Research Center for Analytical Sciences, College of Chemistry, Nankai University, 94 Weijin Road, Tianjin 300071, China.
Anal Chem. 2010 Feb 15;82(4):1365-70. doi: 10.1021/ac902450f.
Metal-organic frameworks (MOFs) are one kind of highly porous crystalline materials, which are constructed by metal-containing inorganic nodes and organic linkers. With large surface area and high thermal stability, MOFs have great potential as sorbents for the preconcentration of trace analytes. However, such application of MOFs to the analysis of real samples has not been reported before. Here we report the utilization of MOF-5 as sorbent for in-field sampling and preconcentration of atmospheric formaldehyde before thermal desorption (TD) GC/MS (TD-GC/MS) determination without the need for any chemical derivatization. MOF-5 gave a 53 and 73 times better concentration effect than Tenax TA (organic polymers) and Carbograph 1TD (graphitized carbon black), respectively, for TD-GC/MS determination of formaldehyde. MOF-5 showed good performance for in-field sampling and preconcentration of formaldehyde from air samples with a relative humidity less than 45%. The collected formaldehyde on MOF-5 sorbent was stable for at least 72 h at room temperature before TD-GC/MS analysis. One tube packed with 300 mg of MOF-5 lasted 200 cycles of adsorption/TD without significant loss of collection efficiency. The breakthrough volume of such a tube was 1.2 L of 28.35 mg m(-3) formaldehyde at a sampling flow rate of 100 mL min(-1). The use of MOF-5 for in-field sampling and preconcentration in combination with TD-GC/MS for the determination of formaldehyde offered a linear range covering 3 orders of magnitude, and a detection limit of 0.6 microg m(-3). The precision for six replicate cycles of in-field sampling and preconcentration for TD-GC/MS determination using one 300 mg MOF-5 packed tube ranged from 2.8% to 5.3%. The tube-to-tube reproducibility of three MOF-5 tubes prepared in parallel was 7.7%. The developed method was applied to analysis of local indoor and outdoor air samples for formaldehyde and validated by the standard method TO-11A of the United States Environmental Protection Agency. The concentration of formaldehyde and the recovery of spiked formaldehyde in the air samples ranged from 12 to 48 microg m(-3), and from 93% to 107%, respectively.
金属有机骨架（MOFs）是一种高度多孔的结晶材料，由含金属的无机节点和有机连接体构成。MOFs 具有大的表面积和高热稳定性，作为痕量分析物的预浓缩吸附剂具有很大的潜力。然而，MOFs 在分析实际样品中的这种应用尚未有报道。在这里，我们报告了利用 MOF-5 作为吸附剂，在热解吸（TD）GC/MS（TD-GC/MS）分析之前，对大气中的甲醛进行现场采样和预浓缩，而无需任何化学衍生化。MOF-5 对 TD-GC/MS 测定甲醛的浓缩效果分别比 Tenax TA（有机聚合物）和 Carbograph 1TD（石墨化炭黑）好 53 倍和 73 倍。MOF-5 对相对湿度小于 45%的空气样品中的甲醛进行现场采样和预浓缩具有良好的性能。收集在 MOF-5 吸附剂上的甲醛在室温下至少稳定 72 小时，然后再进行 TD-GC/MS 分析。一根装有 300 毫克 MOF-5 的管在没有明显损失收集效率的情况下，可进行 200 次吸附/TD 循环。这样一根管的穿透体积为 1.2 升，采样流速为 100 毫升/分钟，甲醛浓度为 28.35 毫克/立方米。MOF-5 用于现场采样和预浓缩，与 TD-GC/MS 联用测定甲醛，提供了一个涵盖 3 个数量级的线性范围，检测限为 0.6 微克/立方米。使用一根装有 300 毫克 MOF-5 的管进行 6 次现场采样和 TD-GC/MS 测定的重复循环的精密度为 2.8%至 5.3%。三个平行制备的 MOF-5 管的管间重现性为 7.7%。所建立的方法用于分析当地室内和室外空气样品中的甲醛，并通过美国环保署的标准方法 TO-11A 进行了验证。空气中甲醛的浓度和加标甲醛的回收率范围分别为 12 至 48 微克/立方米和 93%至 107%。
