Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA.
Lab Chip. 2017 Nov 21;17(23):4089-4096. doi: 10.1039/c7lc00796e.
Colorimetry with microfluidic devices has been proven to be an advantageous method for in situ analyses where limited resources and rapid response for untrained users are desired. Image analysis using a small camera or cell phone can be easily incorporated for an objective readout, eliminating variations from normal differences in color perception and environmental factors during analysis. The image analysis using the parameter hue, for example, has been utilized as a highly effective, objective analysis method that correlates with the psychological way color is perceived. Hue analysis, however, is best used for colorimetric reactions that result in distinct changes from one color to a markedly different color and can be inadequate to distinguish between subtle or monotonal (colorless-to-colored) color changes. We address this with three unique color manipulation (i.e., tinting) techniques that provide greater discrimination with such color changes, thus yielding improved limits of detection for various colorimetric reactions that may have previously been limited. Tinting is invoked through dyeing the reagent substrate, colored printing the device, or colored lighting during image capture, and is shown to effectively shift the background color of the reaction detection area. Hydrogen peroxide, a constituent of peroxide-based explosives, is associated with a monochromatic color change upon reaction, and this is used to demonstrate the effectiveness of the tinting methods in improving the limit of detection from an undetectable color change to 0.1 mg mL.
微流控器件比色法已被证明是一种有利的原位分析方法，适用于需要有限资源和快速响应且无需培训用户的情况。使用小型相机或手机进行图像分析可以轻松实现客观读数，消除了分析过程中颜色感知和环境因素的正常差异所带来的变化。例如，使用参数色调进行图像分析已被用作与颜色感知的心理方式高度相关的有效、客观的分析方法。然而，色调分析最适用于导致颜色从一种颜色明显变化为明显不同颜色的比色反应，并且可能不足以区分细微或单调（无色到有色）的颜色变化。我们通过三种独特的颜色处理（即调色）技术解决了这个问题，这些技术可提供更好的颜色变化区分度，从而提高了各种可能以前受到限制的比色反应的检测限。调色是通过给试剂底物染色、给设备彩色印刷或在图像采集过程中使用彩色照明来实现的，它可以有效地改变反应检测区域的背景颜色。过氧化氢是过氧化物基爆炸物的组成部分，与反应后发生的单色颜色变化有关，这表明调色方法可有效提高检测限，将无法检测到的颜色变化提高到 0.1mg/mL。
