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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #156501
Title: AUTOMATIC GENERATION OF ULTRAPURE HYDROXIDE ELUANT FOR CARBOHYDRATE ANALYSIS OF ENVIRONMENTAL SAMPLES 1567

Author
item Martens, Dean
item Loeffelmann, Kevin

Submitted to: Journal of Chromatography
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/17/2003
Publication Date: 1/23/2004
Citation: Martens, D.A., Loeffelmann, K.L. 2004. Automatic generation of ultrapure hydroxide eluant for carbohydrate analysis of environmental samples. Journal of Chromatography. 1039:33-37.

Interpretive Summary: Rapid analysis of plant and soil carbohydrate concentrations may prove to be extremely important in understanding the rate of carbon cycling in the terrestrial system as plant carbohydrates compose between 20 and 60% of the plant carbon at senescence. Ion exchange separation of the monosaccharide composition of the carbohydrate concentration in soils provides evidence of the source of the plant carbon present in soil, but efficient analysis of many soil samples requires synthesis of sodium hydroxide (NaOH) solutions employed in the ion exchange separations. Although NaOH has many advantages for ion exchange separations, NaOH solutions are prone to adsorption of atmospheric carbon dioxide resulting in production of carbonates that can affect the chromatography. Production of NaOH solutions for separation of carbohydrates 'online' through system software eliminates the problems of prepared NaOH solutions and results in faster chromatographic analysis with improved sensitivity and precision with a comparison with established NaOH systems for determination of terrestrial carbohydrates. This manuscript documents the improved methodology and shows significantly reduced concentrations of NaOH in the laboratory waste streams.

Technical Abstract: High performance anion exchange chromatography (AEC) coupled with pulsed amperometric detection (PAD) under alkaline conditions has significantly improved our understanding of the function of carbohydrates in cycling of terrestrial carbon. The use of NaOH as an eluant has many advantages for anion analysis, but NaOH solutions are also an excellent trap for atmospheric CO2 resulting in eluant carbonate ion contamination. To minimize the carbonate contamination, eluant generation technology has been marketed that produces ultra pure hydroxide (OH) eluants on demand. Application of this technology significantly reduced the amounts of OH present in the waste stream and provided faster chromatographic runs with greater sensitivity and precision for determining the monosaccharide composition from environmental samples. Minimizing the salt concentration to < 50 mM from acid hydrolysis extractions injected (25 'l injection volume) on column improved reproducibility of analyte retention times and separations. Eluant generation technology eliminated inconsistent OH eluant preparation that is often due to carbonate contamination. The contamination increases retention time variability for monosaccharides released by hydrolysis of biological samples.