Diffuse reflectance FTIR (DRIFT) analyses of Solid Phase Organic Chemistry (SPOC) resins using a DRIFT cup with a reduced sample volume, the DRIFT microcup, are presented. The use of this microcup only requires <1 mg of resin. The spectra are comparable with DRIFT spectra acquired using a conventional DRIFT accessory, but the amount of sample consumed in analysis is appreciably less. The use of a DRIFT accessory with a smaller sample compartment strongly redu-Combinatorial Chemistry (CC) is currently receiving much attention as an approach to drug discovery [1] [2] . Solid phase organic chemistry (SPOC) is often used as a tool for CC in order to generate libraries of organic compounds. During the initial stages, before constructing a library, the conditions for the reaction on the resin beads have to be optimised. Since relatively little knowledge has been obtained on organic reactions on solid supports besides peptide and nucleic acid synthesis, this is one of the bottlenecks in constructing libraries of organic compounds [3] . The optimisation is usually done by performing a sequence of reactions on a single compound tethered to the resin. However, when working with SPOC, the organic chemist cannot use his favourite analytical tools, solution state NMR and TLC to monitor the optimisation of the reactions. IR spectroscopy using KBr pellet spectra has widely been used as an analytical tool for SPOC [4] [5] [6] [7] [8] . The KBr pellet method suffers from the drawback that the water present in the KBr obscures the 3400Οͺ3000 cm Οͺ1 region of the spectrum. Since this is one of the few available windows unperturbed by the peaks of the resins, the KBr pellet method is not particularly suitable in this case. Moreover, the KBr pellet method consumes multimilligram quantities of resin beads. Recently it was reported that IR microscopy [9] [10] [11] [12] [13] can efficiently be used, consuming only a single bead in analysis. . However, IR microscopes are not widely available, expensive and their operation is not trivial. DRIFT is a more widely accessible and economical IR technique. A drawback of this technique is that it requires more material for analysis. We demonstrate the use of a DRIFT cup with a reduced sample volume, the DRIFT microcup, as an alternative