An apparatus for extracting an analyte from a liquid sample, the apparatus comprising: a) an upper first microcolumn and a lower second microcolumn in series, allowing flowing of the sample from the first microcolumn into the second microcolumn, each microcolumn (112;212) having an entrance, an exit, and a passage therebetween for passage of a liquid sample containing an analyte therethrough, whereby the first microcolumn defines a first passage and the second microcolumn defines a second passage, each microcolumn (112;212) further having a full diameter bed region (130;230) nearest the entrance, a reduced diameter bed region (131;231) between the full diameter bed region (130;230) and the exit, and a tip region nearest the exit, a first shelf defined by a step in diameter between the full diameter bed region (130;230) and the reduced diameter bed region (131;231), and a second shelf defined by a step in diameter between the reduced diameter bed region (131;231) and the tip region; b) a first layered construction having a top and a bottom extending across the first passage of the first microcolumn and being positioned atop its first shelf, comprising from top to bottom: (i) an upper mesh flow distributor and (ii) an upper compression layer, the first layered construction located in the full diameter bed region of the first microcolumn; and c) a second layered construction having a top and a bottom extending across the second passage of the second microcolumn and being positioned atop its second shelf, comprising from top to bottom: (iii) an extraction layer of microparticulate extraction medium and (iv) a lower compression layer, the second layered construction located in the reduced diameter bed region of the second microcolumn. a) an upper first microcolumn and a lower second microcolumn in series, allowing flowing of the sample from the first microcolumn into the second microcolumn, each microcolumn (112;212) having an entrance, an exit, and a passage therebetween for passage of a liquid sample containing an analyte therethrough, whereby the first microcolumn defines a first passage and the second microcolumn defines a second passage, each microcolumn (112;212) further having a full diameter bed region (130;230) nearest the entrance, a reduced diameter bed region (131;231) between the full diameter bed region (130;230) and the exit, and a tip region nearest the exit, a first shelf defined by a step in diameter between the full diameter bed region (130;230) and the reduced diameter bed region (131;231), and a second shelf defined by a step in diameter between the reduced diameter bed region (131;231) and the tip region; b) a first layered construction having a top and a bottom extending across the first passage of the first microcolumn and being positioned atop its first shelf, comprising from top to bottom: (i) an upper mesh flow distributor and (ii) an upper compression layer, the first layered construction located in the full diameter bed region of the first microcolumn; and c) a second layered construction having a top and a bottom extending across the second passage of the second microcolumn and being positioned atop its second shelf, comprising from top to bottom: (iii) an extraction layer of microparticulate extraction medium and (iv) a lower compression layer, the second layered construction located in the reduced diameter bed region of the second microcolumn.