A detection method of gold nanoparticles in chromatography paper has been developed for a simple, cost-effective and reliable quantitation of immunochromatographic strip test. The time courses of the solution resistance in chromatography paper with the gold nanoparticles solution are electrochemically measured by chrono-impedimetry. The dependence of the solution resistance on the concentration of gold nanoparticles has been successfully observed. The main factor to increase the solution resistance may be obstruction of the ion transport due to the presence of gold nanoparticles. The existence of gold nanoparticles with 1.92 × 10 9 particles/mL in an indistinctly-colored chromatography paper is also identified by a solution resistance measurement. This indicates that the solution resistance assay has the potential to lower the detection limit of the conventional qualitative assay.Keywords Immunochromatography, chromatography paper, gold nanoparticles, solution resistance

Electrochemical characterizations of chromatography paper-based electrochemical sensors are presented by means of chronoamperometory (CA), cyclicvoltammetry (CV), and impedance (IMP) measurement. Samples with co-planar electrodes with dropped solution, height-limited solution, and solution within a sheet of chromatography paper, were tested. It was found that the height limitation, reduction of diffusion coefficient, and thin solution layer between paper and chip substrate can impact the shapes of CA and CV, which was confirmed by computer simulations. It was also found that solution resistance due to ion conduction in paper sensor will be reduced because of ion conductivity reduction.