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1.
The interaction between three kinds of antiseptic compounds and components of intercellular lipids in the stratum corneum
was characterized in terms of thermodynamics at pH 7.5 and 25°C, and the different mechanisms used to penetrate the stratum
corneum were clarified. Anionic surfactants such as benzalkonium chloride and benzethonium chloride mainly bound to cholesterol
(CH) and cholesterol sulfate with high affinity (105–106 M−1) to extract endogenous CH from the stratum corneum and penetrated through the intercellular route. Chlorhexidine gluconate
also bound to CH and accumulated in the stratum corneum without removing endogenous CH. An amphoteric surfactant of dodecyldiaminoethylglycine
hydrochloride seemed to be incorporated into the lipid bilayer and bound to ceramide with its polar end close to the lipid
polar heads by hydrophobic interaction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
2.
3.
S. Vecchio 《Journal of Thermal Analysis and Calorimetry》2006,84(1):271-278
The standard sublimation enthalpies of (2,4,5-trichlorophenoxy)acetonitrile
and (2,4,5-trichlorophenoxy)aniline were determined by isothermal thermogravimetry
using the Langmuir equation and by non-isothermal differential scanning calorimetry
for comparison. The used procedure was previously tested using three reference
compounds: benzoic acid, succinic acid and salicylic acid. The results compared
to those reported in literature show an excellent agreement for two of the
three compounds while the third agrees quite well. For (2,4,5-trichlorophenoxy)acetonitrile
and (2,4,5-trichlorophenoxy)aniline, the extrapolation of data at 298.15 K
were obtained, respectively: ΔsubH°(298
K)={(106±4) and (101±4)} kJ mol–1.
From Clausius Clapeyron equation obtained after the determination of the vaporization
constant α′, the following standard sublimation entropies for
(2,4,5-trichlorophenoxy)acetonitrile and (2,4,5-trichlorophenoxy)aniline equal
to ΔsubS°(298
K)=(251 and 237) J K–1 mol–1,
respectively, were derived, with an error of ±4 J K–1
mol–1 equal for the studied herbicides. 相似文献
4.
A simple and fast flow injection fluorescence quenching method for the determination of iron in water has been developed.
Fluorimetric determination is based on the measurement of the quenching effect of iron on salicylic acid fluorescence. An
emission peak of salicylic acid in aqueous solution occurs at 409 nm with excitation at 299 nm. The carrier solution used
was 2 × 10−6 mol L−1 salicylic acid in 0.1 mol L−1 NH4+/NH3 buffer solution at pH 8.5. Linear calibration was obtained for 5–100 μg L−1 iron(III) and the relative standard deviation was 1.25 % (n = 5) for a 20 μL injection volume iron(III). The limit of detection
was 0.3 μg L−1 and the sampling rate was 60 h−1. The effect of interferences from various metals and anions commonly present in water was also studied. The method was successfully
applied to the determination of low levels of iron in real samples (river, sea, and spring waters). 相似文献
5.
M.-H. Wang Z.-C. Tan Q. Shi L.-X. Sun T. Zhang 《Journal of Thermal Analysis and Calorimetry》2006,84(2):413-418
The
heat capacities of 2-benzoylpyridine were measured with an automated adiabatic
calorimeter over the temperature range from 80 to 340 K. The melting point,
molar enthalpy, ΔfusHm,
and entropy, ΔfusSm,
of fusion of this compound were determined to be 316.49±0.04 K, 20.91±0.03
kJ mol–1 and 66.07±0.05 J mol–1
K–1, respectively. The purity of the compound
was calculated to be 99.60 mol% by using the fractional melting technique.
The thermodynamic functions (HT–H298.15) and (ST–S298.15) were calculated based
on the heat capacity measurements in the temperature range of 80–340
K with an interval of 5 K. The thermal properties of the compound were further
investigated by differential scanning calorimetry (DSC). From the DSC curve,
the temperature corresponding to the maximum evaporation rate, the molar enthalpy
and entropy of evaporation were determined to be 556.3±0.1 K, 51.3±0.2
kJ mol–1 and 92.2±0.4 J K–1
mol–1, respectively, under the experimental
conditions. 相似文献
6.
A. Ruiz Medina M. L. Fernández de Córdova A. Molina Díaz 《Analytical and bioanalytical chemistry》1999,365(7):619-624
A new, sensitive and very simple spectrofluorimetric biparameter sensor is described for the determination of salicylamide
and/or salicylic acid in pharmaceutical preparations. The method integrates the transitory retention and fluorescence detection
of both compounds on Sephadex QAE A-25 resin packed into a conventional flow-through cell. A monochannel manifold with two
alternative carriers is used. At pH 2.0 (first carrier) salicylic acid is selectively retained on the solid support and after
developing the analytical signal it is desorbed. At pH 11.0 (second carrier) both salicylic acid and salicylamide are simultaneously
and transitorily retained on the solid, the analytical signal now corresponding to both analytes. The monochromators were
tuned at 260 (excitation) and 415 (emission) nm, respectively. The calibration graph for salicylamide is linear over the range
0.01 to 0.32 μg mL–1 and for salicylic acid from 0.04 to 1.0 μg mL–1 in the presence of each other. The relative standard deviation and the sampling frequency for the determination of salicylamide
(0.20 μg mL–1) and salicylic acid (0.50 μg mL–1) were 1.1% and 35 h–1, and 0.9% and 45 h–1, respectively. Good results on application to individual determination or mixture resolution in pharmaceutical samples testify
to the usefulness of the proposed sensor.
Received: 20 April 1999 / Revised: 7 June 1999 / Accepted: 12 June 1999 相似文献
7.
Michael Winklmair Andreas J. Schuetz M. G. Weller Reinhard Niessner 《Fresenius' Journal of Analytical Chemistry》1999,363(7):619-624
A new, sensitive and very simple spectrofluorimetric biparameter sensor is described for the determination of salicylamide
and/or salicylic acid in pharmaceutical preparations. The method integrates the transitory retention and fluorescence detection
of both compounds on Sephadex QAE A-25 resin packed into a conventional flow-through cell. A monochannel manifold with two
alternative carriers is used. At pH 2.0 (first carrier) salicylic acid is selectively retained on the solid support and after
developing the analytical signal it is desorbed. At pH 11.0 (second carrier) both salicylic acid and salicylamide are simultaneously
and transitorily retained on the solid, the analytical signal now corresponding to both analytes. The monochromators were
tuned at 260 (excitation) and 415 (emission) nm, respectively. The calibration graph for salicylamide is linear over the range
0.01 to 0.32 μg mL–1 and for salicylic acid from 0.04 to 1.0 μg mL–1 in the presence of each other. The relative standard deviation and the sampling frequency for the determination of salicylamide
(0.20 μg mL–1) and salicylic acid (0.50 μg mL–1) were 1.1% and 35 h–1, and 0.9% and 45 h–1, respectively. Good results on application to individual determination or mixture resolution in pharmaceutical samples testify
to the usefulness of the proposed sensor.
Received: 20 April 1999 / Revised: 7 June 1999 / Accepted: 12 June 1999 相似文献
8.
Xinxiu Deng Xiaohui Chen Weiming Cheng Zhenduo Shen Kaishun Bi 《Chromatographia》2008,67(7-8):559-566
For the first time a simple, rapid, and specific liquid chromatographic–mass spectrometric (LC–MS) method for simultaneous
quantification of 15 lignans from Schisandra chinensis (Turcz.) Baill. fruit has been developed and fully validated. Samples were ultrasonically extracted with methanol. Chromatographic
separation was performed on a C18 column with methanol–0.1% aqueous acetic acid 72:28 (v/v) as mobile phase at a flow rate of 0.8 mL min−1; the run time was 40 min. The analytes were monitored by selected ion monitoring (SIM) with electrospray ionization (ESI).
Fifteen regression equations revealed good linear relationships (r
2 > 0.99) between peak area and concentration. Within-batch and between-batch precision of the method for the 15 lignans was
<9.5% and accuracy was 93.1–107.5%. The validated method was successfully used to determine the 15 compounds in the fruits
of Schisandra
chinensis procured from different regions of China. The results indicated the method could be used for quality control of Schisandra chinensis fruit and might also useful for further studies of lignans. 相似文献
9.
A. Zalga Z. Moravec J. Pinkas A. Kareiva 《Journal of Thermal Analysis and Calorimetry》2011,105(1):3-11
The preparation and characterization of the M′–M′′–O nitrate–tartrate (M′ = Ca, Ba, Gd and M′ = W, Mo) precursor gels synthesized
by simple, inexpensive, and environmentally benign aqueous sol–gel method is reported. The obtained gels were studied by thermal
(TG/DSC) analysis. TG/DSC measurements revealed the possible decomposition pathway of synthesized M′–M′′–O nitrate–tartrate
gels. For the synthesis of different metal tungstates and molybdates, the precursor gels were calcined at different temperatures
(650, 800, and 900 °C). According to the X-ray diffraction (XRD) analysis data, the crystalline compounds CaMo1-x
W
x
O4 doped with Ce3+ ions, BaMo1-x
W
x
O4 doped with Eu3+ ions and Gd2Mo3O12 were obtained from nitrate–tartrate gels annealed at 650–900 °C temperatures. The XRD data confirmed that the fully crystalline
single-phase powellite, scheelite, or Gd2(MoO4)3 structures were formed already at 650 °C. Therefore, the suggested sol–gel method based on the complexation of metal ions
with tartaric acid is suitable for the preparation of mixed tungstates–molybdates at relatively low temperature in comparison
with solid-state synthesis. 相似文献
10.
Trilochan Swain 《Journal of Thermal Analysis and Calorimetry》2011,103(3):1111-1117
A new inorganically template metaphosphate of Co(II) complex has been synthesized and characterized by different measurements
such as DSC, FT-IR, C–H–N–O–S, ESR, TG-DTA and X-RD. Differential Scanning Calorimeter (DSC) elucidated negative specific
heat of the system and has used to evaluate some thermo dynamical constants like activation energy (E
a), frequency factor (A), enthalpy and entropy of that system. The specific heat capacity of the system is measured both in atmospheric O2 and N2 atmosphere at different heating rates of 278, 283, 293 and 298 K min−1 in room atmosphere and 288 K min−1 in N2 atmosphere. 相似文献
11.
M. Hampl J. Leitner K. Růžička M. Straka P. Svoboda 《Journal of Thermal Analysis and Calorimetry》2007,87(2):553-556
The heat capacity and the heat content of
bismuth niobate BiNb5O14 were
measured by the relaxation time method, DSC and drop method, respectively.
The temperature dependence of heat capacity in the form C
pm=455.84+0.06016T–7.7342·106/T
2 (J K–1
mol–1) was derived by the least squares method
from the experimental data. Furthermore, the standard molar entropy at 298.15
K S
m=397.17 J K–1
mol–1 was derived from the low temperature
heat capacity measurement. 相似文献
12.
Thiocarbamoylation of 5-aminosalicylic acid with tetramethylthiuram disulfide afforded 5-(N′,N′-dimethylthioureido)salicyclic acid. Treatment of the latter with mineral acids or Ac2O gave 5-isothiocyanatosalicylic acid whose reaction with ethanolamine yielded 5-[N′-(2-hydroxyethyl)thioureido]salicylic acid. The latter underwent cyclization under the action of TsOH to form 5-(2-thiazolin-2-ylamino)salicylic
acid.
For Part 2, see Ref. 1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2315–2318, December, 1999. 相似文献
13.
Guillard E Tfayli A Manfait M Baillet-Guffroy A 《Analytical and bioanalytical chemistry》2011,399(3):1201-1213
The outermost layer of the mammalian skin, the stratum corneum (SC), represents the main skin barrier. The SC lipids have
a very exceptional composition, as the main lipid classes are ceramides (CER), long-chain fatty acids and cholesterol. Information
on the function of each CER subclass and on the relation between CER lipid organisation and composition is of great importance
to unravel the mechanism controlling the skin barrier function. Raman spectroscopy has been increasingly used for the study
of intra- and inter-molecular structures of long-chain lipid compounds. In this study, we employed Raman spectroscopy to evaluate
the effect of (1) the chain length and (2) the polar head architecture on the conformational order and organisational behaviour
of CERs. The relation between the structure and the stability of the organisation was studied by monitoring the thermotropic
response of each CER in the temperature range between 25 and 95 °C. This work enabled the determination of a correlation between
the gauche/trans ratio in the νCC region and the state of the lateral packing. Moreover, it was shown that –OH groups in the α position of
the fatty acids reduce the stability while long alkyl chains reinforces the intra- and inter-chains order. 相似文献
14.
Mahmoud M. Al Omari Mohammad B. Zughul J. Eric D. Davies Adnan A. Badwan 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(3-4):227-235
The complexation of terfenadine (Terf) with β-cyclodextrin (β-CD) in solution and solid state has been investigated by phase solubility diagram (PSD), differential scanning calorimetry
(DSC), powder X-ray diffractometry (PXD) and proton nuclear magnetic resonance (1H-NMR). The PSD results indicated that the salt saturation with the buffer counter ion (citrate−2, H2PO4−1 and Cl−1 ions) of Terf (pK
a = 9.5) and the hydrophobic effect play in tandem to increase the value of the complex formation constant (K11) measured at different conditions of pH, ionic strength, buffer type and buffer concentration. The correlation of the free
energy of complex formation (ΔG11) with the free energy of inherent solubility of Terf (ΔGSo) obtained by changing the pH, ionic strength and buffer concentration was used to measure the contribution of the hydrophobic
effect (desolvation) to complex formation. The hydrophobic effect was found to constitute 57.8% of the driving force for complex
stability, while other factors including specific interactions contribute −13.4 kJ/mol. 1H-NMR spectra of Terf–citrate and Terf–HCl salts gave identical chemical shift displacements (ΔΔ) upon complexation, thus
indicating that the counter anions are positioned somewhere outside of the β-CD cavity. DSC, XRPD and 1H-NMR proved the formation of solid Terf/acid/β-CD ternary complexes. 相似文献
15.
The physical–chemical properties and fatty acid composition of sheep subcutaneous, tallow, intestinal, and tail fats were
determined. Sheep fat types contained C16:0, C18:0, and C18:1 as the major components of fatty acid composition (19.56–23.40, 20.77–29.50, 32.07–38.30%, respectively). Differential scanning
calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major
peaks (T
peak) of tallow and intestinal fats were similar and determined as 31.25–24.69 and 7.44–3.90 °C, respectively, for crystallization
peaks and 15.36–13.44 and 45.98–44.60 °C, respectively, for melting peaks in DSC curves; but those of tail fat (18.29 and
−2.13 °C for crystallization peaks and 6.56 and 33.46 °C for melting peaks) differed remarkably from those of other fat types. 相似文献
16.
Aki H. Koizumi E. Okamoto Y. Yamamoto M. 《Journal of Thermal Analysis and Calorimetry》2001,64(1):293-297
The interactions of benzalkonium chloride (BC)with components of stratum corneum, a model system of intercellular lipids in
human stratum corneum and homogenized rat stratum corneum were characterized in terms of thermodynamics at pH 7.5 and 37°C.
BC was strongly bound to cholesterol and cholesterol sulfate with higher affinities (105~106 M-1) than to any other components of the stratum corneum by hydrophobic interaction and ionic interaction, respectively. BC binding
to the model system of intercellular lipids significantly decreased only in the absence of cholesterol. It is indicated that
cholesterol and its derivatives play an important role in the penetration and/or accumulation of BC in stratum corneum.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Tapas Ghosh 《Transition Metal Chemistry》2006,31(4):560-565
Reaction of VOSO4 with the tridentate ONO donor ligand derived from the condensation of acetylhydrazide with either 2-hydroxybenzaldehyde (H2L1) or 2-hydroxyacetophenone (H2L2) (general abbreviation H2L) in an equimolar ratio in the presence of two equivalents of sodium acetate in aqueous-methanolic medium in air produces
yellow dioxovanadium(V) complexes of the type, [VvO2(H+-L)], (1) and (2) in good yield. Aerial oxygen is most likely the oxidant (for the oxidation of VIV→VV) assisted by the ligand basicity. Complexes are characterized by elemental analyses and by i.r., n.m.r. and u.v.–vis. spectroscopies.
I.r. spectra of the complexes indicate the tridentate dinegative forms of the ligands. The 1H-n.m.r. spectrum of (2) in CD3CN solvent indicates the presence of a strongly deshielded N–H proton. Conductivity measurements in DMF solution indicate
that the complexes are non-electrolytic and so the H+ ion is strongly bonded probably with the uncoordinated imine-N nitrogen of the coordinated Schiff base moiety. Both complexes
exhibit only the LMCT band in the u.v. region in MeOH and they are electroactive, displaying an irreversible reduction peak
near −0.35 V versus s.c.e. in methanol solution. Methanol solutions of the complexes are reversibly reduced by ascorbic acid to the corresponding
VIV analogue as is evident from their u.v.–vis. spectra. The CH2Cl2 suspension of these complexes (1) and (2) reacts separately with 8-hydroxyquinoline (Hhq) in air to produce the mixed-ligand complexes of the type [VvO(L)(hq)]. 相似文献
18.
G. Imokawa S. Akasaki O. Kuno M. Zama M. Kawai Y. Minematsu 《Journal of Dispersion Science and Technology》2013,34(4-5):617-641
In order to clarify the roles of lipids in the water-holding property of stratum corneum, the forearm skin of healthy male volunteers was treated with acetone/ether (1/1) or sodium dodecyl sulfate (5%) for 1-30 min. A prolonged treatment period of 5-30 min produced a chapped and scaly appearance of the stratum corneum without any inflammatory reactions. Under these conditions, there was a marked decrease in the water-holding capacity of the stratum corneum accompanied by a selective loss of stratum corneum lipids such as cholesterol, cholesterol esters, and sphingolipids. Two daily applications of the isolated stratum corneum lipids to experimentally induced dry skins caused a significant increase of conductance, accompanied by a marked improvement in the level of scaling. Meanwhile, the isolated sebaceous lipids exhibited no significant recovery in both the conductance value and the scaling. Out of chroma-tographically separated fractions of the stratum corneum lipids, topical applications of ceramide fraction induced the highest increase in the conductance value. Topical applications of synthesized pseudo-ceramides also showed a significant recovery of the water-retaining properties accompanied by an improvement in the scaling only when the polar group has an amide bond in the major linkage. Analysis of the alkyl chain structures has revealed that a structural requirement for the recovery of the water retaining capacity is the presence of saturated-straight alkyl chains, not unsaturated or branched alkyl chains. These structural characteristics required for water-retaining function also paralleled their capacity to form multiconcentric lamellae vesicles in vitro which is also capable of acquiring bound water as shown by DSC thermograms. The present study suggests that ceramides with relatively shorter alkyl chain length serve as a water modulator in the multi-lipid bilayers through the stratum corneum. 相似文献
19.
Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the
fusion enthalpy and temperature determination of the biuret (NH2CO)2NH (synthesis by-product of the urea fertilizer (NH2)2CO). Recommended values are Δm
H = (26.1 ± 0.5) kJ mol−1, T
m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems
to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature
of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested. 相似文献
20.
The
melting and crystallisation behaviour of poly(m-xylene
adipamide) (MXD6) are investigated by using the conventional DSC, X-ray diffraction
and polarised light microscopy. Triple, double or single melting endotherms
are obtained in subsequent heating scan for the samples after isothermal crystallisation
from the melt state at different temperatures. The lowest melting peak can
be ascribed to the melting of secondary crystals. The melting of primary crystals
causes the medium melting peak and the highest melting peak is attributed
to the melting of recrystallised species formed during heating. Following
the Hoffman–Weeks theory, the equilibrium melting temperature is equal
to 250°C and the equilibrium melting enthalpy ΔH
m
0
to 175 J g–1. Then, using the Lauritzen–Hoffmann
theory of secondary crystallisation, the analyse of the spherulitic growth
shows that the temperature of transition between the growing regimes II and
III is equal to 176°C. Finally the Gibbs-Thomson relationship allows the
determination of the distribution function of crystalline lamellae. 相似文献