Determination of Amino Sugars in Environmental Samples with High Salt Content by High-Performance Anion-Exchange Chromatography and Pulsed Amperometric Detection Karl Kaiser and Ronald Benner* Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29205 Amino sugars were determined in natural samples, in- cluding seawater, using high-performance anion-exchange chromatography with pulsed amperometric detection and a new off-line sample cleanup procedure. Samples were hydrolyzed with 3 M HCl for 5 h (100 °C) and neutralized with an ion retardation resin. Before injection, salts and organic contaminants were removed with a strong cation exchanger in the Na + form. Detection limits for amino sugars were between 1 and 4 nM (signal-to-noise ratio 3), allowing for the first time quantification of amino sugars in seawater without preconcentration. Precision was 2 -1 1 % at the 2 0 nM level. The relatively simple and rapid sample preparation makes it suitable for routine analyses. Carbohydrates are among the most abundant organic mol- ecules in the biosphere. They play important roles in cellular metabolism and recognition as well as in structural polymers. 1 In addition to being important cellular components, carbohydrates comprise a major fraction of nonliving organic matter (1-30%) in terrestrial and aquatic environments. 2 Molecular characterizations have identified neutral sugars (normal, deoxy, and methylated aldoses), N-acetylated amino sugars, and acidic sugars. 3,4,5 Of these classes of carbohydrates, neutral sugars have been studied extensively and provide important information on the origin of dissolved organic matter and its diagenetic state. 6,7 Much less is known about the abundance and distribution of amino sugars. In part, this situation exists because of the lack of suitable methods for the analysis of amino sugars. The most common amino sugars are glucosamine (GlcN), galactosamine (GalN), and muramic acid (MA). GlcN and GalN are widely distributed in microorganisms, plants, and animals. 8,9 Chitin, a polymer of N-acetyl GlcN, is an important structural polymer in fungi, invertebrates, and algae. 9,10 MA, the lactoyl ether of GlcN, exclusively occurs in bacterial cell walls and has been used to estimate bacterial biomass in natural samples. 9,11,12 Gas chromatography/ mass spectrometry (GC/ MS) methods have been successfully applied for the determination of amino sugars in bacterial polysaccharides 13,14 and soils. 15,16 However, GC analysis involves sample vaporization, which can lead to losses of sugars and time-consuming derivatization procedures. Due to these limitations, liquid chromatography using electrochemical 17,18 or fluorometric detection 19,20 has become increasingly popular. A recent method employs microscale LC coupled with MS for trace analysis of muramic acid. 21 High-performance anion-exchange chromatography (HPAEC) separates mono- and oligosaccharides due to subtle differences in the pK a of the hydroxyl groups on a pellicular strong anion-exchange resin. Coupled with pulsed amperometric detection (PAD) it permits quantification of carbo- hydrates at the femtomole level. 18 Derivatization is not needed, and the whole analysis avoids the use of organic solvents. Nevertheless, samples with a complex matrix require an efficient purification step prior to chromatography to prevent column and detector fouling and the potential overestimation of individual amino sugars due to coeluting compounds. It is mandatory that inorganic salts are removed prior to sample analysis, which is * Corresponding author: (e-mail) benner@ biol.sc.edu. (1) Dwek, R. A. Chem. Rev. 1996 , 96, 683-720. (2) Romankevich, E. A. 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