Sensitive methods are required for in situ monitoring of volatile organic compounds (VOCs). Herein, carbon nanotube (CNT) sponges were investigated as a new type of adsorbent for enriching trace aromatic VOCs. A square pillar configuration (3 mm × 3 mm × 45 mm, 5 mg) of a CNT sponge was enclosed in a glass tube (4 mm i.d.). After accumulating the sample vapor, a direct current pulse (26 V, 0.5-3.0 s) through the CNT sponge allowed narrow desorption bandwidths of 0.48-0.84 s (with a photoionization detector) and 1.2 s (with a flame ionization detector) and high desorption efficiency (>96.5%). Gas chromatographic analysis of a nine-component VOC mixture (100 mL adsorption volume) gave enrichment factors of 88 (benzene) to 323 (toluene and m-xylene) with detection limits in the range of 0.9-2.6 ppb (v/v). These results demonstrate that CNT sponges are a promising preconcentrator material for trace detection of VOCs. The adsorption breakthrough experiments exhibited good correlation with the kinetic adsorption and Langmuir isotherm models. The maximum adsorption capacities of the CNT sponge increased in the order benzene (0.13 mg/g) < toluene (2.45 mg/g) < ethylbenzene (13.90 mg/g) < o-xylene (14.31 mg/g), with R2 values of >0.95. The rollup phenomena observed during multicomponent adsorption were explained by the competitive displacement or adsorption affinities of aromatic VOCs. The feasibility of the CNT sponge preconcentrator in a real environment was tested for interfering species (NO2 and NH3), laboratory air, and a human breath sample and demonstrated similar performance as in the controlled nine-component tests.

中文翻译：

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碳纳米管海绵是芳香族挥发性有机化合物的富集材料。

原位监测挥发性有机化合物（VOC）需要灵敏的方法。在本文中，碳纳米管（CNT）海绵被研究作为一种新型的吸附剂，用于富集痕量芳族VOC。将CNT海绵的方柱构造（3mm×3mm×45mm，5mg）封入玻璃管（内径4mm）中。累积样品蒸气后，通过CNT海绵的直流脉冲（26 V，0.5-3.0 s）允许0.48-0.84 s（使用光电离检测器）和1.2 s（使用火焰离子检测器）的较窄解吸带宽，并且高解吸效率（> 96.5％）。气相色谱分析九组分VOC混合物（吸附体积为100 mL）时，富集系数为88（苯）至323（甲苯和间二甲苯），检出限为0.9-2.6 ppb（v / v）。这些结果表明，CNT海绵是用于VOC痕量检测的有前途的预浓缩器材料。吸附突破实验显示出与动力学吸附和Langmuir等温模型的良好相关性。CNT海绵的最大吸附容量按苯（0.13 mg / g）<甲苯（2.45 mg / g）<乙苯（13.90 mg / g）<邻二甲苯（14.31 mg / g）的顺序增加，R2值为> 0.95。多组分吸附过程中观察到的累积现象是由芳香族VOC的竞争性位移或吸附亲和力解释的。对CNT海绵预浓缩器在实际环境中的可行性进行了测试，以检测干扰物（NO2和NH3），实验室空气和人的呼吸样品，并证明了其与受控九成分测试类似的性能。