The performances of four reagents in the sampling and analysis of total isocyanate group in air were evaluated. The reactivities of the reagents 1-(2-methoxyphenyl)piperazine (MOPP), 9- (methylaminomethyl)anthracene (MAMA), tryptamine (TRYP), and 1-(9- anthracenylmethyl)piperazine (MAP) with phenylisocyanate (103719) were compared. Based on experimentation in which a pair of reagents competed for a limited amount of phenyl-isocyanate, reaction rate ratios were determined. MAP and MOPP had similar reactivities, with a mean reaction rate ratio of 1.14. MAP reacted four times faster than MAMA and over three times faster than TRYP. The TRYP derived ureas exhibited greater variability in ultraviolet absorptivities than those derived from MAP or MAMA. The intensity of maximum fluorescence for the MAP ureas was 73% greater than that of the MAMA ureas and 31 times greater than TRYP ureas. Greater variability in fluorescence was observed in the MAMA ureas than in the MAP ureas. In high performance liquid chromatography combined with ultraviolet (UV) and electrochemical (EC) analysis, the average UV response of the MAP ureas was almost five times greater than that of the MOPP ureas. The variability in the UV and EC responses of the MAP ureas was much less than that of the MOPP ureas. The authors conclude that MAP and its ureas perform as well or better than other total isocyanate group reagents, and suggest the further study of this promising reagent.