Evaluation of three water concentration techniques as a prior step to test acute toxicity

• Published in: Environmental toxicology 2000-01, Vol.15 (4), p.345-351
• Main Authors: Diaz-Baez, M C, Cruz, LE, Rodriguez, D, Perez, J, Vargas, C M
• Format: Article
• Language: English
• ISSN: 1520-4081
• DOI: 10.1002/1522-7278(2000)15:4<345::AID-TOX11>3.3.CO;2-F

One of the limitations related to the use of bioassays for evaluating acute toxicity in potable waters is the low concentration of toxicants normally present in such waters. Even though low concentrations of some toxicants are occasionally detectable by chronic toxicity tests, it is very difficult to obtain a response with acute bioassays. As part of the research projects supported by the International Development Research Centre (IDRC) this study was carried out to evaluate simple, inexpensive concentration methods for use in toxicity testing of potable waters. The three concentration methods evaluated in this study were (1) flash evaporation by means of a rotary evaporator operated with a 45 degree C water bath; (2) blue rayon adsorption; and (3) solid phase extraction using reverse-phase disks with octadecylsilica (C sub(18)). Nine solutions with pure chemicals were used to establish the recovery rate by each method. From these experiments, two methods, blue rayon and solid phase extraction were selected to further test environmental samples. Water samples were collected from drinking water treatment plants, rivers, wells, and ponds. The results with pure chemical solutions showed that all extraction/concentration procedures tested were themselves selective. Although flash evaporation showed high recoveries, economical constraints may limit its use. Blue rayon and solid phase extraction may be combined to concentrate different toxicants. Results with the environmental samples for these two last methods indicated that natural water samples which were negative for toxicity showed a toxic response after concentration. Results also suggest that treatment plants may decrease the toxicity of treated effluents but concentration procedures confirmed that toxic effects remain present nonetheless.