TY - JOUR A1 - Quirico, E. A1 - Moroz, Liubov V. A1 - Schmitt, B. A1 - Arnold, Gabriele A1 - Faure, M. A1 - Beck, P. A1 - Bonal, L. A1 - Ciarniello, M. A1 - Capaccioni, F. A1 - Filacchione, G. A1 - Erard, S. A1 - Leyrat, C. A1 - Bockelee-Morvan, D. A1 - Zinzi, A. A1 - Palomba, E. A1 - Drossart, P. A1 - Tosi, F. A1 - Capria, M. T. A1 - De Sanctis, M. C. A1 - Raponi, A. A1 - Fonti, S. A1 - Mancarella, F. A1 - Orofino, V. A1 - Barucci, A. A1 - Blecka, M. I. A1 - Carlson, R. A1 - Despan, D. A1 - Faure, A. A1 - Fornasier, S. A1 - Gudipati, M. S. A1 - Longobardo, A. A1 - Markus, K. A1 - Mennella, V. A1 - Merlin, F. A1 - Piccioni, G. A1 - Rousseau, B. A1 - Taylor, F. T1 - Refractory and semi-volatile organics at the surface of comet 67P/Churyumov-Gerasimenko: Insights from the VIRTIS/Rosetta imaging spectrometer JF - Icarus : international journal of solar system studies N2 - The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument aboard the Rosetta spacecraft has performed extensive spectral mapping of the surface of comet 67P/Churyumov-Gerasimenko in the range 0.3-5 mu m. The reflectance spectra collected across the surface display a low reflectance factor over the whole spectral range, two spectral slopes in the visible and near-infrared ranges and a broad absorption band centered at 3.2 mu m. The first two of these characteristics are typical of dark small bodies of the Solar System and are difficult to interpret in terms of composition. Moreover, solar wind irradiation may modify the structure and composition of surface materials and there is no unequivocal interpretation of these spectra devoid of vibrational bands. To circumvent these problems, we consider the composition of cometary grains analyzed in the laboratory to constrain the nature of the cometary materials and consider results on surface rejuvenation and solar wind processing provided by the OSIRIS and ROSINA instruments, respectively. Our results lead to five main conclusions: (i) The low albedo of comet 67P/CG is accounted for by a dark refractory polyaromatic carbonaceous component mixed with opaque minerals. VIRTIS data do not provide direct insights into the nature of these opaque minerals. However, according to the composition of cometary grains analyzed in the laboratory, we infer that they consist of Fe-Ni alloys and FeS sulfides. (ii) A semi-volatile component, consisting of a complex mix of low weight molecular species not volatilized at T similar to 220 K, is likely a major carrier of the 3.2 p.m band. Water ice contributes significantly to this feature in the neck region but not in other regions of the comet. COOH in carboxylic acids is the only chemical group that encompasses the broad width of this feature. It appears as a highly plausible candidate along with the NH4+ ion. (iii) Photolytic/thermal residues, produced in the laboratory from interstellar ice analogs, are potentially good spectral analogs. (iv) No hydrated minerals were identified and our data support the lack of genetic links with the CI, CR and CM primitive chondrites. This concerns in particular the Orgueil chondrite, previously suspected to have been of cometary origin. (v) The comparison between fresh and aged terrains revealed no effect of solar wind irradiation on the 3.2 mu m band. This is consistent with the presence of efficient resurfacing processes such as dust transport from the interior to the surface, as revealed by the OSIRIS camera. (C) 2016 Elsevier Inc. All rights reserved. KW - Comets KW - Organic chemistry KW - Infrared observations KW - Meteorites KW - Spectrophotometry Y1 - 2016 U6 - https://doi.org/10.1016/j.icarus.2016.02.028 SN - 0019-1035 SN - 1090-2643 VL - 272 SP - 32 EP - 47 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Islam, Khan Md. Shaiful A1 - Schweigert, Florian J. T1 - Comparison of three spectrophotometric methods for analysis of egg yolk carotenoids JF - Food chemistry N2 - Carotenoids accumulated in the egg yolk are of importance for two reasons. Firstly they are important pigments influencing customer acceptance and secondly they are essential components with positive health effects either as antioxidants or as precursor of vitamin A. Different analytical methods are available to quantitatively identify carotenoids from egg yolk such as spectrophotometric methods described by AOAC (Association of Official Analytical Chemists) and HPLC (High Performance Liquid Chromatography). Both methods have in common that they are time consuming, need a laboratory environment and well trained technical operators. Recently, a rapid lab-independent spectrophotometric method (iCheck, BioAnalyt GmbH, Germany) has been introduced that claims to be less time consuming and easy to operate. The aim of the current study was therefore to compare the novel method with the two standard methods. Yolks of 80 eggs were analysed as aliquots by the three methods in parallel. While both spectrometric methods are only able measure total carotenoids as total beta-carotene, HPLC enables the determination of individual carotenoids such lutein, zeaxanthin, canthaxanthin, beta-carotene and beta-apocarotenoic ester. In general, total carotenoids levels as obtained by AOAC were in average 27% higher than those obtained by HPLC. Carotenoid values obtained by the reference methods AOAC and HPLC are highly correlated with the iCheck method with r(2) of 0.99 and 0.94 for iCheck vs. AOAC and iCheck vs. HPLC, respectively (both p < 0.001). Bland Altman analysis showed that the novel iCheck method is comparable to the reference methods. In conclusion, the novel rapid and portable iCheck method is a valid and effective tool to determine total carotenoid of egg yolk under laboratory-independent conditions with little trained personal. (C) 2014 Elsevier Ltd. All rights reserved. KW - AOAC KW - Carotenoid KW - HPLC KW - iCheck KW - Spectrophotometry KW - Yolk Y1 - 2015 U6 - https://doi.org/10.1016/j.foodchem.2014.09.045 SN - 0308-8146 SN - 1873-7072 VL - 172 SP - 233 EP - 237 PB - Elsevier CY - Oxford ER -