In this paper, the non-isothermal differential scanning calorimetry
(DSC) was employed to investigate the cure process and to determine the kinetic
parameters of the curing reaction of the unsaturated polyester resin catalyzed
with promoter-cobalt(II)octoate and free-radical initiators. The initiators
were formed by the oxidation process of acetylacetone with 60% hydrogen peroxide
in the presence of the catalyst-sulphuric acid and the solvents: propano-1,2-diol
or the mixture of propano-1,2-diol and hydroxypolyether TG 500. As a reference,
the typical curing system containing ethyl methyl ketone hydroperoxide (Luperox)
and promoter was used.
It was found that the cure process of the
unsaturated polyester resin with the new initiators/cobalt(II)octoate was
described through lower maximum peak temperatures (Tmax)
and lower values of the total heat of the curing reaction (ΔHR) in comparison with Luperox/cobalt(II)octoate.
The computed values of activation energies were in the range of 40.8–44.9
and 80.4–87.6 kJ mol–1 for unsaturated
polyester resin cured with the new initiators/cobalt(II)octoate. The values
of activation energies were little lower or comparable to those obtained when
Luperox/cobalt(II)octoate system was used (45.8 and 82.3 kJ mol–1).
Authors:Mirosław Hawrył, Małgorzata Niemiec, and Monika Waksmundzka-Hajnos
Two-dimensional separations were performed on polar bonded stationary phase of type cyanopropyl-silica and diol-silica by use of non-aqueous eluents (polar modifier dissolved in n-heptane) as the first direction eluents and aqueous eluents (organic modifier — MeOH dissolved in water) as the second direction eluents. The chromatographic process was performed in micro scale using 5 × 5 cm plates, small volumes of eluents, and 10 μL of plant extracts to obtain satisfying separation. Plates developed in horizontal chambers were dried and observed in UV light (254 nm and 366 nm) photographed by digital camera and derivatized by 1,1-diphenyl-2-picrylhydrazyl (DPPH) to detect antioxidants (free radical scavengers) or derivatized by Naturstoff reagent to detect phenolic compounds (characteristic luminescence of some phenolic compounds). The above experiments give the possibility to construct fingerprints for investigated Mentha species and varieties and preparations containing the herb. It can be used in quality control of the plant material and its antioxidative activity.
Authors:Robert Skibiński, Genowefa Misztal, Łukasz Komsta, and Agata Korólczyk
Chromatographic behavior in normal-phase thin-layer chromatography has been investigated for six atypical antipsychotic drugs (amisulpride, clozapine, olanzapine, quetiapine, risperidone, and ziprasidone). The drugs were separated on silica gel, alumina, NH
, CN, diol, and polyamide plates with mixtures of
-hexane and six polar modifiers (acetone, dioxane, diethylamine, ethanol, isopropanol, and tetrahydrofuran) as mobile phases. The linearity of relationships between
and volume fraction of modifier, the logarithm of the volume fraction, the molar fraction, and the logarithm of the molar fraction was tested. The results usually fitted the
> 0.9. The best separation was achieved on silica gel plates with ethanol-
-hexane, 1 + 1 (
), containing 1.5% aqueous ammonia, as mobile phase.
The intestinal microflora
has been adapted to utilize, as a source of energy, complex carbohydrates that escape hydrolysis by human digestive enzymes, for example fructo-oligosaccharides (FOS). The ability of intestinal microflora to utilize carbohydrates in complex mixtures is of particular interest, even though few data have been reported. This paper presents the results obtained using an innovative analytical approach based on instrumental HPTLC-AMD (automated multiple development) to investigate the metabolic behavior of
MB 239 as a case study. Raffinose, FOS (sucrose, 1-kestose, nystose, fructosyl-nystose), lactose, and their monomeric moieties glucose, galactose, and fructose were simultaneously present as carbon sources in the solution to be fermented by the bacterium. The method proposed has enabled quantitative monitoring of sugar concentrations during the entire time-course of the processes. The complex sugar mixtures were separated by use of acetonitrile-acetone-water mobile phases on diol layers derivatized with 4-aminobenzoic acid.
Authors:Łukasz Komsta, Robert Skibiński, Anita Iwańczyk, and Genowefa Misztal
The normal-phase thin-layer chromatographic behavior of five statin-like drugs — atorvastatin, cerivastatin, fluvastatin, lovastatin, and simvastatin — has been investigated. Chromatograms on silica gel, diol, and CN layers were developed with binary mobile phases containing hexane and a polar modifier in different proportions. The
values obtained with all the mobile phases were then used to calculate
equations, assuming linear dependence of
on the volume fraction of the mobile phase modifier, on the mole fraction of the modifier, and on their logarithms. The correlation between regression coefficients within and between models were investigated in depth. The coincidence between regression coefficients were also investigated by calculating
rank correlation, and the similarity between modifiers was also checked by use of dendrograms.
Authors:A. Rekondo, L. Irusta, and M. Fernández-Berridi
The thermal behaviour of a new kind of hybrid system based on silanized poly(ether-urethanes) (SPURs) has been analyzed by
thermogravimetric analysis (TG). The influence of the chemical nature of employed alkoxysilanes, polyether diol molecular
weight and the physical state of the obtained hybrids (cured and non-cured) has been studied. The results show that in the
non-cured state, aminosilane-based systems present a higher stability compared with those based on isocyanatesilane. However,
in the cured state, both types of hybrids present a similar thermal stability, but much higher than their corresponding partners
before the curing process. The presence of the inorganic silica network improves the thermal stability of all the systems
Authors:Lidia Jasińska, A. Balas, J. Haponiuk, G. Nowaczyk, and S. Jurga
New cross-linked poly(esterurethanes) (PEU) based on unsaturated olygo(alkyleneester)diol
(OAE), 4,4’-diphenylmethane diisocyanate (MDI) and styrene or methyl
methacrylate as curing monomers were prepared. The synthesis of PEU was performed
in two steps. In the first step OAE was obtained from adipic acid, maleic
anhydride and ethylene glycol. In the second step a prepolymer was obtained
in a reaction of OAE with different amounts of 4,4’-diphenylmethane
diisocyanate followed by crosslinking using previously mentioned curing monomers.
The influence of structure of the poly(esterurethanes) on thermal and dynamic
mechanical properties is studied. Thermogravimetric analysis shows that cross-linked
poly(esterurethanes) demonstrate high thermal stability. Moreover the dynamic
mechanical thermal analysis shows that the presence of styrene cross-linking
chains in polymers lead to the phase separation in cross-linked poly(esterurethanes).
Authors:P. Ramanjaneyulu, Y. Sayi, T. Newton Nathaniel, A. Reddy, and K. Ramakumar
Boron concentration has been determined in groundwater samples, collected from Khuchch, Gujarat, India, by prompt gamma neutron
activation analysis (PGNAA) after selective separation and pre-concentration by solvent extraction with 10% 2-ethyl hexane
1,3-diol in CHCl3. Solvent extraction separation helped to eliminate the interfering elements in PGNAA determination of boron. The sensitivity
of PGNAA is found to be 18.83 cps/mg B based on the slope of a calibration plot obtained by carrying out measurements on synthetic
boric acid samples containing boron in the range of 30–150 μg. Detection limit of the method is 0.2 μg/g counted for 35,000
seconds at a sample size of 15 gram. The precision (relative standard deviation at 1σ level) and accuracy of the method is
5%. The analytical results of the present method agreed well with well-established spectrophotometric determination of boron
as boron-curcumin complex and inductively coupled plasma atomic emission spectroscopy (ICP-AES).
m- and p-Chloroanisole were dechlorinated in the presence of a supported noble-metal catalyst (Pd/C or Rh–Pt/C) at 30 °C in a solution
of 2-propanol containing NaOH. The addition of a small amount of methanol (1% v/v) to the 2-propanol solution greatly enhanced
the rate of dechlorination of p-chloroanisole with Pd/C but retarded the rate with Rh–Pt/C. Other primary alcohols (1% v/v) enhanced m-chloroanisole dechlorination over Pd/C in the following order: methanol (enhancement factor, 10.6) > ethanol (3.3) > 1-propanol
(2.1) > 1-butanol (1.0). When a secondary alcohol (2-butanol), tertiary alcohol (t-butyl alcohol), diol (ethylene glycol), or triol (glycerin) was added at 1% (v/v), the dechlorination rates were unchanged
or retarded. We found that Pd/C was activated effectively by pretreatment with a solution of 2-propanol/methanol (99:1 v/v)
– 14] . Methanol solutions in some respects show similar properties to those of aqueous solutions and in others they resemble DMF solutions. Recently, we have turned our attention to systems containing a diol as a non-electrolyte. The wide applications