14 



12 



^ 10 



U 8 



a. 



% 



<jy 4 

 U 



Log Cs^"^^ Concentration - 



1.15 Log Salinity - 1.22 



^^ Expected 

 O Measured 



6 8 10 



SALINITY ( P.P.T.) 



16 



Figure 6. --Hypothetical relation between concentration of cesium 137 from fallout and salinity in the 



Trent-Neuse estuary. 



change in average depth of the water. Cesium 

 137 occurs at concentrations of only 14 to 23 

 ^//c./lOO 1. of surface sea waters in the North 

 Atlantic. Extension of figure 6 in a seaward 

 direction would therefore require a dramatic 

 reversal of the upward trend with a dilution to 

 much lower concentrations. 



INTERFERENCE BY HIGH 



CONCENTRATIONS OF 



CALCIUM IN TRACE 



ANALYSIS BY 



ATOMIC ABSORPTION 



SPECTROPHOTOMETRY 



Douglas A. Wolfe and Twyla A. Miner 



Trace analysis of biological materials by 

 atomic absorption is remarkably free of inter- 

 ferences, and analyses of many elements at 

 concentrations in the parts-per-million range 

 can be made by direct comparison of ab- 



sorbancies of sample solutions with those of 

 standard solutions of the elements. The inter- 

 ferences occasionally encountered in atomic 

 absorption usually result from spectral over- 

 lapping, ionization in the flame, or formation 

 of chemical compounds. In the analysis of very 

 concentrated solutions, variable efficiency of 

 atomization and light scattering by solid parti- 

 cles in the flame may also interfere. Calcium 

 is known to interfere with the analysis of sev- 

 eral elements. We noted this interference 

 during analyses of oyster shells, which contain 

 about 98 percent calcium carbonate and for 

 which instrumental response was not linear 

 with concentration of the samples. To adapt 

 the use of atomic absorption to the analysis of 

 molluscan shells, we investigated the effects of 

 high calcium concentrations on atomic absorp- 

 tion by copper, manganese, and zinc. 



Analyses were made on an atomic absorption 

 spectrophotometer equipped with a "high 

 solids" burner head (absorption path 10 cm.). 

 Absorption in the premix air-acetylene flame 

 was measured at 3,247 A (copper), 2,794.8 A 



17 



