Optimisation of the storage of natural freshwaters before organotin speciation

The speciation of organotin compounds is essential due to the species-depen dent toxicity, especially in natural waters. Precautions have to be taken d uring sampling and storage of waters in order to prevent degradations and l asses. Experimental design methodology has been used to study the condition s of stability of organotins after water sampling in rivers. The modelling of results allows the determination of optimal conditions of preservation. After acidification at pH=4 with nitric acid, the storage in polyethylene c ontainers at 4 degreesC in the dark is suitable to preserve the most degrad able trisubstituted (butyl-and phenyl-) species over 1 month. These conditi ons of sampling and storage are applied to two different freshwaters. The r ate of species decomposition appears to be only dependent on the water natu re, whatever the organotin concentrations in the sample. Speciation could b e so preserved between 1 and 3 months. (C) 2000 Elsevier Science Ltd. All r ights reserved.