The Dow Chemical Company

Richard G Melcher

Hernan J Cortes

Robert A Bredeweg

Ritchie A Wessling

Terrence McCabe

Gary L Jewett

Paul L Morabito

Joseph F Hiller

Earl E Burt, Iii

Paul J O'Connor

E Deniz Yalvac

Donald D Schmidt

A chemical analysis method for the determination of a first organic acid in the presence of a second organic acid both of which are in a solution to be analyzed, the pK.sub.a of the first acid being at least 2 pK.sub.a units larger than the pK.sub.a of the second acid. The method includes three steps. The first step if to form a pH adjusted solution to be analyzed by adjusting the pH of the solution to be analyzed to be between the pK.sub.a of the first acid and the pK.sub.a of the second acid so that the first acid is predominately in its unionized form and so that the second acid is predominately in its ionized form. The second step is to partition the pH adjusted solution to be analyzed from a receiving solution with a semipermeable membrane, the semipermeable membrane being more permeable to the unionized form of the first acid than to the ionized form of the second acid, the first acid being soluble in the receiving solution so that the first acid permeates into the membrane from the pH adjusted solution to be analyzed and then permeates out of the membrane into the receiving solution. The last step is to determine the concentration of the first acid in the receiving solution so that the concentration of the first acid in the solution to be analyzed can be estimated.

Membrane method for the determination of an organic acid

A reversed permeation membrane assembly and method for collecting one or more compounds of interest from a sample solution. The membrane assembly includes a semi-permeable membrane of predetermined thickness and length, and having inner and outer surfaces. The membrane is attached adjacent its outer surface to a substantially rigid membrane support, and a non-porous barrier contacts the outer surface of the membrane to prevent permeation of compounds beyond the outer surface in use. In a preferred embodiment, the semi-permeable membrane assumes a substantially tubular conformation through which sample solution may be passed. The membrane support also preferably features a tubular conformation within which the semi-permeable membrane is mounted. Because of its unique structure and improved efficiency, the assembly of the present invention may be incorporated for in-line use with liquid and gas chromatography devices and GC/MS units. In some applications, the extractant can even be flowed through the membrane cell to collect analytes and directly to an LC column for analysis in a substantially non-stop manner.

Apparatus and method for reversed permeation membrane extraction of

A three step flow injection analysis method for determining the degree of neutralization of phenol in solution. The first step is to flow a stream of a carrier liquid, such as water, along one side of a two sided semipermeable membrane, such as a silicone rubber membrane. The second step is to flow a stream of water along the other side of the membrane to a detector, such as a flow through ultraviolet spectrometer, the detector being responsive to the concentration of the phenol in the flowing stream of water. The third step is to add a volume of the solution to the flowing stream of carrier liquid so that the solution is carried to the first side of the membrane where a portion of the phenol permeates across the membrane into the flowing stream of water to be detected by the detector, the degree of neutralization of the phenol in the solution being a function of the response of the detector. The results of the method are substantially unaffected by variations in the concentration of the phenol.

Method for the determination of the degree of neutralization of phenol

Apparatus and method for extracting a component from a sample across a membrane into an extractant and then injecting the extracted sample component into a chromatographic eluent and onto a chromatographic column to chromatographically analyze the extracted sample component. In essence, the advance provided by this invention is that the extractant and the eluent are the same and only one pump is used for pumping the eluent and extractant. In prior apparatus and methods in this field, the extractant and the eluent were separate and each had its own pump.

Apparatus for membrane assisted liquid chromatography

In one embodiment the invention is a method for on-column valved injection gas chromatography by on-column injecting more than 5 microliters and less than one milliliter of sample consisting of a solvent and a component of interest into a retention gap/capiliary column system with an injection valve at a first carrier gas flow rate, followed by a substantially higher carrier gas flow rate to blow the solvent of the sample out of the system at a rapidly increased rate and then a return to a lower flow rate to chromatograph the component of interest. In another embodiment, less than 5 microliters of sample consisting of a solvent and a component of interest is on-column injected into a capillary column using an injection valve and a relatively high column inlet pressure of gas to move the sample from the injection valve into the colunm rapidly and with reduced carryover. Then, the pressure of carrier gas is reduced to a normal pressure for chromatography of the component of interest.

Method for on-column injection gas chromatography

A chromatographic method for the determination of individual phenols in water by adding a halogenating agent to the water, e.g., using the bromate-bromide reaction to generate tribromide ions which react with the phenols to form bromo-derivatives of the phenols, then to permeate the bromo-derivatives across a membrane, e.g., a silicone rubber membrane, into a liquid extractant, e.g., a dilute aqueous solution of sodium hydroxide and acetonitrile, and then determining the permeated bromo-derivatives in the liquid extractant by chromatography, e.g., by injecting the liquid extractant containing the permeated bromo-derivatives into a reverse phase liquid chromatographic system. The use of a membrane is essential in the present invention because it allows the use of a high enough concentration of halogenating agent to completely halogenate most any sample and provides for the removal of the halo-derivatives from the halogenation reaction site before any substantial degradation of the halo-derivatives occurs from a relatively high concentration of halogenating agent. Total phenols as a group can be determined by modifying the method to use backflow liquid chromatography to eliminate potential interferences and to elute the halo-derivatives in a single chromatographic peak.

Method for the determination of phenols in water

A method for rapid and sensitive membrane assisted Flow Injection Analysis. A sample, containing a component to be analyzed, is injected into a flowing stream of carrier liquid and flowed past one side of a two-sided membrane. A receiving liquid is flowed past the other side of the membrane. The component to be analyzed is absorbed by the membrane from the carrier stream, is desorbed into the receiving stream and is carried to a detector for analysis in less than about 5 minutes. Critically, the partition coefficient of the component to be analyzed between the membrane and the receiving liquid is less than about 1.times.10.sup.1.

Membrane assisted flow injection analysis

Method for membrane assisted liquid chromatography

Method for quantitatively analyzing substances containing elements other than carbon, hydrogen and oxygen by (1) adsorbing such substances on a particulate, substantially dust and contaminant free carbonized product prepared by (A) first partially dehydrochlorinating a normally crystalline vinylidene chloride polymer at temperatures below the melting point of such polymer to an extent of at least about 5 percent of theoretical HCl loss, then (B) completing the dehydrochlorination of such material, in the substantial absence of oxygen, by heating the material to carbonizing temperatures of from about 600.degree.C to about 1200.degree.C; then (2) analyzing the substance adsorbed on such carbonized product.

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Midland, MI, United States of America

Richard G Melcher