Factorial Design Optimization of Solid-Phase Microextraction for High-Performance Liquid Chromatography−Ultraviolet Spectrometry Analysis of Polycyclic Aromatic Hydrocarbons in Cigarette Filter Tar

A simple and rapid procedure for the determination of polycyclic aromatic hydrocarbons (PAHs) in cigarette filter tar using solid-phase microextraction (SPME) was developed. The analysis was carried out using high-performance liquid chromatography equipped with an ultraviolet detector. The effects of the SPME experimental parameters on the extraction recovery were studied simultaneously using a central composite design (CCD) after a 2^6?2 fractional factorial experimental design. The SPME variables of interest were the extraction temperature, the extraction time, and the stirring speed, as well as the pH and the concentrations of NaCl (%, w/v) and acetonitrile (ACN). The optimal SPME conditions were as follows: an extraction temperature of 65°C, an extraction time of 50 min, a stirring speed of 800 rpm, 0% NaCl (w/v), 10% ACN in the sample, and a source pH of 8.0. The extraction calibration plots were linear over the range of 0.25?20 ng mL^?1 (r² > 0.9912) and the limits of detection (LODs) for the 6 PAHs studied were from 0.17–5.02 ng cigarette^?1. The relative standard deviation (RSD) ranged from 7.1–13.5% for intra-day variation and from 8.5–18.4% for inter-day variation. The performance of the proposed method was evaluated for extraction and determination PAHs in real samples (various brands of cigarettes). The total amounts of all of the studied PAHs found in the filter tar of the three brands of cigarettes were 320.2, 17.9, and 66.7 ng cigarette^?1, respectively.     

Degradation of toluidine red,an oil soluble azo dye by Halomonas strain IP8 at alkaline condition

A salt tolerant bacteria, Halomonas strain IP8, was used for the degradation of an oil soluble azo dye, Toluidine Red (C.I. no. 12120). The effect of different culture conditions such as initial dye concentration, pH, NaCl percent (w/v) and temperature were studied at static condition using the one-factor-at-a-time method (OFAT) method as optimization technique. According to the results, the optimized conditions were 25?mg/l dye concentration, pH 9.5, 5% (w/v) NaCl, and temperature 35?°C. The decolorization mechanism was analyzed through UV–vis spectrophotometric method, high-performance liquid chromatography (HPLC), and gas chromatography-mass spectrometer (GC-MS) analyses. UV–vis scan of supernatants before and after treatment suggested that decolorization was accrued under degradation mechanism rather than inactive surface adsorption. HPLC analysis confirmed this conclusion. The identified metabolite from GC-MS results was 1-diazo 2-naphtol at m/z 170?±?1. A pathway was proposed for dye degradation based on the identified fragment by GC-MS analysis.     

Enhancing dewaterability of sewage sludge by the application of tween-20 during bioleaching: Performance evaluation and mechanistic study

Dewatering is recognized as an important method for treating sewage sludge before its disposal. In this paper, the nonionic surfactant Tween-20 was used for the first time to improve the dewaterability of sewage sludge during bioleaching. The specific resistance to filtration (SRF), water content (WC) and bound water content (BW) of the sludge cake were used to evaluate sludge dewaterability. The results indicated that a 1?g/L Tween-20 dosage with an inoculum ratio of 20%, a S⁰ dosage of 2?g/L and a FeSO₄?·?7H₂O dosage of 10?g/L provided oxidation efficiencies up to 100% for Fe²⁺ and 65.8% for S⁰. The SRF of the bioleached sludge decreased to as low as 0.81?×?10¹²?m/kg from the initial 12.6?×?10¹²?m/kg for raw sludge. A WC of 47.16% was achieved while 48.1% of BW was released during bioleaching. The results from this study indicate that adding of an appropriate amount of Tween-20 to sewage sludge is a promising method to enhance dewaterability by bioleaching.     

Spectrophotometric study of the complexation equilibria of iron(III) with 3-hydroxypicolinic acid and determination of iron in pharmaceutical preparations

The complexation equilibria of iron(III) with 3-hydroxypicolinic acid (hypa) have been studied spectrophotometrically in 40% (v/v) ethanol—water medium at 25°C and an ionic strength of 0.1 M NaClO₄. The equilibria occurring in solution were established and the basic characteristics of the complexes formed were determined. The spectral study of the reaction solutions containing equimolar concentrations or an excess of one component in the pH range 1.5 to 10.5 gave the evidence for the formation of [FeLH]²⁺, [FeL]⁺ and [FeL₂]^? complex species, depending upon the pH of the medium (LH₂ symbolising the molecular form of hypa). The possible complex transitions that occur in solution were demonstrated using graphical and logarithmic analysis of the absorbance—pH graphs. A simple, rapid, sensitive and selective method for spectrophotometric determination of trace levels of iron(III) was proposed based on the formation of Fe(hypa)₂ complex at pH 5.5 (λ = 440 nm, ? = 1.5 × 10⁴ dm³ mol^?1 cm^?1). The interference of a large number of foreign ions was investigated. The method has been applied successfully to the analysis of multivitamin and mineral preparations containing iron.     

Modeling Kinetics of Anaerobic Co-Digestion of Poultry Litter and Wheat Straw Mixed with Municipal Wastewater in a Continuously Mixed Digester with Biological Solid Recycle Using Batch Experimental Data

The half-saturation rate coefficient and maximum rate constant in the Monod model, yield coefficient defined as the ratio of microbial mass to substrate mass, and endogenous decay coefficient are important kinetic parameters for design of anaerobic digestion. These parameters are usually determined from a continuous stable operation of anaerobic digestion, which is more difficult and complex than batch operation in laboratory scale. In this study, a novel method has been developed to determine those parameters from data of batch experiments. To verify this method, kinetics of batch anaerobic co-digestion of poultry litter and wheat straw mixed with municipal wastewater at three total solid (TS) levels (2, 4, and 8% TS) and 50% volatile solid (VS) of wheat straw (VSWS) were investigated. The results showed that the maximum specific methane volume (209?mL (initial g?VS)^?1)) was reached at 4% TS of 50% VSWS. Using the developed method, the kinetic parameters of endogenous decay coefficient, yield coefficient, maximum rate constant, and half-saturation coefficient were determined to be between 0.57?×?10^?3 and 1.2?×?10^?3?d^?1, 0.00938 and 0.0644?g volatile suspended solid (VSS) (VS)^?1, 1.394 and 13,797?d^?1, and 1.6?×?10^?8 and 99,996?g. The kinetic parameters obtained were used to simulate kinetic behaviors of a continuous mixed digester with biological solid recycle. The simulated results showed that the dilution rate was very significant for methane volume produced, VS and VSS concentrations in digestion operation. The maximum methane volume could be predicted to be 3071 and 4152?mL for 2 and 4% TS, respectively.     

Alkaline hydrolysis of cinnamaldehyde to benzaldehyde in the presence of β‐cyclodextrin

A facile, novel, and cost‐effective alkaline hydrolysis process of cinnamaldehyde to benzaldehyde under rather mild conditions has been investigated systematically in the presence of β‐cyclodextrin (β‐CD), with water as the only solvent. β‐CD could form inclusion complex with cinnamaldehyde in water, with molar ratio of 1:1, so as to promote the reaction selectivity. The complex has been investigated experimentally and with computational methods. ¹H‐NMR, ROESY, UV–Vis, and FTIR have been utilized to analyze the inclusion complex. It shows that the equilibrium constant for inclusion (Ka) is 363 M^?1, and the standard Gibbs function for the reaction, ΔγG (298 K), is ?14.6 kJ mol^?1. In addition, the structures of the proposed inclusion compounds were optimized with hybrid ONIOM theory. Benzaldehyde could be obtained at an yield of 42% under optimum conditions [50°C, 18 h, 2% NaOH (w/v), cinnamaldehyde:β‐CD (molar ratio) = 1:1]. To explain the experimental data, NMR, FTIR, and elemental analysis results were used to determine the main reaction by‐product 1‐naphthalenemethanol. A feasible reaction mechanism including the retro‐Aldol condensation of cinnamaldehyde and the Aldol condensation of acetaldehyde and cinnamaldehyde in basic aqueous β‐CD solution has been proposed. The calculated activation energy for the reaction was 45.27 kJ mol^?1 by initial concentrations method. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

A Rapid Method for Simultaneous Analysis of Lignan and γ‐Tocopherol in Sesame Oil by Using Normal‐Phase Liquid Chromatography

A novel method for rapid and simultaneous analysis of three lignans and γ‐tocopherol in sesame oil has been established based on a one‐step solvent extraction followed by normal‐phase liquid chromatography. The briefness of the experimental procedure, use of 5 mL of n‐hexane/isopropanol (98:2, v/v) for extraction without any further cleanup process, short analysis time (10 min), and excellent sensitivity and selectivity demonstrated the advantages of this practical and efficient method. All the analytes exhibited satisfactory recoveries ranging from 95.4 to 103.4% at three spiked levels, with the relative SD ranging from 1.1 to 4.4%. The limits of quantitation of this method for four analytes were in the range of 0.3–1.0 μg g^?1. The validated method was successfully applied to the coinstantaneous determination of lignan and γ‐tocopherol in five real sesame oil samples. Furthermore, the results of this study were compared with previously reported method and standard method.     

Synthesis of ion-selective imprinted polymer for manganese removal from environmental water

In this study, ion-imprinted polymer was prepared for manganese(II) by formation of binary (1-(2-pyridylazo)-2-naphthol) complex in methanol (porogen) following copolymerization with 4-vinylpyridine (VP), ethyleneglycoldimethacrylate (EDMA), and 2,2??-azobisisobutyronitrile (AIBN) as a functional monomer, cross-linking agent, and initiator, respectively. The standardized effects of the independent variables and their interactions were also investigated using Pareto chart. Results of the two-level fractional factorial design (2^4-1) based on an analysis of variance demonstrated that only pH of solution, amount of polymer, and adsorption time were seen to be statistically significant. For optimization of manganese removal from aqueous solution by manganese-imprinted polymer (Mn-IP) a three-factor, three level Box-Behnken design techniques combining with response surface methodology (RSM) was used on 15 different experimental data obtained in a batch study. The significance of independent variables and their interactions were tested by the analysis of variance (ANOVA) with 95% confidence limits. The optimal conditions were 9.7, 44.4?mg, and 19.1?min for pH of solution, amount of polymer, and adsorption time, respectively. Under the optimized experimental conditions, the detection limit of the proposed procedure followed by ICP-OES was found to be 0.6???g?L^?1. Furthermore, the distribution ratio and selectivity coefficients of manganese and other selected ions were investigated. The method was applied to the determination of manganese in water samples.     

Preparation and characterization of carboxymethyl starch under ultrasound‐microwave synergistic interaction

Using native cassava starch as raw materials, carboxymethyl starch (CMS) was prepared by ethanol solvent method under the ultrasound‐microwave synergistic interaction. And the structure of CMS was characterized employing Fourier transform infrared (FTIR) spectrometer, scanning electron microscopy (SEM), X‐ray diffraction (XRD) and thermogravimetric analyzer. Typically, the optimal synthesis conditions for the preparation process confirmed by orthogonal experiment L₁₈ (6¹ × 3⁶) were shown as follows: the ultrasonic treatment temperature was fixed to 35°C and two steps alkalization was employed; the ultrasonic time was 40 min before alkalizing and the ultrasonic power was 220 W; the amount of sodium hydroxide was 8.8 g, the microwave alkalization time was 2 min; the amount of monochloroacetic acid was 11.34 g; the amount of 95% (v/v) ethanol was 70 mL; the microwave etherification time was 3 min. The degree of substitution of prepared CMS was 1.089 ± 0.041, which was increased 30.4% compared with the prepared sample without ultrasound‐microwave synergistic treatment. FTIR results showed that the strong ? COO? characteristic absorption peaks of the stretching vibration were observed at 1613 and 1421 cm^?1, which proved that the carboxymethylation of cassava starch was occurred. SEM results suggested that there were many cracks and dents on CMS granules; and, XRD results indicated that the carboxymethylation of starch occurred both in amorphous region and crystalline region, the noticeable damage of crystalline region by carboxymethylation was observed. Thermogravimetric analysis (TG) and derivative TG showed that thermal stability of CMS changed better compared with native starch. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40906.     

Oxidation-precipitation of magnetic Fe3O4/AC nanocomposite as a heterogeneous catalyst for electro-Fenton treatment

Abstract

The oxidation-precipitation method was used for the synthesis of Fe₃O₄/AC. The characterization of the catalyst was accomplished by XRD, FT-IR, FE-SEM, BET, and VSM techniques. The obtained results indicated that magnetite nanoparticles were successfully prepared with cubic spinel structures and uniform distribution on the surface of activated carbon by the oxidation-precipitation method. The effect of operating parameters was evaluated to determine the optimum operating condition for the electro-Fenton (EF) removal of catechol as a phenolic pollutant model. At the optimum operating conditions (pH 3, Fe₃O₄/AC: 0.9?g L^?1, Catechol: 8.0?×?10^?4?mol L^?1 at I: 120?mA), the catechol and COD removal reached 98.2 and 76.1% in 120?min, respectively. Only 2.1% of ferrous and 3.44% of ferric ions were leached into the solution. Regarding the results from utilization of oxidant scavengers (isopropanol and BQ), it can be inferred that hydroxyl radical (responsible for 57% catechol removal) and superoxide anion radical (responsible for 40% catechol removal) is the main oxidants in acidic (pH 3) and basic (pH 10) conditions, respectively. The kinetics of EF removal of catechol was studied and the rate constant for the pseudo-first-order kinetic model was found to be 3.37?×?10^?2min^?1 (R² = 0.9924). The GC-MS analysis was carried out to detect the intermediate products and a possible degradation mechanism was proposed. The reusability of Fe₃O₄/AC was examined for six cycles. It can be concluded that Fe₃O₄/AC is an applicable ultimate catalyst for EF removal of organic pollutants.     

Inherent safer design for chemical process of 1,4-dioldiacetate-2-butene oxidized by ozone

Abstract

Oxidation reaction is the typical thermal runaway reaction, and the reaction of 1, 4-dioldiacetate-2-Butene oxidized by ozone was investigated in this study. Firstly, the thermal hazards of the oxidative exothermic reactions were identified and evaluated combined process risk assessment method. The Qualitative Assessment for Inherently Safer Design (QAISD) was used to identify the risk of the reaction process. Meanwhile, the Reaction Calorimeter (RC1^e) was used to obtain the thermal properties of the oxidation reaction. Then the inherent safer designs (ISD) were proposed according to the risk assessment results to increase the level of safety of chemical industry technique. 1) ISD I: reaction temperature was improved to –5?°C, and ventilation rate was improved to 200?L?h^?1. 2) ISDII: using a tubular reactor as reaction vessel. The results indicated that the severity of the reaction hazard was reduced by 43%, and safety was improved significantly via two ISDs. Moreover, the inherent safety level of the reaction was increased by 63% and 43.4% via ISD Iand II, respectively. The reaction process get closer to inherent safety theories of “minimize,” “substitute,” and “moderate”.     

Development of a method to determine Ni and Cd in biodiesel by graphite furnace atomic absorption spectrometry

This paper proposes a low cost, simple, fast method for determining Ni and Cd in biodiesel samples by graphite furnace atomic absorption spectrometry (GFAAS). The method was evaluated in biodiesel from different sources. Tungsten was used as a permanent modifier and the samples were prepared in the form of microemulsions, by mixing about 0.5 g of biodiesel with 5 g of surfactant (Triton X-100) in volumetric flasks and completing the volume with HNO₃ 1% (v/v). The detection limits obtained for Ni and Cd in microemulsions were ≤0.9 and 0.1 μg L⁻¹, respectively. The relative standard deviation (% R.S.D., n = 12) was ≤8.20% for Ni (washed animal fat sample) and ≤4.71% for Cd (sunflower oil sample). Accuracy was checked based on addition and recovery experiments, which yielded recovery rates varying from 93% to 108% for Ni and from 98% to 116% for Cd. Sample preparation is rapid and easy, and the use of an inorganic standard for calibration makes this sample preparation procedure suitable for routine applications.     

Solid-phase extraction for simultaneous separation and preconcentration of Fe(III) and Zn(II) traces using three chelatants and Ramelak bark-derived activated carbon as a new bio-sorbent

This article introduces a comparative study for the simultaneous separation and preconcentration of Fe(III) and Zn(II) traces in various water samples using three well-known ligands as chelating agents and activated carbon (AC) derived from Ramelak bark as a new bio-sorbent prior to the determination by ?ame atomic absorption spectrometry. The chelating agents were 4,4’-[(4-Cyano-phenyl)methylene]bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (CMBM), diethyldithiocarbamate (DDTC) and ammonium pyrrolidine dithiocarbamate (APDC). CMBM was synthesized by a procedure reported in the literature. The newly prepared AC was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared (FTIR) Spectrometry. The analytical parameters affecting the separation efficiency of the analytes including pH, shaking time, chelating agent volume (concentration), sorbent mass, sample ?ow rate and elution conditions were investigated and discussed. Common coexisting ions did not seriously interfere with the separation, showing the good selectivity of the proposed method. The calibration graph was linear in the range of 0.35–70, 0.50–80, 0.9–100, 0.55–75, 0.75–90 and 1.0–120 ng mL^?1 for Fe-CMBM, Fe-DDTC, Fe-APDC, Zn-CMBM, Zn-DDTC and Zn-APDC, respectively. Under optimized conditions, the limits of detection were 0.11, 0.13, 0.27, 0.16, 0.22 and 0.30 ng mL^?1 for Fe-CMBM, Fe-DDTC, Fe-APDC, Zn-CMBM, Zn-DDTC and Zn-APDC, respectively. The proposed method has been applied to the determination of Fe(III) and Zn(II) in different water samples with satisfactory recovery percentages. The developed method, validated with standard reference materials, was used successfully in determining the concentrations of metal ions in water samples.     

Effect of microwave sintering on the properties of copper oxide doped Y-TZP ceramics

The effect of various amounts of copper oxide (CuO) up to 1?wt% on the densification behaviour and mechanical properties of 3?mol% yttria-tetragonal zirconia polycrystal (Y-TZP) were studied by using microwave (MW) sintering method. The MW sintering was performed at temperatures between 1100?°C and 1400?°C, with a heating rate of 30?°C/min. and holding time of 5?min. The beneficial effect of MW in enhancing densification was also compared for the undoped and 0.2?wt% CuO-doped Y-TZP when subjected to conventional sintering (CS) method. The results showed that significant enhancement in the relative density and Vickers hardness were observed for the undoped Y-TZP when MW-sintered between 1100?°C and 1250?°C. It was revealed that the 0.2?wt% CuO-doped Y-TZP and MW sintered at 1250–1300?°C could attain ≥?99.8% of theoretical density, Vickers hardness of about 14.4?GPa, fracture toughness of 7.8 MPam^1/2 and exhibited fine equiaxed tetragonal grain size of below 0.25?µm. In contrast, the addition of 1?wt% CuO was detrimental and the samples exhibited about 50% monoclinic phase upon sintering coupled with poor bulk density and mechanical properties. The study also revealed that the addition of 0.2?wt% CuO and subjected to conventional sintering produced similar densification as that obtained for microwave sintering, thus indicating that the dopant played a more significant role than the sintering method.     

高效液相色谱法测定1,1,3-三甲基-3-苯基茚满

采用SpherisorbC18色谱柱,以甲醇 水(95:5)为流动相,流速1 0ml.min 1,254nm为检测波长,建立测定1,1,3 三甲基 3 苯基茚满的高效液相色谱法。进样量在1 6～32μg范围内线性关系良好(r=0.9998)。回收率在98%～102%,RSD不大于0.73%。方法操作简单,分析快速、准确,适用于1,1,3 三甲基 3 苯基茚满的质量控制分析。     

Cloud Point Extraction and Preconcentration for the Determination of Cu and Ni in Natural Water by Flame Atomic Absorption Spectrometry

Abstract

In this work, a new cloud point extraction (CPE) method was developed for the separation and preconcentration of copper and nickel. The analyte was complexed with 3‐[(8‐{[(E)‐2‐hydroxyimino‐1‐methylpropylidene] amino}‐1‐naphthyl) imino]‐2‐butanone oxime (H₂mdo) in the initial aqueous solution and octylphenoxy polyethoxy ethanol (Triton X‐114) was added as a surfactant. After phase separation, based on the cloud point in the mixture, and dilution of the surfactant‐rich phase with methanol containing 0.1 mol l^?1 HNO₃, the enriched analytes were determined by flame atomic absorption spectrometry. After optimization of the complexation and extraction conditions (i.e. pH=8.5, H₂mdo=3×10^?4 mol l^?1, Triton X‐114=0.1% (w/v)) the enhancement factors of 65 and 59 and detection limits of 0.14 and 0.2 ng ml^?1 were obtained for copper and nickel respectively. The proposed method was applied to the determination of copper and nickel in several natural water samples with satisfactory results.     

A new,highly potent 1,8‐naphthalimide‐based fluorescence turn‐off chemosensor capable of detecting Cu(II) ions in real‐world water samples

The synthesis of a new 1,8‐naphthalimide‐based fluorescence turn‐off chemosensor for the effective detection of Cu(II) ions is reported. The chemosensor MAST was characterised by mp, Fourier Transform‐infrared (FTIR), ultraviolet‐visible (UV‐vis), fluorescence, ¹H‐NMR and ¹³C‐NMR spectroscopy, and mass spectrometry. After treatment with Cu(II) ions in coexistence with various competitive metal ions in a dimethylsulphoxide (DMSO)/4‐(2‐hydroxyethyl)‐1‐piperazineethanesulphonic acid (HEPES) buffer solution (v/v, 1:1; pH 7.4), the chemosensor demonstrated high selectivity towards Cu(II) ions and a fluorescence quenching of 83.67% was observed. In addition, a good linear response for the chemosensor detecting Cu(II) ions was obtained over the concentration range 0.2–1 μm . The combined results of UV‐vis and fluorescence titrations with the Job plot yielded a 1:1 stoichiometric interaction of the chemosensor with Cu(II) ions. The association constant and detection limit were calculated as 1.37 x 10⁶ m ^?1 and 1.69 x 10^?8 m , respectively. Based on results, the quenching response of MAST towards Cu(II) ions could be ascribed to the reverse‐photoinduced electron transfer (PET) mechanism. Finally, the proposed chemosensor was applied to quantify Cu(II) ions in real‐world water samples and excellent recovery rates of 98–105.8% were obtained.     

Molecular absorption spectrophotometric method for the determination of phosphorus in biodiesel

A molecular absorption method is proposed for the determination of phosphorus in biodiesel. The samples are mineralized using an ashing procedure at 550 °C followed by dissolution of the residue. The analytical procedure is based on the formation of a blue molybdenum complex. 1-amino-2-naphthol-4-sulfonic acid is used as reducing agent. The method was applied to biodiesel samples prepared from soy, canola and sunflower oils and from bovine fat. The limit of detection is 0.57 mg P kg⁻¹ and the limit of quantification is 1.7 mg P kg⁻¹. The observed mean relative standard deviation is about 5%. The simplicity of the procedure added to its precision, accuracy and low cost suggest that it is an excellent option for the determination of phosphorus in biodiesel.     

Study of the bio‐production of carotenoids by Sporidiobolus salmonicolor (CBS 2636) using pre‐treated agro‐industrial substrates

BACKGROUND: The increasing industrial demand for carotenoids has aroused interest in their bio‐production, and the need to reduce production costs has encouraged the use of low cost industrial substrates, such as agro‐industrial residues. Thus the objective of this research was the bio‐production of carotenoids by Sporidiobolus salmonicolor using agro‐industrial substrates (corn steep liquor and sugarcane molasses), pre‐treated with acids (sulphuric and phosphoric). RESULTS: Bio‐production was carried out in an orbital shaker using a 10% (v/v) inoculum, incubation at 25 °C, and agitation at 180 rpm for 120 h in a non‐illuminated environment. The carotenoids were recovered using liquid N₂ combined with dimethylsulphoxide for cell rupture, and an acetone/methanol mixture (7:3 v/v) for extraction. CONCLUSION: The complete second‐order design allowed for optimisation of the carotenoid concentration obtained from industrial substrates pre‐treated with acids (sulphuric and phosphoric), obtaining a total carotenoid content of 541.5 µg L^?1 using 10 g L^?1 sugarcane molasses, 5 g L^?1 corn steep liquor and 5 g L^?1 yeast hydrolysate at 25 °C, with agitation at 180 rpm and an initial pH of 4.0. Copyright © 2008 Society of Chemical Industry     

Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Eight Kinds of Vegetable Oils in Solution

A detailed kinetic study was performed for the reaction of the aroxyl radical (ArO?) with eight vegetable oils 1–8, which contain different concentrations of α‐, β‐, γ‐, and δ‐tocopherols and ‐tocotrienols (‐Tocs and ‐Toc‐3s). The second‐order rate constants (k_s) and aroxyl radical absorption capacity (ARAC) values for the reaction of ArO? with vegetable oils 1–8 (rice bran 1, perilla 2, rapeseed 3, safflower 4, grape seed 5, sesame 6, extra virgin olive 7, and olive oils 8) were measured in ethanol/chloroform/D₂O (50:50:1, v/v/v) solution at 25 °C using stopped‐flow spectrophotometry. The k_s value (16.1 × 10^?3 L g^?1 s^?1) of rice bran oil 1 with the highest activity was 8.0 times larger than that (2.02 × 10^?3) of olive oil 8 with the lowest activity. The concentrations (in mg 100 g^?1) of α‐, β‐, γ‐, and δ‐Tocs and ‐Toc‐3s contained in the vegetable oils 1–8 were determined using high performance liquid chromatography‐mass spectrometry/mass spectrometry (HPLC‐MS/MS). From these results, it was clarified that the ArO?‐scavenging rates (k_s) (i.e., the relative ARAC value) obtained for the vegetable oils 1–8 may be well explained as the sum of the product of the rate constant () and the concentration ([AOH‐i]/10⁵) of AOH‐i (Tocs and Toc‐3s) included in vegetable oils. The results suggest that the ARAC assay method might be used in the evaluation of antioxidant activity of general food extracts.