This review deals with the measurement of nitric oxide (NO) using the chemiluminescence assay. A preliminary discussion is offered to explain the chemical basis for this assay and emphasize the importance of measuring NO. After reviewing some practical aspects and caveats of the chemiluminescence assay, we review its application in a variety of research and clinical settings, such as measurement of breath NO and serum nitrates. The importance of avoiding confounding effects of dietary nitrates when assessing the NO system in humans is discussed and new data are provided on the confounding effects of atmospheric NO on measurement of breath NO. The utility and ease of the chemiluminescence assay for these applications is contrasted with the challenge of using chemiluminescence for correlation of vascular tone and NO production, studies in which real-time measurements are required. Although the chemiluminescence assay is one of the most reliable, rapid and reproducible assays available, it is optimal for gas phase measurements and may be suboptimal for measurement under certain circumstances. This chapter complements several more general reviews of the methodology for measuring NO.Article available at http://analusis.edpsciences.org or http://dx.doi.org/10.1051/analusis:2000280455 Need for measuring NOIt is clear that NO is essential in a significant number of normal physiological processes. However, the scope of its importance also spans pathophysiology of disease, such as in cardiogenic shock [14,15]. Inhaled NO is used for diagnostic purposes, and has therapeutic value, in diseases such as pulmonary hypertension [16][17][18], asthma and chronic obstructive lung diseases [12,[19][20][21]. NO may even promote regression of diseases, such as atherosclerosis [22,23].In view of the broad biological importance of this molecule, it is not surprising that basic and clinical research pertaining to NO has been so prolific. However, a computerised search of the past five years' literature found NO measurements reported in only 1089 of 26123 articles dealing with NO. Since many scientists don't measure NO, perhaps we should make the case for measurement explicit.There are four major reasons why one should consider measuring NO: Non specificity of NO inhibitorsPharmacological experiments are useful in studying NO and its effects. Nevertheless, the non-specificity of NO inhibitors [24][25][26] impairs one's ability to draw sound mechanistic conclusions. For instance, N G -monomethyl-L-arginine (L-NMMA), a NOS antagonist, displays hemodynamic effects that are not solely mediated by its ability to inhibit NO synthesis [27]. L-NMMA can also be metabolized to yield NO. Furthermore, even high doses of NOS inhibitors do not completely prevent NO synthesis [28]. Without measuring NO one cannot be assured that the observed effects resulting from administration of a NOS inhibitor reflect the complete loss of NO, nor can one exclude non-specific effects of these inhibitors. The existence of multiple endothelium-derived vasodilatorsIt i...

Main text Hazardous air pollutants (HAPs) are toxic air pollutants that are mainly emitted from man-made sources such as chemical processes, automobiles, power plants, and refineries, building materials, and cleaning solvents. Some HAPs are emitted from wildfires and chemical leak. HAPs are regulated and monitored to protect public health and the environment because they cause severe health effects such as cancer, damages to the immune system, reproductive and respiratory health problems. For this supplementary comparison, a multicomponent mixture of HAPs in nitrogen has been chosen at an amount-of-substance fraction level of 100 nmol mol-1 that is closer to their emission levels from their sources. The supplementary comparison is designed to underpin calibration capabilities using HAPs gas mixtures that are prepared gravimetrically as transfer standards. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).