Abstract: Eight alditols were separated in ~80 min as their borate complexes by stepwise elution with three borate buffers on a column packed with Hitachi 2633 resin. The alditols in the eluate were derivatized automatically to colored, fluorescent products by applying sequential reactions of periodate oxidation and Hantzsch condensation, and the products were detected either photometrically or fluorimetrically. This automated method allowed simultaneous determination of 20-500 and 20-200 nmol amounts of alditols by photometric and fluorimetric monitorings, respectively. The lower limits of detection were ~2 and 0.5 nmol, respectively. The interference by aldoses was slight. Aldoses may be also determined as alditols by direct injection of aqueous solutions to which excess amounts of sodium borohydride have been added. This method was applied with success to urinary alditol assay and to molecular weight determination by end group analysis.

Abstract: Alditols were determined in aqueous solution using a novel indirect photometric technique as a post-column detection method. It allowed the use of the common UV detector for these transparent analytes. The method is based on the decrease of absorbance (λ = 347 nm) due to the competitive complexation of molybdate by the chloranilate ion (colored complex) and an alditol (colorless complex). The experimental conditions were defined in a preliminary study which related the sensitivity for each analyte to the formation constant of its molybdate complex. D-Glucose, which forms a weak complex, does not interfere. The method was applied to the HPLC determination of mixtures of alditols with separation on a calcium column. The calibration curves are linear in the concentration range 0-100 mg L-1. It demonstrates that indirect photometric detection may be used for the selective determination of specified analytes, in contrast with its usual application as a universal detection technique.

Abstract: An anion-exchange column coupled with an amperometric sensor was used for the quantitative analysis of alditols and simple sugars. The sensing electrode is composed of cuprous oxide dispersed in a graphite powder-polyethylene composite matrix. The resulting Cu2O-carbon composite electrode is stable in alkaline media and possesses good sensitivity, wide linear dynamic ranges and low detection limits for alditols, mono- and disaccharides. Alditols and carbohydrates are weakly ionizable compounds, so an anion-exchange column was employed for their chromatographic separation with an alkaline eluent. The separation problems due to the presence of low but uncontrolled amounts of carbonate in the alkaline mobile phase have been largely solved by the addition of Ca2+ or Ba2+ at a millimolar level and the consequent formation of carbonate insoluble salts. Using this strategy, the alkaline eluent provides improved separations without compromising the column's lifetime, electrode performance and chromatographic system. Under the optimal operating conditions, the detection limits of D-sorbitol, D-mannitol and D-glucose were 50, 40 and 80 pmol, respectively, with a linear concentration range up to 5 mM. Examples of applications, which include the separation and detection of D-sorbitol, D-mannitol and common sugars present in food samples, are illustrated. 35 References