An　improved　sheath-flow　interface　used　to　couple　capillary　electrophoresis　(CE)　with　inductively　coupled　plasma　mass　spectrometry　(ICP-MS)　and　a　microwave-assisted　extraction　used　to　extract　each　arsenic　species　in　seafood　were　developed　in　this　work.　The　improved　sheath-flow　interface　completely　avoids　laminar　flow　in　CE　capillary　caused　by　the　suction　from　ICP-MS,　makes　electric　supply　more　stable　in　CE,　and　transports　analyte　solution　to　ICP-MS　easily　and　more　efficiently.　CE-ICP-MS　coupled　with　our　interface　have　two　quantitative　analysis　modes:　continuous　sample-introduction　mode　and　collective　sample-introduction　mode.　The　collective　sample-introduction　technique　greatly　reduced　the　dead　volume　of　interface　to　approximately　zero,　obviously　avoided　the　excessive　dilution　of　analyte.　and　eventually　led　to　a　much　lower　detection　limit　and　a　much　better　electrophoretic　resolution.　This　was　demonstrated　by　the　better　symmetry　and　narrow　peak　widths　(10-12s)　and　much　lower　detection　limits　(0.030-0.042　mu　g/L)　of　four　species　of　arsenic　determined　with　collective　sample-introduction　mode.　With　the　help　of　this　improved　sheath-flow　interface　and　the　microwave-assisted　extraction,　we　have　successfully　separated　and　determined　four　arsenic　species,　As(III),　As(V),　monomethylarsonic　acid　(MMA)　and　dimethylarsinic　acid　(DMA)　in　dried　Mya　arenaria　Linnaeus　and　Shrimp　samples　using　CE-ICP-MS　within　10　min　with　a　relative　standard　deviation　of　2-4%　(peak　areas,　n　=　6)　and　a　recovery　of　96-105%.　(c)　2008　Elsevier　B.V.　All　rights　reserved.