Abstract: A thermal electron source suitable for use in an electron capture detector comprises a source of stable ultra-violet light, an ultra-violet transparent support member (20,31) located in the path of the ultra-violet light (41) and a thin photo-emissive metallic layer (1A, 24, 33) coated over the surface of the support member remote from the source. In one form the source is a cylindrical mercury vapor lamp (1) with the photo-emissive layer coated directly on the lamp. The coated lamp may then be enclosed within a cylindrical anode (8) with a gas flow between them and the electrical current is measured between the anode and cathode. In an alternative arrangement a planar geometrical assembly is provided. Preferably the photo-emissive material is gold and the carrier gas is an argon-methane mixture.

Abstract: A material is traced to its origin or the flow pattern of a fluid medium is defined by incorporating into the material or fluid medium a perfluorinated C.sub.9 -C.sub.18 polycyclic hydrocarbon containing at least two bridgehead carbon atoms linked through a bridge containing at least one carbon atom, collecting a sample of the material or fluid medium after distribution or flow, and analyzing the sample for the presence of the perfluoro compound.

Abstract: Microencapsulated spheroids containing a coded, volatile electron absorbing substance are dispersed into a material to be regulated such as crude oil in a tanker. Samples of the material such as an oil spill are collected and the source of the material is determined by electron capture gas chromatographic detection of the electron absorbing substance.