固相萃取-高效液相色谱法对玉米、甘蔗及土壤中硝磺草酮残留量的检测

Determination of Mesotrione Residues in Maize,Sugarcane and Soil by SPE-HPLC

[目的]建立一种以SAX固相小柱萃取、高相液相色谱（HPLC）法检测玉米、甘蔗及土壤中的硝磺草酮的残留的方法。[方法]比较不同的固相萃取小柱、淋洗液及其p H值对玉米籽粒和甘蔗茎秆中硝磺草酮添加回收率及净化效果的影响,并采用气相色谱-质谱（GC-MS）和高相液相色谱（HPLC）对净化前后的甘蔗茎秆和玉米粒的组分进行比较。[结果]采用SAX固相萃取小柱,以甲醇为淋洗液,洗脱液的pH值2~3时提取和净化的效果较好。甘蔗上干扰硝磺草酮检测的物质主要是香豆满、异丁香酚、松柏醇等芳香族物质;玉米上主要干扰物质为亚油酸、辛酸、2,4-二烯醛等。在甘蔗茎秆及土壤中添加0.05~1 mg/kg,平均回收率在89.0%~98.3%之间,相对偏差（RSD）为2.4%~5.7%。在玉米和土壤中添加0.01~1 mg/kg水平,回收率在72.6%~102.0%之间,RSD为1.6%~5.4%,硝磺草酮在甘蔗上的定量限（LOQ）为0.05 mg/kg,在玉米上的LOQ为0.01 mg/kg。[结论]硝磺草酮在甘蔗、玉米土壤中的半衰期为17.9~18.1 d,属于易降解农药,苗期施药,成熟期收获的甘蔗茎杆、玉米籽粒中硝磺草酮的残留量均〈0.01 mg/kg。

[Aims] A method for detection of mesotrione residues in maize, sugarcane and soil was developed by solid-phase extraction （SPE） and high performance liquid chromatography （HPLC）. [Methods] The effects of various SPE column, elution agents and pH values on recovery rate of mesotrione in corn grain and sugarcane stalk as well as purification effect were compared. The components of corn grain and sugarcane stalk before and after cleanup were compared by GC-MS and HPLC. [Results] When the samples were leached with methanol, cleaned up with SAX, the pH ofelution agents was 2-3, the purification of the extracts were found to be the most suitable. The main substances which interfered with the analysis of mesotrione in sugarcane stalk and corn grain were coumaran, isoeugenol, coniferol and linoleic acid, octoic acid, 2,4-decadienal, respectively. The results showed that the average recoveries in sugarcane were 89.0-98.3% with relative standard deviations of 2.4-5.7% at spiked levels of 0.05, 0.1 and 1 mg/kg, the average recoveries in maize were 72.6-102.0% with relative standard deviations of 1.6-5.4% at spiked levels of 0.01, 0.1 and 1 mg/kg. The limits of quantification in sugarcane and maize were 0.05 and 0.01 mg/kg, respectively. [Conclusions] The half-lives in soil ranged from 17.9 to 18.1 d. The final residues were all below 0.01 mg/kg at harvest time, which belongs to pesticides of easy degradation.