A versatile and low-cost chip-to-world interface: Enabling ICP-MS characterization of isotachophoretically separated lanthanides on a microfluidic device

Microfluidics offer novel and state-of-the-art pathways to process materials. Microfluidic systems drastically reduce timeframes and costs associated with traditional lab-scale efforts in the area of analytical sample preparations. The challenge arises in effectively connecting microfluidics to off-chip analysis tools to accurately characterize samples after treatment on-chip. Fabrication of a chip-to-world connection includes one end of a fused silica capillary interfaced to the outlet of a microfluidic device (MFD). The other end of the capillary is connected to a commercially available CEI-100 interface that passes samples into an inductively coupled plasma mass spectrometer (ICP-MS). This coupling creates an inexpensive and simple chip-to-world connection that enables on-chip and off-chip methods of analyzing the separation of rare earth elements. Specifically, this is demonstrated by utilizing isotachophoresis (ITP) on a microfluidic chip to separate up to 14 lanthanides from a homogenous sample into elementally pure bands. The separated analyte zones are successfully transferred across a 7 nL void volume at the microchip-capillary junction, such that separation resolution is maintained and even increased through the interface and into the ICP-MS, where the elemental composition of the sample is analyzed. Lanthanide samples of varying composition are detected using ICP-MS, demonstrating this versatile and cost-effective approach, which maintains the separation quality achieved on the MFD. This simple connection enables fast, low-cost sample preparation immediately prior to injection into an ICP-MS or other analytical instrument.