Membrane sampler for interference-free flow injection NO determination in biological fluids with chemiluminescence detection Original Research Article

The development of a chemiluminescence (CL) method based on the perm-selective properties of a Nafion–cellulose acetate (CA) composite membrane for the monitoring of nitric oxide (NO) in biological fluids is described. Horseradish peroxidase (HRP) was used as NO trapping solution, forming the stable compound HRP–NO. The HRP was denatured and the trapped NO was released and detected by using the luminol–H2O2 system. Using a mixed (size-exclusion and polar-based) transport control, the interference effects of various compounds were minimized. The method was used for NO monitoring in simulated samples, by using a blood specimen as sample matrix. The 3σ detection limit is 0.9×10−6 mol and linear semi-log calibration plot in the range 1.8×10−6 to 2.7×10−3 mol NO was constructed. The applied methodology was further used to prolong the NO lifetime in order to increase the sensitivity of its determination. This was based on the increase of the response in the presence of certain reductive species, which act as NO preservatives in biological fluid samples.