Permeative amine or acid introduction for very weak acid detection in ion chromatography

Patent metadata

Field	Value
Publication number	US-2017199167-A1
Application number	US-201615377833-A
Country	US
Kind code	A1
Filing date	Dec 13, 2016
Priority date	Jan 7, 2016
Publication date	Jul 13, 2017
Grant date	—

Abstract

A permeative amine/acid introduction device (PAID) is placed after a conventional KOH eluent suppressed conductometric anion chromatography (SCAC) system. The PAID converts the suppressed eluites from the acid form to the corresponding salt. For example, when the analytes are acids, they are converted to the corresponding ammonium salt (NR 2 H+HX→NR 2 H 2 + +X − ) and allows very weak acids HX (pK a ≧7.0) that cannot normally be detected by SCAC to be measured by a second conductivity detector following the PAID. Permeative reagent introduction is dilutionless, can be operated without pumps and provides good mixing with low band dispersion (as small as 30 μL). An exemplary amine is diethylamine (DEA), which was chosen as the amine source due to its low pK b value (pK b 3.0), high vapor pressure, and low toxicity and low odor.

First claim

What is claimed is:

1 . A device for forming a salt of a weakly dissociating acid or base plumbed following a chromatographic separation of a mixture containing said acid or base by passage of said mixture through a chromatographic medium, said device comprising a permeable membrane in contact with a volatile base or acid on one side of said permeable membrane, allowing the passage of said volatile base or acid from said solution into another side of said permeable membrane, said device configured for integration into a chromatographic system downstream of said chromatographic medium such that an effluent from said chromatographic medium containing said weakly dissociating acid or base flows in fluidic contact with the other side of said permeable membrane.

2 . The device according to claim 1 , wherein said permeable membrane is in a tubular configuration having a lumen and said lumen contains effluent from said chromatographic medium containing at least one of said weakly dissociating acid or base.

3 . The device according to claim 2 , wherein said effluent contains silicate.

4 . The device according to claim 1 , wherein said membrane is within the lumen of an outer jacket, and said volatile acid or said volatile base is in an annulus formed by an outer surface of said membrane and an inner surface of said outer jacket.

5 . The device according to claim 1 , wherein said membrane is gas permeable and liquid impermeable.

6 . A chromatographic system comprising:
(a) a device for forming a salt of a weakly dissociating acid or base plumbed following a chromatographic separation of a mixture containing said acid or base by passage of said mixture through a chromatographic medium, wherein said device comprises:
(i) a permeable membrane in contact with a volatile base or acid on one side of said permeable membrane, allowing the passage of said volatile base or acid from said solution into another side of said permeable membrane, said device configured for integration into a chromatographic system downstream of said chromatographic medium such that an effluent from said chromatographic medium containing said weakly dissociating acid or base flows in fluidic contact with the other side of said permeable membrane, and
wherein said device is in fluidic connection with a column containing said chromatographic medium, and also in fluidic connection with a detector configured to detect said salt of said weakly dissociating acid or base.

7 . The chromatographic system according to claim 6 , said system further comprising a suppressor in fluidic connection with said column and located downstream from said column, and upstream from said detector.

8 . The chromatographic system according to claim 7 , said system further comprising a sample injector in fluidic connection with said column and located upstream from said column.

9 . The chromatographic system according to claim 7 , said system further comprising an eluent generator in fluidic connection with said column and located upstream from said column.

10 . A method for improved detection of weakly dissociating acids or bases in an ion chromatographic separation of a sample mixture comprising said weakly dissociating acids or bases, said method comprising:
(a) passing said sample mixture through a chromatographic medium forming an effluent, flowing said effluent adjacent to a first surface side of a permeable membrane in a permeant membrane device, said membrane having a second surface side in contact with a volatile base or acid, such that said volatile base or acid permeates said membrane contacting said weakly dissociating acids or bases, thereby forming a salt thereof in said effluent; and (b) flowing said effluent comprising said salt of said acid or base into a detector configured to detect said salt, thereby detecting said salt.

11 . The method according to claim 10 , wherein said improved detection produces a signal from said detector greater in magnitude for said salt of said acid or base than a corresponding signal produced for said acid or base in an identical method in the absence of said permeant membrane device.

12 . The method according to claim 10 , wherein said effluent comprises silicate.

13 . A device for forming a salt of a weakly dissociating acid or base plumbed following a chromatographic separation of a mixture containing said acid or base by passage of said mixture through a chromatographic medium, said device comprising:
(a) an impermeable component defining an internal compartment, comprising;
(i) at least one of an acid and a base introduction section contiguous and fluidically connected with at least one of a respective weakly dissociating acid and weakly dissociating base extraction section, said at least one of said acid and base introduction section comprising at least one of a respective acid and base inlet port and at least one of a respective acid and base waste outlet port; and
(b) a permeable membrane in contact with at least one of a volatile base or acid on a first side of said permeable membrane to allow passage of said at least one of said volatile acid and base from said mixture into a second side of said permeable membrane, said device configured for integration into a chromatographic system downstream of said chromatographic medium such that an effluent from said chromatographic medium containing said weakly dissociating acid or base flows in fluidic contact with said second side of said permeable membrane.

14 . The device according to claim 13 , wherein said permeable membrane is disposed within a cavity of said impermeable component, and said impermeable component is formed of a material that is impermeable to liquid components of said mixture.

15 . The device according to claim 14 , wherein said impermeable component and said permeable membrane are spaced apart from each other to facilitate fluid flow between an outer surface of said permeable membrane and an inner surface of said impermeable component.

16 . The device according to claim 13 , wherein said at least one weakly dissociating acid extraction section or weakly dissociating base extraction section is fluidly connected to a detector.

17 . A method for improved detection of weakly dissociating acids or bases in an ion chromatographic separation of a sample mixture comprising said weakly dissociating acids or bases, said method comprising:
(a) introducing, in an acid or base introduction section of a permeable membrane device, an acid or a base to a surface of a permeable membrane via an acid or base introduction port; (b) permeating said membrane with said acid or base and contacting said weakly dissociating acids or bases within an internal compartment of said membrane; (c) traversing said weakly dissociating acids or bases along a length of said acid or base introduction section to enter a weak acid or base extraction section; (d) introducing deionized water into said weak acid or base extraction section, via a water introduction port; and (e) contacting a surface of said membrane with said deionized water, thereby extracting protonated weakly dissociating acid or deprotonated weakly dissociating base and carrying said protonated weakly dissociating acid or deprotonated weakly dissociating base out of said permeable membrane device and to a detector.

Assignees

• Univ Texas

Inventors

• Dasgupta Purnendu K
• Shelor Charles Phillip
• Liao Hongzhu

Classifications

• G01N2030/965

  suppressor columns · CPC title

• B01D15/363

  Anion-exchange · CPC title

• G01N30/96 Primary

  using ion-exchange (G01N30/02, G01N30/90 take precedence) · CPC title

• B01D15/367

  Ion-suppression · CPC title

• G01N27/44756

  Apparatus specially adapted therefor · CPC title