Development And Application Of A Dynamic Range Conductivity Detector For Ion Chromatograph

Ion chromatograph is a branch of liquid chromatograph,which is mainly used for the analysis of anions and cations.For the analysis of ions in organic amines,small molecular organic acids and other components,the unique selectivity of ion chromatography can be demonstrated.Since the advent of ion chromatograph in 1975,ion chromatographic analysis has developed rapidly,and has been widely used in water quality analysis,product quality testing,chemical product analysis,purity testing of petroleum products and other fields.Ion chromatograph is generally composed of four parts: injection system,separation system,detection system and data processing system.Detector is an important component of ion chromatograph,and its performance mainly affects the key parameters such as minimum detection concentration,qualitative and quantitative repeatability.A detector which can realize one-time sampling and simultaneously separate ions in different concentration ranges is an excellent detector.At present,the detectors of ion chromatograph are mainly divided into three types: conductivity detector,ultraviolet visible spectrophotometer detector and electrochemical detector.Conductivity detector is the most commonly used detector in ion chromatograph.In this paper,a new type of digital signal conductivity detector,dynamic range conductivity detector,is developed.It can automatically select and switch the appropriate range according to the change of conductance signal in the conventional analysis and detection.It solves the difficult problem of simultaneous analysis when the content of various ion components in the sample varies greatly,and avoids the shift error of traditional conductance.At present,there is a gap in the development of ion chromatograph at home and abroad,which is mainly reflected in the performance parameters of ion chromatograph,including baseline noise and baseline drift,minimum detection concentration,qualitative repeatability,quantitative repeatability and instrument linearity.In this paper,according to JJG 823-2014 National Metrological Verification Rules of Ion Chromatograph,the performance parameters of the ion chromatograph equipped with the dynamic range conductivity detector developed by this project were tested.At the same time,compared with other instruments at home and abroad,valuable data were formed,which provided data support for the development of ion chromatograph.In this paper,ion chromatograph equipped with dynamic range detector was used to analyze cyanobacteria with complex matrix.The ion composition of cyanobacteria was tested effectively.The simultaneous measurement of one injection and multiple ions was realized.The efficiency of the measurement was improved and the application of the instrument was expanded.This research mainly includes the following four parts: 1.Design and development of dynamic range conductivity detector: including selection,design and processing of flow cell and control circuit,assembly and debugging of detector.2.Performance evaluation of conductivity detector: including minimum detection concentration,linear range and linear coefficient.3.Performance parameters test and data analysis of ion chromatograph equipped with dynamic range conductivity detector.4.Conductive detectors are used for the analysis of anions and cations in cyanobacteria samples.