Derivatives　of　N-acylhomoserine　lactones　(HSLs)　with　different　alkanoyl　side　chains　occur　as　quorum　or　diffusion　sensing　molecules　in　Gram-negative　bacteria　and　their　quantitative　chemical　analysis　became　important　as　a　possible　way　to　follow　regulation　processes　of　their　pathogenicity　towards　plants　and　animals.　The　lactone-ring　of　HSLs　is　chemically　and　biologically　not　stable:　the　corresponding　serines　can　be　formed　in　alkaline　conditions　and　these　may　presumably　behave　inactive　for　the　biological　system.　A　fast　and　MS　compatible　liquid　chromatographic　method　applying　high　pressure　(ultra　performance　liquid　chromatography)　with　diode　array　detection　was　optimized　for　the　rapid　quantitative　determination　of　HSLs　and　their　corresponding　hydrolysis　products.　The　technique　was　used　to　follow　and　model　the　hydrolysis　reactions　of　HSLs　as　function　of　pH　under　controlled　conditions.　Moreover,　the　method　could　be　triggered　to　allow　a　confirmation　in　the　assignment　of　the　potential　HSLs　in　real　samples　by　analysis　of　the　real　samples　before　and　after　hydrolysis.　Quantitative　performance　characteristics　and　the　character　of　the　hydrolysis　reaction　were　studied　as　well.　The　optimized　method　was　successfully　applied　to　a　bacterial　culture　supernatant　real　sample　containing　HSLs.　(c)　2007　Elsevier　B.V　All　rights　reserved.