Caroline A. Davis and Christopher R. Harrison
The recent development of paper based diagnostic systems has inspired further investigations into the utility of paper based structures for analytical work. Here we present our development of a low-cost alternative to traditional liquid chromatography systems. Although liquid chromatography is a commonly used separation technique, its applicability can be limited due to the expense and large in size of the instruments; in particular, this makes offsite analysis very difficult.
For our device the chromatographic support is cellulose based paper; this allows us the freedom to derivatize the support with the desired stationary phase through the use of various borate compounds. To achieve pressurized, directional flow through the paper chromatographic support the paper is embedded in polydimethylsiloxane (PDMS). This affords us a number of advantages, particularly with respect to the detection systems. As PDMS is transparent and non-conductive we can incorporate spectrophotometric and electrical detection systems directly into the structure of the device. Furthermore, proper design of the device, including T injection designs used in traditional lab-on-a-chip devices frees us from the need for an expensive, switching valve injection system. Finally, the low back pressure that results from the monolithic nature of the paper chromatographic support means that the entire system can be operated with inexpensive syringe or peristaltic pumps. We will present our advances on these designs and the results of our trials with developing ion exchange stationary phases.
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