Anaerobic Co-Digestion of Vegetable and Fruit Market Waste in LBR + CSTR Two-Stage Process for Waste Reduction and Biogas Production

Applied Biochemistry and Biotechnology - Vegetable and fruit waste (VFW) is becoming a heavy burden of municipal waste disposal because of its huge amount, but it is a potentially valuable resource...     

Analysis of Nanafrocin in Foodstuffs of Animal Origin by LC–MS–MS

A new, rapid, and efficient method, multiple reaction monitoring liquid chromatography–tandem mass spectrometry, has been developed for analysis of nanafrocin in foodstuffs of animal origin. The researchers used a C₁₈ stationary phase coupled with triple-quadrupole tandem mass spectrometry in negative-electrospray mode. The limits of detection (LOD) and quantification (LOQ) were 0.005 and 0.01 mg kg^?1, respectively, in the matrixes. Detector response was found to be a linear function of concentration over the range 0.005–0.1 mg kg^?1 in each matrix. Mean overall recovery (n = 10) of nanafrocin varied from 71 to 101%. The results show that identification and quantification of nanafrocin residues in foodstuffs of animal origin can be successfully achieved by use of the proposed LC–MS–MS method.     

Evaluation of Target Efficiencies for Solid–Liquid Separation Steps in Biofuels Production

Development of liquid biofuels has entered a new phase of large scale pilot demonstration. A number of plants that are in operation or under construction face the task of addressing the engineering challenges of creating a viable plant design, scaling up and optimizing various unit operations. It is well-known that separation technologies account for 50–70% of both capital and operating cost. Additionally, reduction of environmental impact creates technological challenges that increase project cost without adding to the bottom line. Different technologies vary in terms of selection of unit operations; however, solid–liquid separations are likely to be a major contributor to the overall project cost. Despite the differences in pretreatment approaches, similar challenges arise for solid–liquid separation unit operations. A typical process for ethanol production from biomass includes several solid–liquid separation steps, depending on which particular stream is targeted for downstream processing. The nature of biomass-derived materials makes it either difficult or uneconomical to accomplish complete separation in a single step. Therefore, setting realistic efficiency targets for solid–liquid separations is an important task that influences overall process recovery and economics. Experimental data will be presented showing typical characteristics for pretreated cane bagasse at various stages of processing into cellulosic ethanol. Results of generic material balance calculations will be presented to illustrate the influence of separation target efficiencies on overall process recoveries and characteristics of waste streams.     

Simultaneous Analysis of Selected Typical Antibiotics in Manure by Microwave-Assisted Extraction and LC–MS n

Analysis of antibiotics in the environment has become an urgent issue. A novel method entailing microwave-assisted extraction (MAE) and high-performance liquid chromatography–electrospray mass spectrometry (LC–MS ⁿ ) has been developed for determination of selected typical antibiotics, including quinolones, sulfonamides, and tetracyclines, in manure. Compared with ultrasonic extraction, MAE significantly increased recovery of fluoroquinolones (63–106%), sulfonamides (64–133%), and tetracyclines (64–109%) from manure. Acetonitrile acidified with formic acid buffer solution (pH 4.0) was used for extraction of swine manure whereas chicken manure was extracted with 0.1 M EDTA–McIlvaine buffer solution. Limits of quantification (LOQ) for all compounds were in the range 5.12–168.4 μg kg^?1 dry matter, which were satisfactory for analysis of all samples. The suitability of the method was assessed by analysis of manure from six different sites.     

Production of Zinc-Doped Yttrium Ferrite Nanopowders by the Sol–Gel Method

Zinc-doped yttrium orthoferrite nanocrystals having the perovskite structure were prepared by coprecipitation of yttrium, zinc, and iron hydroxides. The limiting zinc doping level of the yttrium ferrite to yield a ZnFe₂O₄ spinel second phase was determined. The yttrium orthoferrite particle size was found to be a nonmonotone function of dopant concentration. The specific magnetization of yttrium ferrite nanocrystals increases with increasing zinc doping level from 0.242 A m²/kg (in undoped YFeO₃) to 1.327 A m²/kg (the ratio (1–x)YFeO₃: xZn (x = 0.4)) at Т = 300 K in 1250-kA/m field. A zinc ferrite impurity in samples enhances the ferromagnetism of the material.     

Studying Solid-Phase Processes in Metakaoline–Sodium Hydroxide Mixtures by Means of Isoconversion Analysis

Russian Journal of Physical Chemistry A - Processes of the thermal treatment of 6Al2Si4O7: 12NaOH mixtures for the synthesis of zeolites are studied. The mixtures are subjected to ultrasonic...     

Evaluation of Accuracy for the Measurement of Octanol–Water Partition Coefficient by MEEKC

Microemulsion electrokinetic chromatography (MEEKC) has been widely used as an indirect tool to measure octanol–water partition coefficients (logP _ow) of various kinds of compounds. In this paper, we present for the first time a mathematical model of the precision of logP _ow (ΔlogP _ow) as a function of the deviation of migration time (Δt _m) in MEEKC, and more importantly evaluated the accuracy of the MEEKC. Our model shows that for a given microemulsion system, there is an interval of migration times, where a high precision in the determination of logP _ow can be obtained. However, when the migration time approaches either the migration time of the electroosmotic flow or that of the microemulsion phase, the precision of logP _ow deteriorates rapidly. The model was experimentally verified by the microemulsion system with migration times of 6.50 and 32.00?min for the electroosmotic flow and microemulsion phase, respectively, and we found the useful logP _ow interval to be 0.50–5.50. The paper also demonstrates that the calibration constants between migration times t _m and predicted logP _ow values could be transferred with high accuracy from one MEEKC system to another as long as both systems are set up to use the same operational parameters.     

Quick and Sensitive Determination of Fluoroquinolones by Capillary Electrophoresis–Potential Gradient Detection

Abstract

A rapid, capillary electrophoresis–potential gradient detection method was developed for determining three fluoroquinolones: rufloxacin, enoxacin, and moxifloxacin. The fluoroquinolones were baseline separated within 3.5 min with background electrolyte composed of 50 mM acetic acid and 6 mM potassium hydroxide at pH 3.7. For the first time, electrokinetic injection was applied in capillary electrophoretic separation of fluoroquinolones, and an average of ca. 10-fold improvement in detection limits was observed. The method was applied to a fortified chicken tissue sample with detection limits (S/N = 3) of 22–24 ng g^?1, suggesting the potential of the method for determining fluoroquinolone residues in real samples.     

Evaluation of Sempervivum tectorum L. Flavonoids by LC and LC–MS

A reversed-phase high-performance liquid chromatography method with UV detection was developed for determination of [(N-morpholine)methylene]daunorubicin hydrochloride (DD-M) during studies of its stability. In this LC method the following were used: an RP-column, the mobile phase—acetonitrile:methanol:solution A (9:1:10 v/v/v) [solution A contains 2.88 g of sodium laurilsulfate and 1.6 mL of phosphoric acid(V)] with a flow rate of 1.4 mol L⁻¹ and quinine hydrochloride as an internal standard. The detection wavelength was 254 nm. The method was validated with regard to linearity, limit of detection, limit of quantitation, selectivity and precision. Hydrolysis of the DD-M catalyzed by hydrogen ions in hydrochloric acid and a spontaneous reaction of the DD-M degradation under the influence of the water in sodium hydroxide took place. The thermodynamic parameters of these reactions—energy, enthalpy and entropy of activation—were calculated. It was observed that a positive salt effect occurred in hydrochloric acid.

     

Improved Method for the Determination of Cyanuric Acid in Animal Feed by GC–MS

A specific and sensitive analytical method for the quantitative determination of cyanuric acid in animal feed was developed. Sample preparation involved the diethylamine/acetonitrile/water extraction of feed using sonication and shaking. The extract was subjected to clean-up by dual solid phase extraction using mixed mode anionic and cationic extraction cartridges. After removal of clean-up solvent, cyanuric acid was converted to a tert-butyldimethylsilyl derivative and was determined by gas chromatography–mass spectrometry in the selected ion monitoring mode. ¹³C ₃ ¹⁵ N₃-cyanuric acid was employed as the internal standard. The calibration curve was found to be linear up to 4 mg kg^?1. LOD and LOQ were determined to be 0.06 to 0.4 mg kg^?1 for fish and chicken feed. The mean recovery of cyanuric acid was 96 to 98% with relative pooled standard deviation of 1.8–7.4% in the range of 0.5 to 100 mg kg^?1 for fish and chicken feed. The validated method was applicable for analysing cyanuric acid in animal feed.     

Evaluation of the Standard Potential of the Ag/AgCl Electrode in a 50 wt-% Water–Ethanol Mixture

This paper deals with the evaluation of the standard potential of the Ag/AgCl electrode in a water–ethanol mixture (50 wt-%). A potentiometric method was applied using a cell without liquid junction. Mean activity coefficients of HCl in the same mixture have been also determined. The measurements were performed in the HCl molality range from 0.005 to 0.1 mol⋅kg⁻¹. The Debye–Hückel theory and Pitzer’s model, based on the interactions present in the solution, have been applied. Good agreement was found between the results obtained with the two approaches. Uncertainties of the Pitzer parameters and interionic forces are discussed based on the values found. The variation of the standard potential as a function of the temperature was used to calculate the transfer thermodynamic functions. The effects of the solvent composition on the thermodynamic properties of HCl allow to highlight structural changes in water–ethanol mixtures.     

Influence of Acid–Base Characteristics of Hierarchical Cu/Zr-MTW Zeolites on their Catalytic Properties in 1,3-Butadiene Production from Ethanol–Water Mixtures

Theoretical and Experimental Chemistry - The nature of mineralizing agent (HF, NH4F) and the Si/F ratio in the synthesis conditions is found to affect the formation of Zr- and Cu-containing acid...     

Effect of the Calorific Intensity of Combustion Chamber on Production of Synthesis Gas in Partial Oxidation of Methane–Oxygen Mixtures in the Combustion Mode

Optimal design of a flow-through chemical reactor with increased calorific intensity was experimentally sought for in partial oxidation of natural gas by oxygen at oxidant excess factors in the range 0.27 < α < 0.4. It was shown that this reactor with a chamber for additional turbulent mixing of the starting components, turbulizer, and supercritical pressure difference at the outlet from the combustion chamber can provide a combustion mode close to the process in the plug-flow reactor. The increase in the calorific intensity of the combustion chamber of the reactor as a result of a decrease in its volume leads to full conversion of the starting reagents and to lower carbon-black formation.     

Ignition of Quiescent Lean Propane–Air Mixtures at High Pressure by Nanosecond Repetitively Pulsed Discharges

We present an experimental study of lean mixture ignition by nanosecond repetitively pulsed (NRP) discharges. The plasma is created in a lean propane/air mixture at pressure up to 10 bar and equivalence ratio 0.7, premixed in a constant volume vessel. We characterize the initial spark radius, the ignition kernel development and the flame propagation as a function of pressure (up to 10 bar) and the pulse energy (1–6 mJ per pulse). Comparisons with a conventional igniter show that better results are obtained with NRP discharges in terms of flame propagation speed, in particular at high pressure, due to the increased wrinkling of the flame front that is induced by NRP discharges.     

Conductivity of Lithium-Conducting Nafion Membranes Plasticized by Binary and Ternary Mixtures in the Sulfolan–Ethylene Carbonate–Diglyme System

Russian Journal of Electrochemistry - The electrotransport characteristics of the polymer electrolyte based on lithiated Nafion-115 membrane plasticized by high-boiling dipolar aprotic...     

Determination of Essential and Toxic Elements in Tropical Fruit by Microwave-Assisted Digestion and Inductively Coupled Plasma–Mass Spectrometry

The concentrations of eight essential (Co, Cr, Cu, Mn, Ni, Se, V, and Zn) and five toxic elements (Al, As, Cd, Hg, and Pb) were determined in 457 samples of commonly consumed fresh tropical fruit including bananas (Musa acuminata), kiwi (Actinidia deliciosa), mangos (Mangifera indica), and pineapple (Ananas comosus) from supermarkets from Seoul, Busan, Gangneung, Daegu, Daejeon, and Gwangju, South Korea. The samples were digested by microwave-assisted combustion using HNO₃ and H₂O₂ and determined by inductively coupled plasma mass spectrometry. The Hg concentrations were evaluated by furnace-gold amalgamation direct mercury analysis. The techniques were validated by linearity, limits of detection and quantification, precision, recovery, and the analysis of a NIST-1570a spinach leaves certified reference material. The concentrations of essential elements varied considerably among the tropical fruit. Overall, the tropical fruit was higher in Mn (0.027–13.2?µg/g) and Zn (0.514–2.20?µg/g), while lower in Co (0.002–0.005?µg/g) and V (0.001–0.002?µg/g). The concentrations (µg/g) of toxic elements were 0.001 (kiwi) to 0.003 (mango) for As and Cd, 0.0004 (pineapple) to 0.002 (banana) for Hg, and 0.005 (kiwi) to 0.013 (mango) for Pb. The calculated values of estimated dietary intake, target hazard quotients and hazard indices were lower than one and the safety limits established by World Health Organization. The tropical fruits were therefore safe and did not pose any threat to consumers.     

Evaluation of solubility and diffusion coefficients in polymer film–vapor systems by sorption experiments

Sorption experiments are commonly used to determine the equilibrium and kinetics of mass-transfer processes of vapors in polymeric materials. Electrogravimetry is recognized as a powerful technique. A discussion of the standard theoretical approach to determine solubility and diffusion coefficients is presented. The reduced mathematical expression commonly used for calculations of D values is discussed. A consistency test to check for common deviations caused by the experimental complexity is discussed and resolved.The sorption of hexanol and ethyl caproate into a metallocene polyethylene and an ionomer was measured by electrogravimetry. Transport was characterized through the solubility and the diffusion coefficients. The formalism presented was used in these experiments and is commented upon.