Results
The first part of the experiment had the purpose of becoming oriented with the procedure
and to make sure that the concentration of unknown solutions could accurately be identified. This

first set of five standard solutions and their measure potentials created the calibration curve with
the line of best fit of
y
=−
451.6
x
+
2497
and an acceptable correlation value of -0.9997
(Figure 4). This equation was used to relate the potential to the log(conc.) of nitrogen in the
samples, then that was converted into concentration of nitrogen in mg/L, and the average of these
values were 6.07 mg/L with a standard deviation of 0.179 mg/L for NA and 10.5 mg/L with a
standard deviation of 0 mg/L for NB (Table 1). The theoretical value of NA was 6.5 mg/L with a
standard deviation of 0.8 mg/L and the value for NB was 10.8 mg/L with a standard deviation of
0.9 mg/L.
Figure 4.
This is the calibration curve created from standard solutions with known
concentrations of nitrogen. It is a plot of potential in mV versus log(concentration of N in mg/L).
From this graph, the concentration of the validation samples of NA and NB were interpolated
and extrapolated.
Table 1:
Unknown Solution Concentrations (NA/NB) in mg/L for three trials, with averages, and
standard deviation
Trial
NA Solution Concentration
NB Solution Concentration

(mg/L)
(mg/L)
1
5.86
10.5
2
6.17
10.5
3
6.17
10.5
Average
6.07
10.5
Standard
Deviation
0.179
0
To check the validity of the NA and NB results determined in this experiment, a t-test at
the 95% confidence level was performed between the experimental and theoretical values. The t-
test proved that the experimental value of NA was not statistically significant and therefore is
reliable (Table 2). On the contrary, the t-test proved that the experimental value of NB was
proven to be statistically significant and therefore not reliable (Table 2).
Table 2.
This table displays the results and conclusions of the t-tests (at the 95% confidence
level) performed on the validation samples NA and NB.
NA
NB
T-test inequality
0.43 > 0.44
0.3 > 0
Conclusion
Inequality does not hold,
therefore it is no statistically
significant
Inequality holds, therefore it
is statistically significant
Another set of five standard solutions were made to make a second calibration curve for
the testing of the environmental samples. This calibration curve had a linear fit of
y
=−
372.5
x
+
2493
and a correlation of -0.9939 (Figure 5). Just like the calibration curve
before, it was used to find the concentration of nitrogen (mg/L) in the environmental samples.
The average concentration of the sample above the dam of Acton lake was 20.63 mg/L of
nitrogen with a standard deviation of 0.3908 mg/L (Table 3). The average concentration of the
sample below the dam of Acton lake was 15.85 mg/L nitrogen with a standard deviation of
0.1959 mg/L (Table 3). Lastly, the average concentration of the sample under the Morning Sun

Rd. bridge over 4 Mile Creek was 13.17 mg/L nitrogen with a standard deviation of 0.1414 mg/L
(Table 3).

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- Spring '12
- YasminJessa
- Chemistry, Bases, mg/L, environmental samples, Acton Lake