High-performance liquid chromatography (HPLC) plays an important role in industry and scientific research because it supports reliable and versatile separation analysis. Although the highly efficient technique of ultra-fast separation has become popular in recent years, there is also a need for portable, compact and lightweight HPLC. This allows the immediate on-site production of analytical results and the completion of analysis before the nature of analytes changes in fields such as environmental monitoring and clinical diagnosis. The size and weight of conventional HPLC equipment limit its use to fixed locations in laboratories, which makes it difficult to meet on-site demands. Miniaturized HPLC devices require smaller samples, consume less solvent and energy, and produce only small amounts of waste. They also enable multiple analysis because several devices can be installed in the same space as the footprint of conventional equipment.

 

To create a compact lightweight HPLC device driven by battery or AC power, the group miniaturized each HPLC component while maintaining high levels of performance and utility. The photo below shows the prototype of the device. A pump, a sample injector, a column and a detector are accommodated in a B5-size space, and the whole device weighs only around 2 kg.

 

 

A separation column and a detector (microelectrode) were integrated into a chip measuring 4 × 6 cm. Particles of 3 μm in diameter were packed into the column, which had a length of 30 mm and a diameter of 0.8 mm.

 

 

The pumping mechanism is based on the principle of electro-osmosis (EO) – a phenomenon in which water flow toward the negative electrode is generated when a DC voltage is applied to both ends of a water-filled glass capillary tube. Unlike conventional mechanical pumps, current pumps are characterized by minimal flow rate variations. In this pump, solvent is pushed along by water under electro-osmotic flow in a piece of porous silica (diameter: 4 mm; height: 4 mm) rather than in a capillary tube. The flow rate can be adjusted by changing the voltage applied.

 This research was supported by JST.

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