Development And Applications Of High Field And Fast Capillary Electrophoresis Ion Analysis System

A new high-speed capillary electrophoresis（HSCE）device has been developed for the rapid detection of environmental trace contaminants in the field.The device utilizes a"notched tube"fast translational platform for spontaneous injection or electrokinetic injection,fused silica capillary for separation,and capacitively coupled contactless conductivity detection（C⁴D）to detect.With a high-voltage field ranging from 667 to 1205V/cm,HSCE was capable of achieving ultra-fast separation of anions and cations within just 30 seconds.The system was successfully used to rapidly detect common cations in drinking water as well as anions associated with explosive substances.（1）We have developed a high-speed capillary electrophoresis ion analysis system that utilized a notched tube rapid injection device fabricated with 3D printing technology.The"notched tube"translational spontaneous injection device consists of printed gears,racks and brackets with stepper motors,Arduino UNO controllers,and serial screens.The notched tube was mounted in parallel within the injection device and oriented vertically to the capillary.With the help of a stepper motor,it was moved horizontally,facilitating the spontaneous injection of the sample into the capillary.This was achieved by sweeping through the slot of the notched tube which contained both the buffer solution and the sample.The system was initially used to explore the separation conditions of cations,followed by an evaluation of its performance.The results indicated that,under the optimal separation conditions,the four cations（NH₄⁺,K⁺,Na⁺,Li⁺）could be efficiently separated with baseline separation time of less than12 s.Moreover,the detection limits of NH₄⁺,K⁺,and Na⁺were found to be 7,7,and 9μM,respectively.（2）Based on the system in（1）,a high-speed capillary electrophoresis ion analysis system featuring a cooling device was developed.The system incorporates a special designed detection cell,named the"cooling-C⁴D"integrated cell,which integrates the C⁴D detection head with a coolant channel.This detection cell was fabricated with the aid of stereo lithography apparatus（SLA）and was connected to the cooling device.The system utilized a circulating coolant,cooled by the Peltier,to remove any excess Joule heat generated in the capillary tube,thus effectively reducing the Joule heat effect.Consequently,this system allowed for a higher concentration of buffer solution to be utilized,resulting in improved separation resolution between signal peaks and enhanced electrical stacking.Furthermore,it enabled direct injection of the undiluted sample.Under optimum separation conditions,six most common cations(NH₄⁺,K⁺,Na⁺,Li⁺,Mg²⁺,Ca²⁺)could be fully separated within 22 s.The detection limits of these cations were in the range of 2.5-5.2μM,and the theoretical plate ranged from 7.7×10⁴/m to 9.4×10⁴/m.（3）The integrated detection cell“cooling-C⁴D”mentioned in item（2）has undergone significant improvements.The system was able to separate typical explosive tracer anions（Cl O₃^-,Cl O₄^-,NO₃^-,N₃^-）and common interfering ions(SCN^-,SO₄^2-,CO₃^2-,PO₄^3-).Additionally,the separation conditions of three inner-wall modified capillaries were studied using different buffer solutions to achieve optimal separation of actual samples.Results showed that N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride（TMA）coated capillaries works best for separating Cl O₃^-,Cl O₄^-,and NO₃^-under acidic buffer conditioins.Samples were successfully separated,achieving baseline separation of ions within 30 seconds.