The Real-Time Detection System Of On-line Chromatograph

Gas chromatography (GC) is a common method of chemical analysis now. It has the advantage of wide measuring range, fast analysis speed and good stability, so it is widely used in many fields. But traditional detection method usually lags behind the experimental process, this makes it difficult to achieve the optimization control. There is an urgent need for the modern laboratory to change from the original off-line mode to online mode.This paper designed a real-time inspecting system of on-line chromatograph based on the research of Gas chromatography. It included two parts:hardware design and software design. The core of hardware was the automatic liquid injector. Since the on-line Gas chromatograph could only achieve the auto injection of gas before, it achieved the auto injection of micro-liquid by the principle of differential pressure control. What’s more, we developed a parallel system of columns through changing the construction of Gas chromatography to increase the detection efficiency. The software was designed for this system by VB language. It achieved the communication of software and S7-200PLC through OPC (OLE for Process Control), realized the function of hardware automatic control. By evaluating various filtering algorithms and peak identification algorithms, we chose the moving average filtering algorithm to filter the chromatographic data, and a deformation algorithm based on the first derivation to distinguish peaks. The software workstation also provided users a simple and friendly work interface, which made it very convenient for users to operate.The experiments shows that the on-line chromatograph is convenient to use and of high reliability, can achieve the requirements of real-time analysis.