carry-over problems

<p>Dear all,</p><p>I use for the Dextrorphan determination an Acqiity UPLC System (binery pump) connected with an API 5500 Qtrap.</p><p>Unfortunately I have carry-over problems. About 10% is the carry-over from sample to sample.</p><p>In my UPLC-method I use a "Partial Loop With Needle Overfill"-injection mode. Further I use these Wash Solvents:</p><p>Weak: 100% ACN</p><p>Strong + Seal Wash: 0.1%FA/ACN (90%/10%)</p><p>What can I do to minimize this problem?</p><p></p><p>Kind regards,</p><p>Simone</p>