In-line Reaction Research Articles

Highly Flexible Fibre-Optic ATR-IR Probe for Inline Reaction Monitoring

Near infrared (IR) applications have considerably profited from the use of flexible and robust fibre-optical probes. So far, a comparable technique for mid-IR was not available due to low stability and lack of robustness of the fibres. We report the use of a newly developed miniaturised diamond ATR-probe with high chemical resistance and pressure resistance based on robust fibre optics. The routine and convenient application in a glove box to highly air- and oxygen-sensitive reactions on a millilitre scale is reported, as well as the monitoring of a solventless reaction on a litre scale.

Advances in capillary electrophoretically mediated microanalysis: An update

This review, as a continuation of an earlier report, gives an overview of recent developments, over the period from 2003 until now, in the use of capillary electrophoretic techniques for the in-line study of enzymatic reactions, derivatization, and chemical reactions. The article is divided into two parts: (i) in-line enzymatic reactions and (ii) in-line derivatization and chemical reactions. The first part introduces electrophoretically mediated microanalysis (EMMA) and discusses and illustrates the different modes of EMMA. A literature overview on enzymatic reactions is provided. The second part starts with an introduction of the procedures and the nomenclature used in the area of in-line derivatization and chemical reactions based on EMMA. Reported derivatization and chemical reaction procedures are discussed and summarized.

Increasing the efficiency of in-capillary electrophoretically mediated microanalysis reactions via rapid polarity switching.

We report herein a new approach to enhance the sensitivity or speed of CE-based methods that involve in-line reactions. Rapid polarity switching (RPS) is used as a novel means for in-line mixing of two reactant solutions via rapid (1-5 s) and sequential switching of the applied potential field. By employing the RPS approach with a model chemical reaction, that between creatinine and alkaline picrate, significant enhancement in sensitivity (or a decrease in analysis time) is realized. Both increased convection and electrophoretic stacking of the ionic reagent appear to contribute to the rise in apparent reaction rate. When coupled with in-line chemistry of the Jaffe method for creatinine, the RPS methodology allows for 3-fold faster determination of creatinine in the concentration range needed for the analysis of clinical blood serum specimens. The new approach also allows the analysis to be performed without the need for the cumbersome and problematic enhanced sensitivity cell.

Analysis of single and tandem cylinder data using an orthogonal Volterra model approach

The development of a definitive predictive model that accurately accounts for the nonlinear hydrodynamics and structural response behavior observed in arrays of closely spaced risers on deep water structures will require a more detailed understanding of this fluid–structure interaction. Through the analysis and interpretation of data from model basin tests on single and paired tandem cylinder configurations this study is directed at uncovering the nature of some aspects of this nonlinear response behavior using an orthogonal third-order Volterra technique that can delineate between linear, quadratic and cubic nonlinear frequency dependent behavior. As part of the analysis procedure the data was organized in input–output pairs that would provide logical groupings of the measured quantities. The data pairs presented in this study include wave excitation and inline cylinder displacement, wave excitation and transverse cylinder displacement, wave excitation and inline reaction force, and, upstream cylinder and downstream cylinder response. This information is presented in terms of spectral and coherence plots. The single cylinder data is presented as a means to contrast the behavior of the tandem cylinders. Both configurations were analyzed at two different pretensions adding another dimension to this investigation. It is shown that although a primary variable such as displacement may be more easily measured, pretension and force measurements provide an important key to our understanding of this difficult problem.

In-line reaction monitoring of a methyl methacrylate and N, N-dimethylacrylamide copolymerization reaction using near-infrared spectroscopy.

Fast and accurate monitoring of monomer concentration during copolymerization reactions is of much interest. It is known that near-infrared spectroscopy (NIRS) can be used to monitor polymerization reactions. Here, a free radical solution copolymerization reaction between methyl methacrylate and N,N-dimethylacrylamide is considered. NIR spectra were measured in-line with a transflectance probe. The spectra of both involved monomers are very similar, making monitoring with NIRS challenging. It is shown that the NIRS calibration can be set up with only a few (5) off-line measured mixtures. Several validation methods for such a NIRS calibration model are discussed and tested. NIRS is used to follow conversion of the two monomers in a copolymerization reaction on-line.

Kinetic study of angiotensin converting enzyme activity by capillary electrophoresis after in-line reaction at the capillary inlet

The in-capillary reaction of angiotensin converting enzyme (ACE) with the tripeptide substrate hippuryl– l-histidyl– l-leucine was studied. ACE activity was determined by the quantitation of the product, hippuric acid, at 230 nm. Reaction occurred at the capillary inlet during a predetermined waiting period, followed by the electrophoretic separation of the compounds. When the set-up was reversed, i.e. reaction at the opposite side after short-end injection of enzyme and substrate, separation was achieved in less than 5 min. Using the Lineweaver–Burk equation, an average Michaelis constant for ACE from rabbit lung was calculated to be 1.16±0.12 m M, a value consistent with previously reported data.

Determination of passive-sampled sulphur dioxide in ambient air as sulphate ion by flow injection analysis with an in-line reaction column

A modified FIA method was developed for the determination of sulphur dioxide (SO 2) in ambient air collected by a passive sampler. SO 2 was oxidized by hydrogen peroxide and determined as sulphate ion in solution. Barium-dimethylsulfoazo-III complex was used as spectrophotometric reagent. A BaSO 4-immobilized in-line reaction column was introduced into the flow system to increase the sensitivity and reproducibility. An in-line cation exchange column was used to eliminate triethanolamine, which was used as the absorbent reagent in the passive sampler. Sulphate ions can be analyzed in the range of 0.08–10.00 mg l −1 with the R.S.D. less than 1.6% at the rate of 15 samples h −1. It was satisfactory to apply this method to the analysis of sulphur dioxide in ambient air and the results agreed with those obtained by ion chromatography.

New Procedure for Fumonisins B1 and B2 in Corn and Corn Products by Ion Pair Chromatography with o-Phthaldialdehyde Postcolumn Derivatization and Fluorometric Detection

Fumonisins are a group of naturally occurring mycotoxins produced by Fusarium moniliforme. An analytical method for fumonisins B1 and B2 in corn and related foods has been developed that utilizes ion pair chromatography with a postcolumn reaction technique. Samples were prepared and purified by tandem solid phase extraction columns (SAX and C18). The fumonisins were derivatized with o-phthaldialdehyde and N-acetyl-l-cysteine in an in-line reaction coil. Ion pair liquid chromatography with fluorescence detection is used for the separation and detection. Absolute recoveries of fumonisins ranged from 54 to 110% at 0.04 and 0.08 μg/g. The detection limit of this method is 20 ng. This procedure is relatively simple and provides a screening method for fumonisins in corn and related foods. Keywords: Determination; fumonisin; solid phase extraction; ion pair chromatography; o-phthaldialdehyde; postcolumn reaction; fluorometric

The stereochemical course of the ribulose-5-phosphate kinase-catalyzed reaction.

Spinach-leaf ribulose-5-phosphate kinase catalyzes the reaction of (Rp)-[beta, gamma-18O, gamma-18O]adenosine 5'-(3-thiotriphosphate) with ribulose 5-phosphate to form ribulose 1-[18O]phosphorothioate 5-phosphate. This product is incubated with CO2, Mg2+, and ribulose-bisphosphate carboxylase to form the [18O]phosphorothioate of D-glycerate. Reduction of this material using phosphoglycerate kinase/ATP, glyceraldehyde-3-phosphate dehydrogenase/NADH, triose-phosphate isomerase, and glycerol-phosphate dehydrogenase/NADH produces glycerol 3-[18O]phosphorothioate, which is subjected to ring closure using diethylphosphorochloridate. This in-line reaction produces a diastereoisomeric mixture of glycerol 2,3-cyclic phosphorothioates. 31P NMR spectroscopy was used to analyze the 18O content of the products. The anti-diastereoisomer, which is the major isomer formed and corresponds to the downfield 31P NMR signal (Pliura, D.H., Schomburg, D., Richard, J.P., Frey, P.A., and Knowles, J.R. (1980) Biochemistry 19, 325-329), retains the 18O label. This observation indicates that the ribulose-5-phosphate kinase reaction proceeds with inversion of configuration at phosphorus. The reaction is, therefore, unlikely to involve the participation of a covalent phosphoryl-enzyme intermediate.