Gálvez R, Pedrero M, Buyo F, Manuel de Villena F J, Pingarrón J M
Departamento de Química Analítica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Spain.
Fresenius J Anal Chem. 2000 Jul;367(5):454-60. doi: 10.1007/s002160000352.
The electroanalytical behavior of the reduction of the herbicides aziprotryne (2-azido-4-isopropylamino-6-methylthio-1,3,5-triazine) and desmetryne (4-isopropylamino-6-methylamino-2-methylthio-1,3,5-triazine) in oil-in-water emulsions is reported. This medium allows the differential pulse polarographic determination of these s-triazines directly from their sample extracts in an appropriate organic solvent. Sodium pentanesulfonate was chosen as the most suitable surfactant to be used as emulsifying agent, whereas ethyl acetate was selected as the organic solvent to form the emulsions. The peak current was maximum in a 0.3 mol L(-1) HClO4 medium of the continuous aqueous phase for aziprotryne, and at pH 3.0 for desmetryne, and the potential became more negative as the pH increased for both herbicides. The limiting current is diffusion controlled and the electrode process is irreversible. Four electrons are involved in the overall electrochemical reduction process as determined by controlled potential coulometry, whereas the alpha n(a) values suggested that two electrons are involved in the rate-determining step. Using differential pulse polarography, aziprotryne and desmetryne can be determined in the emulsified medium over the concentration ranges 1.0 x 10(-7)-1.0 x 10(-4) mol L(-1), with limits of detection of 4.5 x 10(-8) mol L(-1) and 6.6 x 10(-8) mol L(-1), respectively. The method was applied to the determination of aziprotryne and desmetryne in spiked irrigation water. At concentration levels of 6.0 x 10(-7) mol L(-1) aziprotryne and 4.0 x 10(-7) mol L(-1) desmetryne, recoveries of 94 +/- 3% and 94 +/- 4%, respectively, were obtained after preconcentration on Sep-Pack C18 cartridges. Finally, partial least-squares regression (PLSR) has been used for treatment of the polarographic data obtained from mixtures of aziprotryne, desmetryne and simazine in oil-in-water emulsions. The size of the calibration set was of 29 samples by ninety two current measurements at different potentials. Prediction of the herbicides concentration within the range 1.0 x 10(-6)-1.0 x 10(-5) mol L(-1) was possible.
报道了除草剂叠氮津（2-叠氮基-4-异丙氨基-6-甲硫基-1,3,5-三嗪）和敌草净（4-异丙氨基-6-甲氨基-2-甲硫基-1,3,5-三嗪）在水包油乳液中还原的电分析行为。这种介质允许直接从其在合适有机溶剂中的样品提取物中通过差分脉冲极谱法测定这些均三嗪。选择戊烷磺酸钠作为最适合用作乳化剂的表面活性剂，而选择乙酸乙酯作为形成乳液的有机溶剂。对于叠氮津，在连续水相的0.3 mol L⁻¹高氯酸介质中峰电流最大，对于敌草净，在pH 3.0时峰电流最大，并且两种除草剂的电位都随着pH值的增加而变得更负。极限电流受扩散控制，电极过程不可逆。通过控制电位库仑法确定，整个电化学还原过程涉及四个电子，而αn(a)值表明速率决定步骤涉及两个电子。使用差分脉冲极谱法，可以在乳化介质中测定叠氮津和敌草净，浓度范围为1.0×10⁻⁷ - 1.0×10⁻⁴ mol L⁻¹，检测限分别为4.5×10⁻⁸ mol L⁻¹和6.6×10⁻⁸ mol L⁻¹。该方法应用于加标灌溉水中叠氮津和敌草净的测定。在叠氮津浓度为6.0×10⁻⁷ mol L⁻¹和敌草净浓度为4.0×10⁻⁷ mol L⁻¹的水平下，在Sep-Pack C18柱上预浓缩后，回收率分别为94±3%和94±4%。最后，偏最小二乘回归（PLSR）已用于处理从水包油乳液中叠氮津、敌草净和西玛津混合物获得的极谱数据。校准集大小为29个样品，通过在不同电位下进行92次电流测量。可以预测除草剂浓度在1.0×10⁻⁶ - 1.0×10⁻⁵ mol L⁻¹范围内。
