Expanding the capabilities of microfluidic gradient elution moving boundary electrophoresis for complex samples

Gradient elution moving boundary electrophoresis (GEMBE) is a robust, continuous injection separation technique that uses electrophoresis to drive electrically charged analytes into a capillary or microfluidic channel for detection, while opposing electroosmosis and controlled variable pressure-driven flow prevent other sample components-for example, cells, proteins, or particulates in complex samples that can interfere with analysis-from entering the channel. This work expands the sample-in/answer-out analytical capabilities of GEMBE for complex samples by demonstrating the quantitative analysis of anions, implementing aqueous background electrolyte (BGE) solutions at neutral pH, and introducing the use of additives to the sample solution to optimize performance. Dirt was analyzed quantitatively, with the sole preparatory step of suspension in an aqueous BGE solution at neutral pH, for dissolved chloride, nitrite, nitrate, sulfate, and oxalate using GEMBE with capacitively-coupled contactless conductivity detection. In addition to altering the pH of the BGE solution, optimization of the analysis of dirt and whole blood was achieved using various commercially available additives. These results, taken together with previous demonstrations of GEMBE for the analysis of complex samples, underscore the uncomplicated versatility of GEMBE, facilitate effective analysis of biological complex samples using BGE solutions at physiological pH, and offer a sufficient set of techniques and tools to build a foundation for the analysis of a broad range of complex samples.