Study On Ion Chromatography On-line Pretreatment Teachnology And Its Analysis In Food

In recent years, food safty has drawn extensive attention both at home and abroad due to frequent occurence of its problems. The latest2or three years has witnessed rapid development of ion chromatography technology and its application in the field of food safety testing, which has become one of the most important testing method. However, due to complication and diversity of food samples’matrix, the pretreatment of ion chromatography has been a headache.Conventional offline sample preparation usually adopts such methods as dilution, filter and settlement, but it is time-consuming, arduous and expensive. And from the actual situation, the treated samples still cannot meet the requirements of ion chromatography on-line analysis.In this study, the ion chromatography-on-line pretreatment system is established by using the ion chromatography-on-line pretreatment coupling technique and valve switch technology and allocating various on-line pretreatment column, and successfully applied to the test of nitrite, nitrate,sulfite and bromate in food. Compared with traditional off-line pretreatment, this online pretreatment is characterized by simple operation, high automatic degree, low cost and good reproducibility.Besides, the structure, principles and advantages of the ion chromatography on-line pretreatment system are also analyzed in details in this study.Sample added and recovery experiments show that average recovery of nitrite (n=6) is90.9%-105.6%with relative standard deviations (RSDs) of3.1%-6.3%; average recovery rate of nitrate (n=6)is90.7%-105.4%with RSDs2.7%-4.6%. Under the offline pretreatment, nitrite average recovery (n=6) is90.9%-105.6%with RSDs of3.1%～6.3%, nitrate average recovery (n=6) by90.8%～104.3%with RSDs of3.2%～6.5%. It can be seen the reproducibility of on-line pretreatment is better than offline pretreatment.The ion chromatography-on-line pretreatment system is successfully applied to test of nitrite in food and the results of add recovery experiments indicate that the average recovery rate of nitrite (n=6) is in the range of82.9%-105.2%with relative standard deviations (RSDs) of2.9%-5.6%. However, under the off-line pretreatment, the average recovery rate of nitrite (n=6) is85.8%-108.6%with RSDs3.3%-6.4%. Thus, the reproducibility of on-line pretreatment is better than offline pretreatment.The ion chromatography-on-line preparation system combining off-line ultra-filtration is also used to detect bromate in flour product, which will help solve the matrix interference, pollution analysis system and other issues.The on-line pretreatment technology proposed in this study, as an efficient, convenient, and automatic new sample preparation method will become the forefront of the topic and important research direction of the ion chromatographic analysis.