Yu Chunhe, Liu Qing, Lan Lidan, Hu Bin
Department of Chemistry, Wuhan University, Wuhan 430072, China.
J Chromatogr A. 2008 Apr 25;1188(2):124-31. doi: 10.1016/j.chroma.2008.02.065. Epub 2008 Feb 23.
Two sample preparation methods, dual solvent-stir bars microextraction (DSSBME) and U-shaped hollow fiber-liquid phase microextraction (U-shaped HF-LPME), are proposed and critically compared for high-performance liquid chromatography (HPLC)-ultraviolet (UV)/mass spectrometry (MS) analysis of Sudan dyes in this paper. In DSSBME, the organic solvent was confined to a pair of hollow fiber membrane fixed on a stir bar, which can stir by itself, while the hollow fiber in U-shaped HF-LPME was fixed by two microsyringes. The significant factors affecting the microextraction of Sudan dyes in both microextraction techniques have been examined and no obvious difference in the effect of extraction solvent, pH and salt concentration on the extraction efficiency of Sudan dyes was observed except extraction time and stirring speed. Both microextraction techniques were similar in terms of analytical performance from aqueous solutions (LODs ranged from 0.09 to 0.95 microgL(-1) by HPLC-UV and 2.5-6.2 microgL(-1) by HPLC-MS; the absolute LODs ranged from 0.9 to 11.25 pg by HPLC-UV and 5-21.2 pg by HPLC-MS), however, DSSBME was more stable (lower stirring speed required), less sample consuming and much shorter time required to reach extraction equilibrium; while U-shaped HF-LPME was easier to operate and no more special device required. The two microextraction techniques combined with HPLC-UV/MS were successfully applied to the analysis of real samples including strawberry sauce, capsicum oil, salted egg, and two kinds of chilli sauce. Although the LODs of HPLC-UV are lower than that of HPLC-MS by a factor of 10 in this work, the absolute LODs for both HPLC-UV and HPLC-MS are comparable. HPLC-UV cannot identify the suspicious peaks at the same retention time as that of Sudan II and III in salted egg, while HPLC-MS can give exact information of Sudan I-IV in real sample analysis and is more reliable. The sensitivity of HPLC-MS is enough for real sample analysis.
本文提出了两种样品制备方法，即双溶剂搅拌棒微萃取（DSSBME）和U形中空纤维液相微萃取（U形HF-LPME），并对其用于高效液相色谱（HPLC）-紫外（UV）/质谱（MS）分析苏丹染料进行了严格比较。在DSSBME中，有机溶剂被限制在固定在搅拌棒上的一对中空纤维膜中，搅拌棒可自行搅拌，而在U形HF-LPME中，中空纤维由两个微量注射器固定。研究了两种微萃取技术中影响苏丹染料微萃取的重要因素，结果发现，除萃取时间和搅拌速度外，萃取溶剂、pH值和盐浓度对苏丹染料萃取效率的影响无明显差异。两种微萃取技术从水溶液中的分析性能相似（HPLC-UV法的检出限为0.09至0.95 μg L⁻¹，HPLC-MS法为2.5至6.2 μg L⁻¹；HPLC-UV法的绝对检出限为0.9至11.25 pg，HPLC-MS法为5至21.2 pg），然而，DSSBME更稳定（所需搅拌速度更低），样品消耗更少，达到萃取平衡所需时间更短；而U形HF-LPME操作更简便，无需更多特殊装置。这两种微萃取技术与HPLC-UV/MS联用成功应用于实际样品分析，包括草莓酱、辣椒油、咸蛋和两种辣椒酱。尽管在本研究中HPLC-UV的检出限比HPLC-MS低10倍，但HPLC-UV和HPLC-MS的绝对检出限相当。HPLC-UV无法识别咸蛋中与苏丹II和III保留时间相同的可疑峰，而HPLC-MS在实际样品分析中能给出苏丹I-IV的确切信息，更可靠。HPLC-MS的灵敏度足以用于实际样品分析。
