Nicholas School of the Environment, Duke University, 140 Science Drive, Durham, NC, 27708-0187, USA.
Civil and Environmental Engineering, Pratt School of Engineering, Department of Civil and Environmental Engineering, Duke University, 121 Hudson Hall, Box 90287, Durham, NC, 27708-0187, USA.
Rapid Commun Mass Spectrom. 2019 Nov 30;33(22):1683-1694. doi: 10.1002/rcm.8512.
Approximately 7 million liters of Corexit® dispersants were applied during the 2010 Deepwater Horizon oil spill to facilitate the dispersion of crude oil. At the time of application, the exact chemical composition of Corexit® was relatively unknown. Characterization of Corexit® 9500 was performed using high-resolution mass spectrometry to further understand the complexity of the nonionic surfactant components of this mixture.
Corexit®9500 was analyzed by ultra-high-performance liquid chromatography (UHPLC) coupled to a high resolution Orbitrap Fusion Lumos mass spectrometer operated in positive electrospray ionization mode and a charged aerosol detector. Chromatographic conditions were optimized to efficiently separate isobaric and isomeric compounds. Polyethoxylated nonionic surfactants in Corexit® 9500 were identified using the following criteria: accurate mass (<3 ppm), retention time, and homologue series; in addition, interpretation of high-resolution tandem mass spectra was used to annotate tentative component structures.
More than 2000 polysorbate nonionic surfactants in 87 homologue series were detected. Polysorbate surfactants were characterized by the type of molecular basis group (sorbitan, isosorbide, or fatty acid), degree of esterification (n = 0-4), ester chain length (C6-C24), and ester saturation, in addition to polydispersion by ethoxylation. Isomeric compounds were differentiated by LC/HRMS/MS analysis with product ion assignment. Results from the charged aerosol detector showed that the diesters (23.9 ± 0.78%) were the most abundant component in Corexit® 9500 followed by dioctyl sodium sulfosuccinate (DOSS) (19.2 ± 1.5%), triesters (17.3 ± 1.5%), and monoesters (15.7 ± 2.3%).
Our analytical approach facilitated the characterization of polysorbate surfactants within Corexit® 9500 and allowed a systematic study to differentiate isomeric and isobaric compounds, when standards were not available. The characterized composition of Corexit® 9500 will facilitate future studies to determine the chemical and biological transformation kinetics and byproducts of Corexit® 9500 under environmental conditions.
在 2010 年的深水地平线石油泄漏事件中，大约有 700 万升的 Corexit®分散剂被用于促进原油的分散。在应用时，Corexit®的确切化学成分相对未知。使用高分辨率质谱对 Corexit®9500 进行了表征，以进一步了解该混合物中非离子表面活性剂成分的复杂性。
通过超高效液相色谱（UHPLC）与高分辨率轨道阱融合卢莫斯质谱仪联用，在正电喷雾电离模式和带电气溶胶检测器下分析 Corexit®9500。优化了色谱条件，以有效地分离等摩尔和同系物化合物。Corexit®9500 中的聚氧乙烯非离子表面活性剂是根据以下标准确定的：精确质量（<3ppm）、保留时间和同系物系列；此外，还使用高分辨率串联质谱的解释来注释暂定的组分结构。
在 87 个同系物系列中检测到 2000 多种聚山梨醇酯非离子表面活性剂。聚山梨醇酯表面活性剂的特征是分子基础基团的类型（山梨糖醇、异山梨醇或脂肪酸）、酯化度（n=0-4）、酯链长度（C6-C24）和酯化程度，以及乙氧基化的多分散性。通过 LC/HRMS/MS 分析和产物离子分配对同系物进行了区分。带电气溶胶检测器的结果表明，二酯（23.9±0.78%）是 Corexit®9500 中最丰富的成分，其次是二辛基磺基琥珀酸钠（DOSS）（19.2±1.5%）、三酯（17.3±1.5%）和单酯（15.7±2.3%）。
我们的分析方法促进了 Corexit®9500 中聚山梨醇酯表面活性剂的表征，并允许在没有标准品的情况下系统地研究同系物和等摩尔化合物的差异。Corexit®9500 的特征组成将有助于未来的研究，以确定 Corexit®9500 在环境条件下的化学和生物转化动力学和副产物。
