https://rua.ua.es/dspace/bitstream/10045/57890/5/2015_Barbosa_etal_BiotechAdv_preprint.pdf

Strategies for the one-step immobilization–purification of enzymes as industrial biocatalysts

Since the discovery of perchlorate in the ground and surface waters of several western states, there has been increasing interest in the health effects resulting from chronic exposure to low (parts per billion [ppb]) levels. With this concern has come a need to investigate technologies that might be used to remediate contaminated sites or to treat contaminated water to make it safe for drinking. Possible technologies include physical separation (precipitation, anion exchange, reverse osmosis, and electrodialysis), chemical and electrochemical reduction, and biological or biochemical reduction. A fairly unique combination of chemical and physical properties of perchlorate poses challenges to its analysis and reduction in the environment or in drinking water. The implications of these properties are discussed in terms of remediative or treatment strategies. Recent developments are also covered.

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Perchlorate Chemistry: Implications for Analysis and Remediation

A contactless capacitively coupled conductivity detector for capillary electrophoresis is introduced. The detector consists of two electrodes which are placed cylindrically around the outer polyimide coating of the fused-silica capillary with a detection gap of 2 mm. The electrodes form a cylindrical capacitor, and the electric conductivity of the solution in the gap between the electrodes is measured. A high audio or low ultrasonic frequency for coupling of the ac voltage is used in order to minimize the influence of reactance of the liquid. For an improved version of the detector, two syringe cannulas are used as the electrodes and the capillary is simply assembled into the tubing. This allows an easy placement of the detector on various positions along the capillary. The limit of detection of inorganic cations and anions is 200 ppb, as determined for sodium and chloride, respectively.

Contactless conductivity detection for capillary electrophoresis.

An oscillometric detector for capillary electrophoresis (CE) has been described. Two 2-mm silver rings separated by 1 mm were painted over the polyimide coating of a fused-silica capillary (75-μm i.d. and 360-μm o.d.) and used as electrodes for oscillometric measurements. A function generator was used to apply a sinusoidal signal over one of the electrodes; the other one was connected to a current-to-voltage converter. The rectified signal is proportional to the admittance of the cell, which is a function of the inner solution conductivity in the region of the electrodes. Electropherograms of alkaline and alkaline-earth cations showed good signal-to-noise ratio. For typical electrophoretic conditions, the limit of detection for lithium was 1.5 μM, and there was good linearity (R = 0.998 for eight data points) up to 2 mM. Indirect conductivity detection of quaternary ammonium salts was achieved by using potassium acetate running buffer, showing results similar to those from conventional conductometric dete...

An Oscillometric Detector for Capillary Electrophoresis

We gratefully recognize the support from the Spanish Government, CTQ2013-41507-R, Colciencia (Colombia) and CNPq (Brazil). The predoctoral fellowships for Mr dos Santos (CNPq, Brazil) are also recognized. A. Berenguer-Murcia thanks the Spanish Ministerio de Ciencia e Innovaciun for a Ramon y Cajal fellowship (RyC-2009-03813).

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Importance of the Support Properties for Immobilization or Purification of Enzymes

Capillary electrophoresis combined with suppressed conductivity detection is a highly sensitive and selective method for the determination of UV-transparent ionic species. Using direct injection techniques (no electrostacking), minimum detection limits for common organic and inorganic ions are in the range of 1-10 ppb. Suppressors are made from short ion-exchange membrane capillaries and are placed between the separation capillary and the detector cell. The suppressor is placed in the destination vial, which contains regenerant and the ground electrode. The method is dependent on the presence of electroendoosmotic flow in the capillary to transport analyte and buffer ions through the suppressor

Determination of cations and anions by capillary electrophoresis combined with suppressed conductivity detection

New membrane-based electrolytic suppressor device for suppressed conductivity detection in ion chromatography

A suppressor for use in ion chromatography including at least an effluent flow channel separated by a charged membrane from a suppressor flow channel. A screen of the same charge as the membrane is placed in at least the effluent flow channel. Preferably, a similar screen is placed in the regenerant flow channel. The screen increases the dynamic capacity of the membrane suppressor.

Modified membrane suppressor and method for use

Factors controlling ion-exchange selectivity in suppressed ion chromatography

A method of streamlining and lowering the cost of operation of ion chromatography as well as improving detection limits is disclosed. The apparatus includes chromatographic separating means through which a sample is eluted in an eluent solution including an electrolyte. The apparatus includes suppressor means having a chromatography effluent compartment means separated from a detector effluent compartment means by an ion exchange membrane, forming a chromatography effluent flow channel and a detector effluent channel, respectively. Electrode means are disposed in communication with both flow channels for passing an electric current transverse to the solution that is passing through them. The chromatography effluent flows through the chromatography effluent flow channel of the suppressor and through detector means which detects resolved ionic species therein. The effluent from the detector means is then recycled through the detector effluent flow channel and forms a sump for electrolyte ions passing across the chromatography effluent as well as supplying the water for the electrolysis reaction generating acid (or base) for suppression.

John R. Stillian

Papers

Determination of cations and anions by capillary electrophoresis combined with suppressed conductivity detection

New membrane-based electrolytic suppressor device for suppressed conductivity detection in ion chromatography

Modified membrane suppressor and method for use

Factors controlling ion-exchange selectivity in suppressed ion chromatography

Ion chromatography system using electrochemical suppression and detector effluent recycle