Storage and processing of estuarine water samples for trace metal analysis by atomic absorption spectrometry

Abstract

Saline water samples from the Delaware Bay estuary were sampled, processed, and stored in a variety of ways to allow different methods of maintaining their integrity to be compared. Samples were processed onboard ship, immediately after collection, by extraction with ammonium pyrollidinedithiocarbamate in methyl isobutyl ketone. Duplicate samples were processed onshore after a variety of storage procedures. All samples were analyzed for copper and iron by atomic absorption spectrometry. Only samples filtered (<1 μm), acidified, and stored frozen gave extractable copper and iron results comparable with those for samples extracted immediately after collection. Cold storage with sample acidification in polyethylene containers appeared less satisfactory. Organic extracts from samples processed onboard are best retained in all-Teflon containers pending complete digestion and analysis onshore. Unless clean (ultra-filtered air) conditions can be ensured onboard, the estuarine water samples are best returned in a filtered, acidified, and frozen condition for onshore processing.