Differential ionisation of natural antioxidant polyenes in electrospray and nanospray mass spectrometry

Carotenoids are natural products with high economic relevance for the pharmaceutical industries and are a common subject for biochemical research. Reported here is a comparative study of the ionisation of carotenoids by electrospray mass spectrometry (ESI-MS) and nanospray mass spectrometry (nanoESI-MS). The results demonstrate that, along with solvent choice, the influence of the different ionisation processes of ESI and nanoESI are fundamental in determining how ionisation is achieved and which ions (molecular ion or protonated molecule) are observed in MS. The increased understanding afforded by this study will help in the development of unequivocal microanalytical methods for carotenoids and related antioxidant polyenes.     

A Convenient Method to Obtain 4,5-Dihydro-1H-Methylpyrazoles by A Ring Transformation Reaction

A convenient method for the synthesis of alkyl[aryl]-substituted 5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-methylpyrazole (2) from a new ring transformation reaction of alkyl[aryl]-substituted-5-hydroxy-5-trifluoromethyl-4,5-dihydro-1H-1-pyrazolethiocarboxyamide (1) with methylhydrazine in THF, and the thermal dehydration of 2, are reported.     

Incoherent scattering of 59.54 keV gamma rays for some rare earth elements at low photon momentum transfers

Incoherent scattering functions S(x, Z) for six rare earth elements were evaluated from accurately measured whole atom differential incoherent scattering cross sections for 59.54 keV γ-rays scattered at 30°, 45°, 60° and 90° scattering angles corresponding to 1.24, 1.84, 2.40 and 3.39 Å⁻¹ photon momentum transfers. Our results for S(x, Z) are the first for these rare earth elements.     

Fluorene: An extended experimental thermodynamic study

This work reports new experimental thermodynamic results on fluorene. Vapor pressures of both crystalline and liquid phases were measured using a pressure gauge (capacitance diaphragm manometer) and Knudsen effusion methods over a wide temperature range (292.20 to 412.16) K yielding accurate determination of enthalpy and entropy of sublimation and of vaporization. The enthalpy of sublimation was also determined using Calvet microcalorimetry. The enthalpy of fusion was derived from vapor pressure results and from d.s.c. experiments. Static bomb calorimetry was used to determine the enthalpy of combustion of fluorene from which the standard enthalpy of formation in the crystalline phase was calculated. The enthalpy of formation in the gaseous phase was calculated combining the result derived for the crystalline phase with the enthalpy of sublimation.     

Analytical applications of membrane extraction in chromatography and electrophoresis

An overview of the analytical applications of membrane-based systems for sample enrichment in chromatography and capillary electrophoresis is presented. A brief introduction to the different types of membranes and the main forces related to the transport through them is also given.     

Comparative study of epithelial and fibroblastic cell lines as an alternative cytotoxicity test to the Draize method

Several methods are being used with considerable advantage as alternatives to the Draize test, although some technical difficulties still persist. This work compared the sensitivity of HeLa and NCTC L 929 cells to evaluate the cytotoxicity of shampoos used by adults and children (undiluted and diluted to 25, 5, 1, and 0.1%), and eye drops and their containers and surfactants (diluted to 30, 10, 1, and 0.1%). Nondiluted adult shampoos and their 25 and 5% dilutions were cytotoxic for both cell lines. When diluted to 1%, only one of the shampoos was noncytotoxic, whereas among those diluted to 0.1%, only one was cytotoxic. Children's shampoos were cytotoxic when not diluted or diluted to 25%. From those diluted to 5%, only one was noncytotoxic for both cell lines. The cytotoxic tests showed that the eye drops and their containers were noncytotoxic. Surfactants were cytotoxic when diluted to 30 and 10% and noncytotoxic when diluted to 1 and 0.1%. An excellent correlation (r = 0.95) was demonstrated between the sensitivity of the HeLa and NCTC L929 cells in the evaluation of cytotoxicity reactions.     

Synthesis of New Xanthones,I

Condensation of salicylic acid and C-methylphloroglucinol gave the already known 1,3-dihydroxy-2-methylxanthone ( 1 ) along with two new compounds: 1,3-dihydroxy-4-methylxanthone ( 2 ) and a second one tentatively presented as being 1,3-dihydroxy-2-methyl-4-(2-hydroxybenzoyl)xanthone ( 3 ). The UV., IR., NMR, and mass spectra for the two first compounds are reported and their structures discussed on the basis of δ-values for H(2), H(4), CH₃(4) and CH₃(2). The UV. and IR. spectra for the third compound are reported too.