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 inorganic (mostly trace metals), anthropogenic contamination in freshwater lake systems in a relatively densely populated area of Antarctica. Among the different types of material tested for sample storage, Teflon(R) is the cleanest (lowest blanks), easiest to prepare, and gave the most precise and reliable results. Properly treated HDPE (high-density polyethylene) is also suitable for most trace elements (including Pb), but gave relatively high Zn blanks, and required lengthy and more complex cleaning procedures. Low-density polyethylene (LDPE) was found to be unsuitable for many elements of environmental significance. Irrespective of the type of container used for sample storage, reagents, sampling gear, and storage bottles must be properly treated prior to usage, and all phases of the sampling and analysis must be performed under very strict specifications, and thoroughly tested for contamination. The methods and the experience acquired during this pilot study can be applied in general to minimise contamination during sampling, sample storage and sample treatment for analysis of waters with ultra-low trace element concentrations.