Volatilisation of ferrocene from ionic liquids: kinetics and mechanism

The evaporation of dissolved ferrocene from non-volatile ionic liquids under a flow of nitrogen gas has been monitored voltammetrically and modelled mathematically. The rate of volatilisation was found to depend on the surface tension of the ionic liquid, and a model is presented.     

Modelling of the simple shear flow of a flow-aligning nematic

The shear flow induced deformations of a nematic liquid crystal layer have been modelled numerically for the case of flow-aligning nematics. The director deviation from the plane of shear, which was predicted earlier for special surface orientation angles, has been confirmed. This deformation takes a form of director rotation about the axis perpendicular to the layer plane. As a result, transverse flow of the nematic arises. The rotation angle is close to pi at sufficiently strong shear stress, and the director is oriented at the usual flow alignment angle in a significant part of the layer. The director coming out of the shear plane should not be treated as a separate effect taking place during the flow, but rather as a way in which the usual flow-aligned structure is achieved.     

Centrifugal separation in the recovery of intracellular protein from E. coli

A 1000 l fermenter has been used to produce a feed of E. coli containing high levels of β-galactosidase. The individual unit operations have been investigated for the primary recovery of the enzyme, i.e. cell harvesting, cell disruption and cell debris removal. The cell separation yield was found to be in excess of 99%. Four passes through a high-pressure homogenizer released 95% of the enzyme. Approximately 87% of the β-galactosidase could be recovered after cell debris removal. The performance of the centrifuge during solid-liquid separation could be modelled using simple curve-fitting techniques.     

A Crystalline Quartz,Laser-Excited Fluorescence,Photoacoustic, and Two-Photon Photoionization Detector for HPLC

Abstract

A crystalline quartz flow cell has been developed for simultaneous fluorescence, photoacoustic effect, and two-photon photoionization detection of aromatic compounds in HPLC eluents. Excimer laser-excited three mode detection of naphthalene, 7,8-benzoflavone, N-ethylcarbazole, and anthracene in 70/30 v/v acetonitrile/water is exhibited. The flow cell is suitable for use with deoxygenated solvent systems and is orientation independent.     

A new generator of unsteady-state flow regime in tubular membranes as an anti-fouling technique: A hydrodynamic approach

A new generator of pulsatile flow has been developed. It consists of a rotating distributor disc judiciously perforated and placed in front of the entrance plane of a tubular membrane bundle. A laboratory-scale apparatus was built with a five membrane bundle. Two configurations were studied: upstream-disc-position (UDP) and downstream-disc-position (DDP). The main new feature is that the pulsatile flow is generated only in the membranes whereas no variation of flow or pressure occurs elsewhere in the equipment. The hydrodynamic behaviour was successfully modelled; experimental and calculated data are in good agreement. Filtration tests with an aqueous suspension of bentonite showed a close relation between the permeate flux and the pulsatile crossflow velocity. First results are encouraging: a reduction in crossflow velocity of 50% with the same power consumption per unit permeate flux as required for steady crossflow filtration.     

Mass and energy flow management in the sector of surface treatment

Vehicle refinishing body shops are concerned by the environmental policy against photochemical air pollution caused by VOC emissions. For supporting these small enterprises the mass and energy flow model IMPROVE has been developed. Based on an LCA-approach, the process steps of vehicle refinishing are modelled. The model IMPROVE helps to disseminate the consequences of product substitution in comparison to so far used products and techniques in the body shop. For the dissemination of experiences practical guidelines have been developed. Moreover, a comprehensible tool for the Solvent Balance is being offered. Thus, various means are available for consulting and also for strategic production planning for the SME in the sector.     

Shear flow induced deformations of planar cholesteric layers

The shear flow induced deformation of the planar cholesteric structure is modelled numerically, taking into account long pitch flow-aligning material. Three pitch-to-thickness ratios in five configurations are considered. Unwinding of the cholesteric helix due to the flow alignment is found. This process has a threshold character, when the mid-plane director is perpendicular to the plane of shear; otherwise it is continuous. The transverse component of the flow is always present. At high stress, the director in the prevailing part of the layer is oriented at the flow-aligning angle.     

Studies towards the total synthesis of Sch 56036; isoquinolinone synthesis and the synthesis of phenanthrenes

The isoquinolinone hemisphere of Sch 56036 has been prepared using a modified Pomeranz-Fritsch reaction and the synthesis of the phenanthrene core has been modelled via a Suzuki coupling and subsequent ring closing metathesis.     

Towards online,continuous monitoring for rheometry of complex fluids

This paper presents an overview of the developments that have been made towards the design of an inline rheometer that has the capabilities for monitoring in real time the viscous constitutive parameters of non-Newtonian fluids in a pipe flow. This has potential applications for a wide range of fluids, including hydrocolloid solutions and polymer solutions. This is of relevance to many industries, for example the pharmaceutical, lubrication, food and printing industries. The use of mathematical algorithms for inferring rheological parameters from properties of flow field statistics is explored. Particular focus is given to the development of a flow cell rheometer containing a T-junction geometry with the capacity to induce a range of shear rates in the vicinity of the bend, and a distribution of elongational viscosities along the back-wall. Such features create an information-rich flow field that is beneficial for the development of a rheometer with a fast response time that is suitable for commercial purposes.     

Multi-scan reversible cyclic voltammetry: is the ultimate condition approached and, if so, how fast?

A previous article shows that, after an infinite number of cycles, reversible cyclic voltammetry will attain an ultimate state characterized by properties that were identified in that study. Here, reversible multi-scan cyclic voltammetry has been modelled with a view to assessing the circumstances under which the ultimate state is attainable in an experimentally realistic time. The prediction has been confirmed that, under very specific conditions, the ultimate condition is attained after only a few scans. Under less restrictive conditions, one property of ultimacy is developed rapidly, but others evolve more slowly, or not at all. Modelling shows that the multi-scan voltammetric current may be analyzed into several components, of which the ultimate current is the purely periodic component.     

Parallel factor analysis combined with PLS regression applied to the on-line monitoring of Pichia pastoris cultures

Various key variables (biomass, substrate and product) of bioprocesses should be monitored in order to retrieve useful information on the system, with the biomass (the cell density) the principal target. Although several analytical methods have been adapted and used to monitor the evolution of cell density evolution in cultures, a general method for performing this determination has not yet been established, as each technique has its own advantages and drawbacks. In the present work, noninduced glycerol batch cultures (for which biomass and substrate are the key variables) were monitored using multiwavelength fluorescence spectroscopy. The data gathered were modelled via PARAFAC-PLS chemometric methodologies, resulting in important qualitative and quantitative information about the behaviours of different biogenic fluorophors in batch cultures of the yeast Pichia pastoris. This information was used to predict the target process variables in such cultures; this permitted the applicability of this combined technique to bioprocess monitoring to be assessed.     

Evaluation of migration behaviour of therapeutic peptide hormones in capillary electrophoresis using polybrene-coated capillaries

Modelling electrophoretic mobility as a function of pH can be simultaneously used for determination of ionization constants and for rapid selection of the optimum pH for separation of mixtures of the modelled compounds. In this work, equations describing the effect of pH on electrophoretic behaviour were used to investigate migration of a series of polyprotic amphoteric peptide hormones between pH 2 and 12 in polybrene-coated capillaries. Polybrene (hexadimethrin bromide) is a polymer composed of quaternary amines that is strongly adsorbed by the fused-silica inner surface, preventing undesired interactions between the peptides and the inner capillary wall. In polybrene-coated capillaries the separation voltage must be reversed, because of the anodic electroosmotic flow promoted by the polycationic polymer attached to the inner capillary wall. The possibility of using polybrene-coated capillaries for determination of accurate ionization constants has been evaluated and the optimum pH for separation of a mixture of the peptide hormones studied has been selected. Advantages and disadvantages of using bare fused-silica and polybrene-coated capillaries for these purposes are discussed.     

An analysis of local flow effects in flow-induced orientation and crystallization

An analysis is presented of the effects of external flow kinematics on the so-called local flow in seeded, flow-induced crystallization and orientation. The flow field around a growing crystal or nucleation seed is modelled by the Stokes flow equations past a prolate ellipsoid of high aspect ratio. Exact solutions for various flow kinematics, worked out elsewhere by the singularity method, are applied here to the analysis of local gradients. The results show that along the symmetry axis of the spheroid, the extensional gradients which result for various free-stream velocity fields are primarily the result of the constant-velocity free-stream component. However, free-stream, extensional flow can significantly enhance the region of such high gradients. Along the symmetry plane of the spheroid, primarily shearing gradients result, with small extensional gradients occurring when the free-stream flow has extensional components. Results of chain extension and birefringence calculations are also presented and discussed.     

Improved mesenchymal stem cell seeding on RGD-modified poly(L-lactic acid) scaffolds using flow perfusion

Arg-Gly-Asp (RGD) has been widely utilized to increase cell adhesion to three-dimensional scaffolds for tissue engineering. However, cell seeding on these scaffolds has only been carried out statically, which yields low cell seeding efficiencies. We have characterized, for the first time, the seeding of rat mesenchymal stem cells on RGD-modified poly(L-lactic acid) (PLLA) foams using oscillatory flow perfusion. The incorporation of RGD on the PLLA foams improves scaffold cellularity in a dose-dependent manner under oscillatory flow perfusion seeding. When compared to static seeding, oscillatory flow perfusion is the most efficient seeding technique. Cell detachment studies show that cell adhesion is dependent on the applied flow rate, and that cell attachment is strengthened at higher levels of RGD modification.     

Analysis of a reversible five-point bending configuration based on a novel two-sense support

A novel two-sense support for flexural tests has been designed and manufactured in Ikerlan. The aim of this support is to do two-sense bending fatigue tests. In order to reduce the displacement corresponding to a given stress, a novel test configuration, designated as five-point bending, is modelled analytically. Basically, it is a three-point configuration with two supports at the ends that exert forces in the same sense as the applied load. In this way, a partial clamping is obtained that can be modelled by concentrated loads. The model has been checked carrying out quasi-static three-point and five-point bending tests at different spans in unidirectional carbon/epoxy composite specimens. Flexural modulus and the out-of-plane shear modulus have been obtained by linear regression in both cases, after having obtained experimentally the stiffness of the system.     

A Simultaneous,Laser-Excited Fluorescence,Photoacoustic, and Two-Photon Photoionization Detector for Liquid Chromatography

Abstract

A laser-excited windowless flow cell has been developed for simultaneous fluorescence, photoacoustic, and two-photon photoionization detection of aromatic compounds in HPLC eluents. Sensitive three-mode detection of acridine, naphthalene, 7,8-benzoflavone, N-ethylcarbazole, and anthracene in 70/30 V/V acetonitrile/water is demonstrated with conservative detection limits in the nanogram range and below.     

Modelling of GC and HPLC separations of simazin and atrazin by experimental design methodology

Summary Experimental Design methodology allows the modelling and optimization of the chromatographic separation of similar pesticides (triazine family) by GC and HPLC. The GC separation of simazin and atrazin is well modelled by a first degree equation, involving injected volume, carrier gas pressure and rising oven temperature. The LC is modelled by a second degree equation, depending on injected volume, eluent flow and composition. These calculated models allow easy optimization of the separations, using isoresponse curves.     

Construction of a New Flow‐through Cell for Screen Printed Electrodes

In this paper a new flow‐through cell for voltammetric determinations using screen printed electrodes is described. This cell is much simpler than one with similar performances described in a previous work. This new flow‐through cell has been coupled to a multisyringe flow injection system (MSFIA) and to a multiport selection valve allowing the online calibration using the standard addition method. The uses of the MSFIA, together with the small volume of the flow cell and the reduced surface area of the solid phase electrode (SPE) have considerably reduced the volume of reagents and samples to be used. This system has allowed obtaining similar or better detection limits than those obtained using other techniques and flow analysis devices such as SIA, FIA, LOV and microfluidic channels. Graphite ink has been used for the development of screen‐printed electrodes. The determination of Cd and Pb with ASV has been made through its co‐deposition with Bi. For this, Bi(III) solution and the sample were mixed in line. Due to the creation of a new Bi film in each voltammetric cycle, very well defined and reproducible peaks corresponding to Cd and Pb have been obtained. The use of Bi is one of the most important advantages of this system, since it is a recognized substitute for Hg, and its impact on the environment is much lower due to its reduced toxicity. The fact of being an automatic system, the low cost of its components, its simplicity and ease of handling, make it a system that could be useful for monitoring tasks in fieldwork, or measurements on board.     

An Electrochemical Flow Cell For The Detection Of Metal Complexes

Abstract

An electrochemical flow cell has been developed using reticulated vitreous carbon (RVC) coated with a thin film of mercury. The flow cell and electrode components are inexpensive and easily constructed. Reproducible results have been obtained for concentrations as low as 100 ppb. Peak currents were dependent on flow rate, electrode size, and mercury deposition time. Oxygen interference was reduced by nitrogen purging to enable analysis of sub-ppm metal concentrations. The cell was tested as a detector for metal complexes eluated from a modified gel permeation chromatographic column.