Extraction of biogenic amines using sorbent materials containing immobilized crown ethers

Three sorbent materials (A18C6-MS, DA18C6-MS and AB18C6-MS) based on the crown ether ligands, 1-aza-18-crown-6, 1,4,10,13-tetraoxa-7,16-diazacyclo octadecane and 4′-aminobenzo-18-crown-6, respectively, were prepared by the chemical immobilization of the ligand onto mesoporous silica support. The sorbents were characterized by FT-IR, scanning electron microscopy-energy dispersive X-ray microanalysis, elemental analysis and nitrogen adsorption-desorption test. The applicability of the sorbents for the extraction of biogenic amines by the batch sorption method was extensively studied and evaluated as a function of pH, biogenic amines concentration, contact time and reusability. Under the optimized conditions, all the sorbents exhibited highest selectivity toward spermidine (SPD) compared to other biogenic amines (tryptamine, putrescine, histamine and tyramine). Among the sorbents, AB18C6-MS offer the highest capacity and best selectivity towards SPD in the presence of other biogenic amines. The AB18C6-MS sorbent can be repeatedly used three times as there was no significant degradation in the extraction of the biogenic amines (%E > 85). The optimized procedure was successfully applied for the separation of SPD in food samples prior to the reversed-phase high performance liquid chromatography separation.     

Withanolides from Withania adpressa

From the leaves of Withania adpressa, a plant endemic to Sahara of Morocco and Algeria, the novel steroidal lactone (22R)‐14α,15α,17β,20β‐tetrahydroxy‐1‐oxowitha‐2,5,24‐trien‐26,22‐olide (= (15S,17S)‐14,15,17,20‐tetrahydroxy‐22,26‐epoxyergosta‐2,5,24‐triene‐1,26‐dione; 1 ), was isolated, along with three known compounds, withanolides F ( 2 ), J ( 3 ), and oleanolic acid. Their structures were mainly solved by in‐depth 1D‐ and 2D‐NMR (including ADEQUATE) experiments, as well as by HR‐MS analyses and chemical evidence.     

Inactivation of food-borne enteropathogenic bacteria and spoilagefungi using pulsed-light

The lethality of high-intensity pulsed-light emissions from low and high ultraviolet (UV) light sources on predetermined microbial populations has been investigated. Prior to treatment, the bacterial enteropathogens Bacillus cereus, Escherichia coli, and Salmonella enteritidis and the food-spoilage fungi Aspergillus niger and Fusarium culmorum were seeded separately onto the surface of either tryptone soya yeast extract or malt extract agar plates. Prescribed microbial population densities were applied to the test media and these samples were exposed to one of two light sources. These were low-pressure, xenon filled, flash lamps that produced either high or low UV intensities. They were operated in pulsed mode, being driven by a stacked Blurnlein table generator. Microbial samples were treated by exposure to different numbers of light pulses. The treated bacterial populations were reduced by ~8 log orders after 1000 light-pulses of the higher UV intensity light and the fungal counts had a corresponding reduction of 4.5 log orders. The fungus, Aspergillus niger, was shown to be significantly more resistant in spore form to the intense UV light compared with Fusarium culmorum. This resistance has been attributed to the high level of UV absorbance associated with the dark pigment present in A. niger. The pulsed light source of lower UV intensity was shown to be significantly less effective in reducing microbial populations     

Inactivation of pathogenic and spoilage microorganisms in a testliquid using pulsed electric fields

Experiments have been carried out to investigate the effect of pulsed electric fields (PEFs) on the inactivation of microbial populations suspended in liquids using nonflowing and continuous flowing test chambers. Electric fields of ~30 kV/cm, and a pulse duration of 500 ns, were generated from a coaxial table Blumlein pulse forming network (PFN) and applied to a parallel plate, circular electrode test configuration. Sample microorganisms were grown under standardized conditions and were introduced into test liquids in order to produce known population densities within the treatment celt. The organisms investigated include the mold Aspergillus niger, the yeast Sacckaromyeces cerevisiae, and the bacterial pathogens Bacillus cereus, Staphylococcus aureus, and Pseudomonas aeruginosa. The PEF studies were undertaken at a sample temperature range of 25°C-30°C, and the effect of the number of pulses on the test microbial population was studied. The results of this investigation showed that the greater the number of pulses applied, the larger the corresponding reduction in microbial cells/spores obtained. With the exception of dormant fungal spores, all of the test organisms were reduced by -3 to 4 log orders after 3000 pulses. The number of B. Cerus cells was reduced by -7.5 log orders after 15 000 pulses, of which 10 000 pulses were applied in a flowing system followed by 5000 pulses in a static system     

Comparative study of Cu-ZSM-5 and Fe-ZSM-5 in the SCR of NOx with i-C4H10

Catalytic activity tests were carried out on Cu-ZSM-5 and Fe-ZSM-5 catalysts for the reduction of NOx with i-C₄H₁₀. Formation of CO was the major drawback of Fe-ZSM-5 catalyst, which was attributed to the presence of iron oxide particles. Increasing the Si/Al ratio appeared to slightly strengthen Cu-ZSM-5 catalyst in the presence of water vapor.     

In situ derivatization hollow fibre liquid-phase microextraction for the determination of biogenic amines in food samples

Hollow fibre liquid-phase microextraction with in situ derivatization using dansyl chloride has been successfully developed for the high-performance liquid chromatography-ultraviolet (HPLC-UV) determination of the biogenic amines (tryptamine, putrescine, cadaverine, histamine, tyramine, spermidine) in food samples. Parameters affecting the performance of the in situ derivatization process such as type of extraction solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Under the optimized conditions (extraction solvent, dihexyl ether; acceptor phase, 0.1 M HCl; extraction time, 30 min; extraction temperature, 26 °C; without addition of salt), enrichment factors varying from 47 to 456 were achieved. Good linearity of the analytes was obtained over a concentration range of 0.1–5 μg mL⁻¹ (with correlation coefficients of 0.9901–0.9974). The limits of detection and quantification based on a signal-to-noise ratio of 3–10, ranged from 0.0075 to 0.030 μg mL⁻¹ and 0.03 to 0.10 μg mL⁻¹, respectively. The relative standard deviations based on the peak areas for six replicate analysis of water spiked with 0.5 μg mL⁻¹ of each biogenic amine were lower than 7.5%. The method was successfully applied to shrimp sauce and tomato ketchup samples, offering an interesting alternative to liquid–liquid extraction and solid phase extraction for the analysis of biogenic amines in food samples.     

Hexanoyl chitosan/ENR25 blend polymer electrolyte system for electrical double layer capacitor

Single salt polymer electrolytes based on hexanoyl chitosan‐ENR25 were prepared by employing LiN (CF₃SO₂)₂ or LiCF₃SO₃ as the doping salt. Elastic property of hexanoyl chitosan was enhanced with the incorporation of ENR25. DSC studies revealed immiscibility of hexanoyl chitosan and ENR25, and dissolution of salt was favored in ENR25 phase. Conductivity enhancement was observed in the blends as compared with the neat hexanoyl chitosan. The maximum conductivities achieved for LiCF₃SO₃‐ and LiN (CF₃SO₂)₂‐comprising electrolyte systems were 1.6 × 10^?8 and 5.0 × 10^?7 S cm^?1, respectively. Deconvolution of spectra bands in the v_as (SO₂^?) mode of LiN (CF₃SO₂)₂ and v_s (SO₃^?) mode of LiCF₃SO₃ has been carried out to estimate the relative percentage of free ions and associated ions. The findings were in good agreement with conductivity results. Electrical double layer capacitor (EDLC) was fabricated with hexanoyl chitosan/ENR25 (90:10)‐LiN (CF₃SO₂)₂‐EmImTFSI electrolyte and activated carbon‐based electrodes. The conductivity and electrochemical stability window of hexanoyl chitosan/ENR25‐LiN (CF₃SO₂)₂‐EmImTFSI were ~10^?6 S cm^?1 and 2.7 V, respectively. The performance of the EDLC was analyzed by cyclic voltammetry (CV) and galvanostatic charge‐discharge (GCD). From GCD, the specific capacitance of EDLC was 58.0 F g^?1 at 0.6 mA cm^?2. The specific capacitance was found to decrease with increasing current density.     

The influence of polarity on trigatron switching performance

This paper reports on a study into the effect of trigger voltage polarity and main gap voltage polarity on the switching performance of a pulse charged trigatron. The four polarity combinations possible, two homopolarity (trigger voltage and main gap voltage of the same polarity) and two heteropolarity (trigger voltage and main gap voltage of opposite polarity), were studied and compared in terms of their effect upon the switching range, delay time to breakdown, jitter, and voltage collapse time. It was found that the two heteropolarity configurations were superior to the homopolarity configurations in terms of the above switching characteristics, with the positive trigger/negative main gap heteropolarity configuration performing the best. The results are discussed, and an explanation of the influence of the polarity configuration on switching is suggested in terms of the discharge initiation mechanisms and subsequent development     

Factors affecting and methods of improving the pulse repetitionfrequency of pulse-charged and DC-charged high-pressure gasswitches

The results of this paper describe some of the factors which affect the repetitive operation of high-pressure gas switches (spark gaps) for both pulse-charged and DC-charged operation. Also discussed are methods which may be employed to improve the pulse repetition frequency (PRF) of spark gaps operating under such conditions. Under pulse-charged conditions, the voltage recovery process of the spark gap has been shown to be restricted following partial density recovery by the residual ion population. This restriction may be minimized by applying a suitable bias voltage across the gap to remove the ion influence. It is also possible to manipulate the voltage-pressure (V-p) breakdown characteristic of a spark gap in order to improve the rate of rise of recovery voltage by reducing the recovery voltage dependence upon gas pressure. The combination of these effects has been shown to reduce the voltage recovery time of pulse-charged spark gaps from several hundred milliseconds to several milliseconds. Under DC-charged conditions, where no “dead time” is available for voltage recovery, it is possible to employ corona discharge effects, which occur in highly nonuniform fields, to stabilize and control the breakdown process. The use of corona stabilization has enabled the operation of a self-closing spark gap at a PRF of more than 5 kHz, without employing gas flow techniques. A triggered version of a corona-stabilized spark gap has also been developed which has demonstrated single run capabilities of 10⁷ (4 h continuous operation at 700 pps) and a lifetime of ~10 shots (maintenance free, sealed switch). The triggered corona switch has also demonstrated controlled switching up to a PRF of 1.2 kHz     

Ni2+ supported on hydroxyapatite-core-shell γ-Fe2O3 nanoparticles: a novel,highly efficient and reusable lewis acid catalyst for the regioselective azidolysis of epoxides in water

In this research, Ni²⁺ supported on hydroxyapatite-core-shell magnetic γ-Fe₂O₃ nanoparticles (γ-Fe₂O₃@HAp-Ni²⁺) as a novel, efficient, reusable and heterogeneous catalyst was reported. In this protocol, we used this catalyst for the ring opening of epoxide with sodium azide in water. The catalyst can be readily isolated using an external magnet and no obvious loss of activity was observed when the catalyst was reused in seven consecutive runs. The mean size and the surface morphology of the nanoparticles were characterized by transmission electron microscopy, scanning electron microscope, vibrating sample magnetometry, X-ray powder diffraction and Fourier transform infrared techniques.