a single - or multi - well sample preparation apparatus and method for desalting , concentrating and depositing samples prior to further analysis such as by maldi tof mass spectrometry . the apparatus in accordance with an embodiment of the present invention includes a plurality of wells each in fluid communication with a respective outlet or drainage opening , optionally containing a three dimensional membrane structure preferably comprising a plurality of sorptive particles entrapped in a porous polymer matrix so as to form a device capable of carrying out solid phase extraction . the apparatus is designed to allow for direct spotting onto a maldi target , thereby eliminating a transfer step . also disclosed is a method of sample preparation , deposition and analysis using the apparatus of the present invention .