Prediction of chromatographic parameters for some anilines by molecular connectivity

Summary The possible relation existing between R_F values obtained by thin-layer chromatography for a group of anilines with connectivity indices proposed by Kier and Hall has been studied. Using multivariable regression the corresponding connectivity functions, selected for their respective correlation coefficients, standard deviations, Snedecor's F and Student's t were obtained. Regression analysis of the connectivity functions gives a correct prediction of the experimental elution sequence for this group of substances on silica gel stationary phases and various mobile phases of different polarity. The corresponding random and stability studies of the different prediction models selected were carried out, showing good stability and null randomness in all cases.     

Thermochemical properties of benzoic acid derivatives VIII. Enthalpies of combustion and formation of o-, m-, and p- t-butylbenzoic acids

The enthalpies of formation in the crystalline state at 298.15 K of o-, m-, and p-t-butyl-benzoic acids have been determined by static-bomb calorimetry. Vapour-pressure determinations were made by the Knudsen-effusion technique and the sublimation enthalpies at the mean temperatures of the measurement ranges have been derived for the three acids. The values obtained are:

     

93.

Numerical Study of Pore Sizes Distribution in Gels     

Juan Primera  Anwar Hasmy  Thierry Woignier 《Journal of Sol-Gel Science and Technology》2003,26(1-3):671-675

We introduce a new numerical technique for the calculation of the pore size distribution in two-dimensional disordered systems. Our method is based on a triangulation technique which allows a closer measurement of pores surface without any morphological hypothesis.In this work, we focus our calculations in simulated gels. Such materials are modeled in two different conditions: by means of the Diffusion-Limited and Reaction-Limited Cluster-cluster Aggregation algorithms, DLCA and RLCA, respectively. In both situations, when the particles concentration decreases, the average pores size increases. The more compact cluster in RLCA, compared with DLCA, is consistent with the pore size distribution we have calculated. The simulated mean pore size is quantitatively in agreement with experimental data from literature.     

94.

Gravimetrische Halogenbestimmung in organischen Verbindungen nach dem Hydrierverfahren     

Mlinkó  S. 《Mikrochimica acta》1961,49(6):854-859

Zusammenfassung Es wurde eine gravimetrische Halogenbestimmung zur Analyse organischer Substanzen ausgearbeitet. Die Pyrolyse und Hydrierung wird in ammoniakhaltigem Wasserstoffstrom ausgeführt, die gebildeten Ammoniumhalogenide werden in einem nach dem Hydrierrohr geschalteten Absorptionsrohr gesammelt. Die Analyse läßt sich durch Wägung des Absorptionsrohres ausführen. Gleichzeitige Gegenwart von Schwefel stört die Analyse nicht.

---

Summary A gravimetric method has been worked out for determining the halogens in organic materials. The pyrolysis and hydrogenation are conducted in a current of hydrogen containing ammonia, and the ammonium halides formed are collected in an absorption tube attached to the hydrogenation tube. The analysis can be done by weighing the absorption tube. The presence of sulfur does not interfere with the analysis.

---

Résumé On a élaboré un dosage gravimétrique des halogènes dans l'analyse des substances organiques. On réalise la pyrolyse et l'hydrogénation dans un courant d'hydrogène contenant de l'ammoniac et l'on recueille les halogénures d'ammonium formés dans un tube à absorption disposé après le tube à hydrogénation. On peut effectuer l'analyse en pesant le tube à absorption. La présence simultanée du soufre ne gêne pas l'analyse.

     

95.

Correlation between transport and equilibrium properties through the ternary interaction parameter for cosolvent and cononsolvent polymeric systems     

C. M. Gómez  V. Soria  A. Campos 《Colloid and polymer science》1992,270(3):197-206

A study of the ternary polymer systems dimethyl formamide-ethyl acetate-polystyrene, chloroform-1,4 dioxane-polystyrene and tetrahydrofuran-chloroform-polystyrene was carried out by viscosity and light scattering at 298 K. A good correlation has been found between the excess intrinsic viscosity, unperturbed polymer dimensions, second virial coefficient and the excess Gibbs free energy by using a ternary interaction parameter, dependent on molecular weight. This modification enables the conversion between transport and equilibrium properties.     

96.

Studies of the silica reduction process by carbon     

J. Bialoskórski 《Journal of Thermal Analysis and Calorimetry》1990,36(6):2029-2032

The reduction of amorphous silica by carbon black was studied in argon atmosphere by use of MOM Derivatograph C. The apparent kinetic parameters of the process were determined. The possible mechanism of reaction was proposed.

---

Zusammenfassung Unter Verwendung eines MOM Derivatograph C wurde in Argonatmosphäre die Reduktion von Siliziumdioxid mit Ruß untersucht. Es wurden die scheinbaren kinetischen Größen des Prozesses bestimmt und ein möglicher Reaktionsmechanismus vorgeschlagen.

     

97.

Parallel and multiplexed bead-based assays and encoding strategies     

Yingyongnarongkul BE  How SE  Díaz-Mochón JJ  Muzerelle M  Bradley M 《Combinatorial chemistry & high throughput screening》2003,6(7):577-587

Advances in high throughput screening (HTS), together with the rapid progress in combinatorial chemistry, genomic and proteomic sciences have dramatically stimulated the development of a variety tools to enable the drug discovery process to become more efficient. Major future challenges in HTS include obtaining high density and good quality data based on assays that are rapid, reliable, inexpensive, sensitive, simple and miniaturised. This paper reviews the development and role of bead-based assays for HTS including DNA and single nucleotide polymorphism (SNP) assays, particularly from a multiplex perspective and evaluating the recent advances in bead-based arrays. The encoding strategies that are commonly used in bead-based assays are highlighted, while the importance of magnetic beads in genomic and proteomic purifications is discussed. In conclusion, bead-based assays offer a powerful promising approach for many aspects of drug discovery.     

98.

Optical Properties of Model Compounds of Polyaniline     

Sze-Ming Yang  Hsin Juan Chen  Jiann Shen Lin 《中国化学会会志》1988,35(1):39-44

The UV and visible spectra of six model compounds were studied. These compounds can be considered as models of polyaniline in the reduced, cation radical, partially oxidized and oxidized forms. After treatment of a mixture of equal molar quantities of the reduced form (DPPD) and the oxidized form (QDIM) with acid, the following reaction was observed: DPPD(I)+QDIM(III)+2H⁺=2DPPD⁺(II) After similar treatment of the partially oxidized form (V) with acid, the radical cation salt formed. The UV and visible spectra of polyaniline in the reduced form, oxidized form and conductive form are similar to the spectra of DPPD, QDIM and DPPD⁺ or radical cation salt of V respectively. We propose that the polyaniline synthesized by chemical oxidation of aniline consists of oxidized and reduced repeat units. Upon protonation a redox reaction (or electron rearrangement) occurs and forms delocalized radical cations (polarons) in the polymer chain which are highly conductive.     

99.

On-line filtration system for determining total chromium and chromium in the soluble fraction of industrial effluents by flow injection flame atomic absorption spectrometry     

López-García I  Merino Meroño B  Campillo N  Hernández-Córdoba M 《Analytical and bioanalytical chemistry》2002,373(1-2):98-102

Two manifolds were assessed for the purpose of determining both the total chromium content and that present as a soluble form in industrial effluents by flow injection flame atomic absorption spectrometry (FI-FAAS). To determine the chromium content in the soluble fraction the samples were used without additional treatment, a 0.45 microm filter being included in the FI system. To determine the total chromium content, the samples were acidified with nitric acid 20% (v/v) and heated for 30 s in a microwave oven (temperatures of about 70 degrees C were reached). The problem posed by the very different concentration range in which total and soluble chromium are present was overcome by using programmed flow rate methodology and by only partially emptying the sample loop. A personal computer controlled both the rotation speed of a peristaltic pump and the volume of sample injected into the system, thus obtaining the dispersion degree required. Using the manifold proposed, the chromium content in the soluble fraction can be determined in the 0.5-20 microg mL(-1) range using a 10 microg mL(-1) single standard for calibration. To determine the total chromium content, a calibration line in the 20-200 microg mL(-1) range was obtained using a single 50 microg mL(-1) chromium standard solution. The reliability of the semi-automatic devices was verified by comparing the results obtained with those found by treating the samples and using both FAAS in a conventional way and a spectrophotometric method using diphenylcarbazide at the 95% confidence level (ANOVA test). The proposed procedures showed a RSD lower than +/-3%.     

100.

Electrodeposition of cobalt on stainless steel foils. Preparation of57Co sources for Mössbauer experiments     

R. González-Ramírez  H. Jiménez-Domínguez  O. Solorza-Feria  E. Ordóñez-Regil  A. Cabral-Prieto  S. Bulbulian 《Journal of Radioanalytical and Nuclear Chemistry》1993,174(2):291-298

Conditions for the electrodeposition of⁵⁹Co and⁵⁷Co on stainless steel foils have been studied. A set of electrolytic parameters has been determined to get a reasonably good electrodeposited sample. The⁵⁷Co electrodeposited foil was then introduced in a quartz tube to be annealed in an argon flow. The final product was a 11 Ci Mössbauer source for college experiments which was succesfully tested by obtaining spectra of stainless steel and sodium nitroprusside.     

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	$\text{ΔH}{}_{\mathrm{f}}{}^{\mathrm{o}}\text{(c, 298.15 K)/kJ mol}{}^{\mathrm{?1}}$	$\text{ΔH}{}_{\mathrm{s}}\text{/kJ mol}{}^{\mathrm{?1}}$
o-t-butylbenzoic acid	476.2 ± 1.9	99.8 ± 0.4	(at 314.6 K)
m-t-butylbenzoic acid	504.3 ± 1.6	103.0 ± 0.5	(at 326.5 K)
p-t-butylbenzoic acid	502.9 ± 1.7	103.8 ± 0.4	(at 334.1 K)

Numerical Study of Pore Sizes Distribution in Gels

We introduce a new numerical technique for the calculation of the pore size distribution in two-dimensional disordered systems. Our method is based on a triangulation technique which allows a closer measurement of pores surface without any morphological hypothesis.In this work, we focus our calculations in simulated gels. Such materials are modeled in two different conditions: by means of the Diffusion-Limited and Reaction-Limited Cluster-cluster Aggregation algorithms, DLCA and RLCA, respectively. In both situations, when the particles concentration decreases, the average pores size increases. The more compact cluster in RLCA, compared with DLCA, is consistent with the pore size distribution we have calculated. The simulated mean pore size is quantitatively in agreement with experimental data from literature.     

Gravimetrische Halogenbestimmung in organischen Verbindungen nach dem Hydrierverfahren

Zusammenfassung Es wurde eine gravimetrische Halogenbestimmung zur Analyse organischer Substanzen ausgearbeitet. Die Pyrolyse und Hydrierung wird in ammoniakhaltigem Wasserstoffstrom ausgeführt, die gebildeten Ammoniumhalogenide werden in einem nach dem Hydrierrohr geschalteten Absorptionsrohr gesammelt. Die Analyse läßt sich durch Wägung des Absorptionsrohres ausführen. Gleichzeitige Gegenwart von Schwefel stört die Analyse nicht.

---

Summary A gravimetric method has been worked out for determining the halogens in organic materials. The pyrolysis and hydrogenation are conducted in a current of hydrogen containing ammonia, and the ammonium halides formed are collected in an absorption tube attached to the hydrogenation tube. The analysis can be done by weighing the absorption tube. The presence of sulfur does not interfere with the analysis.

---

Résumé On a élaboré un dosage gravimétrique des halogènes dans l'analyse des substances organiques. On réalise la pyrolyse et l'hydrogénation dans un courant d'hydrogène contenant de l'ammoniac et l'on recueille les halogénures d'ammonium formés dans un tube à absorption disposé après le tube à hydrogénation. On peut effectuer l'analyse en pesant le tube à absorption. La présence simultanée du soufre ne gêne pas l'analyse.

     

Correlation between transport and equilibrium properties through the ternary interaction parameter for cosolvent and cononsolvent polymeric systems

A study of the ternary polymer systems dimethyl formamide-ethyl acetate-polystyrene, chloroform-1,4 dioxane-polystyrene and tetrahydrofuran-chloroform-polystyrene was carried out by viscosity and light scattering at 298 K. A good correlation has been found between the excess intrinsic viscosity, unperturbed polymer dimensions, second virial coefficient and the excess Gibbs free energy by using a ternary interaction parameter, dependent on molecular weight. This modification enables the conversion between transport and equilibrium properties.     

Studies of the silica reduction process by carbon

The reduction of amorphous silica by carbon black was studied in argon atmosphere by use of MOM Derivatograph C. The apparent kinetic parameters of the process were determined. The possible mechanism of reaction was proposed.

---

Zusammenfassung Unter Verwendung eines MOM Derivatograph C wurde in Argonatmosphäre die Reduktion von Siliziumdioxid mit Ruß untersucht. Es wurden die scheinbaren kinetischen Größen des Prozesses bestimmt und ein möglicher Reaktionsmechanismus vorgeschlagen.

     

Parallel and multiplexed bead-based assays and encoding strategies

Advances in high throughput screening (HTS), together with the rapid progress in combinatorial chemistry, genomic and proteomic sciences have dramatically stimulated the development of a variety tools to enable the drug discovery process to become more efficient. Major future challenges in HTS include obtaining high density and good quality data based on assays that are rapid, reliable, inexpensive, sensitive, simple and miniaturised. This paper reviews the development and role of bead-based assays for HTS including DNA and single nucleotide polymorphism (SNP) assays, particularly from a multiplex perspective and evaluating the recent advances in bead-based arrays. The encoding strategies that are commonly used in bead-based assays are highlighted, while the importance of magnetic beads in genomic and proteomic purifications is discussed. In conclusion, bead-based assays offer a powerful promising approach for many aspects of drug discovery.     

Optical Properties of Model Compounds of Polyaniline

The UV and visible spectra of six model compounds were studied. These compounds can be considered as models of polyaniline in the reduced, cation radical, partially oxidized and oxidized forms. After treatment of a mixture of equal molar quantities of the reduced form (DPPD) and the oxidized form (QDIM) with acid, the following reaction was observed: DPPD(I)+QDIM(III)+2H⁺=2DPPD⁺(II) After similar treatment of the partially oxidized form (V) with acid, the radical cation salt formed. The UV and visible spectra of polyaniline in the reduced form, oxidized form and conductive form are similar to the spectra of DPPD, QDIM and DPPD⁺ or radical cation salt of V respectively. We propose that the polyaniline synthesized by chemical oxidation of aniline consists of oxidized and reduced repeat units. Upon protonation a redox reaction (or electron rearrangement) occurs and forms delocalized radical cations (polarons) in the polymer chain which are highly conductive.     

On-line filtration system for determining total chromium and chromium in the soluble fraction of industrial effluents by flow injection flame atomic absorption spectrometry

Two manifolds were assessed for the purpose of determining both the total chromium content and that present as a soluble form in industrial effluents by flow injection flame atomic absorption spectrometry (FI-FAAS). To determine the chromium content in the soluble fraction the samples were used without additional treatment, a 0.45 microm filter being included in the FI system. To determine the total chromium content, the samples were acidified with nitric acid 20% (v/v) and heated for 30 s in a microwave oven (temperatures of about 70 degrees C were reached). The problem posed by the very different concentration range in which total and soluble chromium are present was overcome by using programmed flow rate methodology and by only partially emptying the sample loop. A personal computer controlled both the rotation speed of a peristaltic pump and the volume of sample injected into the system, thus obtaining the dispersion degree required. Using the manifold proposed, the chromium content in the soluble fraction can be determined in the 0.5-20 microg mL(-1) range using a 10 microg mL(-1) single standard for calibration. To determine the total chromium content, a calibration line in the 20-200 microg mL(-1) range was obtained using a single 50 microg mL(-1) chromium standard solution. The reliability of the semi-automatic devices was verified by comparing the results obtained with those found by treating the samples and using both FAAS in a conventional way and a spectrophotometric method using diphenylcarbazide at the 95% confidence level (ANOVA test). The proposed procedures showed a RSD lower than +/-3%.     

Electrodeposition of cobalt on stainless steel foils. Preparation of57Co sources for Mössbauer experiments

Conditions for the electrodeposition of⁵⁹Co and⁵⁷Co on stainless steel foils have been studied. A set of electrolytic parameters has been determined to get a reasonably good electrodeposited sample. The⁵⁷Co electrodeposited foil was then introduced in a quartz tube to be annealed in an argon flow. The final product was a 11 Ci Mössbauer source for college experiments which was succesfully tested by obtaining spectra of stainless steel and sodium nitroprusside.