DETERMINATION OF SIMAZINE IN WATER SAMPLES BY WAVE-GUIDE SURFACE-PLASMON RESONANCE

We assessed a new sensing device based on the monitoring of immunobind ing reactions using waveguide surface plasmon resonance (WSPR) for the determination of simazine in water samples. Standard solutions betwee n 0.1 and 1.0 mu gl(-1) analysed in triplicate showed a mean within-da y variability of 5%. Calibration curves for the same standards conduct ed on five consecutive days showed a 14% mean day-to-day variability. The detection limit calculated as three standard deviations below the mean blank value was 0.2 mu g(-1). The upper limit of the working rang e calculated as a 90% decrease in the blank signal was 2.4 mu gl(-1). The cross-reactivity of atrazine and terbuthylazine was 61 and 63%, re spectively. The recovery from spiked natural ground- and surface-water samples ranged from 55 to 153% for spikes ranging from 0.1 to 1.0 mu Lgl(-1). For the II surface- and 8 ground-water samples tested, the co rrelation coefficient between WSPR and high pressure liquid chromatogr aphy/gas chromatography (HPLC/GC) values was significant (p<0.05) when the chromatography values were calculated as the weighted sum of sima zine and atrazine, taking into account the predetermined cross-reactiv ity of the latter in the WSPR determination. The present system is the refore better suited for screening groups of pesticides than for the d etermination of a single molecule. An attempt at analysing a soil wate r sample proved unsuccessful due to interference probably resulting fr om strong non-selective polyanion-polycation binding to the transducer surface which includes a basic amino dextran. The total duration of o ne determination, 22 min, enables almost immediate measurements withou t any sample pretreatment other than 0.45 mu m filtration. No signific ant alteration of the sensor was observed after 200 determinations.