Praćenje ostataka sulfonilurea u zemljištu u realnim uslovima primenom visoko-pritisne tečne hromatografije / Monitoring of residues of sulfonylurea in soil under real conditions by using high pressure liquid chromatography

In this thesis a fast and selective method for determination and monitoring of residues sulfonylurea herbicides (SU) (nicosulfuron, oxasulfuron, tribenuron methyl, tritosulfuron, triasulfuron, rimsulfuron and prosulfuron) in soil, by applying high-performance liquid chromatography with UV detector with diode array diodes (HPLC-UV-DAD) was developed. The separation of the sulfonylurea was performed by use of a Zorbax Eclipse XDB-C18 column. In order to define appropriate conditions of analysis, the influence of the most significant the experimental factors was investigated and defined. The following optimal conditions for gradient elution: mobile phase acetonitrile (A) and 0.1% acetic acid (B) t = 0 min, 52% A; t = 2-2.5 min, 47% A; t = 2.5-5 min, 52% A were adopted at a constant flow rate of 1 mL min-1 and column temperature of 250C. On basis of the response of the analytical signal, its reproducibility and linearity, the wavelength of 240 nm was adopted as an appropriate. The influence of the matrix was expressed and therefore for the quantitative determination of investigated SU in soil samples application of HPLCUV-DAD methods was used MMC calibration curve. In the analysis of extracts of nocontaminated soil limits of quantitation for nicosulfuron, oxasulfuron, tribenuron methyl, tritosulfuron, triasulfuron, rimsulfuron and prosulfuron was achieved 3.16 µg kg-1 , 3.40 µg kg-1 , 3.76 µg kg-1 , 4.13 µg kg-1 , 3.60 µg kg-1 , 3.04 µg kg-1 and 2.97 µg kg-1 , respectively. The method by using liquid chromatography-tandem mass spectrometry (HPLC-MSMS) was defined in order to find more sensitive, more selective and more accurate way to determine concentration SU in soil. HPLC-MS-MS was used as the reference technique for checking results that have been obtained by HPLC with UV-DAD detector. An efficient procedure preparation of soil samples for the purpose chromatographic determination of SU was defined. Using a mixture of dichloromethane-acetonitrile (2: 1, v / v), acidified with acetic acid (0.8%, v / v), with the addition of urea (0.3 g / 10 g soil) was applied as the most effective way for extraction SU. Microwave extraction process in a closed system allowed the best conditions for the extraction of SU. In order to extract SU from matrix exctracts soil the solid phase the extraction (SPE) with silica gel as an adsorbent was used. The defined method for determination of investigated vi SU, as well as the developed procedure of sample preparation, was successfully applied in the analysis of real samples of soil. The correctness of procedure of sample preparation was confirmed with very good values of recovery test which was applied in the analysis by using HPLC-UVDAD. The accuracy of the developed method for determination of SU was confirmed by coupled analysis soil samples using HPLC-MS-MS. The results of parallel analysis does not differ significantly at 95% confidence level. It was obtained using Student t-test (paired). The method developed in this thesis was used for monitoring the dissipation of nicosulfuron, rimsulfuron, oxasulfuron prosufuron, in different commercial doses of application during 50 days in field at three different depths (0-15 cm, 15- 30 cm and 30-45 cm) and for laboratory conditions at two temperatures (25ºC and 30ºC). The half-life time (DT50) of investigated SU were calculated by use of Mitttag-Lefler function in experiments under laboratory conditions at 25ºC. The values of DT50 for nicosulfuron, prosufuron and oxasulfuron read: 0.65 days (50 g ha-1 a.k.), 0.64 days (160 g ha-1 a.k.) and 0.66 days (30 g ha-1 a.k.), respectively. In the same type of experiments at 30ºC we get DT50 for nicosulfuron equals 0.20 days (50 g ha-1 a.k.) and for prosulfuron equals 0.49 days (50 g ha-1 a.k.). The values of DT50 on experiments in field were obtain also by use of Mitttag-Lefler's function, and half-life times for nicosulfuron, rimsulfuron, oxasulfuron and prosufuron from the commercially recommended doses, equal 72 minutes (0.05 days), 0.23 days, 0.12 days and 0.15 days, respectively. Significantly greater dissipation which was determined in this thesis was probably caused by the influence of abiotic and biotic processes as well as environmental factors.