[The method of multicomponent determination of herbicides of various chemical classes in water].

In the work there are considered results of the development of the multicomponent method of measurement of concentration of herbicides of various chemical nature under their joint presence in the water. There was justified the optimality of application of HPLC-DAD (the working wavelength of 240 nm) for the determination of levels of 10 active ingredients of herbicides of class of sulfonylurea (metsulfuron-methyl, nikosulfuron, sulfometuron-methyl, thifensulfuron-methyl, triflusulfuron-methyl), imidazolinone (imazapyr, imazethapyr), 2,6-Bis[(4,6-dimethoxy-2- pyrimidinyl)oxy]benzoic acid (bispyribac acid), triazol-pyrimidines (Penoxsulam), a benzoylpyrazole compound (Topramenzone). For the concentrating and cleaning of samples of water there were used cartridges for solid-phase extraction of Oasis HLB - the macro porous copolymer made on the basis of the balanced ratio of 2 monomers - lipophilic divinylbenzene and hydrophilic N-vinylpirrolidone. The range of the detected concentrations in water was volatile between 0.0005 and 0.005 mg/L, values of standard deviation vary in the range of 1.8-3.9%. Chlorine-containing acidic herbicides were analyzed by the method of GC-ECD and GC-MS (IE) after preliminary converting of compounds into flying derivatives with the use of diazomethane. Satisfactory extraction of substances from a water sample may be achieved by classical extraction in the system "liquid-liquid" with the application of Methyl tert-butyl ester. For cleaning of the derivatized sample there were used cartridges for solid-phase extraction on the basis of silica gel. The range of the determination of 9 active ingredients referring to classes of phenoxy-acetic acid (2,4- D, MCPA), pyridinecarboxylic (aminopyiralid, picloram, clopyralid), benzoic acids (dicamba), benzothiadiazinone (bentazone), biphenyl ester (acifluorfen) and a chloroacetamide (acetochlor) - 0.0001-0.001 mg/L, SD values vary in the range of 1.8-33%.

[Determination of residual amounts of chlorothalonil in peaches: problems of gas chromatographic identification with the use of electron capture detector].

In the work there are presented results of studies on the validation of the gas chromatographic (GC) methodfor the determination of chlorothalonil residue amounts in peaches with the use of electron capture detector (ECD). For the analytical control there was selected such stone fruit crop as the peach, referring to the crops, the most contaminated with residue amounts ofpesticides. There was justified the necessity of the inclusion in the procedure of the detection of the method of confirmation, based on mass spectrometry detection (MSD) (the type of ionization - electron impact). The significant source of the obtaining of incorrect data in the identification with the use of ECD of ions are shown to be phthalates, visualized in the chromatogram as intense and/or broad peaks. Mass spectra of compounds of the class ofphthalates are characterized by the dominant peak of the ion with the value of (mass/ charge) 149, just on this peak the detection of low molecular weight phthalates occurs in various matrices, on the spectrum there are also recorded typical ions corresponding to fragments of radical residues. The combination of the use of various types of the detection allows to prove that the revealed response (detector signal) is caused just by the analyte, but not the impurities, and optionally to optimize chromatographic conditions towards to the obtaining reliable results. The lower limit of the quantitation of chlorothalonil in peach fruits accounts for 0.01 mg/kg, determined with a signal/noise ratio of 10. The range of measured concentrations is volatile between 0.01-0.1 mg/kg, recovery rate of chlorothalonil from samples of peaches, established according to results of the analysis of model samples with the introduction of the substance in four points along the detection range, was 84-102%, the SD value of the repeatability varies in the range of 2.0-5.8%.