碱蒸馏/超声波衍生化-气相色谱-质谱法测定土壤中的偏二甲肼

建立了碱蒸馏/超声波衍生化预处理的气相色谱-质谱法测定土壤中偏二甲肼的分析方法。通过碱蒸馏预处理方法,以水杨醛为衍生化试剂,采用超声波加速衍生化反应,在选择离子检测( SIM)模式下进行定量分析,衍生化产物的特征离子为m/z 164。考察了碱蒸馏、超声波衍生化条件的影响,并对衍生化条件进行优化,方法的线性范围在0.4~30 mg/L之间,方法检出限为0.0078 mg/kg。以此方法测定已知浓度的土壤样品,目标化合物的含量在10~100 mg/kg之间,回收率在76％~108％之间,相对标准偏差在12％~19％之间。与分光光度法、索氏提取/超声波衍生化-气相色谱-质谱法相比较,本方法检出限显著优于二者。     

Preparation and structures of 6- and 7-coordinate salen-type zirconium complexes and their catalytic properties for oligomerization of ethylene

A series of salen-type zirconium complexes of the general formula LZrCl₂ (L = N,N′-ethylenebis(salicylideneiminate), 3a; N,N′-ethylenebis(3,5-di-tert-butylsalicylideneiminate), 3b; N,N′-ethylenebis(5-methoxysalicylideneiminate), 3c; N,N′-ethylenebis(5-chlorosalicylideneiminate), 3d; N,N′-ethylenebis(5-nitrosalicylideneiminate), 3e; N,N′-o-phenylenebis(salicylideneiminate), 4a; N,N′-o-phenylenebis(3,5-di-tert-butylsalicylideneiminate), 4b; N,N′-o-phenylenebis(5-methoxysalicylideneiminate), 4c; N,N′-o-phenylenebis(5-chloro-salicylideneiminate), 4d) were prepared. The crystal structures of 6- and 7-coordinate zirconium complexes 4b and [4b · OCMe₂] were determined by X-ray crystallography, which reveals that a salen-type zirconium complex possesses a labile coordination site on the Zr center with a relatively stable framework and that the coordination and the dissociation of O-donor molecules occur readily at this site. The catalytic properties of 3(a-e) and 4(a-d) were studied for ethylene oligomerization in combination with Et₂AlCl as co-catalyst. Complex 3c featuring a methoxy-substituted salen ligand displayed higher activity than its analogous precursors having chloro and nitro groups as substituents. The catalytic reactions by 3(a-e) and 4(a-d) gave C₄-C₁₀ olefins and low-carbon linear α-olefins in good selectivity.