EVALUATION OF A FREEZE-CONCENTRATION TECHNIQUE FOR ENRICHMENT OF NATURAL ORGANIC-SUBSTANCES IN WATER

A freeze concentration method was tested for its ability to concentrate uncharacterized organic carbon, measured by TOC analyzer, in tap water derived from a surface water reservoir in eastern Massachusetts. Freeze concentration was carried out in polypropylene bottles of 2 liter volume, stirred at either 140 rpm or 400 rpm, and placed in a freezer at either -15-degrees-C or -25-degrees-C. No effect of stirring speed or freezer temperature on the recovery efficiency was found except possibly at high (> 10x) concentration factors. For theoretical concentration factors below approximately ten, measured TOC was reproducible but substantially less than the theoretical value (e.g., for a theoretical value of 10, the measured concentration factor was only 4.3. At higher concentration factors, the ratio of the actual to theoretical concentration decreased further and became variable from experiment to experiment. Lack of quantitative recovery of TOC indicates the likelihood that selective concentration of different components of this material occurred.