Biomedical Engineering Reference
In-Depth Information
calculations. A confidence limit for each was 95% ( = 0.05). The t-values presented indicate
the respective probabilities that the amounts of the influent metal bound at each position
were the same for both the native and modified materials. The results indicated that
modification of the biomaterial did significantly decrease the binding capacities of the
D.
innoxia
for each metal at each position in the sequential exposure sequence.
The F-values listed in Table 3 indicated the respective probabilities that the variances of the
mean values between the native and modified biomaterials were statistically different. There
were two cases a clear (>95%) difference in the variances was indicated; 1) the conditions
when cadmium was the first metal exposed to the column and 2) when nickel was the third
metal introduced to the biosorbent material. In both cases, larger variances were observed
for cadmium binding to the chemically modified material, with a percent relative standard
deviation (%RSD) of 27.22% compared to 4.86% for the native material. The binding of
nickel showed similar behavior with a 25.97% RSD for its binding to the modified material
in comparison to an RSD of 4.50% for the native biosorbent. This suggested sites involved in
the binding of Cd
2+
initially exposed to the material and those pertaining to Ni
2+
binding as
the third exposure metal ion were the least homogeneously affected by the chemical
modification (i.e., esterification ) reaction.
Cd position 1 Cd position 2 Cd position 3
P T ≤ t (two tail) 1.01E-04 3.72E-05 3.18E-07
P F ≤ f (one tail) 0.024 0.258 0.261
Ni position 1 Ni position 2 Ni position 3
P T ≤ t (two tail) 1.58E-03 2.73E-03 2.86E-03
P F ≤ f (one tail) 0.119 0.419 0.006
Zn position 1 Zn position 2 Zn position 3
P T ≤ t (two tail) 3.14E-07 1.66E-06 8.53E-07
P F ≤ f (one tail) 0.390 0.484 0.492
Table 3. Comparing influent metal bound at each position for the native and modified
biomaterials. The P T ≤ t value indicated the statistical probability that the mean values for
the native and modified
D. innoxia
are the same. The P F ≤ f value indicated the probability
that the variances of the two means are the same.
One question that arose with regard to the sequential exposure of the sorbent to chemically
similar metal ions is whether there is a statistically significant difference in the binding
capacities as a function of the position of the metal in the exposure sequence (i.e., first,
second, or third). This is related to the possible presence of cooperativity in the formation
(or elimination) of binding sites for one metal because of the earlier binding of another metal
ion to a (presumably) nearby site.
Table 4 summarizes a comparison of influent metal binding capacities within each of the
studies based on metal position in the sequence using a Student t-test at 95% confidence.
The t-values listed suggest there is no statistical difference in the amount of influent metal
bound for either the native or modified biomaterials based on the position of each metal in
the exposure sequence. Conversely, the F-values suggested statistical differences in the
