Colorimetric solid phase with spatially separated extraction and detection,zones as a rapid, effective and economic method for the optical detection of cyanide in complex samples is described. The system is seven times more sensitive for the optical detection of cyanide than the same class of chemical sensors used under homogeneous conditions. The application of the method in the detection of (i) endogenous cyanide in colored plant samples. and of (ii) hydrogen cyanide in tobacco smoke is shown. The optical detection of multiple anions within a single sample has been demonstrated in principle for the detection of both CN- and SCN-. Immobilized aquacyano-corrinoids and immobilized vitamin B12 are applied as chemical sensors, and cyanide is qualitatively identified by the violet color (lambda(max) = 583 nm) of the corresponding dicyano-complex. Quantitative determinations with diffuse reflectance spectroscopy (DRUV-vis) are possible in the linear range up to 0.2 mg/L with a LOD of 1 mu g/L. Alkyl-modified silica particles are employed for immobilization of the indicator on the surface of the solid phase (detection zone), and for removal of colored hydrophobic interferents, (extraction zone).