Hehe, the low concentration did not reach the detection limit, so there was no peak. Solution: (1) Concentrate the sample as described on the second floor. (2) I think the simplest thing is to adjust the range of the detector and improve the sensitivity of the detector to a higher level. (3) It is feasible to increase the sample size in theory. For the same sample, the peak height and peak area are different with different injection quantity, and the peak will increase with the increase of injection quantity (not a simple proportional relationship).