A miniature liquid electrode discharge-optical emission spectrometric system integrating microelectrodialysis for potassium screening in serum
An automated microelectrodialysis (μED)-liquid electrode discharge (LED)-optical emission spectrometric (OES) system was developed with the aim of potassium screening in serum, especially for a micro-sample volume. Potassium in serum was on-line extracted via a μED process and subsequently introduced into the LED microplasma to perform the optical emission detection at λem 766.5 nm. The optical emission intensity of potassium was measured using a charge-coupled device (CCD) spectrometer for quantitative analysis. A few important parameters governing the extraction of potassium by μED and its detection by LED-OES were investigated. The present system provides an excellent capability for eliminating matrix interference with a protein removal efficiency of >99%, by consuming a serum sample volume of 20 μL for each analysis. The entire analytical process, including sample introduction, pretreatment and detection, takes no more than 90 s. A detection limit of 0.6 mg L−1 was obtained along with a linear range of 2–70 mg L−1 and a RSD value of 4.8% at 5 mg L−1 potassium. The practical applicability of the μED-LED-OES system was demonstrated by the determination of potassium in serum certified reference materials and real human serum samples. The present system offers a potential strategy for screening the variation of the concentration of potassium in patients.