Protocol

Volatile Sampling from Biological Sources by the Closed-Loop-Stripping Technique

Max Planck Institute for Chemical Ecology, Department of Bioorganic Chemistry, D-07745 Jena, Germany

¹Corresponding author (boland{at}ice.mpg.de)

INTRODUCTION

The closed-loop-stripping technique with absorber traps (e.g., charcoal, porous polymers) can be used to collect volatiles from different biological sources, for example, plants and insects. One notable advantage of the method is the high signal-to-noise ratio that can be achieved by continuous sampling of the volatiles from a producing source within a closed environment. The equipment required for the technique is inexpensive and can be easily adapted to the demands of the analyzed subject. Moreover, the system can be operated in the field since only air and a battery are needed. The volatiles can be recovered from the trap by thermodesorption or by elution with solvents. Solvent elution has the advantage that unknown compounds can be subjected to chemical transformations facilitating structure elucidation. Only very low amounts of solvents (20-40 µL) are needed to elute the microcarbon traps (1.5-5 mg). Single traps efficiently absorb volatiles up to the lower microgram range. Higher concentrations may result in insufficient trapping. In this protocol, we describe the collection of volatiles released from lima bean leaves (Phaseolus lunatus) after damage by feeding larvae of Spodoptera littoralis. The enclosed volume of air containing the emitted volatiles is circulated through miniature charcoal traps for 4 h or more. For analysis, the traps are eluted with dichloromethane.