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Two-Dimensional detection in ion chromatography: sequential conductometry after suppression and passive hydroxide
R Al-Horr1, P K Dasgupta, R L Adams
1Department of Chemistry and Biochemistry, Texas Tech University, Lubbock 79409-1061, USA.
Analytical Chemistry
|October 19, 2001
Summary
This study introduces a new ion chromatography method for sensitive anion detection. The technique uses sequential suppressed and nonsuppressed ion chromatography (IC) for improved analysis of common and weak acid anions.
Area of Science:
- Analytical Chemistry
- Separation Science
Background:
- Ion chromatography (IC) is a common technique for anion analysis.
- Detecting very weak acid anions requires specialized methods due to low ionization.
Purpose of the Study:
- To develop an improved ion chromatography method for sensitive detection of common and weak acid anions.
- To investigate the use of a membrane device for passive KOH introduction and a second conductivity detector.
Main Methods:
- Sequential suppressed and nonsuppressed IC was employed.
- A membrane device introduced KOH into the eluent stream via Donnan forbidden leakage.
- A second conductivity detector measured the stream against a low KOH background.
- Different cation exchange membranes and device configurations (planar, tubular, FFAH) were evaluated.
Main Results:
- The method achieved sensitive detection of both common and weak acid anions.
- The filament-filled annular helical (FFAH) device configuration enhanced hydroxide mixing.
- Low noise levels (< or = 7 nS/cm) and band dispersion (< 82 microL) were achieved with the FFAH device.
- Weak acids were detected as negative peaks against a low KOH background.
Conclusions:
- The improved IC method offers sensitive and effective detection of a wide range of anions.
- The membrane-based KOH introduction and FFAH device design are key to the method's performance.
- This technique provides a valuable advancement for anion analysis in various chemical applications.