Three Artefact

Debromination with ageing has been observed in the indigoid components of purple [171,172], and photochemical breakdown patterns of the three anthocyanidins contained in Arrabidaea chica red dye, produced by Andean Indian cultures in the tenth to fifteenth centuries, have been hypothesized [173]. Although identifying dye sources in ancient artefacts is quite difficult, it is helped considerably by understanding the fading and degradation mechanisms. 

The apparent shift of the maximum away from the linear O-H. .. O geometry is an artefact of projecting around the cylindrical axis. If this graph were plotted in the three dimensions of real space, the maximum would be seen to lie on the horizontal axis. 

HSQC rather than HMQC-based transfer schemes have recently in particular been employed in various indirectly detected two- and three-dimensional 111/X/Y correlation experiments involving multi-step coherence-transfer in either direction.38 40 43 44 The application of PFG s appears to be essential to obtain a sufficiently clean spectrum that is free of artefacts, and in many cases the pulse sequence shows only a satisfactory performance if composite pulses, with a larger excitation bandwidth than normal ones, are employed.21,38,39,43 The pulse schemes yield generally phase-sensitive spectra with pure absorptive lines and do not suffer from splitting or broadening of the cross peaks as a consequence of the undesired evolution... 

Equation (4.20) was proposed by Hoskuldsson [65] many years ago and has been adopted by the American Society for Testing and Materials (ASTM) [59]. It generalises the univariate expression to the multivariate context and concisely describes the error propagated from three uncertainty sources to the standard error of the predicted concentration calibration concentration errors, errors in calibration instrumental signals and errors in test sample signals. Equations (4.19) and (4.20) assume that calibrations standards are representative of the test or future samples. However, if the test or future (real) sample presents uncalibrated components or spectral artefacts, the residuals will be abnormally large. In this case, the sample should be classified as an outlier and the analyte concentration cannot be predicted by the current model. This constitutes the basis of the excellent outlier detection capabilities of first-order multivariate methodologies. 

The tetrahydroisoquinolone (1), iV-methylcorydaldine, has been isolated from Papaver bracteatum,6 and it is apparently a true constituent, not an artefact. The (+)-(i )- and (-)-(5)-forms of salsolidine (2) have been prepared by the reduction with sodium borohydride of the dihydroisoquinolines [3 R = (+)-(i )-PhCHMe, (-MS)-PhCHMe, (—)-(S)-PhCHEt, or (-)-(S)-C10H7CHMe] (which were prepared in three steps from 3,4-dimethoxyphenylacetaldehyde and RNH2) followed by hydrogenolysis over 10% Pd(OH)2 on carbon.7... 

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