. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography ANALYTICAL METHODS IN OCEANOGRAPHY When introduced in chloride salt solution in distilled water, the response to changes in ashing temperature is, in each instance, relatively simple. The analytical sensitivity falls off at temperatures above 500 °C, as increasing amounts of metal are lost from the atomizer during the ashing cycle. When the salts are introduced in natural seawater, observed sensi- tivity changes are more complex. As with distilled w
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography ANALYTICAL METHODS IN OCEANOGRAPHY When introduced in chloride salt solution in distilled water, the response to changes in ashing temperature is, in each instance, relatively simple. The analytical sensitivity falls off at temperatures above 500 °C, as increasing amounts of metal are lost from the atomizer during the ashing cycle. When the salts are introduced in natural seawater, observed sensi- tivity changes are more complex. As with distilled water, sensitivity drops above a critical temperature, which is different for each element, because of loss of the element from the atomizer during ashing. How- ever, below this temperature, the sensitivity drops instead of leveling off as with simple solutions. The cause of this sensitivity loss is unknown, although it must be caused by either lowered instrument response arising from large nonspecific absorption and considerably decreased light level reaching the photomultiplier or, more likely, chemical interference by the major seawater salts. Such chemical interference might be caused by suppression of dissociation of molecular species of the analyte element in the molecule and atom cloud by the presence of large quantities of more easily dissociable salts. This would be analogous to the suppression of ionization, achieved for many elements in flames or arcs by the addition of large quantities of easily ionizable elements. Sodium chloride at a concentration of g/1. has a larger suppression effect than seawater with a total salt content of g/1. The effect is thus not simply deter- mined by the total quantity of elements in the sample but is also de- pendent upon the composition of the matrix. The complexity of the 500 1000 1500 ASHING TEMPERATURE CO Figure 9. Effect of ashing temperature on the absorbance of injections of 20-ppb spike of manganes
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