The invention relates to a method for producing \u03b1,\u03b2-unsaturated aldehydes, wherein a catalytic aldol condensation of charged aldehydes is carried out in the presence of an aqueous base within a continuous-flow reactor. The responses are grouped into sets of responses corresponding to at least two object movement states. The guide layer is doped in a manner such that the first and second interfaces are capable of supporting the plasmon modes, respectively, and is of a thickness such as to bring about the accumulation of the plasmon modes in proximity to the first and second interfaces, outside the layer, and substantially a suppression of the plasmon modes, inside the layer. The dust chute includes mounts that allow lateral adjustment of the dust chute with respect to the bevel support. The captured analyte is then eluted from the extraction chamber by forcing an elution fluid to flow through the extraction chamber and along the second flow path.