Portable Capillary-Microplasma\nOptical Emission Spectrometer:\nGold-Labeled and Silver-Stained Signal Amplification for Carcinoembryonic\nAntigen Detection

Signal amplification techniques based on catalytic silver\ndeposition\non immunogold labels have been used for immunoassays. However, conventional\ninstruments often suffer from limitations in point-of-care testing\ndue to their bulky size, high cost, and complex operation. We herein\ndesigned an integrated, portable 3D-printed device by integrating\ncapillary liquid electrode glow discharge (CLEGD) with optical emission\nspectrometer (OES) for the sensitive determination of carcinoembryonic\nantigen (CEA) in tiny samples. Without the need for additional devices,\nthe sample solution is automatically drawn into the discharge chamber\nunder the action of capillary force and applied high voltage; Ag(I)\nin the analyte is atomized and excited in the discharge plasma, resulting\nin Ag atomic emission lines at 328.1 nm. The system enables the detection\nof 10<sup>1</sup>–10<sup>6</sup> ng mL<sup>–1</sup> Ag(I)\nand further quantification of carcinoembryonic antigen concentration.\nUnder optimized conditions, the compact equipment achieves CEA detection\ncomparable to that of ICP-OES, with a linear range of 1–500\nng mL<sup>–1</sup> and a limit of detection as low as 0.9 ng\nmL<sup>–1</sup>.