The Dow Chemical Company

Reid S Willis

Timothy S Stevens

Andrew J Strandjord

Robert A Bredeweg

Brenton S Coyne

David S Brink

Mark W Spence

David L Simeroth

Dale J Backlund

A new use for a process gas chromatography liquid injection valve of the Bendix type, i.e., a valve having a distal heated vaporization chamber, a central sample chamber, a valve stem bore intersecting both chambers, a radially grooved valve stem positioned within the valve stem bore and an air actuator for moving the valve stem back and forth in the valve stem bore. The heated vaporization chamber is removed and is not used. Instead, a carrier gas is now flowed through the remaining chamber of the valve. The valve is mounted on a process vessel or a process conduit (and not on a gas chromatograph) so that the valve stem of the valve now can be extended from the valve and into the process liquid in the process vessel or conduit. The groove of the valve stem fills with sample and then the valve stem is retracted into the valve so that the groove is positioned within the remaining chamber, i.e., what was used as a sample chamber is now is used as a vaporization chamber. The liquid in the groove can then evaporate into the carrier gas and be carried to a gas chromatograph or other analyzer.

Fluid sampling for gas chromatograph with modified sampling valve

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

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Martinez, CA, United States of America

Reid S Willis