The disclosure relates to a device for removing and analyzing a sample from a polymerization reactor including one or more sample conduits for removing a sample from the reactor and transferring the sample to a sample flash tank, whereby the conduits are in communication with the reactor and are provided with at least two sampling valves; a sample flash tank for separating said solid particles and evaporated gas, whereby the sample flash tanks are connected to the conduits and provided with a device for analyzing evaporated gas, and including a sample receiver for purifying the solid particles. The receivers are connected to the sample flash tanks and provided with an apparatus for analyzing the solid particles. The disclosure includes a method for improving a polymerization reaction.