Method for the Determination of N‐Nitrosodiethanolamine in Coconut Diethanolamide Using HPLC with Dual‐Wavelength UV–Vis Detector

A simple and novel method based on high‐performance liquid chromatography with dual‐wavelength ultraviolet detection at 234 and 254 nm has been developed for the determination of underivatized N‐nitrosodiethanolamine in coconut diethanolamide. The correlation coefficient obtained shows that the method is correct.     

Metal Triflate‐Catalyzed Regio‐ and Stereoselective Friedel–Crafts Alkenylation of Arenes with Alkynes in an Ionic Liquid: Scope and Mechanism

In the metal triflate‐catalyzed hydroarylation of alkynes, employing an ionic liquid dramatically enhanced the catalytic activities, resulting in broadening the scope of substrates (arenes and alkynes). In some cases, even reactions that were not possible in conventional organic solvents proceeded smoothly in ionic liquids. Moreover, the ionic liquid phase containing catalyst could be readily recovered by simple decantation of the organic layer after reaction and reused for the following runs without any significant loss of activity. Mechanistic studies including ¹³C NMR analysis of reaction intermediates and isotope experiments confirmed for the first time that this type of reaction proceeds via vinyl cationic intermediates.