Dynamics of field-amplified sample stacking
Dynamics of field-amplified sample stacking
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DOI：
10.1017/s0022112005005975
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发表时间：
2005-11-25
影响因子：
3.7
通讯作者：
Santiago, JG
中科院分区：
文献类型：
--
作者：
Bharadwaj, R;Santiago, JG
场放大样品堆积(FASS)利用电导率梯度和由此产生的非均匀电迁移通量来增加分析物离子的浓度。对于初始样品浓度远小于背景电解质(BGE)浓度的情况，理想的最大浓度增强等于伽马，即样品溶液的电导率与BGE的电导率之比。但在实际应用中，分子扩散和对流弥散都限制了浓度的提高。我们给出了利用FASS提高浓度的理论和实验研究。我们将FASS过程模拟为两个背景电解质离子和多个样品物种在已知的初始浓度梯度上的电迁移、扩散和平流。采用正则微扰方法和广义Taylor色散分析方法，推导了面积平均物种守恒方程和电场方程。该模型预测了FASS过程中背景电解液浓度场、电场和样品离子分布的时空发展。通过片上FASS实验对该模型进行了验证。我们使用酸化聚氧乙烷(PEO)涂层来最小化电渗流(EOF)引起的分散，从而评估最感兴趣的低(但有限的)分散区域。利用基于电荷耦合器件的荧光定量成像技术对非定常浓度场进行了定量化，并对模型进行了验证。这个经过实验验证的模型对于开发样品堆积分析设备的优化设计是有用的。
Field-amplified sample stacking (FASS) uses conductivity gradients and resulting non-uniform electromigration fluxes to effect concentration increases of analyte ions. For cases where the initial sample concentration is much smaller than the background electrolyte (BGE) concentration, the ideal maximum concentration enhancement is equal to gamma, the ratio of conductivity of the sample solution to that of the BGE. However, in practice both molecular diffusion and convective dispersion limit concentration enhancement. We present a theoretical and experimental study of concentration enhancement using FASS. We model the FASS process as electromigration, diffusion, and advection of two background electrolyte Ions and multiple sample species across a known initial concentration gradient. Regular perturbation methods and a generalized Taylor dispersion analysis are used to derive area-averaged species conservation and electric field equations. The model predicts the spatial and temporal development of background electrolyte concentration field, electric field, and sample-ion distribution of the FASS process. We have validated this model using on-chip FASS experiments. We use an acidified poly(ethylene oxide) (PEO) coating to minimize dispersion due to electro-osmotic flow (EOF), and thereby evaluate the low(but finite) dispersion regime of most interest. We have used CCD-based quantitative epifliuorescence imaging to quantify unsteady concentration fields and validate the model. This experimentally validated model is useful in developing optimal designs of sample stacking assay devices.