For the detection of trace substances, the traditional manual labeling method can easily contaminate the sample and greatly reduce the analysis results. Similarly, for non-aqueous matrices such as gasoline, diesel, heavy oil, etc., it is particularly difficult to add standards due to the inability of standard samples to be effectively miscible. Therefore, the English blue labeling technology is mainly used in combination with English blue pre concentration (to detect trace ions, the standard concentration is very low and easy to contaminate), or in combination with English blue matrix elimination technology (organic phase is difficult to label).
The implementation method of English blue labeling is to quantify the sample and standard separately, and then enter the pre concentration column or matrix elimination column in order and be retained. They are both eluted by the eluent and then enter the analysis system. The entire process avoids manual labeling and mixing, achieving very ideal parallel performance.
Taking the detection of anions in gasoline as an example, the use of indigo matrix elimination technology is required, and ordinary NaCl standard samples are insoluble in gasoline. There are reports that use the principle of NaCl slightly soluble in ethanol to produce ethanol NaCl standard samples for analysis, or use TBA salt ethanol solution for addition. However, the actual effect is not ideal. Due to the large variation of NaCl solubility in ethanol with external factors such as temperature, it brings about significant instability. In addition, due to the inability to guarantee the uniform distribution of ethanol NaCl in gasoline, the peak of the standard sample often appears deformed, tailing, and other situations, and the recovery rate is not ideal.
By using the technique of eliminating the English blue matrix and adding English blue standards, it is possible to directly add inorganic anions to gasoline samples as standard samples, with symmetrical peak shapes and high recovery rates, resulting in satisfactory results.