title: A novel ion-exclusion chromatography-mass spectrometry method to measure concentrations and cycling rates of carbohydrates and amino sugars in freshwaters.
abstract: The concentrations of free neutral carbohydrates and amino sugars were determined in freshwater samples of distinct matrix complexity, including meso-, eu- and dystrophic lakes and ponds, using high-performance ion-exclusion chromatography (HPIEC) coupled to mass spectrometry (MS). In contrast to other methods, our approach allowed the quantification of free neutral carbohydrates and amino sugars at low nM concentrations without derivatization, de-salting or pre-concentration. New sample preparation procedures were applied prior to injection employing syringe and hollow fiber filtration. Analytes were separated on a strong cation exchange resin under 100% aqueous conditions using 0.1% formic acid as a mobile phase. To minimize background noise in MS, analytes were detected in a multiple reaction monitoring scan mode with double ion filtering. Detection limits of carbohydrates and amino sugars ranged between 0.2 and 2nM at a signal-to-noise ratio >5. Error ranged between 1 and 12% at 0.5-500nM levels. Using a stable isotope dilution approach, both the utilization and recycling of glucose in Lake Zurich was observed. In contrast, N-acetyl-glucosamine was equally rapidly consumed but there was no visible de novo production. The simple and rapid sample preparation makes our protocol suitable for routine analyses of organic compounds in freshwater samples. Application of stable isotope tracers along with accurate measures of carbohydrate and amino sugar concentrations enables novel insights into the compound in situ dynamics.
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Seestrasse 187, CH-8802 Kilchberg, Switzerland. Electronic address: khornak1@gmail.com.
authors.forename: Karel
authors.initials: K
authors.lastname: Horňák
authors.affiliation: Limnological Station, Institute of Plant Biology, University of Zurich, Seestrasse 187, CH-8802 Kilchberg, Switzerland. Electronic address: pernthaler@limnol.uzh.ch.
authors.forename: Jakob
authors.initials: J
authors.lastname: Pernthaler
mesh_terms: D000117:Acetylglucosamine / Q000032:analysis; D000606:Amino Sugars / Q000032:analysis*; D002241:Carbohydrates / Q000032:analysis*; D002850:Chromatography, Gel / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry*; D006601:Hexoses / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007554:Isotopes; D060106:Lakes; D013058:Mass Spectrometry / Q000379:methods*; D059629:Signal-To-Noise Ratio
chemical_list: D000606:Amino Sugars; D002241:Carbohydrates; D006601:Hexoses; D007554:Isotopes; D000117:Acetylglucosamine
keywords: Amino sugars; Carbohydrates; Freshwater; Ion-exclusion chromatography; Mass spectrometry; Stable isotope tracers