y b x m The voltage was plugged in for y to determine the concentration x Since

# Y b x m the voltage was plugged in for y to determine

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y – b = x m The voltage was plugged in for y to determine the concentration, x. Since the log of the concentration was taken for the calibration curve, the antilog (to the tenth power) was taken of x value determined from the above equation. For the three NA samples and the three NB samples, the three concentrations of each were added and divided by three to determine the mean and then the standard deviation. To determine how much stock solution was needed to be make the diluted buffer, the dilution equation was mused. M 1 V 1 = M 2 V 2 Where M 1 , was the concentration (molarity) of the original nitrate stock solution; M 2 was one of the five wanted concentrations (1, 2, 4, 6, and 10 mg/ L N). V 1 was the desired volume and V 2 was the known volume of the original solution. To make the ion strength adjusting solution (ISA), stoichiometry was utilized to determine the amount of grams of (NH 4 ) 2 SO 4 needed. The molar mass of (NH 4 ) 2 SO 4 was multiplied by number of moles to obtain the number of grams needed. To make the stock solution KNO 3 , the same methodology as the ISA solution was also employed to determine the grams of salt needed by multiplying the molar mass of the salt with its proposed volume. Results In order to properly utilize the technique for testing water concentration, the known concentrations of the artificial validation samples were given as a basis of comparison to the trials conducted on the same samples (Table 1). With consideration to the standard deviation, the possible concentrations for NA were between 4.8 and 7.2 mg N/L and the possible concentrations for NB were between 7.6 and 11.2 mg N/L (Table 1). In relation to this data, the experimented concentration for NA was 6.3 mg N/L and for NB was 9.9 mg N/L, within the given ranges from the previous table and the standard deviation for NA was 0.12 and 0.09 for NB (Table 2.1 and 2.2). The concentrations for the artificial validation samples were calculated using the least squares analysis line, y=-377.7x+2498, from the calibration curve generated by the standard solutions (Figure 1). By plotting the log of the concentrations versus the potential mV, the least squares line was identified (Figure 1 and Figure 2). Through the use of the ISE probe, the voltage, measured in V but converted to mV, was found and through the use of the calibration curve, the log of the concentration and the anti-log of the concentration was found to give the averages and standard deviations. With a different calibration curve based on similar standard solutions, the second calibration curve gave a least squares analysis line of y=-394.0x+2592 for the environmental samples (Figure 2). From this calibration curve, the concentrations for the two Hueston Woods samples were calculated. The first sample from Hueston Woods had a concentration of 5.1 mg N/L and a standard deviation of 0.14 (Table 3.1). The second sample from Hueston Woods had a concentration of 5.5 mg N/L and a standard deviation of 0.08 (Table 3.2). The first sample from the Formal Gardens had a concentration of 1.8 mg N/L and a standard deviation of 0.11 (Table 4.1). The second sample from the Formal Gardens had a concentration of 2.3 mg N/L and a standard deviation of 0.03 (Table 4.2). In order to determine wether the data was significantly  #### You've reached the end of your free preview.

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• Spring '12
• YasminJessa
• Chemistry, Water supply, Nitrate, Hueston Woods, Formal Gardens
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