Calibration of NO sensors for in-vivo voltammetry: laboratory synthesis of NO and the use of UV-visible spectroscopy for determining stock concentrations.
The increasing scientific interest in nitric oxide (NO) necessitates the development of novel and simple methods of synthesising NO on a laboratory scale. In this study we have refined and developed a method of NO synthesis, using the neutral Griess reagent, which is inexpensive, simple to perform, and provides a reliable method of generating NO gas for in-vivo sensor calibration. The concentration of the generated NO stock solution was determined using UV-visible spectroscopy to be 0.28+/-0.01 mmol L(-1). The level of NO(2) (-) contaminant, also determined using spectroscopy, was found to be 0.67+/-0.21 mmol L(-1). However, this is not sufficient to cause any considerable increase in oxidation current when the NO stock solution is used for electrochemical sensor calibration over physiologically relevant concentrations; the NO sensitivity of bare Pt-disk electrodes operating at +900 mV (vs. SCE) was 1.08 nA micromol(-1) L, while that for NO(2) (-) was 5.9 x 10(-3) nA micromol(-1) L. The stability of the NO stock solution was also monitored for up to 2 h after synthesis and 30 min was found to be the time limit within which calibrations should be performed.
Brown
Finbar O
FO
Sensors Development Unit, Bioelectroanalysis Laboratory, Department of Chemistry, National University of Ireland, Maynooth, Co, Kildare, Ireland.
Finnerty
Niall J
NJ
Bolger
Fiachra B
FB
Millar
Julian
J
Lowry
John P
JP
D002138:Calibration; D004563:Electrochemistry / Q000295:instrumentation*; D009569:Nitric Oxide / Q000032:analysis* / Q000138:chemical synthesis; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*
D009569:Nitric Oxide