AN INVESTIGATION INTO THE CAUSE OF MEMORY EFFECTS ASSOCIATED WITH THE CONVERSION OF H2O TO H-2 FOR D/H MEASUREMENT

The D/H ratio of hydrogen in natural substances is usually measured via the intermediate of water which is reduced back to hydrogen for isotopic measurement in a mass spectrometer. Unfortunately, inlet systems used to manipulate water have memory effects which reduce the accuracy of the D/H measurement and imposes constraints upon the minimum sample size which can be considered for an isotope analysis. An inlet system was constructed for the purpose of identifying the cause of the memory and to establish the magnitude of this effect. A number of experiments demonstrated that the major source of memory was adsorption of water onto surfaces in the mainly glass components of the system. A method of determining magnitude of the memory effect present in an inlet system is described, enabling a memory effect correction to be applied. Possible methods of completely eliminating memory effects are discussed.