The Dow Chemical Company

Dionex Corporation

Lee Scientific, Inc.

Timothy S Stevens

Hamish Small

Martin A Langhorst

Theodore E Miller, Jr

Robert A Bredeweg

Thomas L Peters

James C Davis

Hernan J Cortes

Curtis D Pfeiffer

Bruce E Richter

Andrew J Strandjord

William Charles Harris

Daniel J Swart

Gary L Jewett

Brenton S Coyne

Lawrence W Nicholson

Nile Nelson Frawley

Osro W Randall, Iii

Reid S Willis

Mark W Spence

Hernan Cortes

Deborah E Diedering

L David Rothman

An anion-exchange chromatographic packing composition which comprises: a substrate which consists essentially of particles having cation-exchanging sites at least on their available surfaces, the particles being of a diameter of between about 1 to about 75 microns; and a liquid coating which consists essentially of a hydrophilic, water soluble, film forming resin having anion-exchanging sites which attract available cation-exchanging sites of the substrate, wherein the liquid coating is retained by electrostatic bonds on the available surfaces of the substrate particles. The invention further includes a chromatographic column and process using the described packing composition.

High performance anion-exchange chromatographic packing composition

An analytical chemistry apparatus and method for introducing a reagent into a flowing stream of liquid carrier in order to quantitatively analyze one or more components of a sample added into the carrier. The reagent is permeated across a short section of membrane having relatively large pores. The use of such a membrane: (a) allows the membrane to be protected from physical damage by covering it with a perforate structure; (b) significantly reduces bandspreading across the membrane reagent addition device; (c) reduces the pressure drop across the membrane reagent addition device; and (d) still allows for the permeation of an effective amount of the reagent into the carrier. The reagent is preferably pressurized to minimize leakage of carrier across the membrane and the reagent can be self-pressurized by essentially completely filling the reagent reservoir of the invention with reagent and then hermetically sealing the reservoir.

Method for reagent addition to a flowing liquid carrier stream

The overall mass transport efficiency of hollow fiber membrane separation cells is increased by introducing segmented flow into the bores of the fibers. The invention is preferably practiced by dispersing a gas segmentation phase into a continuous liquid phase and feeding the dispersion into the bores of the fibers to form alternating flowing segments of gas and liquid.

Apparatus for membrane-permeation separations using segmented flow

Porous ceramic plugs are cast in place in chromatographic columns in order to provide supports for chromatographic beds in liquid chromatography devices and restrictors in supercritical fluid chromatographic devices. The supports are cast in place by fusing a silicate containing solution, such as one containing potassium silicate, which has been drawn into the outlet end of the column.

Chromatography columns with cast porous plugs and methods of fabricating

Packing tube membranes or membrane channels for Ion Chromatography with inert or charged ion exchange beads greatly increases overall suppressor efficiency. The length of membrane required is reduced, e.g. from 20 feet to 5 feet and bandspreading is reduced from 870 .mu.l to 200 .mu.l. This significant increase in efficiency is attributed to the mixing action of the packing on the flow stream which results in convective radial transport much more rapid than the diffusion controlled transport observed in unpacked membranes. The technique is also described for developing more efficient liquid chromatographic post-column reactors for adding reagent to the column effluent to increase detection sensitivity.

Liquid chromatographic method and apparatus with a packed tube membrane

The invention relates to a membrane assisted analytical chemical method for the determination of the concentration of an organic compound in an aqueous matrix. The membrane partitions the matrix from a receiving fluid. The organic compound permeates the membrane and passes into the receiving fluid which is then analyzed for the permeated compound by, for example, liquid or gas chromatography. The membrane is selected to prevent contamination of the receiving fluid from otherwise interferring components of the matrix. The concentration of the organic compound is above its solubility limit in water which would ordinarily prevent effective use of such a membrane assisted method. However, when the organic compound is emulsified with, for example, a surfactant, then a membrane assisted method is successful. The sensitivity of the method can be improved by using a thermal focusing/gas chromatography technique to concentrate the permeated organic compound from the receiving fluid and the membrane can be protected from physical damage by enclosing it in a perforate structure.

Determining organic compounds using a membrane

The invention is the novel combination of liquid chromatographic separation of water from other components of an injected sample followed by electrochemical detection and quantitation of the separated water.

Apparatus and method for the determination of water by liquid

Apparatus and method for membrane-permeation separations using segmented

A versatile and highly sensitive procedure of indirect photometric chromatography in which a variable capacity pH dependent weakly basic or weakly acidic ion exchange medium is used in the chromatographic column to effect ion separations. Adjusting eluent pH allows increased detection limits without extended analysis time, reduced column efficiency, or the need for a battery of conventional strongly basic/acidic ion exchange columns.

Indirect-photometric chromatography done in and with a variable capacity

An improved chromatographic analytical column, the column containing a pellicular type (agglomerated) anion-exchange packing, comprising: Component A, which comprises a pressure packed bed of substrate particles of insoluble synthetic resin, having cation-exchanging sites at least on their available surfaces, the Component A particles being of low porosity relative to Component B microparticles, described below, and Component B, derived by agglomerating microparticles of insoluble synthetic resin onto the pressure packed bed of Component A particles, the microparticles having a volume average diameter of less than about 1,500 and greater than about 50 Angstroms and having anion-exchanging sites, at least on their outer surfaces, which attract available cation sites of Component A, wherein the microparticles of Component B are attached as a monolayer to the available surfaces of the Component A particles.

High performance analytical column for anion determination

A permselective ion-exchange membrane, preferably comprising hollow fiber(s) immersed within a regenerant, is used to selectively neutralize or suppress the conductivity of electrolyte in a stream of eluent also containing chromatographically separated ions. The invention particularly specifies a chromatographic separating column useful with an electrolyte eluent solution to separate ionic species by elution chromatography, wherein the effluent of the separator column is treated by the described membrane to suppress the conductivity of the electrolyte but not that of the separated ions.

Ion analysis method and apparatus

An improved pellicular type (agglomerated) anion-exchange chromatographic packing composition which comprises:

An ion-exchange composition comprising a substrate of a macroporous synthetic resin having ion-exchanging sites at least on its available surface; and finely divided, synthetic resin particles having a volume average diameter less than 0.1 micron and greater than about 0.005 micron and having, at least on their outer surfaces, ion-exchanging sites which attract the ion-exchanging sites of the substrate, irreversibly attached as a monolayer to the available surface of the substrate. The composition is used for removal and separation of ions, and is especially useful in liquid ion-exchange chromatography.

High performance ion-exchange composition

Analytical method based on converting an acid or base species to water or absorbing the acid species whereby the species of interest is no longer responsive to a detector. Interfering salt(s) is simultaneously converted to a detectable acid or hydroxide derivative(s) in whole or in part. The species of interest is determined indirectly by subtracting the response of the salt derivative (which is proportional to the original salt) from a pre-derivatization response which is proportional to the salt plus base or salt plus acid.

Analytical method for determining acid/salt and base/salt species

Acid or alternately base species concentration in aqueous and non-aqueous samples is quantitated, in the presence of interfering ionic salts, using most preferably differential conductivity detection combined with ion-exchange derivatization, wherein characteristically the acid or base species is derivatized to water, and blended indistinguishably in a required aqueous carrier phase, and the interfering salt(s) is derivatized to a distinguishable hydroxide or acid derivative(s). Using the preferred mode of detector read-out, the calibrated peak of the conductimetric response of the salt derivative(s) is compared to the peak of the conductimetric response of the sample and the response differential is displayed and used to predict the acid or base species concentration. The salt(s) concentration (with some exceptions) may be simultaneously predicted since it is proportional to the first mentioned peak. The technique has utility with respect to acids and bases broadly, and most advantageously is used with respect to strong and moderately strong acids and bases of a pK.sub.a and pK.sub.b value, respectively, of about 2 or less.

Growing community of inventors

Midland, MI, United States of America

Timothy S Stevens