STUDIES OF PRESERVATION OF WATER SAMPLES FOR THE DETERMINATION OF NONIONIC SURFACTANTS

Chloroform, formaldehyde and ions of copper(II) and mercury(II) were t ested as preservatives of water samples for determination of non-ionic surfactants (NS). River water (Warta River, Poznan) was used as hydro biological background. Mainly the concentration of ''native'' NS from river water was measured, but in two series of experiments spikes of T riton X-100 and Marlipal 1618/25 were used. Indirect tensammetric meas urements (ITM) were applied for control of the NS concentration. Forma ldehyde is the most effective compound among the tested preservatives. A concentration of 1% is sufficient for long-term storage while 0.1% is sufficient for short-term storage (up to 6 days). Copper (II) (50 m g l(-1)) or mercury(II) (25 mg l(-1)) may be used for short-term stora ge of water samples while chloroform used alone is ineffective. It may be used together with cooling of a sample (4 degrees C) for short-ter m storage, however, such a pretreatment of samples is more complicated than the use of other preservatives. Refrigeration (4 degrees C) used alone is ineffective. The results concerning high spikes of Triton X- 100 show better preservation than the samples containing only ''native '' NS. Therefore, the experiments with spikes of surfactants may lead to too optimistic conclusions as for preservation of a water samples. Adsorptive stripping tensammetry was applied for observation of biodeg radation of spikes of Marlipal 1618/25 both in preserved and non-prese rved samples. The high potential of this technique for the examination of biodegradation has been demonstrated.