The use of gas chromatographs to detect the content of pesticide residues (such as organophosphorus, organochlorines, BHC, DDT, etc.) has become a relatively widely used method. However, in the actual detection process, after the chromatograph operates stably, a common issue arises: when injecting the standard solution, one or several individual component peaks fail to appear.
Why doesn’t the standard solution show peaks when detecting pesticide residues with a gas chromatograph?
In response to this problem, Nanjing Kejie Testing Technology Development Co., Ltd. provides the following solutions:
- Failure of a single component peak to appear: For example, among the four DDT isomers, 2-DDT or 3-DDD does not show a peak. Since 2-DDT and 3-DDD have adjacent peak elution orders, they tend to merge into a single peak when the chromatographic conditions are inappropriate. In this case, the problem can be addressed by the following approaches:
① Appropriately adjust the N₂ flow rate or column front pressure.
② Appropriately adjust the column oven temperature.
③ Inject the standard solution of the non-peak component individually and observe whether the gas chromatograph responds, so as to determine if the standard solution has expired.
- Failure of multiple components to show peaks: For instance, none of the four DDT isomers appear. First, adjust the chromatographic conditions according to the methods mentioned above. If the peaks still do not appear, the performance of the chromatographic column should be considered. It is recommended to replace the chromatographic column of the gas chromatograph and test again.