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1.
Alain Bitar Tarek Ghaddar Amal Malek Tharwat Haddad Imad Toufeili 《Journal of the American Oil Chemists' Society》2008,85(7):641-646
The odor detection thresholds of carvacrol (5-isopropyl-2-methyl-phenol), thymol (2-isopropyl-5-methyl-phenol) and p-cymene 2,3-diol (2,3-dihydroxy-4-isopropyl-1-methyl-benzene) in sunflower oil, determined by the three-alternative, forced-choice
procedure, were 30.97, 124 and 794.33 mg kg−1, respectively. Sunflower oil containing 13, 70, or 335 mg kg−1 of carvacrol, thymol or p-cymene 2,3-diol, respectively, was judged to be similar (P < 0.01) in taste and odor to its antioxidant-free counterpart. The rate constant of sunflower oil oxidation, measured from
the increase in peroxide value during storage at 25 °C, was 9.2 × 10−9 mol kg−1 s−1 while the rate constants were 9.3 × 10−9, 9.8 × 10−9, and 4.3 × 10−9 mol kg−1 s−1 in the presence of 13 mg kg−1 carvacrol, 70 mg kg−1 thymol, and 335 mg kg−1
p-cymene 2,3-diol, respectively. At a level of 335 mg kg−1, p-cymene 2,3-diol did not impart flavor taints and effected a 46.7% reduction in the rate of oxidation of sunflower oil. These
findings indicate that the diphenolic p-cymene 2,3-diol could potentially replace synthetic antioxidants and is a valuable addition to the antioxidants used by the
food industry in its quest to meet consumer demands for synthetic-additives-free and ‘natural’ foods. 相似文献
2.
Epoxidation of karanja (Pongamia glabra) oil by H2O2 总被引:1,自引:0,他引:1
Vaibhav V. Goud Narayan C. Pradhan Anand V. Patwardhan 《Journal of the American Oil Chemists' Society》2006,83(7):635-640
Epoxidation of karanja oil (KO), a nondrying vegetable oil, was carried out with peroxyacetic acid that was generated in situ from aqueous hydrogen peroxide and glacial acetic acid. KO contained 61.65% oleic acid and 18.52% linoleic acid, respectively,
and had an iodine value of 89 g/100 g. Unsaturated bonds in the oil were converted to oxirane by epoxidation. Almost complete
epoxidation of ethylenic unsaturation was achieved. For example, the iodine value of the oil could be reduced from 89 to 19
by epoxidation at 30°C. The effects of temperature, hydrogen peroxide-to-ethylenic unsaturation ratio, acetic acid-to-ethylenic
unsaturation ratio, and stirring speed on the epoxidation rate and on oxirane ring stability were studied. The rate constant
and activation energy for epoxidation of KO were 10−6 L·mol−1·s−1 and 14.9 kcal·mol−1, respectively. Enthalpy, entropy, and free energy of activation were 14.2 kcal·mol−1, −51.2 cal·mol−1·K−1, and 31.1 kcal·mol−1, respectively. The present study revealed that epoxides can be developed from locally available natural renewable resources
such as KO. 相似文献
3.
Characterization of yam bean (Pachyrhizus spp.) Seeds as potential sources of high palmitic acid oil
W. J. Grüneberg F. D. Goffman L. Velasco 《Journal of the American Oil Chemists' Society》1999,76(11):1309-1312
Seeds from 22 accessions of the yam bean species Pachyrhizus ahipa (14 accessions), P. erosus (5), and P. tuberosus (3) were investigated for oil and protein contents, fatty acid composition of the seed oil, and the total tocopherol content
and composition. Plants from the accessions were grown under greenhouse conditions during one (P. erosus and P. tuberosus) or two years (P. ahipa). The pattern of the investigated seed quality traits was very similar in the three species. Yam bean seeds were characterized
by high oil (from about 20 to 28% in one environment) and protein contents (from about 23 to 34%). Seed oil contained high
concentrations of palmitic (from about 25 to 30% of the total fatty acids), oleic (21 to 29%), and linoleic acids (35 to 40%).
Levels of linolenic acid were very low, from about 1.0 to 2.5%. Total tocopherol content was relatively low in P. erosus (from 249 to 585 mg kg−1 oil) and P. tuberosus (from 260 to 312 mg kg−1 oil) compared with the levels found in P. ahipa grown under identical conditions (508 to 858 mg kg−1 oil). In all the samples, γ-tocopherol was predominant, accounting for more than 90% of the total tocopherol content. The
combination of high oil and protein contents, together with high palmitic acid, low linolenic acid, and high γ-tocopherol
concentration, makes these crops an interesting alternative as sources of high palmitic acid oil for the food industry. 相似文献
4.
Sebnem Selen Isbilir Hakki M. Ozcan Hulya Yagar 《Journal of the American Oil Chemists' Society》2008,85(3):227-233
Lipase was isolated from bay laurel (Laurus nobilis L.) seeds, some biochemical properties were determined. The bay laurel oil was used as the substrate in all experiments.
The pH optimum was found to be 8.0 in the presence of this substrate. The temperature optimum was 50 °C. The specific activity
of the lipase was found to be 296 U mg protein−1 in optimal conditions. The enzyme activity is quite stable in the range of pH 7.0–10. The enzyme was stable for 1 h at its
optimum temperature, and retained about 68% of activity at 60 °C during this time. K
m
and V
max values were determined as 0.975 g and 1.298 U mg protein−1, respectively. Also, storage stability and metal effect on lipolytic activity were investigated. Enzyme activity was maintained
for 9, 12, and 42 days at room temperature, 4 and −20 °C, respectively. Ca2+, Co2+, Cu2+, Fe2+, and Mg2+ lightly enhanced bay laurel lipase activity. 相似文献
5.
Interprovenance variation was examined in the composition of Moringa oleifera oilseeds from Pakistan. The hexane-extracted oil content of M. oleifera seeds harvested in the vicinity of the University of Agriculture, Faisalabad (Punjab, Pakistan), Bahauddin Zakariya University
(Multan, Pakistan), and the University of Sindh, Jamshoro (Sindh, Pakistan), ranged from 33.23 to 40.90%. Protein, fiber,
moisture, and ash contents were found to be 28.52–34.00, 6.52–7.50, 5.90–7.00, and 6.52–7.50%, respectively. The physical
and chemical parameters of the extracted M. oleifera oils were as follows: iodine value, 67.20–71.00; refractive index (40°C), 1.4570–1.4637; density (24°C), 0.9012–0.9052 mg/mL;
saponification value, 177.29–184.10; unsaponifiable matter, 0.60–0.83%; color (1-in. cell), 1.00–1.50 R+20.00–30.00Y; smoke
point, 198–202°C; and acidity (% as oleic acid), 0.50–0.74. Tocopherols (α, γ, and δ) accounted for 114.50–140.42, 58.05–86.70,
and 54.20–75.16 mg/kg, respectively, of the oils. The induction periods (Rancimat, 20 L/h, 120°C) of the crude oils were 9.64–10.66
h and were reduced to 8.29–9.10 h after degumming. Specific extinctions at 232 and 270 nm were 1.80–2.50 and 0.54–1.00, respectively.
The major sterol fractions of the oils were campesterol (14.13–17.00%), stigmasterol (15.88–19.00%), β-sitosterol (45.30–53.20%),
and ͤ5-avenasterol (8.84, 11.05%). The Moringa oils were found to contain high levels of oleic acid (up to 76.00%), followed by palmitic, stearic, behenic, and arachidic
acids up to levels of 6.54, 6.00, 7.00, and 4.00%, respectively. Most of the parameters of M. oleifera oils indigenous to different agroclimatic regions of Pakistan were comparable to those of typical Moringa seed oils reported in the literature. The results of the present analytical study, compared with those for different vegetable
oils, showed M. oleifera to be a potentially valuable oilseed crop. 相似文献
6.
Analytical characterization of hemp (Cannabis sativa) seed oil from different agro-ecological zones of Pakistan 总被引:2,自引:2,他引:2
Farooq Anwar Sajid Latif Muhammad Ashraf 《Journal of the American Oil Chemists' Society》2006,83(4):323-329
Cold-pressed oil content of Cannabis sativa (hemp) seeds from three different agro-ecological zones of Pakistan ranged from 26.90 to 31.50%. Protein, fiber, ash, and
moisture content were found to be 23.00–26.50, 17.00–20.52, 5.00–7.60, and 5.60–8.50%, respectively. Results of some other
physical and chemical parameters of the oil were as follows: iodine value, 154.00–165.00; refractive index (40°C), 1.4698–1.4750;
density (24°C), 0.9180–0.9270 mg ml−1; saponification value, 184.00–190.00; unsaponifiable matter, 0.70–1.25%; and color (1-in cell), 0.50–0.80 R+27.00–32.00 Y.
The induction period (Rancimat, 20 L h−1, 120°C) of the nondegummed and degummed oils ranged from 1.35 to 1.72 h and from 1.20 to 1.49 h, respectively. Specific extinctions
at 232 and 270 nm were 3.50–4.18 and 0.95–1.43, respectively. The hemp oils investigated were found to contain high levels
of linoleic acid, 56.50–60.50%, followed by α-linolenic, oleic, palmitic, stearic, and γ-linolenic acids: 16.85–20.00, 10.17–14.03,
5.75–8.27, 2.19–2.79, and 0.63–1.65%, respectively. Tocopherols (α, γ, and δ) in the nondegummed oils were found to be 54.02–60.40,
600.00–745.00, 35.00–45.60, respectively, and were reduced to 29.90–50.00, 590.00–640.00, and 30.40–39.50 mg kg−1, respectively, after degumming. The results of the present analytical study, compared with those found in the typical literature
on hempseed oils, showed C. sativa indigenous to Pakistan to be a potentially valuable nonconventional oilseed crop of comparable quality. 相似文献
7.
Reza Farhoosh Javad Tavakoli Mohammad Hossein Haddad Khodaparast 《Journal of the American Oil Chemists' Society》2008,85(8):723-729
Pistacia atlantica subsp. mutica (PAM) and kurdica (PAK) kernel oils showed significantly lower unsaturated to saturated fatty acid ratios (6.39, 6.33, respectively) and calculated
oxidizability (Cox) values (3.99, 4.13, respectively) than those of the P. vera L. cv. Ohadi (PVO) kernel oil (8.91, 4.41) samples. The highest peroxide value was observed for the PAK oil (4.07 mequiv kg−1) (PAM, 1.94; PVO, 0.37) samples. Iodine values for the PAM, PAK, and PVO oils were 104.26, 104.77, and 110.66, respectively.
The saponification number of the PVO oil was significantly greater than the PAM and PAK oils, which were statistically not
different. The unsaponifiable contents, which were composed mainly of sterols, ranged from 5.63 to 6.14%. Statistically the
total tocopherols contents of the PAM (818.58 mg α-tocopherol kg−1) and PVO (815.90 mg α-tocopherol kg−1) oils were significantly higher than that of the PAK oil (499.91 mg α-tocopherol kg−1). Total phenolics contents differed significantly, the greatest concentration was for the PAM oil (81.12 mg gallic acid kg−1), followed by the PVO (62.84 mg gallic acid kg−1) and PAK (56.51 mg gallic acid kg−1) oil samples. The wax contents of the oil samples were statistically in the same range, namely 5.67–6.48%. Oxidative stability
data indicated that the PAM oil is the most resistant to the formation of lipid oxidation products, followed by the PAK and
PVO oil samples. 相似文献
8.
Eduardo A. Rodríguez-Leyes Víctor L. González Canavaciolo David Marrero Delange Abel R. Sgambelluri Enríquez Yuliamny Adames Fajardo 《Journal of the American Oil Chemists' Society》2007,84(8):765-767
The present study targeted the whole-fruit oil yield and fatty acid composition from five of the most abundant Arecaceae species grown in Cuba. The oil yields (% dry weight), determined by the Soxhlet extraction technique with hexane, were 25.5,
5.3, 6.9, 5.4, and 6.4% for Roystonea regia, Colpothrinax wrightii, Sabal maritima, Sabal palmetto and Thrinax radiata, respectively. The free fatty acid (FFA) content varied from 2.7 to 6.8%. Fatty acid (FA) profiles of the oils indicated
that lauric acid (13.7–44.4%), myristic acid (9.4–22.4%) and palmitic acid (9.2–17.1%) as major saturated FA; whereas oleic
acid (9.6–42.7%) and linoleic acid (9.3–17.0%) as major unsaturated FA. R. regia fruit seemed the most promising among Arecaceae grown in Cuba because of its high oil yield and low oil FFA content. 相似文献
9.
Sean F. O’Keefe V. A. Wiley D. Wright 《Journal of the American Oil Chemists' Society》1993,70(9):915-917
Oil was extracted from soybeans, degummed, alkalirefined and bleached. The oil was heated at 160, 180, 200, 220 and 240°C
for up to 156 h. Fatty acid methyl esters were prepared by boron trifluoride-catalyzed transesterification. Gas-liquid chromatography
with a cyanopropyl CPSil88 column was used to separate and quantitate fatty acid methyl esters. Fatty acids were identified
by comparison of retention times with standards and were calculated as area % and mg/g oil based on 17:0 internal standard.
The rates of 18:3ω3 loss and 18:3 Δ9-cis, Δ12-cis, Δ15-trans (18:3c,c,t) formation were determined, and the activation energies were calculated from Arrhenius plots. Freshly prepared soy oil had
10.1% 18:3ω3 and no detectable 18:3c,c,t. Loss of 18:3ω3 followed apparent first-order kinetics. The first-order rate constants ranged from .0018±.00014 min−1 at 160°C to .083±.0033 min−1 at 240°C. The formation of 18:3c,c,t did not follow simple kinetics, and initial rates were estimated. The initial rates (mg per g oil per h) of 18:3c,c,t formation ranged from 0.0031±0.0006 at 160°C to 2.4±.24 at 240°C. The Arrhenius activation energy for 18:3ω3 loss was 82.1±7.2
kJ mol−1. The apparent Arrhenius activation energy for 18:3c,c,t formation was 146.0±13.0 kJ mol−1. The results indicate that small differences in heating temperature can have a profound affect on 18:3c,c,t formation. Selection of appropriate deodorization conditions could limit the amount of 18:3c,c,t produced. 相似文献
10.
Samir A. M. Abdelgaleil Magdy I. E. Mohamed Mohamed E. I. Badawy Sailan A. A. El-arami 《Journal of chemical ecology》2009,35(5):518-525
A comparative study was conducted to assess the contact and fumigant toxicities of eleven monoterpenes on two important stored
products insects—, Sitophilus oryzae, the rice weevil, and Tribolium castaneum, the rust red flour beetle. The monoterpenes included: camphene, (+)-camphor, (−)-carvone, 1-8-cineole, cuminaldehyde, (l)-fenchone, geraniol, (−)-limonene, (−)-linalool, (−)-menthol, and myrcene. The inhibitory effect of these compounds on acetylcholinesterase
(AChE) activity also was examined to explore their possible mode(s) of toxic action. Although most of the compounds were toxic
to S. oryzae and T. castaneum, their toxicity varied with insect species and with the bioassay test. In contact toxicity assays, (−)-carvone, geraniol,
and cuminaldehyde showed the highest toxicity against S. oryzae with LC50 values of 28.17, 28.76, and 42.08 μg/cm2, respectively. (−)-Carvone (LC50 = 19.80 μg/cm2) was the most effective compound against T. castaneum, followed by cuminaldehyde (LC50 = 32.59 μg/cm2). In contrast, camphene, (+)-camphor, 1-8-cineole, and myrcene had weak activity against both insects (i.e., LC50 values above 500 μg/cm2). In fumigant toxicity assays, 1-8-cineole was the most effective against S. oryzae and T. castaneum (LC50 = 14.19 and 17.16 mg/l, respectively). Structure-toxicity investigations revealed that (−)-carvone—, a ketone—, had the highest
contact toxicity against the both insects. 1-8-Cineole—, an ether—, was the most potent fumigant against both insects. In
vitro inhibition studies of AChE from adults of S. oryzae showed that cuminaldehyde most effectively inhibited enzyme activity at the two tested concentrations (0.01 and 0.05 M) followed
by 1-8-cineole, (−)-limonene, and (l)-fenchone. 1-8-Cineole was the most potent inhibitor of AChE activity from T. castaneum larvae followed by (−)-carvone and (−)-limonene. The results of the present study indicate that (−)-carvone, 1,8-cineole,
cuminaldehyde, (l)-fenchone, and (−)-limonene could be effective biocontrol agents against S. oryzae and T. castaneum. 相似文献
11.
The desulfurization of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) and their mixture by lyophilized cells
ofPseudomonas delafieldii R-8 was studied in the presence of dodecane. The desulfurization rate for 4,6-DMDBT was found to be about 40% in comparison
with that for DBT. The desulfurization process for DBT and 4,6-DMDBT proceeded simultaneously without preference for either
one. The desulfurization rate for each compound was decreased when they were mixed together. The extent of desulfurization
of 4,6-DMDBT was increased with the increase of cell concentration and the decrease of the volume ratio of oil-to-water used.
The specific desulfurization rate for 4,6-DMDBT could be reached to 10.4 mmol sulfur kg−1 (cell) h−1 [approximately 0.33 mg sulfur g−1 (cell) h−1].Pseudomonas delafieldii R-8 showed high desulfurization capability for straight-run diesel oil (containing 1,807 mg/L of sulfur). About 1,000 mg/L
of sulfur in diesel oil was removed by resting cells of this strain in 24 h of reaction. The specific desulfurization rate
was 8.75 mmol sulfur kg−1 (cell) h−1. 相似文献
12.
Mangesh G. Kulkarni Sudhirprakash B. Sawant 《Journal of the American Oil Chemists' Society》2001,78(7):719-723
The primary aliphatic alcohols n-octanol, n-decanol, and n-dodecanol have been converted to their corresponding symmetrical esters by using HBr and H2O2 in the absence of a solvent. The reaction was carried out at 30, 40, and 50°C and at mole ratios of alcohol to HBr of 1∶0.1,
1∶0.2, 1∶0.3, and 1∶0.5. The rate of the reaction was found to increase with increase in the reaction temperature and concentration
of HBr. The maximal conversion of n-octanol was 72% at 40°C and a mole ratio of n-octanol to HBr of 1∶0.5. The kinetics of the reaction have been established, and the reaction was found to be first-order
with respect to alcohol and bromine concentration in the organic phase, and second-order with respect to both. The second-order
rate constants for n-octanol, n-decanol, and n-dodecanol are 27.08, 32.58, and 37.42 mL mol−1 min−1, respectively, at 40°C. The activation energy for the esterification reaction of n-octanol was found to be 16.32 kcal mol−1. 相似文献
13.
Samia Dabbou Faten Brahmi Ameni Taamali Manel Issaoui Youssef Ouni Mohamed Braham Mokhtar Zarrouk Mohamed Hammami 《Journal of the American Oil Chemists' Society》2010,87(10):1199-1209
The effects of the contents of lipids, pigments, α-tocopherol and phenols were studied in relation to the antioxidant capacity
of five virgin olive oils obtained from five olive cultivars planted in Tunisia (Arbequina, Koroneiki, Leccino, Oueslati and
Chemchali). The antioxidant capacities were evaluated by two different radical scavenging activities: radical scavenging activity
by the DPPH assay (RSA-DPPH) and total antioxidant status by the ABTS test (TAA-ABTS). The highest contents of antioxidant
compounds (75.96, 10.34, 6.32, 15.39 and 241.52 mg kg−1 for oleic acid, O/L ratio, carotenes, chlorophylls and total phenols, respectively) were found for the Koroneiki cultivar
except for α-tocopherol and o-diphenols, which had the highest contents (369 and 160.7 mg kg−1, respectively) in the Leccino and Chemchali cultivars (cvs). Furthermore, the highest antioxidant capacity in virgin olive
oil was observed in the Koroneiki cultivar (0.24 mmol TE kg−1) followed by the Chemchali and Leccino cvs (0.22 and 0.13 mmol TE kg−1) for the TAA-ABTS test. However, the RSA-DPPH activity was higher for the Chemchali cultivar (19.9%) than for the Koroneiki
and Leccino cvs (18.4 and 13.5%, respectively). Correlation between these capacities and the oil composition revealed that
they were mainly influenced by the carotene content, followed by chlorophyll and phenolic contents where the ABTS test was
more pronounced. Then, the antioxidant capacity of the virgin olive oils was correlated with polar components and the lipid
profile which are important for its shelf life. 相似文献
14.
Walnut (Juglans regia L.) oil was extracted with compressed carbon dioxide (CO2) in the temperature range of 308 to 321 K and in the pressure range of 18 to 23.4 MPa. The influence of particle size was
also studied at a superficial velocity of 0.068 cm/s, within a tubular extractor of 0.2 L capacity (cross-sectional area of
16.4 cm2). FFA, sterol, TAG, and tocopherol compositions were not different from those of oil obtained with n-hexane. The main FA was linoleic acid (56.5%), followed by oleic acid (21.2%) and linolenic acid (13.2%). The main TAG was
LLL (linoleic, linoleic, linoleic) (24.4%), followed by OLL (oleic, linoleic, linoleic) (19.6%) and LLLn (linoleic, linoleic,
linolenic) (18.4%). The main component of sterols was β-sitosterol (85.16%), followed by campesterol (5.06%). The amount of
cholesterol was low (0.31 and 0.16% for oils extracted by n-hexane and supercritical fluid extraction, respectively. The CO2-extracted oil presented a larger amount of tocopherols (405.7 μg/g oil) when compared with 303.2 μg/g oil obtained with n-hexane. Oxidative stability determined by PV and the Rancimat method revealed that walnut oil was readily oxidized. Oil extracted
by supercritical CO2 was clearer than that extracted by n-hexane, showing some refining. A central composite, nonfactorial design was used to optimize the extraction conditions using
the software Statistica, Version 5. The best results were found at 22 MPa, 308 K, and particle diameter (Dp) −0.1 mm. 相似文献
15.
Reza Farhoosh 《Journal of the American Oil Chemists' Society》2007,84(3):205-209
Operational parameters of the Rancimat method, including oil sample size, airflow rate, and temperature, were evaluated to
determine their effects on the oxidative stability index (OSI), temperature coefficient, Q
10 number, and shelf-life prediction for soybean oil. Operational parameters of the Rancimat method had statistically significant
effects (P < 0.05) on the OSI. Whenever the oil sample size and airflow rate at a given temperature were such that the air-saturated
condition could be established, the OSIs showed no statistically significant differences. As temperature increased, OSIs decreased,
while their average coefficient of variation (CV) increased. In general, the conditions where the sample was saturated with
air and had a relatively lower CV were an oil sample size of 6 g at all temperatures and airflow rates, then 3-g oil sample
size at low temperatures (100 and 110 °C) and low airflow rates (10 and 15 L h−1). The temperature coefficient and Q
10 number were found to be independent of the oil sample size and airflow rate, and their mean values for soybean oil were calculated
to be −3.12 × 10−2 °C−1 and 2.05, respectively. Oil sample size and airflow rate showed a significant effect on shelf-life prediction for soybean
oil. Therefore, choosing the right levels of these operational parameters in the Rancimat method may produce the least possible
difference between predictions from long-term storage studies and the OSI test. 相似文献
16.
Daniel Escolar María R. Haro Jesús Ayuso 《Journal of the American Oil Chemists' Society》2002,79(8):769-774
Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic
coordinates and the chroma—L
*, a
*, b
*, and C—for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480
and 670 nm. These are as follows: L
*=0.556458(A480)2−2.51145A480+0.55504(A670)2−8.53016A670+98.4089; a
*=0.177372(A480)2+2.1363A480+1.43254(A670)2−0.789231A670−13.9246; b
*=−16.0277(A480)2+79.8932A480−5.06558(A670)2+3.36169A670+31.9405; C=−15.8439(A480)2+78.9312A480−5.26784(A670)2+3.56917A670+33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale
d’Eclairage (CIE) L
*
a
*
b
*
system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex
equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from
the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed
and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables—L
*
, a
*
, b
*
, and C; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R
2-terms also confirmed the validity of the method. 相似文献
17.
MING CHEN HUI-LAN WANG JING GU GUO-WANG DIAO 《Journal of Applied Electrochemistry》2007,37(3):331-337
The water-soluble p-sulfonated sodium salt of calix[8]arene (III) was synthesized. The product was characterized by FT-IR, NMR and UV–Vis spectra.Then
the electrochemical behaviors of p-sulfonated sodium salt of calix[8]arene in NaAc+HAc (pH = 4) buffer solution was studied. In aqueous solution, p-sulfonated calix[8]arene can be oxidized when the potential is more than 0.7 V vs SCE. It was confirmed that the reaction
was a two-electron irreversible electrochemical reaction. The transfer coefficient, α, was measured as 0.7. At 25°, the diffusion
coefficient of p-sulfonated calix[8]arene was determined as 8.6 × 10−7 cm2 s−1. The diffusion activation energy of p-sulfonated calix[8]arene was 18.9 kJ mol−1 at pH = 4. 相似文献
18.
N-vinyl pyrrolidone (NVP) was polymerized in dioxan at 60 ± 0.1°C for 1 h using diphenyl ditelluride as radical initiator.
The system follows ideal kinetics i.e. R
p
α [DPDT]0.5[NVP]. The activation energy and dissociation constant is computed as 46 kJ mol−1 and 1.1 × 10−11 s−1, respectively. The polymer was characterized with the help of FTIR, 1H-NMR, 13C-NMR, ESR spectroscopy. The FT-IR spectrum showed bands at 1660–1680 cm−1 due to combination of >C = O and C–N stretching. The gyromagnetic constant ‘g’ has been computed as 2.2203. The main product of this reaction were poly(N-vinylpyrrolidone)s with phenyl tellanyl ends. The presence of tellurium in polymer is confirmed by ICP analysis. The DSC
shows the T
g
of poly(N-vinylpyrrolidone) is 168°C due to rigid pyrrolidane group. The TGA showed that polymer was stable up to 380°C.The GPC studies
showed that the weight average molecular weight decreases with increase of [DPDT]. 相似文献
19.
M. R. Ganjali P. Norouzi F. Faridbod S. Riahi M. R. Yaftian A. Zamani D. Matt 《Journal of Applied Electrochemistry》2007,37(7):827-833
A Th4+ ion-selective membrane sensor was fabricated from poly (vinyl chloride) (PVC) matrix membrane containing 2-(diphenylphosphorothioyl)-N′,N′-diphenyl acetamide (DPTD) as a neutral carrier, potassium tetrakis (p-chlorophenyl) borate (KTpClPB) as anionic excluder and o-nitrophenyloctyl ether (NPOE) as a plasticizing solvent mediator. The effects of the membrane composition, pH and additive
anionic influence on the response properties were investigated. The sensor, comprising 30% PVC, 63% solvent mediator, 4% ionophore
and 3% anionic additive demonstrates the best potentiometric response characteristics. It displays Nernstian behavior (15.2 ± 0.5 mV
per decade) over the concentration range 1.0 × 10−2–1.0 × 10−6 M. The detection limit of the electrode is 6.3 × 10−7 M (∼140 ng/ml). The response time of the electrode is 30 s .The sensor can be used in the pH range 3.0–9.0 for about 6 weeks.
The membrane sensor was used as an indicator electrode in the potentiometric titration of Th4+ ions with EDTA. It was successfully applied to the determination of thorium ions in binary mixture. 相似文献
20.
Frédéric Destaillats Jean B. Jean-Denis Joseph Arul Robert L. Wolff Paul Angers 《Journal of the American Oil Chemists' Society》2002,79(11):1091-1094
GC analysis was performed to determine regiospecific distribution and FA composition in seed oils of the Aceraceae species,
Acer saccharum and A. saccharinum. The oil content in the seeds was low at 5.0% in A. saccharum and 5.8% in A. saccharinum, and the main FA were linoleic (30.8 and 29.4%), oleic (21.3 and 27.6%), palmitic (10.1 and 10.5%), and cis-vaccenic (9.4 and 7.9%) acids, respectively. In addition, both oils contained long-chain monoenes of the n−9 and n−7 groups,
including 11-eicosenoic, 13-docosenoic, 15-tetracosenoic, 13-eicosenoic, and 15-docosenoic acids, whereas γ-linolenic acid
accounted for 0.8% of total FA in A. saccharum, and 0.5% in A. saccharinum. Regiospecific analysis, performed using the methodology of dibutyroyl derivatives of MAG, indicated that linoleic, oleic,
and linolenic acids were mainly esterified at the internal position of TAG in both seed oils, whereas long-chain monoenes
of the n−7 group were almost exclusively esterified on the external positions. 相似文献