Development of colorimetric ozone detection papers with high ultraviolet resistance using ultraviolet absorbers.

Two types of colorimetric ozone detection paper with high resistance to ultraviolet (UV) light have been developed for outdoor ozone detection. These detection papers incorporate indigo carmine and UV absorbers (UVAs). When exposed to ozone, the papers change color from blue to white, and the ozone concentration can be determined by measuring the reflectance of the papers. However, indigo carmine is strongly affected by UV light, thus making the papers unsuitable for outdoor ozone detection. The authors succeeded in sufficiently improving the resistance of the papers to UV light for them to be used outdoors. This was achieved by using hydrophilic UVAs, namely sodium 2-hydroxy-4-methoxybenzophenone-5-sulfonate and ferulic acid. Without a UVA, the maximum measurement error of the papers derived from UV effect is approximately 290 parts per billion (ppb) x hr when one assumes 8 hr of UV exposure at low- to mid-latitudes (approximately 60 Wh/m2), and this error is too great for accurate ozone measurement. In contrast, the measurement errors of the papers with UVAs are only approximately 60-70 ppb x hr under the same conditions. Ozone measurement accuracies of these detection papers with UVAs are +/- 4.3-4.5% (coefficient of variation [CV]) at 25 degrees C and 60% relative humidity without UV effect. As a result, the improved ozone detection paper with high resistance to UV rays is suitable for outdoor ozone measurements (e.g., for detecting photochemical oxidants).