Sunlight caused interference in outdoor N, N-diethyl-p-phenylenediamine colorimetric measurement for residual chlorine and the solution for on-site work.

Chlorination is the most common method to control water qualities, in some case on-site outdoor measurements are required to measure easily-decaying residual chlorine concentration appropriately without delay. In this study sunlight-induced unexpected colour development (UCD) of N, N-diethyl-p-phenylenediamine (DPD) colorimetric measurement was studied under several sun exposure conditions. The colour development level was evaluated with reference to chlorine concentration (mg/L) and relationships between colour development rate (mg/L min) and intensities of solar were investigated. UCD was found to be related to both exposure intensity and time. By means of exposure experiment under specific wavelength of ultraviolet (UV), it was confirmed that both middle and short wavelength of UV radiation being responsible for such an unexpected measurement. Consequently, a simple device was designed using three commercially available anti-UV films, one of which could effectively prevent the UCD from direct sun exposure.

Cypris larvae (Cirripedia: Balanomorpha) display auto-fluorescence in nearly species-specific patterns.

The identification of balanomorph larvae plays an important role in ecological study and for protection against biofouling. However, it is difficult to identify species of cyprids (settling larvae) of balanomorph barnacles, as they show remarkably similar morphology. Some authors have suggested distinguishing cyprids of different species by carapace length, pigmentation, and fine carapace detail. However, such criteria are only applicable to a narrow range of balanomorph species. Recently, we were have serendipitously found species-specific distribution of fluorescent substances in cultured cyprids obtained from adult balanomorph barnacles, collected near the coast of Japan. Fluorescent patterns (FPs) of cyprids from 11 species were classified into five major groups. Cyprids specimens collected from the field were estimated, based on the FPs and other morphological characteristics (pigmentation and carapace length), after which their species were identified using the following two criteria: the morphology of adults derived from the field cyprids that adhered to a culture dish, and cyprid 12S rRNA gene sequence. The results of species estimation by FPs largely corresponded to the correct species identification. Other FP groups were found in the field cyprids. This study of FPs should be helpful for identification of cyprid species.