Shimadzu Scientific Instruments (SSI) offers the PPSQ-51A single-reactor and PPSQ-53A triple-reactor gradient system protein sequencers. The instruments provide users with higher sensitivity and more reliable analysis of N-terminal amino acid sequences through automated Edman degradation. In addition, they provide an extra level of flexibility because they can detect and identify additional rare and modified amino acids. They are FDA 21 CFR Part 11 compliant when used with SSI’s LabSolutions analysis data system. The systems perform sequence analysis at substantially lower levels using gradient separation and a flow cell that enables high-sensitivity detection of PTH-amino acids. These systems have high analysis stability because they are equipped with a high-performance detector and a solvent delivery pump that provides high pumping performance. With high retention time stability, operators can more confidently identify the correct amino acid.