In order to simplify the device configuration, reduce the cost, improve the instrument stability and anti-interference ability, a new type of double-line flow-injection ion-selective electrode method was proposed, and determination conditions of the method, such as the carrier composition and flow rate, acidity adjusting liquid composition and flow rate, and reaction coil length were optimized. The method was successfully used in simultaneous determinations of K+、Na+、Cl-、Ca2+in serums. Linear ranges of the method were in 2.0~24.0 mmol·L^-1for K+, 102~252 mmol·L^-1for Na+, 20~300 mmol·L^-1for Cl- and 0.7~8.0 mmol·L^-1 for Ca2+, respectively. The relative standard deviation was less than 1.3% (n=11), the recoveries obtained by adding K+,Na+,Cl- and Ca2+in serum samples were in range 96%~104%, the analysis speed was 480 detections/h, and the consumption of the sample was only 45 μL per time. These determination ranges were in normal ranges of human serum’s electrolyte concentrations.
