Precise Measurements of Cesium in the Ocean by Flame Emission Spectrometry

Abstract

An automatic flame emission spectrometer has been developed for measuring traces of cesium in sea water samples with precision enough to demonstrate for the first time some significant concentration variations of this element in the ocean. Extremely reproducible comparisons of standard and unknown solutions are effected by a programmed sample changer employing a novel distribution valve. Temperature effects and influences of gas flow and draft fluctuation are suppressed by carrying out repeated comparisons of small portions of the extracted sample concentrate and of the standard, computing a concentration after each comparison and then averaging the results. Following each recording of the peak emission, the emission from a nearby spectral baseline also is automatically recorded by using a simple accessory added to the monochromator. A Plexiglas refractor slab mounted on an axis in front of the exit slit is rotated a few degrees by pulses from a programmer that is under command of a standard desktop calculator. Analyses of test samples containing about 0.3 µg of cesium replicated better than 0.3%. Surface cesium concentrations in the North Pacific were shown to vary less than 0.5%; however, typically deep water contained about 1.4% lower average concentrations than surface water.