Sample handling in nanoscale chemistry

Sammanfattning: Miniaturization is a strong on-going trend within analyticalchemistry. This has led to an increased demand for newtechnologies allowing smaller volumes of samples as well asreagents to be utilized. This thesis deals with the use of openchip-based reactors (vials); a concept that offers an increasedflexibility compared to the use of closed reactors. The vialsare manufactured by anisotropic etching of silicon.First, a short introduction is given on the benefits ofperforming chemistry in miniaturized formats. Different typesof reactors useful for performing chemistry in nanoscale aredescribed and the advantages and disadvantages of using aclosed contra anopen system are discussed.Precise dosing of nanoliter-sized volumes of liquids incontact mode is performed by using miniaturized pipette tips orcapillaries(Paper I, III&IV). Also, non-contact dosing usingpiezo-electric dispensers is demonstrated by performingnanoliter sized acid-base titrations(Paper II). Standard deviations on the order of 1% wereobtained.Several strategies for handling the evaporation of water,while performing tryptic digests of native myoglobin in lownanoliter sized vials, are demonstrated. An increasedconversion rate of the protein to peptides was observed when ananovial (15 nL) reactor was used compared to the use of aconventional plastic vial (100 µL). Principles based onreducing the driving force for evaporation(Paper III), continuous compensation of evaporatedmaterial(Paper IV)as well as covering the reaction liquid witha volatile liquid lid of solvent(Paper V)are used. The volatile liquid lid is also usedwhen performing PCR in volumes as low as 50 nL(Paper VI).Short descriptions of the analytical methods utilized in thethesis; capillary electrophoresis(Paper III, IV, V&VI), matrix assisted laserdesorption/ionization time of flight mass spectrometry(Paper I)and fluorescence measurements(Paper II&VI)are presented.Finally, an outlook of the developed technologies is giventogether with a discussion concerning possible futurerequirements in miniaturized chemistry.Keywords: capillary electrophoresis, continuouscompensation, enzymatic degradation, evaporation,lab-on-a-chip, liquid lid, MALDI, miniaturization, myoglobin,nanoliter, nanoscale chemistry, parallel, picoliter,piezo?dispenser, polymerase chain reaction, reactor, titration,tryptic digest, vial© Erik Litborn, 2000