Sub-ambient temperature effects on the separation of monosaccharides by high-performance anion-exchange chromatography with pulse amperometric detection - Application to marine chemistry

The effects of column temperature in the range 10-45 degreesC using high-pe rformance anion-exchange chromatography (HPAEC) and pulse amperometric dete ction are described for the determination of monosaccharides. The influence of temperature was tested with an isocratic elution of NaOH at concentrati ons varying from 2.5 to 20 mM and with a post-column addition of 1 M NaOH. The results showed that small changes of temperature greatly affect retenti on times and resolution (R,) of monosaccharides and particularly those of t he both pairs xylose-mannose and rhamnose-arabinose which cannot be simulta neously detected at usual room temperature (similar to 25 degreesC). Our re sults suggest that a subambient temperature of 17 degreesC and an eluent co ncentration of 19 mM are the more appropriate conditions for an acceptable separation (R-s rha / ara = 1.02, R-s man /xyl = 0.70) in a short analytica l run time (35 min). The results showed that within the range of temperatur es studied, enthalpy and entropy are invariant of temperature indicating th at changes in the retention processes are mainly due to temperature than ot her associated changes in the system. This study demonstrated the importanc e of controlling temperature during HPAEC of monosaccharides, both to accom plish highly reproducible retention times and to achieve optimal separation of sugars. This method gave acceptable results for detection of marine sug ars. (C) 2001 Elsevier Science B.V. All rights reserved.