Selective detection approach to ion exclusion chromatography

Journal Article · Wed Mar 15 04:00:00 EST 1989 · Analytical Chemistry; (USA)

DOI:https://doi.org/10.1021/ac00181a010· OSTI ID:5242452

Okada, Tetsuo; Dasgupta, P K ^[1]

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1. Texas Tech Univ., Lubbock (USA)

A helical, filament-filled perfluorosulfonate membrane suppressor is utilized with high concentrations (0.1-1.0 M) of NaCl (sometimes additionally including {le} 1 mM NaOH) as regenerant to convert H{sup +} in the eluent (up to 10 mM HNO{sub 3}) to Na{sup +}. Elution of the weak acid analytes from the suppressor as their Na salts causes an increase in pH, monitored optically by the postsuppressor introduction of an acid-base indicator. Theoretical considerations involve the concentration and K{sub In} of the indicator and their effects on the background absorbance, dynamic range, and analyte response. Results are presented for 4-nitrophenol as indicator (base form monitored at 400 nm) introduced permeatively through a membrane reactor. Analyte acids (pK{sub A} range {approx} 4.5-9.5) are selectively detected; maximum sensitivity is reached in the middle of this pK{sub A} range. The sensitivity for high pK{sub A} acids is poor, caused by a substochiometric suppressor reaction. Detectability for the moderate pK{sub A} acids is in the low micromolar (50 pmol) level, even with a pH 2 eluent. Capability of gradient elution and advantages of a pH 2 eluent are demonstrated. Operational considerations of the membrane suppressor, e.g., adjustment of the suppressor effluent pH by addition of NaOH to the regenerant and relative flow directionality, transmembrane loss of very weak acids in the uncharged form, etc., are discussed in terms of the results.

• DOE Contract Number: FG05-84ER13281
• OSTI ID: 5242452
• Journal Information: Analytical Chemistry; (USA), Journal Name: Analytical Chemistry; (USA) Vol. 61:6; ISSN 0003-2700; ISSN ANCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400105* -- Separation Procedures
CATIONS
CHARGED PARTICLES
CHEMICAL ANALYSIS
CHROMATOGRAPHY
DATA
ELUTRIATION
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
ION EXCHANGE CHROMATOGRAPHY
IONS
NUMERICAL DATA
PH VALUE
QUANTITATIVE CHEMICAL ANALYSIS
SEPARATION PROCESSES