US4925567A
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Baseline stabiilty in gradient ion chromatography by using a nonionic modifier
Assignee: BASF Corp
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Filing: 1989-03-02
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Granted: 1990-05-15
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Expires: 2009-03-02
Abstract
Abstract A stable baseline is achieved in a gradient ion chromatographic analysis by adding a nonionic modifier to the electrolytic eluent. The addition of the modifier may occur at any point upstream of the detector. The nonionic modifier has the effect of shifting the equilibrium of unsuppressed effluent electrolyte towards it nonionic form. For example, the addition of the nonionic modifier shifts both bicarbonate and carbonate towards the nonionic, nonconductive carbonic acid form.
Inventors
- 👤 David L. McAleese
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 03:29
CPC Classifications
G; G01; G01N; G01N30/00; G01N30/96; G01N30/02; G01N30/26; G01N30/28; G01N30/34; G01N2030/342; G01N2030/965; Y; Y10; Y10T; Y10T436/00; Y10T436/25; Y10T436/25375; Y10T436/255
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
218 words
A method of ion chromatography with improved background stability for analyzing a sample solution containing a plurality of anions and using a gradient eluent, the method comprising: A. flowing an electrolytic eluent through an anion exchange chromatographic column; B. injecting, into the flowing electrolytic eluent, an anion solution to be analyzed, the injection taking place upstream of the chromatographic column, the anions being separated in the chromatographic column; C. increasing the ionic strength of the electrolytic eluent as a function of time during the chromatographic separation; D. adding an effective amount of a nonionic modifier to the electrolytic eluent at a point upstream of the detector, the nonionic modifier being a substantially water-soluble compound which is non-reactive with the electrolytic eluent and causes electrolyte anions to combine with hydrogen ions in solution, whereby the electrolyte anions are shifted more towards their nonionic form and which, upon suppression shifts the ionic/nonnionic balance of the electrolytic eluent towards the nonionic form, the shift in balance being controlled so that a substantially balanced baseline results; E. suppressing, in a suppressor column, at least a portion of the ionic strength of an effluent from the chromatographic column; F. passing at least a portion of the effluent emitted from the suppressor column through an electronic property detector, whereby the separated anions are detected.
Claim 2
Independent Claim
218 words
A method of ion chromatography with improved background stability for analyzing a sample solution containing a plurality of anions and using a gradient eluent, the method comprising: A. flowing an electrolytic eluent through an anion exchange chromatographic column; B. injecting, into the flowing electrolytic eluent, an anion solution to be analyzed, the injection taking place upstream of the chromatographic column, the anions being separated in the chromatographic column; C. increasing the ionic strength of the electrolytic eluent as a function of time during the chromatographic separation; D. adding an effective amount of a nonionic modifier to the electrolytic eluent at a point upstream of the detector, the nonionic modifier being a substantially water-soluble compound which is non-reactive with the electrolytic eluent and causes electrolyte anions to combine with hydrogen ions in solution, whereby the electrolyte anions are shifted more towards their nonionic form and which, upon suppression shifts the ionic/nonnionic balance of the electrolytic eluent towards the nonionic form, the shift in balance being controlled so that a substantially balanced baseline results; E. suppressing, in a suppressor column, at least a portion of the ionic strength of an effluent from the chromatographic column; F. passing at least a portion of the effluent emitted from the suppressor column through an electronic property detector, whereby the separated anions are detected.
Claim 3
Dependent Claim
34 words
The method as described in claim 1 wherein the electrolyte in the electrolytic eluent is selected from the group consisting of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, lithium carbonate, and lithium bicarbonate.
Claim 4
Dependent Claim
27 words
The method as described in claim 1 wherein the cation in the electrolytic eluent is a member selected from the group consisting of sodium, potassium, and lithium.
Claim 5
Dependent Claim
24 words
The method as described in claim 1 wherein the anion exchange chromatography column has a silica stationary phase with quaternary ammonium anion exchange sites.
Claim 6
Dependent Claim
24 words
The method as described in claim 1 wherein the anion exchange chromatography column has a polymeric stationary phase with quaternary ammonium anion exchange sites.
Claim 7
Dependent Claim
24 words
The method as described in claim 1 wherein the anion solution to be analyzed is injected into the flowing electrolytic eluent via a valve.
Claim 8
Dependent Claim
27 words
The method as described in claim 1 wherein the nonionic modifier is selected from the group consisting of isopropanol, propanol, methanol, acetonitrile, and dimethylformamide, dioxane, and tetrahydrofuran.
Claim 9
Dependent Claim
23 words
The method as described in claim 1 wherein the nonionic modifier is selected from the group consisting of isopropanol, propanol, methanol, and acetonitrile.
Claim 10
Dependent Claim
13 words
The method as described in claim 1 wherein the nonionic modifier is isopropanol.
Claim 11
Dependent Claim
27 words
The method as described in claim 1 wherein during the chromatographic run, the ionic strength of the eluent is increased by a factor between 2 and 100.
Claim 12
Dependent Claim
27 words
The method as described in claim 1 wherein during the chromatographic run, the ionic strength of the eluent is increased by a factor between 5 and 20.
Claim 13
Dependent Claim
25 words
The method as described in claim 1 wherein during the chromatographic run the concentration of the nonionic modifier is increased between several percent and 200-fold.
Claim 14
Dependent Claim
23 words
The method as described in claim 1 wherein the total concentration of bicarbonate and carbonate in the eluent increases during the chromatographic run.
Claim 15
Dependent Claim
17 words
The method as described in claim 1 wherein the suppressor column is a continuously regenerated suppressor column.
Claim 16
Dependent Claim
18 words
The method as described in claim 14 wherein the suppressor column is a cation exchange fiber suppressor column.
Claim 17
Dependent Claim
18 words
The method as described in claim 14 wherein the suppressor column is a cation exchange micromembrane suppressor column.
Claim 18
Dependent Claim
16 words
The method as described in claim 1 wherein the electronic property detector is a conductivity detector.
Claim 19
Dependent Claim
26 words
The method as described in claim 1 wherein the electronic property detector is selected from the group consisting of conductivity detectors, electrochemical detectors, and pH detectors.
Claim 20
Dependent Claim
33 words
The method as described in claim 1 wherein the ionic strength of the electrolytic eluent is increased by increasing the concentration of at least one electrolyte in the eluent during the chromatographic run.
Claim 21
Dependent Claim
32 words
The method as described in claim 1 wherein the ionic strength of the electrolytic eluent is increased by adding at least one additional electrolyte to the electrolytic eluent during the chromatographic run.
Claim 22
Dependent Claim
26 words
The method as described in claim 1 wherein the concentration of the nonionic modifier is increased as a function of time as the chromatographic run progresses.
Claim 23
Dependent Claim
24 words
The method as described in claim 1 wherein the concentration of the nonionic modifier is increased in a stepwise fashion during the chromatographic run.
Claim 24
Dependent Claim
50 words
The method as described in claim 1 wherein the electrolytic eluent comprises sodium carbonate and sodium bicarbonate and wherein the nonionic modifier is isopropanol, and wherein the concentration of the nonionic modifier is increased in stepwise fashion and the ionic strength of the electrolytic eluent is increased in stepwise fashion.
Claim 25
Dependent Claim
62 words
The method as described in claim 1 wherein the ionic strength of the electrolytic eluent is increased during the run by switching from at least 1 initial electrolyte in the eluent to at least one final electrolyte in the eluent, and wherein the ionic strength of the final electrolytic eluent is substantially greater than the ionic strength of the initial electrolytic eluent.
Claim 26
Dependent Claim
25 words
The method as described in claim 24 wherein the initial electrolyte in the eluent is bicarbonate and the final electrolyte in the eluent is carbonate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-05-14 | 1993-11-13 | 1994-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-05-14 | 1997-11-13 | 1998-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-05-14 | 2001-11-13 | 2002-05-15 | $7700.00 | Window Closed / Lapsed |