Today’s Mass Spectrometers are so sensitive that carryover becomes an issue again. To meet today’s requirements for fast, clean and reproducible LC-MS injection, CTC developed the DLW Option for the PAL System. Now the sample is no longer in contact with the syringe but it is aspirated into a holding loop. The syringe only acts as an aspirator and dispenser device in order to exactly measure the amount of sample which needs to be injected this yields excellent reproducibility. After injection, the whole sample path including the valve and needle is washed from the rear with up to 2 different solvents. Active micro pumps deliver the required or quantity of solvent fast and reliable. An active solenoid valve precisely stops solvent delivery or switches between solvents. At the end of the injection cycle all parts which have been in contact with the sample are completely clan. As a result, near zero carryover is achieved for most components.