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

Abstract 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-H 2 O 2 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

A study of Bi2O3-Modified screen-printed sensors for determination of Cd(II) and Pb(II) by anodic stripping voltammetry

In this article, a study of Bi2O3-modified screen-printed electrodes is given presenting the determination of Cd(II) and Pb(II) by anodic stripping voltammetry (ASV). Initially, the electrode was subjected to cathodic polarisation to reduce the Bi2O3 to metallic bismuth. Then, the target metal cations were electrolytically preconcentrated on the electrode by alloying with bismuth. Following the deposition step, an anodic voltammetric scan was applied in which the metals were oxidised and stripped back into the solution; the voltammogram recorded and the stripping peak heights being related to Pb(II) and Cd(II) concentrations in the sample. Different key parameters were investigated in detail such as the medium used for the Bi2O3 reduction, the Bi2O3 content in the carbon ink, the polarisation range of the sensors, the supporting electrolyte, the stripping waveform, the deposition time, the deposition potential and the long-term stability of the sensors. Under the optimum conditions, the limit of detection was 1.1 g l 1 for Pb( ) and 2.1 g l 1 for Cd( ). The reproducibility of measurements on the same chip (expressed as the RSD [%], for n = 8) was 7.7 % for Pb(II) and 8.4 % for Cd(II) at the 20 g l 1 level