In ion chromatographic analysis, standard samples generally yield comparable spectra but some of the actual sample spectra are often accompanied by some miscellaneous peaks, which are due to matrix interference in ion chromatographic analysis. The following discussion of matrix interference encountered in some ion chromatographic analysis is discussed.
1, maleic acid in the maleic acid and oxalic acid. This is a class of problems that are frequently encountered in analytical chemistry, especially in chromatographic analysis, and is a trace component analysis in a high concentration matrix. The difficulty of this kind of problem is that the matrix and the components to be measured are close to each other and have a large difference in concentration, and the high concentration of the matrix affects the retention behavior of the adjacent components in the column, changing their retention time and peak The The conventional solution to this problem is to reduce the amount of sample, use a high-capacity column and dilute the sample several times, and sequentially inject the sample from low to high in terms of concentration. The biggest advantage of this method is that high concentrations of the substrate are not overloaded and affect the life of the column. I will glypolic acid sample diluted 1000 times the volume of sample analysis, maleic acid and oxalic acid in the chromatogram is clearly visible at the same time glyoxylic acid is not overloaded. But I believe that the method also has some limitations. For some samples whose concentration difference is too large (the mass concentration is more than ten thousand times worse), the high concentration matrix can be eliminated by means of column switching or valve switching. For example, Liang Lina introduced a method for the determination of iodide in saturated brine. The concentration of chloride ions and iodine ions in the solution is 3 million difference, and the column separation can significantly reduce the chloride ion content.
2, high chlorine matrix in the nitrite ion. Chloride in nature is a common, high concentration of anion, because in anion exchange chromatography chloride ion and nitrite ion retention capacity is relatively close, so high chlorine matrix often interfere with the determination of nitrite ions. One solution to this problem is to use an UV detector because the nitrite ion has a strong UV absorption in the 200-220 nm range and the chloride ion absorbs very weak in this range. However, the use of carbonate / bicarbonate eluent, the chloride ion matrix concentration is too high before the nitrite to produce a significant negative peak, submerged nitrite signal. The phenomenon of the author in the use of ion chromatography in the determination of nitrite and nitrate in milk powder encountered, the solution to the use of high-capacity column.
3, water-soluble organic solvents in the inorganic anion. The company treated hydrogenated butanol samples and ion chromatographic inhibition of conductivity detection of butanol in the determination of inorganic anions. After the hydrogen peroxide treatment, the butanol matrix is oxidized to eliminate, so the chromatographic peaks of the ion peak symmetrical no miscellaneous peak interference. It has been reported that the use of self-regenerative inhibition mode in the determination of chloride ions in the retention time of a positive peak, or even drown of chloride ions in the case of the determination of anions such as methanol and isopropanol after dilution with an anion-compatible anion signal. The mechanism of the matrix interference is that the alcohol molecules in the dead volume times the elution (and chloride ion retention time close to), through the suppressor, the alcohol molecules will interfere with sodium ions and hydrogen ions ion exchange, the background conductance , So there is a positive peak.
Qingdao Pu Ren Instrument Co., Ltd. Technology Department Wang Cunjin