What are your chromatographic conditions? If the mobile phase is not strong enough it will be 'dumped' into the next chromatogram. See attached;

https://file.scirp.org/pdf/AJAC_2015051309493283.pdf

need more information before I can help. For the meantime, check at my Researchgate profile and read my question on carryover and how I solveed my problem. Do me a favor to check this for me. Assume you are running from 10 to 100% B gradient in 10 min and your peak is eluted at 7 min, inject the standard once with the said gradient and collect the chromatogram data for 30 min. At 10 min, drop the B to 10% and stay for 5 min to go back to initial condition and immediately ramp B to 100% in 1 min and run for 5 min. Repeat it one mor time. If you still see three peaks reduce in height, then the carryover was not caused by the autosampler but the column.

I agree with the other answers, to really be able to suggest something helpful we would need the chromatographic conditions as well as the stationary phase of the column.

If you are not seeing any change with what you have tried so far then it sounds more like the column chemistry than the autosampler.

first identifying the problem is important.

1. if you are using empower then in functions use inject immediate samples it will only run the gradient with out taking injection. this will give you an idea whether its column or autosampler.

2. if its column change chemistry or gradient.

3. if its autosampler you need to play with needle wash etc.

4. As far as your compound goes its solubility increases as pH decreases to 3 so u can add formic acid in your wash. add acidic additive in the diluent also.

5. more information its even easy to solve the issue.

Step by step approach.

1. wash the system and column.

2. run inject immediate sample, two blanks, std, injec imm. samples, blks.

3. once you aquire this data you will understand by yourself.

I hope this approach helps.