Polyphenylalanine ionic liquid for the extraction and determination of Allura red in food samples

Poly amino acids ionic liquid {3-(3-(7-(diethylamino)-2-carbonyl-2 h-amino-3-propyl)-1-ethyl Bromo imidazole P[Phe][EMI]} was synthesized and characterized with Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance (¹H-NMR), and scanning electron microscopy (SEM). A novel method based on solid-phase extraction and high-performance liquid chromatography for the detection of Allura red (AR) was established. Under optimized conditions, the linear range of AR was 0.01–10.00 μg ml⁻¹, the limit of detection (LOD) was 0.004 μg ml⁻¹ and the enrichment factor was 12.5 (volume of solution/volume of elution). The isothermal adsorption, kinetic model, and Gaussian calculation model was explained by the adsorption mechanism of AR on P[Phe][EMI]. The method was applied to the analysis of real samples with recoveries of 92.0%–102.2% and relative standard deviations of 1.0%–4.6%.     

The effect of amino acids and amino acid analogues on growth of an obligate methanotroph,Methylosinus trichosporium OB3b

The sensitivity of the obligate methanotroph, Methylosinus trichosporium OB3b to a number of amino acid analogues and amino acids has been examined. Sulphaguanidine (5 μg ml^?1) norleucine (100 μg ml^?1) m-fluorophenylalanine (50 μg ml^?1), p-fluorophenylalanine (50 μg ml^?1) and S2-aminoethyl-C-cysteine (1000 μg ml^?1) inhibited growth. Proline, threonine, methionine and lysine (2–4 μg ml^?1) also inhibited growth, but arginine and leucine at similar concentrations had no effect. Attempts were made to isolate amino acid analogue resistant mutants, which would be expected to overproduce amino acids. Two approaches were made, selection of spontaneous and induced mutants in plate culture, and selection of a spontaneous mutant during growth in continuous culture under selective conditions, but no mutants were obtained. Possible reasons for failure to obtain such mutants are discussed.     

Preparation of a composite monolith with functional graphene oxide and its application in the online enrichment of ursolic acid in medicinal plant

In this study, a composite poly(functional graphene oxide-co-N-isopropylacrylamide-co-trimethylolpropane triacrylate-co-ethylene dimethacrylate) (poly(f-GO-co-NIPAAm-co-TMPTA-co-EDMA)) monolith was prepared, in which f-GO was added. The obtained monolith was characterized by nitrogen adsorption–desorption isotherm and scanning electron microscopy. The monolith exhibited a homogeneous and continuous structure, good permeability, and large surface area. The composite monolith was used as solid-phase extraction absorbent in conjunction with high-performance liquid chromatography for enrichment of ursolic acid. The calibration equation was y = 73.3980x + 0.2555, and the linear regression coefficient was 0.9987; The calibration curve was ranged from 1 to 700 μg ml⁻¹; The limit of detection and limit of quantification values were 0.3 and 1.0 μg ml⁻¹, respectively; The intraday and interday precisions were less than 2.6 and 7.4%, respectively. The recovery was in the range of 84.44–111.76%. Moreover, the adsorption amount of ursolic acid on the composite monolith was compared with the monolith without f-GO added and silica gel-C18 adsorbent. The results showed that the composite monolithic column was feasible to be used as an online SPE absorbent, which exhibiting low back pressure, good permeability, and high adsorption capacity. In addition, this method provided the possibility to extract and analyze trace components from medicinal plants.     

A GC–MSD method for analysis of dimethyl sulfate in palm oil-based esterquat

Dimethyl sulfate (DMS) is a quarternizing agent for esteramine used for the synthesis of esterquat. To date there is no reliable published method for quantification of DMS in palm-based esterquat. Esterquat is used in the formulation of personal care and textile cleaning. The process of quaternization is usually incomplete and there will be unreacted DMS. This work presents a new simple method involving solvent extraction of DMS followed by analysis with gas chromatography–mass spectrometry detector to quantify the unreacted DMS. This method was validated as per International Council for Harmonization requirements. This novel method showed good repeatability (relative standard deviation [RSD] < 5%) and inter-day with different analyst reproducibility (RSD < 5%). The limits of detection and quantification were 5 and 10 μg mL⁻¹, respectively. The accuracy of the method was evaluated by the analysis of spiked samples and it was found that good recovery was found at spiking levels of 20, 30, and 50 μg mL⁻¹ with % recovery falling within the 80%–120% acceptable limit. However, at 10 μg mL⁻¹, the percentage recovery was slightly below the recommended limit.     

Influence of different reactor types on Nannochloropsis oculata microalgae culture for lipids and fatty acid production

Greenhouse gases emitted into the atmosphere by burning of fossil fuels cause global warming. One option is obtaining biodiesel. Nannochloropsis oculata was cultured under different light intensities and reactors at 25°C for 21 days with f/2 medium to assess their effects on cell density, lipid, and fatty acids (FAs). N. oculata improved cell density on fed-batch glass tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, yielding 3.5 × 10⁸ cells ml⁻¹, followed by fed-batch Erlenmeyer flask (1 L) at 650 μmol E m⁻² s⁻¹ with 1.7 × 10⁸ cells ml⁻¹. The highest total lipid contents (% g lipid × g dry biomass⁻¹) were 44.4 ± 0.8% for the reactor (1 L) at 650 μmol E m⁻² s⁻¹ and 35.2 ± 0.2% for the tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, until twice as high compared with the control culture (Erlenmeyer flask 1 L, 80 μmol E m⁻² s⁻¹) with 21.2 ± 1%. Comparing the total lipid content at 200 μmol E m⁻² s⁻¹, tubular reactor (7 L) and reactor 1 L achieved 35.2 ± 0.2% and 28.3 ± 1%, respectively, indicating the effect of shape reactor. The FAs were affected by high light intensity, decreasing SFAs to 2.5%, and increased monounsaturated fatty acids + polyunsaturated fatty acids to 2.5%. PUFAs (20:5n-3) and (20:4n-3) were affected by reactor shape, decreasing by half in the tubular reactor. In the best culture, fed-batch tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹ contains major FAs (16:0; 38.06 ± 0.16%), (16:1n-7; 30.74 ± 0.58%), and (18:1n-9; 17.15 ± 0.91%).     

Modified PMMA monosize microbeads for glucose oxidase immobilization

Glucose oxidase (GOD) was immobilized onto modified polymethylmethacrylate (PMMA) microspheres by covalent bonding. Monosize PMMA microbeads with 1.5 μm diameter were produced by dispersion polymerization of methylmethacrylate by using polyvinyl alcohol as a stabilizer. Hydroxyl groups on the microbeads were first converted to aldehyde groups by periodate oxidation. Three amino compounds, namely ammonium hydroxide, ethylene diamine and hexamethylene diamine were incorporated through the aldehyde groups. Then, GOD molecules were immobilized through the spacer-arms by using glutaraldehyde. The highest amount of immobilization and activity were obtained in which hexamethylene diamine was used as the spacer-arm with 14 atom length, and were 2.1 mg g⁻¹ polymer and 129 IU g⁻¹ polymer, respectively. The optimal conditions for GOD immobilization were obtained as follows: pH, 6.0; temperature, 30 °C; immobilization time, 60 min; and GOD initial concentration, 0.10 mg ml⁻¹. The optimal conditions for the GOD-immobilized PMMA microbeads were at pH 6.0 and at a temperature of 30 °C. The K_m and V_max values of the GOD-immobilized PMMA microbeads were, 13.79 mM and 26.31 mM min⁻¹ calculated by non-linear regression, respectively.     

NIR-responsive Fe3O4@PPy nanocomposite for efficient potential use in photothermal therapy

In this work, superparamagnetic Fe₃O₄@PPy nanocomposite with core-shell structure having strong near-infrared (NIR) absorption is synthesized via a facile two-step modified procedure. The prepared nanocomposite samples are characterized by UV–vis, FTIR, SEM, TEM, VSM, and XRD. The effects of laser power density (1.5–2.5 W cm⁻²) and aqueous concentration (0.01–0.2 mg ml⁻¹) of the nanocomposite on the photothermal performance are investigated in the NIR region (808 nm). At 0.1 mg ml⁻¹ concentration, the temperature reaches up to 50.1°C, 64.1°C, and 78.4°C within 10 min, under 1.5 W cm⁻², 2.0 W cm⁻², and 2.5 W cm⁻² NIR laser power density values, respectively. Photothermal conservation efficiency is calculated as 43.9% and the nanocomposite exhibits excellent photothermal stability. In summary, the core-shell Fe₃O₄@PPy nanocomposite is a promising candidate for photothermal therapy and simultaneous magnetic field-guided treatments.     

Preparation of molecularly imprinted fluorescence sensor based on carbon quantum dots via precipitation polymerization for fluorescence detection of tetracycline

A facile and effective method was proposed to prepare the molecularly imprinted fluorescence sensor with carbon quantum dots, which were modified vinyl groups by acrylic acid on the surface. The obtained fluorescence composite material was investigated by transmission electron microscope and Fourier transform infrared spectra. After the experimental conditions were optimized, a linear range of 1.0–60 μmol L⁻¹ was obtained and the detection limit was 0.17 μmol L⁻¹. The novel fluorescence sensor can be successfully used to detect tetracycline in real samples. This study provides a convenient strategy for selective recognition and rapid detection of tetracycline in the complex environment.     

Hyperbranched poly(glycerol esteramide): A biocompatible drug carrier from glycerol feedstock and dicarboxylic acid

Polymer carrier with biodegradable, biocompatible as well as solubility enhancing properties are highly looked upon in the pharmaceutical industry to improve the drug delivery systems. A series of hyperbranched poly(glycerol esteramide) (HPGEA) with M_w of 5000–12,000 Da, degree of branching of 57%–62%, and hydroxyl values of 200–280 mg KOH/g sample were synthesized through polycondensation of N,N-bis(2-hydroxyethyl)stearamide (diethanolamide) and poly(glycerol ester) (PGE). The HPGEAs were characterized by ATR-FTIR, GPC, ¹H and ¹³C-NMR, and DSC. The enthalpy of fusion of HPGEAs (43–84 J g⁻¹) were lower than the commercial polymers (193–391 J g⁻¹), indicating its potential as drug carrier for solid dispersion (SD). HPGEA-based SDs showed substantial enhancement in solubility and release rate than pure drug, commercial polymer-based SDs, as well as commercial formulation. The safety of HPGEAs and HPGEA-based SDs were proven through MTT assay with IC₅₀ of 2400–9800 and 1200–3500 μg ml⁻¹, respectively.     

Self-assembly of thiourea intercalated graphene oxide based dual IIP for the SPE coupled FAAS method development of Cu(II) and Pb(II) determination

A new dual-template surface imprinted polymer for Cu(II) and Pb(II) was synthesized in one pot. Magnetic graphene oxide was self-assembled with low cost and environmentally benign thiourea. Presence of sulfur and nitrogen donor atoms provide hooks for coordination and partial reduction of graphene oxide matrix. It was used as an solid-phase extraction adsorbent for extraction, preconcentration, and coupled with flame atomic absorption spectrometry to manifest performance comparable with inductively coupled plasma atomic emission spectrometry (ICPAES) both in terms of quantification limit as well as interference. The critical experimental parameters such as pH; 4.6, contact time of 15 min and initial concentration of 777 (Q_e; 227 mg g⁻¹) and 800 μg L⁻¹ (Q_e; 273 mg g⁻¹) for Cu(II) and Pb(II), respectively, were optimized using RSM-CCD and artificial neural network. The adsorption process was kinetically faster (50% adsorption in 5 min), following fractal-like-pseudo-second-order (FLPSO) kinetics and Brouers–Sotolongo isotherm model owing to the heterogenous energy landscape. The imprinting factors were in the range of 4–7 in the presence of all coexisting ions. The proposed method was robust in the determination and removal of Cu(II) and Pb(II) from food, ground water, and industry effluents with low limit of detection (Cu(II); 1.03 μg L⁻¹ & Pb(II); 1.79 μgL⁻¹). Spiking and recovery tests were used to assess the method's accuracy. Cu(II)/Pb(II) loaded dual template IIP (DIIP) was utilized to remove anionic dyes with >95% efficiency. Thorough examination of the method and material selectivity (in binary, ternary, and multielement system), multi fold applications of determination, removal of Cu(II), Pb(II), and removal of anionic dyes makes DIIP a promising candidate for environmental remediation.     

Supercritical fluid extraction of walnut kernel oil

The objective of this study was to investigate the effects of the main process parameters on supercritical fluid extraction of walnut (Juglans regia L.) kernel oil. The recovery of walnut kernel oil was performed in a green and high-tech separation process. CO₂ and CO₂ + ethanol mixtures were used as the supercritical solvent. The extraction was carried out at operating pressures of 30, 40 and 50 MPa, operating temperatures of 313, 323 and 333 K, mean particle sizes of 1.78×10⁻⁴, 3.03×10⁻⁴, 4.78×10⁻⁴, 7.00×10⁻⁴ and 9.00×10⁻⁴ m, supercritical CO₂ (SC CO₂) flow rates of 1.67×10⁻⁸, 3.33×10⁻⁸, 6.67×10⁻⁸ and 13.33×10⁻⁸ m³/s and entrainer (ethanol) concentrations of 2, 4, 8 and 12 vol-%. Maximum extraction yield and oil solubility in SC CO₂ obtained at 50 MPa, 333 K, 9.00×10⁻⁴ m, 3.33×10⁻⁴ m³/h were 0.65 kg oil/kg of dry sample and 37.16 g oil/kg CO₂, respectively. The results obtained in this study showed that the crossover pressure effect of walnut kernel oil was at 30 MPa. At 30 MPa and 313 K, the obtained extraction yields above 4 vol-% ethanol reached the organic solvent extraction yield of 68.5 kg oil/kg dry sample. Extraction time was decreased significantly because of the higher solubility of walnut kernel oil in SC CO₂ + ethanol mixtures.     

High-Performance Production of Biosurfactant Rhamnolipid with Nitrogen Feeding

Nitrate is one of the most important factors for fermentative production of rhamnolipid, while it has not yet been conclusively demonstrated that nitrogen limitation or abundance is beneficial for improvement of rhamnolipid production. This study clarified that high concentration of NaNO₃ is conducive for high-performance production of rhamnolipid. An optimum rhamnolipid yield was achieved by 43.3 g L⁻¹ with an initial concentration of NaNO₃ equal to 10 g L⁻¹ during the regular fed-batch fermentation process by Pseudomonas aeruginosa ATCC 9027. Additionally, this rhamnolipid production was further improved to 61.2 g L⁻¹, which was two folds higher than that value obtained during batch fermentation, when the NaNO₃ concentration was maintained about 5 g L⁻¹. Furthermore, specific volume productivity of rhamnolipid was improved by over 30% in the presence of NaNO₃ at concentration ranging from 5 to 6 g L⁻¹ during sequential fed-batch fermentation, resulting a high value of 0.4 and 0.59 g L⁻¹ h⁻¹ within one batch of sequential fed-batch fermentation for a period of 17 days by P. aeruginosa ATCC 9027 and PAO1, respectively. It seems that sustaining high-concentration NaNO₃ during fed-batch fermentation is advantageous for high-performance production of rhamnolipid.     

An advanced method to manufacture hierarchically structured carbide-derived carbon monoliths

The preparation of carbide-derived carbon (CDC) monoliths with a hierarchically structure in the nm and μm range is presented. Basis is the manufacturing of porous cellular SiC ceramics based on a biomorphous approach with μm porosity and subsequent conformal conversion to CDC by reactive extraction with chlorine. The SiC ceramics can be sintered at low temperatures and short times (1500 °C, 2 h) compared to classical preparation methods. The SiC ceramics show a macro pore volume (1–10 μm channel size) of 0.56 ml g⁻¹, which corresponds to 1.5 ml g⁻¹ in the resulting CDC. The final carbon material exhibits an additional nano pore volume of 0.525 ml g⁻¹ with a mean slit pore size of 0.86 nm. Mechanical stabilities of the highly porous CDC are excellent (bending strength 2.1 ± 0.2 MPa, corrected Weibull modulus 8.7, characteristic strength 2.2 MPa and Youngs modulus 10.0 ± 0.5 GPa). The reactive extraction of the carbide monoliths shows very high reaction rates, approx. two dimensions faster (95×) compared to non-porous samples. Thus the manufacturing of the structured carbide and CDC can be performed at lower costs.     

Migration of Bisphenol-A into packaged food simulants: Development of a novel MAE-LDS-ME strategy for the investigation of storage time and temperature

In this research, migration of bisphenol A from epoxy resin into 64 food simulants including tuna fish cans, eggplant cans and cherries cans have been measured. The effective of storage time in the range 0–180 days and storage temperature at 25 and 45°C were investigated. Microwave-assisted extraction and low-density solvent based on microextraction followed by high-performance liquid chromatography has been applied to analyze migrated-BPA. The limit of detection 2.7 ng ml⁻¹ and limit of quantification 9.33 ng ml⁻¹ were obtained for the proposed method. The results confirmed that the migration of BPA has been increased with raising the storage time and temperature. Also, the migration of BPA in oily simulant was higher than acidic simulant. The migrated-BPA concentration range has been measured in the range 3.42–4165 ng ml⁻¹. The highest amount of migrated-BPA has been found for simulant of tuna fish cans at 45°C and the lowest amount of migrated-BPA has been detected for simulant of cherries cans at 25°C.     

A study on the concentration dependence of excimer formation in pyrenyl labelled polystyrene solutions

The fluorescence of pyrenyl labelled polystyrene has been investigated. The ratio of excimer to monomer intensities (I_e/I_m) is found to vary tortuously with increasing concentration (C) and displays two critical concentration points, C⁺ at about 3.2 × 10⁻² g ml⁻¹ and C_m at about 0.32 g ml⁻¹. In the region C⁺ < C < C_m, an abrupt increase of I_e/I_m is revealed because of intermolecular interaction. At C > C_m, the sharp decrease of I_e/I_m is ascribed to entanglements of polymer chains. © 1999 Society of Chemical Industry     

Synthesis of molecularly imprinted polymer by suspension polymerization for selective extraction of p-hydroxybenzoic acid from water

Molecularly imprinted polymer (MIP) for selective extraction of p-hydroxybenzoic acid (p-HB) was synthesized by suspension polymerization using p-HB as template, 4-vinyl pyridine as functional monomer and ethylene glycol dimethacrylate as crosslinker. As characterized by scanning electron microscopy, the MIP particles are spherical, with size ranging from 1 to 8 μm. Compared with the non-imprinted polymer (NIP), the MIP shows higher binding capacity toward p-HB: maximum binding capacity for p-HB being 8.07 μmol g⁻¹ over MIP and 3.88 μmol g⁻¹ over NIP. The adsorption of p-HB on MIP follows the Freundlich model and displays pseudo-second-order kinetics. The results of selective and competitive binding experiments confirm that the molecularly imprinted sites have excellent recognition ability toward p-HB. The results reveal that the MIP is a promising adsorbent for selective extraction of p-HB from water samples. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46984.     

Stability,structure, and antioxidant activity of astaxanthin crystal from Haematococcus pluvialis

Crystallized anthaxanthin was prepared through the cleaning crystallization method and the stabilities during thermal, lighting, and pH treatment, and antioxidant activities in vitro were evaluated. The structural characterizations of astaxanthin crystal were verified by ¹H, ¹³C NMR, and XRD analysis. The stability data showed that the astaxanthin crystal was more sensitive to heat, light, and pH compared to oleoresin. The sucrose had no outstanding influence on the astaxanthin crystal, while the stability of astaxanthin oleoresin slightly increased with the increase of sugar concentration. The XRD and nuclear magnetic resonance spectra elucidated that the astaxanthin crystal was all trans structure. The astaxanthin crystal showed the dominant 1,1′-diphenyl-2-picrylhydrazyl (IC₅₀ 18.65 μmol L⁻¹), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt˙⁺(21.1 μmol L⁻¹), •OH (IC₅₀ 49.46 μmol L⁻¹) and ferric reducing antioxidant power (IC₅₀ 81.60 μmol L⁻¹) activities. The investigated results would be helpful for improving the development of astaxanthin crystal in food products.     

Optimization of ultrasound-assisted extraction of bioactive compounds from B. forficata subsp. Pruinosa

Extracts containing bioactive compounds were obtained from Bauhinia forficata leaves by ultrasound-assisted extraction (UAE) with three different solvents (n-hexane, ethyl acetate, and ethanol) and were compared with those obtained by a conventional method (maceration). Box-Behnken experimental design was applied to examine and optimize the effect of the extraction temperature (40°C-60°C), power (20%-80%), and sample to solvent ratio (1:10 to 1:20 (w/v)) on the total phenolic content (TPC), total flavonoid content (TFC), and the ferric reducing antioxidant power (FRAP) of B. forficata leaf extracts. This experimental design generated second-order polynomial models, which accurately describe the experimental data, allowing the prediction of optimal conditions for the investigated responses. Optimal extraction was achieved under the following conditions: 80% power, temperature of 41°C, and a 1:20 sample to solvent ratio. Under these conditions, the experimental yield was 8.33 ± 0.32%, total phenolic content was 59.47 ± 0.71 mg GAE · g_extract⁻¹, total flavonoid content was 62.30 ± 3.38 mg QE · g_extract⁻¹, and the ferric reducing antioxidant power was 726.7 ± 15.7 μmol Fe(II)EQ · g_extract⁻¹, which were close to the predicted values, which validated the models. The major compounds found in B. forficata extracts were tocopherols, phytol, heneicosane, and β-Sitosterol.     

Is PVC in House Fires the Great Unknown Source of Dioxin?

An estimate of the annual generation of polychlorodibenzodioxins and furans (PCDD/F) in the United States as a result of PVC burning in house fires is made using building data and fire loss statistics and soot and ash samples obtained from laboratory experiments and building fires involving PVC. Using conservative estimates for construction, fire involvement and formation, dioxin generation from PVC in house fires is estimated to be in the range of 0.074 to 8.6g TEQ yr⁻¹ as soot, 0.4 to 14g TEQ yr⁻¹ as ash, and thus 0.47 to 23g TEQ yr⁻¹ total. The maximum likelihood estimate is approximately 0.3g TEQ yr⁻¹ as soot and 1g TEQyr⁻¹ as ash. Any of these estimates constitutes a minuscule fraction of the 9300g annual air emissions or the 20000–50000g (TEQ) annual deposition from the air estimated by EPA.     

Biocatalysis of Chlorophyllase in Ternary Micellar Systems Using Pheophytins as Substrates

The partially purified chlorophyllase, obtained from the alga Phaeodactylum tricornutum, was assayed for its hydrolytic activity towards the pheophytin in ternary micellar systems of hexane/Tris–HCl/surfactant. A wide range of surfactants, sorbitans (Span 20, 40, 60, 80 and 85) and polysorbates (Tween 20, 40, 60, 80 and 85), was used. The use of either 50 μmol dm⁻³ of Span 85 or 1 μmol dm⁻³ of Tween 80 increased the hydrolytic activity of chlorophyllase by 110 and 23%, respectively. The optimum values of pH, enzyme content, incubation time and temperature for the hydrolytic activity of chlorophyllase were determined as 8·25, 8·00 μg protein cm⁻³, 60 min and 27·5°C, respectively. The V_max and K_m values were 6·91 nmole hydrolyzed pheophytin mg⁻¹ protein min⁻¹ and 47·2 nmole pheophytin dm⁻³, respectively, in the Span 85 medium and 10·04 and 121·00, respectively, in the Tween 80 medium. The addition of optimized amounts of individual membrane lipids, L -α-phosphatidylcholine, L -α-phosphatidyl-DL -glycerol and β-carotene increased the hydrolytic activity of chlorophyllase by 50, 36 and 10%, respectively, for Span 85 and 30, 48 and 15%, respectively, for Tween 80. Phytol showed a competitive inhibitory effect on chlorophyllase activity in both Span and Tween systems with a K_i value of 15·5 and 14·3 μmol dm⁻³, respectively. High-performance liquid chromatography and spectrophotometry analyses were used to characterize the end-products of chlorophyllase hydrolytic reaction. © 1997 SCI.