Per-Ola Quist

AstraZeneca | AZ · Operations Quality

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...

We investigate the effect of stirring conditions on the dissolution of United States Pharmacopoeial Convention (USP) prednisone calibrator tablets. The experiments are performed in an automated USP-II dissolution test apparatus. For this study we use a special paddle-propeller, which can be changed from an ordinary paddle to either a pulling or pus...

We investigate the effect of stirring conditions on the dissolution of United States Pharmacopoeial Convention (USP) prednisone calibrator tablets. The experiments are performed in an automated USP-II dissolution test apparatus. For this study we use a special paddle-propeller, which can be changed from an ordinary paddle to either a pulling or pus...

In pharmaceutical production of controlled release tablets and capsules, a rapid and automated at-line dissolution test for quality assurance of semi-products is advantageous. For effective control of the production, the analysis should not take more than about an hour, without loss of correlation to the ordinary (USP) dissolution test of the final...

The natural-abundance 13C NMR spectrum of gramicidin A in a lipid membrane was acquired under magic-angle spinning conditions. With fast sample spinning (15 kHz) at approximately 65 degrees C the peaks from several of the aliphatic, beta-, alpha-, aromatic, and carbonyl carbons in the peptide could be resolved. The resolution in the 13C spectrum wa...

Currently there is much interest in the interactions between lipids and membrane proteins or peptides containing up to about 30 amino acids. New physical methods for such studies are presently being developed or improved, such as surface plasmon resonance techniques fit for lipid bilayers, titration calorimetry and solid-state NMR methods, in parti...

The recently discovered isotropic/nematic phase transition in κ-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...

We report an investigation of the lamellar phase of the system N,N-dimethyldodecylamine oxide (DDAO)/gramicidin D/water. To identify the dominant repulsive interaction between the gramicidin-crammed membranes, we measured the variation (with the membrane volume fraction) of the position of the Bragg peaks in an X-ray diffraction experiment and the...

Mixtures of the added salts NaI and CsI can be used to gradually 'tune' the propensity of kappa-carrageenan (KC) helices to aggregate in solution. We show that this method can be used to resolve the molecular events by which helix formation, under certain conditions, leads to gelation. We also present an overview of the various states of aggregatio...

The solid-state structure of the TMEDA complex of fluorenyllithium is investigated by the 6Li−13C REDOR NMR experiment. The REDOR experiment was performed on 6Li-enriched samples with detection of the natural abundance 13C-signal. This simplifies the interpretation of the data and also the sample preparation. The dipole−dipole couplings between the...

Fluid membranes in multilamellar assemblies exhibit curvature fluctuations limited by interactions between adjacent membranes. By probing the orientational correlations associated with such curvature fluctuations, nuclear spin relaxation rates provide information about membrane interactions. In the first experimental demonstration of this approach,...

A novel liquid crystalline phase has been identified in the κ-carrageenan/NaI/water system. Solutions of ultrasonically degraded carrageenan were prepared in 0.1 M NaI both by direct mixing and by osmotic compression, and a macroscopic phase separation into one anisotropic bottom phase and one isotropic top phase was found in the concentration rang...

Recently we modernized an NMR course for undergraduate chemists. The aim of the new course is to introduce them to the most common applications of NMR. One is NMR imaging (MRI). Here we describe the experimental.

The rectangular phase in the lyotropic system sodium decyl sulphate (SdS)–decanol–water was studied by2H NMR and small-angle X-ray scattering. To investigate the variation in unit cell dimensions, the shape of the ribbons, and molecular segregation within the ribbons with composition, nine samples were prepared. The aspect ratio of the ribbon cross...

The angular dependence of longitudinal 23Na NMR spin relaxation in a lyotropic calamitic nematic phase is determined using a simple rotor technique. Analyzing the director-frame spectral densities, (ω), n = 0, 1, 2, and the quadrupole splitting shows that the experimental data cannot be accounted for in terms of the prolate micellar aggregates bein...

The NMR residual quadrupole coupling of certain nuclei is introduced to determine the surfactant aggregate shape at solid surfaces. The major advantage of the NMR method is the sensitivity of the residual quadrupole coupling to the curvature of the surfacrant aggregate interface. Being insensitive to the adsorption density, the NMR method represent...

The dilute regime of the lamellar phase in the SDS/pentanol/water/dodecane system is investigated by H-2 and Na-23 NMR. From the reduction of the quadrupole splitting on dilution, we determine-the temperature and composition variation in the bilayer bending rigidity kappa. We find an essentially temperature independent kappa = (9 +/- 1) x 10(-21) J...

The microstructure of the rectangular phase in the system sodium decylsulphate/decanol/water is investigated by means of deuterium NMR. By analysing the lineshape from selectively deuteriated decylsulphate and decanol, we separate the effects of (i) the shape anisotropy of the aggregate cross-section and (ii) the inhomogeneous distribution of the t...

The phase diagram of the sodium dodecylsulphate/decanol/water system is studied by2H NMR spectroscopy in the range between the calamitic nematic (N+C) and discotic nematic (N−D) phases. In this narrow range a nematic biaxial phase (NBX) is observed. The phase transitions between the nematic phases are all of first order. The shape of the surfactant...

We demonstrate that the bending rigidity, $\kappa$, of amphiphilic bilayers can be accurately determined from the quadrupole splitting in the NMR spectrum. We study the lamellar phase in the system water/SDS/pentanol/dodecane at layer volume fractions in the range 0.1-1, measuring the quadrupole splittings of water ($^2$H ), counterions ($^{23}$Na)...

Intrinsic structural defects in the lamellar (Lα) phase of the system sodium dodecyl sulphate (SDS)/decanol/water are studied by a combination of NMR H quadrupole splittings of α-deuteriated SDS and small angle X-ray scattering (SAXS). The focus is on the variation of the density and size of the defects with the bilayer composition (decanol/SDS mol...

An aligned sample in the lamellar phase of the sodium dodecylsulphate-decanol-water system is investigated by orientation-dependent 23Na NMR spin-relaxation experiments and x-ray diffraction. A pronounced relaxation anisotropy is observed, implying a nonclassical microstructure where a large fraction of the hydrocarbon-water interface is highly cur...

The 2H NMR two-dimensional quadrupolar-echo spectra of an α-deuterated surfactant in an aligned hexagonal lyotropic liquid crystal were recorded. Whereas only indications of 2H-1H and 2H-2H dipole splittings were observed in the F2 spectra, these residual interactions were displayed in the F1, spectra as an apparently Lorentzian peak. When gated 1H...

Nuclear spin relaxation of quadrupolar nuclei provides access to a wide range of properties of lyotropic liquid crystals, ranging from the molecular ordering and dynamics at the interface to the macroscopic viscoelastic behaviour. We emphasize here the unique capability of the spin relaxation method to provide detailed geometric and dynamic informa...

The orientation dependence of three independent 23Na relaxation rates is determined from measurements on the counterions in a magnetically aligned hexagonal lyotropic liquid crystal. The data allow us to determine the nine director-frame spectral densities that comprise the full information content of the spin-relaxation behavior of a quadrupolar n...

Lyotropic nematic liquid crystals, like their thermotropic counterparts, exhibit collective reorientation modes known as director fluctuations. In this work we consider the effect of director fluctuations on the transverse spin relaxation of quadrupolar nuclei in uniaxial lyotropic nematic liquid crystals, reporting 2H (labeled surfactant) and 23Na...

Nuclear magnetic resonance (NMR) relaxation of quadrupolar nuclei is introduced as a new method for determining micelle size and nematic order in lyotropic nematic mesophases from the dependence of the spin relaxation rates on molecular diffusion over the curved micelle surface. The approach is illustrated by an experimental study of two uniaxial n...

The hexagonal (E) phase in the sodium dodecyl sulphate (SDS)/decanol/water system is investigated by 2H and 23Na nuclear magnetic resonance (NMR) of the selectively deuterated SDS and the sodium counterion. Using macroscopically oriented E phase samples, prepared from the magnetically aligned nematic (NC) phase, we measure the orientation-dependent...

In the first systematic application of the two-dimensional quadrupolar echo (2DQE) method, we study the ²³Na NMR relaxation behavior of counterions in the reversed hexagonal mesophase of the AOT/DâO/isooctane system, consisting of long cylindrical aggregates with the water and ions on the inside. Using a combination of relaxation experiments, per...

The appearance of the N.M.R. spectrum of a quadrupolar nucleus in a lyotropic liquid crystal reflects the molecular organization in the surfactant aggregates. In particular, the spectral lineshape is a sensitive probe of deviations from circular cross-section in rod-like aggregates. This circumstance has been exploited by Chidichimo, Doane et al. t...

The microemulsion phase of the system AOT–D2O–2,2,4-trimethylpentane (TMP) has been studied by water 2H longitudinal and transverse spin relaxation measurements at three frequencies and at temperatures down to –29 °C. Additional information was obtained from n.m.r. signal intensities and quadrupolar line splittings, differential scanning calorimetr...