. 2014 Sep 5;172(6):1620–1632. doi: 10.1111/bph.12832

Table 1.

Specificity and major advantages and disadvantages of techniques of NO assessment with a brief summary

Technique	Sensitivity	Advantages	Disadvantages
EPR	0.05–0.4 nM^a	Direct, considered as a ‘stand alone’ assay; the most specific method, due to NO-specific spin traps	Semiquantitative; expensive, not particularly common instrumentation; complex evaluation requires significant expertise
NO spin trapping followed by spectrometry in magnetic field	0.05–0.4 nM^a
Electrochemistry	0.3–10 nM^b	Direct; continuous; real-time, portable; no chemical contamination of the sample	Difficult to calibrate; influenced by temperature and ambient electrical noise; uncertain specificity (NO-specific membrane or layer); sensitive to electrode tip position
amperometry or voltammetry using NO-specific electrode	0.3–10 nM^b
Fluorometry	0.6–8 nM^c	Direct; sensitive (detection limit in nM range); can be two- or three-dimensional	Uncertain specificity (NO-specific fluorescent dyes); semiquantitative
spectrometry or imaging of fluorophore-labelled NO	0.6–8 nM^c
Griess assay	500 nM^d	Cheap, fast; commercially available ready-to-use kits	Indirect, indicative of NO oxidative products; only measures nitrite (nitrate should be reduced); interferes with dietary and environmental nitrite and nitrate
diazotization assay measures nitrite by photometry	500 nM^d	Cheap, fast; commercially available ready-to-use kits
NOS activity	n.a.	Measures enzymatic production of NO; sensitive; specific	Indirect; non-enzymatic NO formation is not considered; measures active NOS protein under optimized in vitro conditions, does not reflect in situ NO synthesis
biochemical enzyme activity assay	n.a.	Measures enzymatic production of NO; sensitive; specific
RSNO	n.a.	Important NO target besides cGMP; represents downstream NO signalling	Indirect; represents downstream NO signalling; does not reflect actual NO levels
detection of nitrosated proteins/peptides	n.a.
cGMP assays	n.a.	Most known cellular target of NO is sGC resulting in cGMP formation; represents downstream NO signalling	Indirect, assesses effect of NO on sGC; represents downstream NO signalling; does not consider NO-independent cGMP formation
measurement of cGMP level	n.a.
NO donors and NOS inhibitors	n.a.	Use of them completes other assays; helps to understand the role of NO	Alone does not reflect NO production

Mülsch et al., 1992; Khoo et al., 2004; Nedeianu et al., 2004.

Griveau et al., 2013.

Zhang et al., 2014.

Sun et al., 2003. n.a., not applicable.