| 1. |
- Borgström, Johan, et al.
(författare)
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Liquid crystallinity versus gelation of kappa-carrageenan in mixed salts : effects of molecular weight, salt composition, and ionic strength
- 1998
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Ingår i: Langmuir. - WASHINGTON : American Chemical Society. - 0743-7463 .- 1520-5827. ; 14:17, s. 4935-44
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Tidskriftsartikel (refereegranskat)abstract
- The recently discovered isotropic/nematic phase transition in kappa-carrageenan was further examined by macroscopic observations and by NMR. A state diagram, which is the equivalent of a phase diagram but including also nonequilibrium states (in our case a gel), was established in the mixed salt solutions of NaI/CsI where the competition between phase separation and gelation could be studied. The phase boundaries of the nematic phase depended on molecular weight and ionic strength qualitatively as expected for a charged rigid polymer. From these data the persistence length of the kappa-carrageenan helix was estimated as 60-90 nm. The volume fraction of the nematic phase depended sensitively on the overall helical content. In coexisting phases, the helical content was larger in the nematic than in the isotropic phase.
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| 2. |
- Åsberg, Dennis, 1988-, et al.
(författare)
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A quality control method enhancement concept : Continual improvement of regulatory approved QC methods
- 2016
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Ingår i: Journal of Pharmaceutical and Biomedical Analysis. - : Elsevier. - 0731-7085 .- 1873-264X. ; 129, s. 273-281
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Tidskriftsartikel (refereegranskat)abstract
- Quality Control methods (QC-methods) play an important role in the overall control strategy for drug manufacturing. However, efficient life-cycle management and continual improvement are hindered due to a variety of post-approval variation legislations across territories and a lack of harmonization of the requirements. As a result, many QC-methods fall behind the technical development. Developing the QC-method in accordance with the Quality by Design guidelines gives the possibility to do continual improvements inside the original Method Operable Design Region (MODR). However, often it is necessary to do changes outside the MODR, e.g. to incorporate new technology that was not available at the time the original method was development. Here, we present a method enhancement concept which allows minor adjustments, within the same measuring principle, outside the original MODR without interaction with regulatory agencies. The feasibility of the concept is illustrated by a case study of a QC-method based on HPLC, assumed to be developed before the introduction of UHPLC, where the switch from HPLC to UHPLC is necessary as a continual improvement strategy. The concept relies on the assumption that the System Suitability Test (SST) and failure modes are relevant for other conditions outside the MODR as well when the same measuring principle is used. It follows that it should be possible to move outside the MODR as long as the SST has passed. All minor modifications of the original, approved QC-method must be re-validated according to a template given in the original submission and a statistical equivalence should be shown between the original and modified QC-methods. To summarize, revalidation is handled within the pharmaceutical quality control system according to internal change control procedures, but without interaction with regulating agencies.
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