GERSTEL K.K., 1-3-1 Nakane, Meguro-ku, Tokyo 152-0031 Japan.
J Chromatogr A. 2013 Nov 8;1315:70-9. doi: 10.1016/j.chroma.2013.09.070. Epub 2013 Sep 24.
As reproducible coating of stir bars with more polar phases was found to be very difficult, a supporting grid was used in the development of an ethyleneglycol-modified Silicone (EG Silicone) coated stir bar. This new polar coating showed good performance for the extraction of polar solutes, but long term use also showed degradation of the coating due to friction while stirring. In order to address the lower robustness of the EG Silicone stir bar which has a much softer coating compared to a conventional polydimethylsiloxane (PDMS) stir bar, a novel SBSE procedure termed multi-SBSE ((m)SBSE) was developed. (m)SBSE consists of the robust PDMS stir bar stirring at the bottom of the vial and the EG Silicone stir bar attached on the inner side wall of the vial (a magnetic clip is used for the set-up). After extraction, the two stir bars are placed in a single glass desorption liner and are simultaneously thermally desorbed. The desorbed compounds were analyzed by thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). Compared to conventional SBSE, (m)SBSE provides more uniform enrichment of a wide range of odor compounds in aqueous sample since both stir bars can complement each other, while eliminating the damage of the EG Silicone phase during the extraction. The robustness of the EG Silicone stir bar was dramatically increased and more than 30 extraction and desorption cycles were possible without loss in performance. The recoveries for polar solutes such as 2-acetyl pyrrole (logKow: 0.55), benzyl alcohol (logKow: 1.08), guaiacol (logKow: 1.34), and indole (logKow: 2.05) were increased by a factor of about 2-7. The (m)SBSE-TD-GC-MS method showed good linearity (r(2)>0.9913) and high sensitivity (limit of detection: 0.011-0.071 ng mL(-1)) for the test compounds spiked in water. The feasibility and benefit of the method was demonstrated with analysis of odor compounds in roasted green tea. The normalized areas obtained from (m)SBSE showed the best enrichment for most of the selected compounds compared to conventional SBSE using the PDMS stir bar or the EG Silicone stir bar. Fifteen compounds were determined in the range of 0.15-210 ng mL(-1) (RSD<14%, n=6).
由于难以重现性地在搅拌棒上涂覆更具极性的固定相，因此在开发乙二醇改性硅橡胶（EG 硅橡胶）涂层搅拌棒时使用了支撑网格。这种新的极性涂层对极性溶质的萃取表现出良好的性能，但长期使用也会因搅拌时的摩擦而导致涂层降解。为了解决 EG 硅橡胶搅拌棒的耐用性较低的问题，与传统的聚二甲基硅氧烷（PDMS）搅拌棒相比，EG 硅橡胶搅拌棒的涂层软得多，因此开发了一种称为多 SBSE（(m)SBSE）的新型 SBSE 程序。(m)SBSE 由底部的坚固 PDMS 搅拌棒和附着在小瓶内侧壁上的 EG 硅橡胶搅拌棒组成（使用磁夹进行设置）。萃取后，将两个搅拌棒放在单个玻璃解吸衬管中，并同时进行热解吸。解吸后的化合物通过热解吸-气相色谱-质谱法（TD-GC-MS）进行分析。与传统的 SBSE 相比，(m)SBSE 可在水溶液中均匀富集更广泛范围的气味化合物，因为两个搅拌棒可以互补，同时避免萃取过程中 EG 硅橡胶相的损坏。EG 硅橡胶搅拌棒的耐用性大大提高，经过 30 多次萃取和解吸循环后，仍能保持性能不变。极性溶质（如 2-乙酰基吡咯（logKow：0.55）、苯甲醇（logKow：1.08）、愈创木酚（logKow：1.34）和吲哚（logKow：2.05）的回收率提高了约 2-7 倍。(m)SBSE-TD-GC-MS 方法对水中添加的测试化合物具有良好的线性（r(2)>0.9913）和高灵敏度（检测限：0.011-0.071ng mL(-1)）。该方法的可行性和优势已通过分析烤绿茶中的气味化合物得到证明。与使用 PDMS 搅拌棒或 EG 硅橡胶搅拌棒的传统 SBSE 相比，归一化面积的获得对大多数选定化合物的最佳富集。在 0.15-210ng mL(-1)（RSD<14%，n=6）范围内测定了 15 种化合物。
