The PAL 4-fold valve option was developed for automated parallel LC-MS analysis especially required for multiplexed LC-MS interfaces. The accessory consists of 4 injection valves which are loaded in serial mode and switched to inject simultaneously. This allows working with 4 LC columns in parallel which results in enhanced throughput. CTC’s single syringe design allows even for parallel analysis the “cherry picking” sampling mode (random plate access to single wells). Additionally the 4-valve option can be combined with an 8-port stream selector valve for staggered sample injections. Important chromatogram areas can be cut-out and reach the LC-MS inlet. Beside enhanced throughput, this feature helps to keep the MS inlet clean for a prolonged period of time.