Physical and chemical characterization of colloids in natural waters is a major issue to understand the mechanism of circulation of pollutants in natural waters. Although many researchers are interested in colloid interactions, they are not yet well understood, and little is known on the appropriate experimental conditions needed to perform reliable and environmentally significant analysis. The following study is dedicated to the development of well-controlled analytical conditions. It is shown that drastic degradation of the water sample can happen during sample handling, if experimental conditions are inappropriate. The study also points out that multidisciplinary cooperation is necessary in the study of environmental problems. This paper is split in two parts for editorial reasons. The first part of this series reports experimental conditions, used to follow colloid stability reported in the second part of the series.