A miniature liquid electrode discharge-optical emission spectrometric system integrating microelectrodialysis for potassium screening in serum

An automated microelectrodialysis (mED)-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 mu ED process and subsequently introduced into the LED microplasma to perform the optical emission detection at lambda(em) 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 mED 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 mu L 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 mED-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.