Investigations On Microelectrodialysis For Matrix Isolation Coupled To Liquid Electrode Discharge-Optical Emission Spectrometry For Online Detection Of Potassium In Serum

As an atmospheric pressure microplasma generation approach,liquid electrode discharge(LED)has many unique advantages,e.g.,simple device,small size and low power consumption,which provides a promise for the miniaturization of analytical instruments and thus has been paid wide attention in the field of spectral analysis.In this thesis,LED microplasma as a radiation source for optical emission spectrometry(OES),coupling with microelectrodialysis(μED)for matrix isolation,was employed for the detection of potassium in serum.In the experiment,serum sample was online introduced to a μED unit by a sequential injection system.Thereafter,potassium ions in anode chamber could pass through the cation exchange membrane into cathode chamber under a direct current electric field.In this process,the separation of potassium ions from complex serum matrix could be achieved to reduce the matrix interference of the detection of potassium in serum.With 0.12 mol L-1 HNO3 as carrier,potassium ions in cathode chamber were introduced to LED microplasma region,and excited to produce OES.The characteristic emission of potassium obtained was recorded by a charge-coupled device(CCD)spectrometer for quantitative analysis.To avoid the contamination of ion exchange membrane from the residues of high-abundance proteins,all the channels were washed with 0.12 mol L-1 Tris-HCl(pH=7.4)buffer and 1%Triton X-100 after each analysis.Several factors governing the serum μED and LED microplasma performances were investigated,including sampling flow rate,μED time and voltage,carrier flow rate and LED voltage,etc.Only 20 μL of serum sample was required for each analysis by the present μED-LED-OES system.Under the optimal conditions,a detection limit(3a,n=11)of 0.6 mg L-1,a linear range of 2-70 mg L-1 with R2>0.9998,and a precision of 4.8%(n=11)were obtained.Serum potassium contents in the certified reference materials GBW(E)080918-080920 were determined by the present μED-LED-OES system.The reasonable agreements were obtained between the certified and the obtained values,demonstrating the reliability and practicability of the present μED-LED-OES system.In addition,the present system was also employed to determine the concentration of human serum potassium and its variation,giving rise to spiking recoveries of 95-105%.TheμED-LED-OES system provides a novel approach for online rapid determination of potassium in human serum.