In this work, an on-chip electromembrane extraction coupled with the micro solid phase extraction step was developed for extraction, preconcentration, and determination of trace amounts of chromium(VI) in water samples. The method is based on the selective complexation of chromium(VI) with 1,5-diphenylcarbazide followed by extraction and preconcentration in an acceptor phase via the application of an electrical field. For further preconcentration and digital image analysis, the device was coupled to a micro-packed column. After the adsorption of the complex on the sorbent, an intense violet color appeared which was directly analyzed by RGB colorimetry using a smart phone. For carrying out the analysis via a smart phone, an integrated device was required. For this goal, a microfluidic chip consisting of two platforms with spiral channels and embedded electrodes was exploited. The spiral design of the channels was expected to increase the contact surface between the sample solution and extraction phase and prevent the acceptor phase from early saturation. In addition, packing the sorbent can provide acceptable preconcentration and remarkable sensitivity for analysis of digital image components. Considering optimal conditions, the chromium complex was extracted from aqueous sample solutions into 500 μL of an acidified (HCl 100 mM) acceptor solution. The polypropylene membrane was impregnated with 2-nitrophenyl octyl ether containing 15% di-(2-ethylhexyl) phosphate (DEHP), and a relatively low voltage value of 30 V was applied over the supported liquid membrane. Under optimal conditions, a limit of detection down to 10 μg L⁻¹ was obtained by smart phone detection. The calibration curve was linear in the range of 30–1000 μg L⁻¹ with a correlation coefficient of 0.9969. The inter- and intra-assay RSD% values were lower than 7.6%.

中文翻译：

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片上电膜萃取，然后基于数字图像的灵敏比色法测定痕量的Cr（VI）

在这项工作中，开发了一种片上电膜萃取与微固相萃取步骤相结合的方法，用于萃取，预浓缩和测定水中的痕量铬（VI）。该方法是基于铬（选择性络合VI）与1,5-二苯接着在受体相萃取和预浓缩经由电场的施加。为了进行进一步的预浓缩和数字图像分析，将该设备连接到微填充柱上。络合物吸附在吸附剂上后，出现了强烈的紫色，可使用智能手机通过RGB比色法直接对其进行分析。用于通过进行分析要使用智能手机，则需要集成设备。为了这个目标，开发了一种由两个带有螺旋通道和嵌入式电极的平台组成的微流控芯片。通道的螺旋设计有望增加样品溶液和萃取相之间的接触面积，并防止受体相过早饱和。此外，填充吸附剂可以为数字图像成分的分析提供可接受的预浓缩和显着的灵敏度。考虑最佳条件，将铬络合物从样品水溶液中萃取到500μL酸化的（HCl 100 mM）受体溶液中。用含有15％磷酸二（2-乙基己基）酯（DEHP）的2-硝基苯基辛基醚浸渍聚丙烯膜，然后在被支撑的液膜上施加相对较低的30 V电压值。在最佳条件下，检测限低至10μgL^-1是通过智能手机检测获得的。校准曲线在30–1000μgL ^-1范围内呈线性，相关系数为0.9969。批间和批内RSD％值均低于7.6％。