Stability of dissolved metals in environmental aqueous samples: Rideau River surface water, rain and snow

Abstract The stability of nickel, lead, copper, cadmium, aluminium and zinc in the dissolved phase of environmental aqueous samples stored in common containers made of various materials was investigated. The samples were Rideau River surface water, rainwater and snow collected at Carleton University, Ottawa, Canada, and had concentrations of the above metals ranging from 0.5 to 90 ng l −1 , and the samples were not acidified. The container materials studied were high-density polyethylene (HDPE), polypropylene (PP) and Teflon. The rate and the extent of metal loss were dependent on the container material, and the metal. Significant losses were observed in both polyethylene and PP containers even over periods as short as 30 min. The time taken for the concentration of the metals in the dissolved phase to be reduced to half was in the high-density polyethylene containers: 5, 15, and 20 min, for lead, copper and cadmium, respectively. With PP containers, only 15% lead, 25% copper, and 20% cadmium were lost in 2 h of storage. Teflon containers show no loss of dissolved metals from aqueous environmental samples over periods of 24 h, and hence, Teflon is the most suitable container material for the storage of environmental aqueous samples for trace metals for periods up to 24 h. The loss was the same for all environmental aqueous samples, river water, rainwater and snowmelt. This study shows the importance of the container material in preserving the sample integrity of environmental aqueous samples. Dissolved zinc was found to be stable in all the container materials studied. This aspect needs further experimental verification before any generalization is justified.