Melanoidin
Melanoidin served as proxy for a class of organic materials likely to interfere with BC separations. Melanoidin was defined first by Maillard, 1917 (Annales de chimie (Paris) 7: 113-152). A synthesis protocol also has been published: Allard et al. 1997 (Organic Geochemistry 26: 691-703) and Olsson et al. 1978 (Acta Chem. Scandinavica B32: 249-256). Here we advocate a simple approach which requires no specialized technical equipment, involves inexpensive reagents and is not labour-intensive. We produced melanoidin by mixing glucose with urea in deionized water.
Protocol
Urea-glucose melanoidin is prepared by making a solution of 100 g/L D-glucose and 10 g/L urea in Schott glass jars. Caps are screwed on lightly and bottles are kept in a water bath at a temperature of 90 degrees Celsius for 30 days. The solutions in the bottles is stirred every second day to prevent a skin from forming on the surface of the liquid. The solution turns brown overnight. After 30 days, the bottles are removed from the water bath, centrifuged and washed four times to remove any low molecular weight urea and glucose still present and to isolate the insoluble melanoidin. The washed melanoidin is freeze dried and kept sealed in the dark at room temperature for analysis. This method yields approximately 2 g melanoidin per litre solution. The sample was prepared by Univ. Zurich, Switzerland.
Ordering information
Subsamples prepared by this method can be ordered from Michael W. I. Schmidt, Univ. Zurich, Dept. Geography, 8057 Zurich, Switzerland (michael.schmidt@geo.uzh.ch).
Cost: 40 Euro per 1 g subsample.