Kanyanee Tinakorn, Borst Walter L, Jakmunee Jaroon, Grudpan Kate, Li Jianzhong, Dasgupta Purnendu K
Department of Chemistry and Biochemistry, and Department of Physics, Texas Tech University, Lubbock, Texas 79409-1051, USA.
Anal Chem. 2006 Apr 15;78(8):2786-93. doi: 10.1021/ac052198h.
Soap bubbles provide a fascinating tool that is little used analytically. With a very low liquid volume to surface area ratio, a soap bubble can potentially provide a very useful interface for preconcentration where mass transfer to an interfacial surface is important. Here we use an automated system to create bubbles of uniform size and film thickness. We utilize purified Triton-X 100, a nonionic surfactant, to make soap bubbles. We use such bubbles as a gas-sampling interface. Incorporating hydrogen peroxide into the bubble provides a system where electrical conductance increases as the bubble is exposed to low concentrations of sulfur dioxide gas. We theoretically derive the conductance of a hollow conducting spherical thin film with spherical cap electrodes. We measure the film thickness by incorporating a dye in the bubble making solution and laser transmission photometry and find that it agrees well with the geometrically computed thickness. With the conductance of the bubble-making soap solution being measured by conventional methods, we show that the measured values of the bubble conductance with known bubble and electrode dimensions closely correspond to the theoretically computed value. Finally, we demonstrate that sub-ppm levels of SO(2) can readily be detected by the conductivity change of a hydrogen peroxide-doped soap bubble, measured in situ, when the gas flows around the bubble.
肥皂泡提供了一种很少用于分析的迷人工具。由于液体体积与表面积之比非常低，肥皂泡有可能为预浓缩提供一个非常有用的界面，在这种情况下，向界面表面的传质很重要。在这里，我们使用一个自动化系统来制造大小和膜厚度均匀的气泡。我们利用纯化的 Triton-X 100（一种非离子表面活性剂）来制造肥皂泡。我们将这种气泡用作气体采样界面。在气泡中加入过氧化氢会形成一个系统，当气泡暴露于低浓度二氧化硫气体时，其电导率会增加。我们从理论上推导了带有球形帽电极的中空导电球形薄膜的电导率。我们通过在制泡溶液中加入染料并利用激光透射光度法来测量膜厚度，发现其与几何计算厚度非常吻合。通过用传统方法测量制泡肥皂溶液的电导率，我们表明，对于已知气泡和电极尺寸的气泡电导率测量值与理论计算值密切对应。最后，我们证明，当气体在气泡周围流动时，通过原位测量过氧化氢掺杂肥皂泡的电导率变化，可以很容易地检测到亚 ppm 级别的 SO₂。
