Department of Chemistry, Faculty of Science, Chulalongkorn University, Patumwan, Bangkok 10330, Thailand.
Anal Chim Acta. 2012 Sep 26;744:1-7. doi: 10.1016/j.aca.2012.07.003. Epub 2012 Jul 8.
We report the development of an electrochemical paper-based analytical device (ePAD) for the selective determination of dopamine (DA) in model serum sample. The ePAD device consists of three layers. In the top layer, SU-8 photoresist defines a hydrophilic sample application spot on the filter paper. The middle layer was made from transparency film and contained two holes, one for sample preconcentration and the other for the surfactant to allow transfer to the third layer. A screen-printed carbon electrode formed the bottom layer and was used for electrochemical measurements. In the absence of the anionic surfactant, sodium dodecyl sulfate (SDS), the oxidation peaks of DA, ascorbic acid (AA) and uric acid (UA) overlapped. With the addition of SDS, the DA oxidation peak shifted to more negative values and was clearly distinguishable from AA and UA. The oxidation potential shift was presumably due to preferential electrostatic interactions between the cationic DA and the anionic SDS. Indeed, whilst the SDS-modified paper improved the DA current five-fold, the non-ionic Tween-20 and cationic tetradecyltrimethylammonium bromide surfactants had no effect or reduced the current, respectively. Furthermore, only the SDS-modified paper showed the selective shift in oxidation potential for DA. DA determination was carried out using square-wave voltammetry between -0.2 and 0.8 V vs. Ag/AgCl, and this ePAD was able to detect DA over a linear range of 1-100 μM with a detection limit (S/N=3) of 0.37 μM. The ePAD seems suitable as a low cost, easy-to-use, portable device for the selective quantitation of DA in human serum samples.
我们报告了一种用于选择性测定模型血清样品中多巴胺（DA）的电化学纸基分析器件（ePAD）的开发。ePAD 装置由三层组成。在顶层，SU-8 光刻胶在滤纸上定义了一个亲水的样品加样点。中层由透明薄膜制成，包含两个孔，一个用于样品预浓缩，另一个用于允许表面活性剂转移到第三层的孔。一个丝网印刷碳电极形成底层，并用于电化学测量。在不存在阴离子表面活性剂十二烷基硫酸钠（SDS）的情况下，DA、抗坏血酸（AA）和尿酸（UA）的氧化峰重叠。加入 SDS 后，DA 的氧化峰向更负的数值移动，与 AA 和 UA 明显区分开来。氧化电位的移动可能是由于阳离子 DA 与阴离子 SDS 之间的优先静电相互作用。事实上，虽然 SDS 修饰的纸张将 DA 电流提高了五倍，但非离子型吐温-20 和阳离子十四烷基三甲基溴化铵表面活性剂没有影响或降低了电流。此外，只有 SDS 修饰的纸张显示出 DA 氧化电位的选择性移动。使用方波伏安法在 -0.2 至 0.8 V 相对于 Ag/AgCl 进行 DA 测定，该 ePAD 能够在 1-100 μM 的线性范围内检测 DA，检测限（S/N=3）为 0.37 μM。ePAD 似乎适合作为一种低成本、易于使用、便携式的设备，用于选择性定量测定人血清样品中的 DA。
