Single-Channel Microchip for Fast Screening and Detailed Identification of Nitroaromatic Explosives or Organophosphate Nerve Agents

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Abstract
A single-channel chip-based analytical microsystem that allows rapid flow injection measurements of the total content of organic explosive or nerve agent compounds, as well as detailed micellar chromatographic identification of the individual ones, is described. The protocol involves repetitive rapid flow injection (screening) assays--to provide a timely warning and alarm--and switching to the separation (fingerprint identification) mode only when harmful compounds are detected. While micellar electrokinetic chromatography, in the presence of sodium dodecyl sulfate (SDS), is used for separating the neutral nitroaromatic explosive and nerve agent compounds, an operation without SDS leads to high-speed measurements of the "total" explosives or nerve agent content. Switching between the "flow injection" and "separation" modes is accomplished by rapidly exchanging the SDS-free and SDS-containing buffers in the separation channel. Amperometric detection was used for monitoring the separation. Key factors influencing the sample throughput, resolution, and sensitivity have been assessed and optimized. Assays rates of about 360 and 30/h can thus be realized for the "total" screening and "individual" measurements, respectively. Ultimately, such development will lead to the creation of a field-deployable microanalyzer and will enable transporting the forensic laboratory to the sample source.