Anderson Emily C, Fritsch Ingrid
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, USA.
Anal Chem. 2006 Jun 1;78(11):3745-51. doi: 10.1021/ac060001v.
Factors affecting the use of redox magnetohydrodynamics (MHD) to enhance the stripping analysis response to heavy metals have been investigated. The analytes were Pb2+, Cd2+, Cu2+, and Tl+ at concentrations ranging from 5 nM to 2 microM. Co-deposition of analytes with Hg2+ (to form a thin Hg film electrode) occurs along with reduction of a high concentration of Fe3+. The Fe3+ provides the high cathodic current necessary to produce a significant Lorentz force, and therefore enhanced convection and larger stripping signals and sensitivities, when the analysis is performed in the presence of an external magnetic field. The effects of varying Fe3+ concentration (1-100 mM), working electrode size (10 microm-3 mm), and magnetic field strengths (0-1.77 T) generated with electromagnets and NdFeB permanent magnets were investigated. Using 100 mM Fe3+ as the MHD-generating redox species at a 3-mm working electrode and in a magnetic field of 1.77 T, peak areas from linear sweep voltammetry were increased by as much as 159 +/- 5%, compared to the signal obtained in the absence of a magnetic field. Experimental detection limits as low as 5 nM were achieved with only a 1-min preconcentration time. A field strength as low as 0.12 T offers some signal enhancement with 100 mM Fe3+. While linear scan anodic stripping voltammetry was used primarily to obtain the signals after the deposition step, potentiometric stripping analysis was also investigated. Redox MHD is an attractive alternative convection method for applications involving sample volumes too small for mechanical stirring or for in-field applications using portable devices that cannot be complicated by the instrumentation required for mechanical stirring.
研究了影响使用氧化还原磁流体动力学（MHD）增强重金属溶出分析响应的因素。分析物为浓度范围在5 nM至2 μM的Pb2+、Cd2+、Cu2+和Tl+。分析物与Hg2+共沉积（形成薄汞膜电极）的同时，高浓度的Fe3+被还原。当在外部磁场存在下进行分析时，Fe3+提供产生显著洛伦兹力所需的高阴极电流，从而增强对流并产生更大的溶出信号和灵敏度。研究了改变Fe3+浓度（1 - 100 mM）、工作电极尺寸（10微米 - 3毫米）以及由电磁铁和钕铁硼永磁体产生的磁场强度（0 - 1.77 T）的影响。在3毫米工作电极和1.77 T磁场中，使用100 mM Fe3+作为产生MHD的氧化还原物质，与无磁场时获得的信号相比，线性扫描伏安法的峰面积增加了高达159±5%。仅1分钟的预浓缩时间就能实现低至5 nM的实验检测限。低至0.12 T的场强在使用100 mM Fe3+时也能提供一定的信号增强。虽然主要使用线性扫描阳极溶出伏安法在沉积步骤后获得信号，但也研究了电位溶出分析。对于涉及样品体积过小无法进行机械搅拌的应用，或者对于使用便携式设备的现场应用（这些应用不能因机械搅拌所需的仪器而变得复杂），氧化还原MHD是一种有吸引力的替代对流方法。
