title: A novel approach to the measurement of surfactant parameters in arthropod digestive juices.
abstract: In arthropods, the determination of two important parameters of digestive juices, i.e. the total surfactant concentration and the critical micelle concentration (CMC), is challenging due to small sample volumes and low surfactant concentrations. In this work, we report a successful implementation of potentiometric titrations using the surfactant ion-selective electrode (SISE) and the pyrene fluorescence method (PFM) for the determination of the total surfactant concentration and CMC in the digestive juice of terrestrial isopod crustaceans Porcellio scaber. Pooled digestive juice extracts of four (SISE) or two (PFM) animals were used per measurement run. In both cases, digestive juice extracts in 100 μL of deionized water were sufficient for one measurement run. The total surfactant concentration of P. scaber digestive juice was determined to be 9.2 ± 3.5mM and the CMC was approximately 90 μM. Our work presents an important improvement towards easy CMC determination in small volume samples in comparison with the commonly used stalagmometric technique, where much larger sample volumes are usually needed. To date, the total surfactant concentration was not measured in the digestive juices of arthropods other than Homarus vulgaris, Astacus leptodactylus and Cancer pagurus, for which complex separation and analytical techniques were required. Our results obtained by SISE and PFM therefore present the first successful quantification of surfactants and their CMC in small volumes of arthropod digestive juice without prior separation or purification techniques.
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia. Electronic address: tea.romih@student.uni-lj.si.
authors.forename: Tea
authors.initials: T
authors.lastname: Romih
authors.affiliation: Department of Chemistry and Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Ksenija
authors.initials: K
authors.lastname: Kogej
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000 Ljubljana, Slovenia.
authors.forename: Damjana
authors.initials: D
authors.lastname: Drobne
mesh_terms: D000818:Animals; D004063:Digestion; D004064:Digestive System / Q000033:anatomy & histology / Q000737:chemistry; D005260:Female; D033321:Isopoda / Q000033:anatomy & histology / Q000737:chemistry* / Q000502:physiology; D008297:Male; D008823:Micelles; D017524:Slovenia; D013501:Surface-Active Agents / Q000032:analysis / Q000737:chemistry*
chemical_list: D008823:Micelles; D013501:Surface-Active Agents
keywords: Critical micelle concentration; Pyrene fluorescence; Surfactant; Surfactant ion-selective electrode; Terrestrial isopod