Trace metals in water samples: minimising contamination during sampling and storage

Sampling, storage and analytical techniques are described for a pilot study on Antarctic freshwaters. The study was aimed at assessing the level of in organic (mostly trace metals), anthropogenic contamination in freshwater la ke systems in a relatively densely populated area of Antarctica. Among the different types of material tested for sample storage, Teflon(R) is the cle anest (lowest blanks), easiest to prepare, and gave the most precise and re liable results. Properly treated HDPE (high-density polyethylene) is also s uitable for most trace elements (including Pb), but gave relatively high Zn blanks, and required lengthy and more complex cleaning procedures. Low-den sity polyethylene (LDPE) was found to be unsuitable for many elements of en vironmental significance. Irrespective of the type of container used for sa mple storage, reagents, sampling gear, and storage bottles must be properly treated prior to usage, and all phases of the sampling and analysis must b e performed under very strict specifications, and thoroughly tested for con tamination. The methods and the experience acquired during this pilot study can be applied in general to minimise contamination during sampling, sampl e storage and sample treatment for analysis of waters with ultra-low trace element concentrations.