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Gaussian analysis of Raman spectroscopy reveals three significant structures in the liquid acetic acid (AA): linear chains involving C-H⋯OC and O-H⋯OC hydrogen bonding, cyclic dimers and dissociated monomers that can effectively cooperate with hydrogen bonded stacks of linear AA or polymer chains. © the Partner Organisations 2014. Source


It is common belief that in Raman mapping, the sampling depth from which Raman signal is collected originates from a probe laser spot size of approximately 1-5 μm3. Actually, the active pharmaceutical ingredient (API) crystals detected by mapping on the sample surface distribute from surface to over a few tens to hundreds of microns into the sample, as determined by z-slices mapping in this context. It was also found that the score of API crystals detected in a chemical image decrease with their depth into the sample. Therefore, a larger threshold of the binary chemical images can be used to restrict the sampling depth and consequently eliminate the problem of 'saturation' by quantifying merely the amount of API crystals within a sampling volume equivalent to a smaller sampling depth rather than the overall detected crystalline API in the chemical images. Eventually, one single linear quantification calibration was established over the crystallinity from sub-percent (<1%) to over 20% w/w of a model sample by using a simple univariate analysis of binary chemical images method. Copyright © 2013 John Wiley & Sons, Ltd. It is anticipated that the detected Raman intensity would increase with depth z from z1 to z2 and become constant beyond z3. This is because that the material beyond depth z3 becomes not detectable. The sampling depth was thus determined using a wedge sample. Copyright © 2013 John Wiley & Sons, Ltd. Source


In this paper, the author reported two methods to extract spectral or spatial information inherited in the Raman chemical images for linear quantification calibration of crystallinity. The two approaches reported quantification results according to the spectral mean score of overall pixels or the spatial percentage of the pixels with a score greater than and equal to the threshold of the chemical images, respectively. From this study, it can be concluded that, first, sampling method for data collection in mapping has to be optimized to achieve linear quantification calibration through simple univariate analysis approaches. Second, the ordinary way of evaluating/validating a linear quantification technique by best linear correlation coefficient (R2) and root-mean-square error of calibration is disputable and has to be reconsidered. Lastly, with further consideration of root-mean-square relative error of calibration and predicted crystallinity at subpercent, it was found that the spectral mean score method cannot generate reliable quantification results at subpercent crystallinity. Copyright © 2014 John Wiley & Sons, Ltd. In this paper, the author reported two methods to extract spectral or spatial information inherited in the Raman chemical images for linear quantification calibration of crystallinity. The two approaches reported quantification results according to the spectral mean score of overall pixels or the spatial percentage of the pixels with a score greater than and equal to the threshold over the total pixels of the chemical images, respectively. From this study, it can be concluded that, first, sampling method for data collection in mapping has to be optimized to achieve linear quantification calibration through simple univariate analysis approaches. Copyright © 2014 John Wiley & Sons, Ltd. Source


Majumder M.,Pharmaterials Ltd. | Majumder M.,University of Reading | Buckton G.,University College London | Rawlinson-Malone C.F.,Bristol Myers Squibb | And 4 more authors.
CrystEngComm | Year: 2013

The crystal structure of an indomethacin-nicotinamide (1 : 1) co-crystal produced by milling has been determined from laboratory powder X-ray diffraction (PXRD) data. The hydrogen bonding motifs observed in the structure represent one of the most probable of all the possible combinations of donors and acceptors in the constituent molecules. © 2013 The Royal Society of Chemistry. Source


Majumder M.,Pharmaterials Ltd. | Majumder M.,University of Reading | Buckton G.,Pharmaterials Ltd. | Buckton G.,University of London | And 5 more authors.
CrystEngComm | Year: 2011

An X-ray amorphous mixture of carbamazepine and indomethacin transforms upon annealing to produce a novel 1:1 cocrystal, whose structure has been determined from laboratory powder X-ray diffraction (PXRD) data. © 2011 The Royal Society of Chemistry. Source

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