Table 1-2. Relative Standard Deviations 
Group A 
Metal 
Mean, ug/g Wet 
St. Dev. 
Rel. Std. Dev. 
Cd 
0.17 
0.01 
6 
Cr 
1.01 
0.05 
5 
Cu 
2.82 
0.07 
3 
Fe 
88.7 
4.5 
5 
Mg 
802 
58 
7 
Mn 
3.15 
0.10 
3 
Ni 
1.48 
0.06 
4 
Pb 
1.27 
0.04 
3 
V 
0.9 
(0.05) 
6 
Zn 
17.3 
0.5 
3 
Group B 
Al 
17.8 
2.5 
14 
Ca 
439 
61 
14 
Co 
0.19 
.04 
21 
Ti 
0.8 
0.3 
38 
In contrast are the group B metals which consist of Al, Ca, Co, and Ti. As 
shown in Table 1-2, these metals are characterized by a much higher relative 
standard deviation, from 14% to 38%. When plotted in a fashion similar to 
Figure 1-1, they show a much higher degree of scatter. Accordingly, the 
correlation coefficients show no real correlations at the 95% confidence level. 
Although this material has been prepared as a reference material, it is in no 
way equivalent to a standard reference material such as those developed by the 
National Bureau of Standards (NBS) (4). The NBS Standard Reference 
Materials are certified as to their trace element content on the basis of analysis 
by at least three independent techniques. Our material is an internal reference 
material, not a certified standard. 
This material is now in routine use within our laboratory. One sample, 
randomly chosen from the sequence, is included with each group of 15 
unknown samples prepared and analyzed. Thus, there is continuous verification 
of analytical results irrespective of operator, instrument settings, or standards. 
In addition, this material is ideal for methods development and intercalibration 
because of its extremely low variability. Individual organisms from a wild 
7 
