PARENT SESSION
3A Advances in environmental analytical chemistry
9:00 AM to 7:00 PM, Tuesday, 08 May 2001

(T/EH108) A diffusion-based passive sampling system with the use of internal and external standards to improve the accuracy of time-averaged measurements of organic and inorganic pollutants in aquatic environments.

Morrison, G.¹, Björklund-Persson, L.¹, Rauch, S.¹, Kingston, J.², Mills, G.², Greenwood, R.², ^{1 2}

ABSTRACT- The use of spot sampling alone limits the widespread and accurate measurement of pollutants present at fluctuating levels in aquatic environments. Continuous in situ sampling is preferred and time-averaged concentrations can be obtained from either solid- or liquid-phase accumulation after transport across a diffusion-limiting membrane. A limiting aspect of this development is variations of physical (temperature, turbulence) and biological (eg microbial growth) factors which alter diffusion rates for the analytes of interest across the diffusion-limiting membrane. We have developed and field tested a compact and robust passive sampling system which uses different diffusive membranes together with immobilised receiving (e.g. C₁₈ or chelating) phases for the time-averaged measurement of a range of organic and inorganic pollutants. We report how the use of deuterated stable isotopic internal standards: ⁸d-naphthalene (for non-polar organic compounds) and ⁶d-dimethylphthalate (for polar organic compounds) pre-loaded onto the receiving phase prior to use can increase the accuracy of sampling. Field deployments allowed measurements of timed-averaged concentrations of PAH and anti-fouling (diuron and Irgarol) compounds in marine harbour systems. For metal species, a separate cation exchange membrane is deployed alongside the chelating sampler. Ca and Mg are measured and, in environments where these elements are conservative or known to be relatively conservative, allow correction for altered diffusion rate. The correction system was shown to give the desired accuracy by deployment in marine and lake environments. Metals and Ca, Mg were directly determined in the receiving phases by laser ablation-inductively coupled plasma-mass spectrometry.

Key words: Passive sampler, internal standards