A　technique　known　as　field　enhancement　sample　stacking　(FESS)　and　capillary　electrophoresis　(CE)　separation　has　been　developed　to　analyze　and　detect　organic　acids　in　the　three　traditional　Chinese　medicines　(such　as　Portulaca　oleracea　L,　Crataegus　pinnatifida　and　Aloe　vera　L).　In　FESS,　a　reverse　electrode　polarity-stacking　mode　(REPSM)　was　applied　as　on-line　preconcentration　strategy.　Under　the　optimized　condition,　the　baseline　separation　of　eight　organic　acids　(linolenic　acid,　lauric　acid,　p-coumaric　acid,　ascorbic　acid,　benzoic　acid,　caffeic　acid,　succinic　acid　and　fumaric　acid)　could　be　achieved　within　20　min.　Validation　parameters　of　this　method　(such　as　detection　limits,　linearity　and　precision)　were　also　evaluated.　The　detection　limits　ranged　from　0.4　to　60　ng/mL.　The　results　indicated　that　the　proposed　method　was　effective　for　the　separation　of　mixtures　of　organic　acids.　Satisfactory　recoveries　were　also　obtained　in　the　analysis　of　these　organic　acids　in　the　above　traditional　Chinese　medicine　samples.　(C)　2012　Elsevier　B.V.　All　rights　reserved.