| Popis: |
Pesticides monitoring at low concentrations using optical absorption, laser induced fluorescence (LIF), fluorescence lifetime measurements and gas chromatography are reported. The studied pesticides were chlortriasines (athrasine, propasine and simasine) and organophosphoric pesticides (dichlorvos and parathion). Since in normal conditions the chlortriasines show absorption spectra in ultraviolet (around 250 nm), to obtain fluorescence spectra in the visible they were treated with pyridine and ethyl ester of cyanoacetic acid in basic medium. The LIF spectra of chlortriasines are measured at concentrations of pollutants between 5 ppm and 20 ppm. The molecular complex fluorescence spectrum induced by pulsed laser radiation at 545 nm, available from a tunable dye laser, exhibited a maximum of 577 nm; it remained unchanged for three hours, following which the intensity decreases as a consequence of the complex destruction (decomposition). The fluorescence lifetime of the molecular complex measured using a fast photodetector was 2.6 ns, immediately after complex formation. The organophosphoric pesticides were monitored using a rather different initial chemical treatment, at the end of which a quinino-vanado- molibdophosphoric complex (PMo10V2O39)2(C20H24O2N2H2)3 was formed. The fluorescence spectra of these pesticides induced by pulsed laser radiation at 337.1 nm available from a pulsed nitrogen laser (700 ps pulse time width, 300 (mu) J/pulse energy) exhibited a maximum at 445 nm with a FWHM of 80 nm. The low concentration detection limits were 0.2 ppm for P in dichlorvos (dichlorvos concentration 14.18 ppm) and 0.2 ppm for P in parathion (parathion concentration 17.8 ppm). These methods in correlation with optical absorption, classical fluorescence and gas chromatography methods were applied to monitor pesticides in water samples collected from the North Pole zone following two expeditions dated March-April 1995 to Severenaia Zemlia Archipelago and July-August 1996 to Spitzbergen Archipelago. Comments about the monitoring of pesticides content of these samples are made.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only. |
