Abstract: In order to improve the efficiency of mass spectrometry(MS) instrument, a microfluidic paper-based analytical device (μPAD) was designed for sample loading and pre-screening. Samples loaded on μPAD can be split into two separated detection zones. Colorimetric detection with the naked eye can be viewed as fast screening. Samples with significantly lower or higher colorimetric response than threshold may be ignored. For suspicious samples, final detection with much higher sensitivity would be carried out with MS. Using the present method, quantifications of Ang II in raw serum with both colorimetry and MS were achieved. For colorimetric detection, the resulting linear range of 200~1 000 μmol/L was established, and the visual detection limit was in the range of 150~200 μmol/L. For MS detection, the linear dynamic range for Ang II was 5~500 μmol/L. The limit of detection (LOD) was measured to be 19 μmol/L using bradykinin as the internal standard. The result indicates that this protocol would enable easy sample transportation, rapid screening and sensitive MS measurement with a single μPAD device.

Key words: paper-based analytical device, paper spray ionization, fast screening, colorimetric analysis