Development of a rapid extraction procedure for speciation of arsenic in chicken meat

A rapid extraction procedure has been developed for speciation of arsenic in chicken tissue. Water, methanol–water (1:1), and methanol–chloroform (1:1) were tested as extraction media. Individual use of an ultrasonic bath, a microwave oven, or an ultrasonic probe was not sufficient for quantitative recovery of As(III), dimethylarsinate, monomethylarsonate, As(V), and arsenobetaine in spiked samples of chicken tissue. A new extraction procedure using a methanol–water mixture and a microwave oven then an ultrasonic probe enabled extraction of the arsenic species in 7 min with efficiencies ranging from 80 to 100%. HPLC–UV–HG–AFS was used for the determinations. The extraction procedure was 100% efficient when applied to real samples of chicken tissue. AsB (48±5 μg As kg ⁻¹) and one containing-arsenic feed additive, Nitarsone (227±5 μg As kg ⁻¹) were detected.     

Microwave-Assisted Solvent Extraction of Melamine from Seafood and Determination by Gas Chromatography–Mass Spectrometry: Optimization by Factorial Design

Melamine attracts considerable attention because of its toxicity. The determination of melamine in seafood was performed by gas-chromatography–mass spectrometry, using an optimized version of a method adopted by the U.S. Food and Drug Administration. The melamine was extracted by closed-vessel microwave-assisted solvent extraction (MAE), as a valid alternative in sample preparation, to reduce analysis time and provide less ambiguous data. The procedure was optimized by means of experimental factorial design considering the three main variables that affect this process: microwave oven power, the maximum temperature inside the extraction tube, and the hold time. The recovery of melamine in spiked samples was used as the elemental response value of the design. Temperature and hold time had a more positive effect on the response than the microwave power. A significant positive interaction was observed between oven power and hold time. A temperature of 70°C and a hold time of 1 min gave a recovery of 92 ± 5% for a microwave power of 600 W. Under these conditions, the total microwave extraction time was approximately 2 minutes, a much shorter time compared to the ultrasonic bath, which required a total time of 40 min. The repeatability of the method was approximately 3%. The limits of quantification were 0.55 mg kg^?1 for MAE and 1.9 mg kg^?1 for the ultrasonic bath; the linearity was confirmed up to 10 mg kg^?1. In conclusion, the MAE procedure was shown to be an excellent alternative to the official method.     

Recycling of Polyolefins: Part 2: Blends of Several Polymers

Abstract

The aim of the present paper is to study the feasibility of recycling polyolefins with some additives, such as copolymers in order to improve the mechanical properties and increase the useful life of the blends. From analysis of the results of blends of polypropylene(PP) with POD(Blend of recycled Polyolefins), it can be concluded that it is possible to recycle POD up to 20%, the addition of a copolymer to the 12% composition improving the interfacial adhesion. In the case of low density polyethylene(LDPE) mixtures with POD, the optimum improvement in properties is obtained with approximately 10% of POD. The addition of copolymers did not yield any improvement in the properties.     

Thermooxidative degradation of polyethylene. I and II. Structural changes occurring in low-density polyethylene,high-density polyethylene,and tetratetracontane heated in air

Samples of low-density polyethylene (LDPE), high-density polyethylene (HDPE), and tetratetracontane (n-C₄₄H₉₀) free from additives were heated in air at temperatures between 120 and 180°C. As a comparison, “as received” HDPE containing unspecified additives has also been included. The structural changes have been studied with gel chromatography, viscometry, infrared spectroscopy, differential scanning calorimetry, and gravimetric measurements. LDPE, HDPE, and n-C₄₄H₉₀ follow the same course of thermooxidative degradation when they are free from additives and present in the molten state. Both molecular-diminishing and enlargement reactions occur. At temperatures below 150°C molecular enlargement is not observed until after rather long exposure times, whereas at higher temperatures enlargement occurs immediately. The difference is because “peroxide curing” becomes increasingly important above 150°C, whereas ester formation is operating at all temperature levels. Degradation below T_m is restricted to the amorphous phase that results in a different degradation pattern. In accelerated testing work extrapolations of the Arrhenius type in the prediction of structural change are thus not justified, even within the actual narrow temperature range. Neither are changes in commonly used standards like carbonyl content justified as a measure of the changes; for example, in mechanical properties. The stabilizer in the unpurified HDPE not only influences the induction period but also the course of the thermooxidative degradation.     

微波辅助流动萃取槐花中的黄酮类成分

槐花为豆科落叶乔木槐树(Sophora japonica L.)的花蕾,槐花能降低血管的通透性,所含芸香甙(芦丁)对心脏传导系统有抑制作用,能增强收缩力及输出量,降低血压;所含槲皮素可以扩张冠状动脉,降低心肌耗氧量,并能降低血脂。     

Microwave-assisted extraction by fast sample preparation for the systematic analysis of additives in polyolefins by high-performance liquid chromatography

This paper presents a new approach for complete and systematic analysis of organic additives in polyolefins. The proposed procedure is a convenient combination of sample preparation, performed by microwave-assisted extraction (MAE), and direct chromatographic evaluation of extract by high-performance liquid chromatography coupled with ultraviolet and evaporative light scattering detection. In particular two microwave-assisted processes are reported and discussed: the one-step MAE, useful for additives with low-medium dipolarity (like stabilizers, flame retardant, antistatics, slip and processing agents), and the two-step MAE, useful for additives with either high dipolarity (like organic salts, antigasfading, antiacid, nucleating agent) or high molecular mass (like polymeric hindered amine light stabilizers). Both the proposed processes have been tested on representative additives in five commercially common polymeric matrices, demonstrating their satisfactory analytical results, in terms of repeatability and percentage recoveries, and their good performances, in terms of safety and time/solvent consumption, in comparison with those of traditional extraction methods.     

Chemiluminescence study on the oxidation of several polyolefins—I. Thermal-induced degradation of additive-free polyolefins

Chemiluminescence (CL) has been applied to evaluate the oxidation susceptibility of various polyolefins: low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and isotactic polypropylene (i-PP). The intensity of CL emission in inert atmosphere could be related to the previous oxidation level. The thermal stability at 170 °C of the hydroperoxides in LDPE seems to be lower than that in LLDPE or HDPE. The kinetic parameters of the oxidation at 170 °C in oxygen, calculated from CL data, suggest the following stability order: HDPE > LLDPE > LDPEi-PP. The intensity of CL emission was related to the CH₃ content as evaluated by Fourier transform infra-red spectroscopy.     

Comparison of various extraction techniques for isolation and determination of isoflavonoids in plants

In the present paper, the following extraction techniques have been used for extracting isoflavonoids from the species Matricaria recutita, Rosmarinus officinalis, Foeniculum vulgare, and Agrimonia eupatoria L.: supercritical fluid extraction (SFE), pressurized fluid extraction, matrix solid phase dispersion, ultrasonic extraction in an ultrasonic bath (USE) and by means of an ultrasonic homogeniser (HOM), extraction by means of Soxhlet apparatus (SOX), and solid phase extraction. Experimental optimization of all techniques has been carried out using a soybean flour. Subsequent analyses of the extracts were carried out by liquid chromatography with UV detection. The maximum yields of daidzein and genistein were obtained by extraction with the SOX, USE, and HOM techniques. The maximum yields of apigenin and biochanin A from herb samples were obtained by SFE.     

Blends of fatty‐acid‐modified dendrimers with polyolefins

Blends were made by solution and melt‐mixing fatty‐acid‐modified dendrimers with various polyolefins. Small‐angle neutron scattering (SANS) was used to determine the miscibility of the blends. Poly(propylene imine) (PPI) dendrimers G1, G3, and G5 [DAB‐dendr‐(NH₂)_y] with y = 4, 16, and 64, were reacted with stearic acid or stearic acid‐d₃₅ forming amide bonds. The modified dendrimers were then blended with high‐density polyethylene (HDPE), high‐density polyethylene‐d₄ (HDPE‐d₄), low‐density polyethylene (LDPE), amorphous polypropylene (PP), or an ethylene–butylene copolymer (E‐co‐B). Limiting power law behavior shows that all of the blends are immiscible. It is likely that the dendrimers form a second phase, being finely dispersed, but thermodynamically immiscible. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 95–100, 2000     

Microwave-assisted solvent elution technique for the extraction of organic pollutants in water

Solid phase extraction (SPE) with appropriate solid sorbents has been commonly used in the routine extraction of organic pollutants in water. The elution of analytes from the solid sorbents normally takes place by organic solvents under an applied vacuum. In this study, a microwave-assisted solvent elution technique was developed for the elution of analytes from C₁₈ membrane disks during microwave irradiation from a microwave extraction system (MES). Several parameters, namely, elution solvent, elution temperature, duration of elution and the volume of solvent which may affect the elution efficiency of microwave-assisted solvent elution (MASE) technique towards organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), organophosphorus pesticides (OPs), fungicides, herbicides and insecticides from the membrane disk were investigated. Good recoveries above 75% were obtained for most of the organic pollutants using the optimum SPE-MASE technique. The effect of sodium chloride and humic acid on the recoveries on the target analytes were also investigated.     

Extraction of various additives from polystyrene and their subsequent analysis

Summary The extraction of fifteen polymer additives which are used as antioxidants, uv stabilizers, process lubes, flame retardants, and antistats from eight formulations of polystyrene is demonstrated with supercritical carbon dioxide and compared to traditional dissolution/precipitation extractions. The purpose of the study was two fold: 1) the development of a high performance liquid chromatography method(s) for the additives and 2) the determination of the viability of supercritical fluids for extraction of the additives from polystyrene. Nine of the additives were assayed via reversed phase liquid chromatography while, the remaining six additives could not be assayed in this manner. In order to develop an extraction method for the additives, the effects of static extraction time, CO₂ density, and temperature were first investigated. These preliminary extractions revealed that a static period which afforded an opportunity for the polymer to swell combined with a high CO₂ density and temperature above the polymer glass transition yielded quantitative recoveries of the additives. Triplicate extractions of the various polystyrene formulations matched additive recoveries obtained by the traditional dissolution/precipitation method but the former method was faster and used less organic solvent.     

固相膜萃取-超声解吸-气相色谱-质谱法分析水中酞酸酯类化合物

酞酸酯(PAEs)是一种常用的增塑剂,由于其广泛应用已经对环境造成了污染.本研究建立了固相膜萃取-超声解吸-气相色谱-质谱分析水中酞酸酯类化合物的方法.对萃取条件、解吸条件进行了优化,确定了最佳的实验条件.在水浴温度40℃,超声功率50%的条件下超声7 min,测定水中PAEs的检出限(S/N>3)在0.05 ~0.26 μg/L之间;对不同基质空白样品进行加标回收实验,回收率在76.2%~112.3%之间,相对标准偏差小于10%.     

Microwave-assisted Extraction of Rutin and Quercetin from Flos Sophorae

Three microwave-assisted extraction(MAE) procedures were studied. The first procedure was household microwave oven dynamic extraction(HMODE). The second procedure was special microwave oven bath extraction (SMOBE). The third procedure was microwave resonant cavity dynamic extraction (MRCDE). The results obtained by the three microwave-assisted extraction procedures were compared with those obtained by using traditional Soxhlet extraction. The results indicate that the MAE not only took a shorter time, but also simplified the procedure, and made the extraction a higher yield. At the same time the results obtained by the three MAE procedures were also compared with each other.     

Comparison of extraction procedures for methylmercury determination by a SPME-GC-AFS system

In this study the comparison of three different alkaline extraction techniques carried out with methanolic NaOH followed by phenylation derivatization for the determination of methylmercury in marine fish was performed. The investigated three methods differed in the technique how the extraction assisting energy was introduced to the sample. Namely, closed vessel ultrasonic bath, an open vessel technique using an ultrasonic probe and the microwave assisted extraction procedures were characterized and optimized. Optimum values of 3 h at 75 °C for the ultrasonic bath, 25 min for the ultrasonic probe and 6 min at 60 W for the microwave method were obtained. All three methods were validated using the BCR-464 tuna fish certified reference material.     

Adhesion of molded polyethylene using polyethylene gels by microwave heating

Adhesive effect of polyethylene gels on the molded polyethylene by heating with microwaves has been investigated. Polyethylene gels in polar organic solvents such aso-xylene, chlorobenzene,o-dichlorobenzene,m-dichlorobenzene, 1,1,1,2-tetrachloroethane, and 1,1,2,2-tetrachloroethane were used as adhesives. All of these gels showed adhesive effect when heated with microwaves. In particular, the gels in 1,1,2,2-tetrachloroethane showed such strong adhesion that polyethylene plates of 3 mm in thickness and 20 mm in width gave rise to necking by heating for 8 min in a 500 W (2450 MHz) microwave oven.     

Evaluation of different sample extraction strategies for selenium determination in selenium-enriched plants (Alliumsativum and Brassicajuncea) and Se speciation by HPLC-ICP-MS

Several sample extraction techniques have been evaluated in order to obtain highest selenium (Se) extraction efficiency in two types of selenium-enriched plants (Allium sativum and Brassica juncea). Three extracting solutions have been studied for this purpose: 0.1 M HCl, 25 mM ammonium acetate buffer (pH 5.6) and protease in aqueous solution. In each case, the effect of the ultrasonic probe during extraction was also evaluated. Selenium extraction yields were calculated based on the ICP-MS determination of the total selenium content in the corresponding extracts and in the plant tissue after its microwave digestion. The action of ultrasounds allowed the reduction on the extraction time while maintaining good Se recoveries (which ranged from 75 to 120% of the total Se in the plant). The accuracy of total Se determination was controlled by analyzing a reference material (aquatic plant, BCR-670). On the other hand, speciation studies of the extracts were carried out by using ion-pairing reversed phase and size exclusion/ion exchange (Shodex Asshipak) liquid chromatographic columns. The two separation mechanisms were suitable to isolate the main extractable Se species which were identified as Se-methyl selenocysteine and Se-methionine in both systems. The extracts of both plants (A. Sativum and B. juncea) exhibited also the presence of several unknown Se-species.     

Effects of ultrasonic oscillations on linear viscoelastic behaviors of metallocene‐catalyzed linear low density polyethylene and its blends with low density polyethylene

The effects of ultrasonic oscillations on linear viscoelastic behaviors of metallocene‐catalyzed linear low density polyethylene (mLLDPE) and its blends with low density polyethylene (LDPE) were investigated in this article. The experimental results showed that ultrasonic oscillations can increase the cross modulus, characteristic time, plateau modulus, complex viscosity, zero shear viscosity, and flow activation energy of mLLDPE. Molecular weight of mLLDPE increases but molecular polydispersity index decreases in the presence of ultrasonic oscillations. It has been found for mLLDPE/LDPE blends that the addition of LDPE as well as ultrasonic oscillations can decrease the cross modulus but increase the characteristic time of the blends. The complex viscosity, zero shear viscosity, and flow activation energy of the blends increase by the addition of LDPE, but decrease in the presence of ultrasonic oscillations. Shear thinning effect of the blends is improved because of the addition of LDPE. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3030–3043, 2005     

High-temperature creep resistant ternary blends based on polyethylene and polypropylene for thermoplastic power cable insulation

The impact of a small amount of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) on the thermomechanical and electrical properties of blends comprising low-density polyethylene (LDPE) and isotactic polypropylene (PP) is investigated. SEBS is found to assemble at the PP:LDPE interface as well as within isolated PP domains. The addition of 10 wt% SEBS significantly increases the storage modulus between the melting temperatures of the two polyolefins, 110 and 160°C, and results in improved resistance to creep during both tensile deformation as well as compression. Furthermore, the ternary blends display a very low direct-current (DC) conductivity as low as 3.4 × 10⁻¹⁵ S m⁻¹ at 70°C and 30 kV mm⁻¹, which is considerably lower than values measured for neat LDPE. The here presented type of ternary blend shows potential as an insulation material for high-voltage direct current power cables.     

A Microwave Digestion Method for Total Decomposition of Lead and Other Metals in Paint,Soil and Dust

ABSTRACT

A simple, total decomposition method for lead and other metals in paint has been developed. Complete decomposition is achieved through a combination of reagents over several digestive steps in a microwave oven. Results of analysis of several NIST paint SRMs show excellent recoveries ranging from 85.5 to 111%. Additionally, recoveries of a number of trace elements for two soil and one dust NIST SRM were also excellent.     

步进扫描差示扫描量热法研究不同链结构的聚乙烯类聚烯烃热力学特性

采用步进扫描差示扫描量热法研究了几种具有不同链结构的聚乙烯类聚烯烃的热力学性质.结果表明,不同链结构的聚烯烃在热力学平衡熔融态下,其绝对比热容的温度依赖性在实验误差范围内几乎相同;而无论链结构的变化如何,在极低温度下稳定结晶态的热容也非常接近.但在熔融温度范围内,比热容对不同聚烯烃的链结构非常敏感,这是由于在远低于聚烯烃主熔化峰温度范围内,聚乙烯晶体结构中的不同支链的影响.在时间-热流的步进扫描曲线中,具有长支链结构的聚烯烃表现出独特的熔融-再结晶行为,这可能是由于交联点之间较长的受约束链段的运动在熔融过程中得到释放并重排所致.