Characterisation of absorptive sampling with SPME fibres in the EUPHORE photoreactor

The implementation of an experimental set-up for sampling, and characterisation of parameters related to absorptive sampling solid phase microextraction (SPME) in the EUPHORE photoreactor is described. Toluene was taken as probe compound. Optimisation of the sampling and calibration curves are presented. Equilibrium was achieved in just 30s due to the good agitation in the chambers and the LOD was 0.24 ppbV. The precision was +/-0.02 expressed as relative standard deviation (n=9). The inter-fibre reproducibility was +/-0.03 expressed as relative standard deviation. The effect of the temperature and the sun radiation on absorption in the fibre is also studied using a relative method to calculate the ratio K/K(0) (ratio of absorption constants at two different times during the experiment at which temperature and radiation conditions experimented important variations) calculated through known parameters, avoiding in this way the need for external calibrations in the calculation of K. The results showed a difficult to predict dependence of absorption over the combination of temperature and sun radiation and the need to develop sampling systems with absorptive SPME in which sun radiation has no influence. The stability in different conditions of compounds absorbed in the fibre was also subject to study. At room temperature half of the compound absorbed is expected to desorb in 1.21 h. Conversely, when fibres were kept at low temperatures (-86 degrees C) after 21 days, desorption was negligible.