Degrading Sulfadiazine
D. Johnson, C. Harrison
Degrading Sulfadiazine with Bromine
Dustin Johnson, Chris Harrison
Tuesday/8:30-11:30/2
Abstract:
Sulfadiazine is commonly excreted into natural water systems where it has harmful
effects on the environment. Since it can have harmful effects it is important that we find a
method to degrade Sulfadiazine in a safe and effective manner. Our hypothesis is that
Sulfadiazine can be degraded by reacting in a solution of aqueous Bromine. Several tests were
carried out and results indicate that Sulfadiazine can be degraded with a solution of aqueous
Bromine as long as it is carried out in an acidic environment and there is a high enough
concentration of Bromine. Further testing needs to be done to find the effective ratio of Bromine
to Sulfadiazine, and to study the effects of the byproducts of this reaction.
Introduction:
The sulfa-drug sulfadiazine is used as an antibiotic and is generally taken for urinary tract
infections. Sulfadiazine is solely a prescription medication that must be taken following doctor
recommendations. Being an antibacterial, drug regiments must be carried out to completion,
even if symptoms end. This is one reason why excess ends up in the environment.
Sulfadiazine, when used to treat bacterial infection, acts by preventing bacteria cells from
reproducing. Bacteria produce folate that they need for reproduction; sulfadiazine prevents the
cells from producing folate. This prevents them from reproducing, and the existing cells
eventually die, shrinking the infection. Sulfadiazine does not break down in the body. It is
quickly excreted with urine. The drug is not soluble in water, but it can degrade when exposed to
ultraviolet light if the pH is high enough. Therefore, the drug ends up in the environment where
it has potential to cause problems.
Sulfadiazine has a molecular formula C10H10N4O2S as found on page SD-5 of Chemistry
128L Laboratory Manual (Dr. Graeme Wyllie, 2012). The Lab Manual also gives the structure
of sulfadiazine shown in Figure 1. The scientific name of this drug is 4-amino-N-pyrimidin-2-ylbenzenesulfonamide.
Figure 1.
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Degrading Sulfadiazine
D. Johnson, C. Harrison
We chose to study the effects Bromine has on degrading Sulfadiazine. There was some
work carried out by research teams. In their experiment they tried to dissolve Bromine in water
and use that solution to degrade Sulfadiazine. Their data was inconclusive most likely because
Bromine does not dissolve in water easily. So we took this information and found a method used
to make Iodine and Bromine solutions in water which would allow us to test actual solutions of
aqueous Bromine. The method we used to create our Bromine solution was effective because it
used H2SO4 to oxidize Bromine, which does not precipitate out of water like solid bromine.
Bromine is commonly found in water filtration systems and swimming pools in low
concentrations; however the amount required to effectively degrade Sulfadiazine may be too
high for health reasons.
Oxidization of Bromine:
2KBrO3+6H2SO4→Br2+6SO4+6H2O
2NaBr+2H2SO4→Br2+2H20+SO2
Experimental:
Week One:
The first day of our experiment we devised a procedure to create a Bromine solution in
water. Since Bromine does not dissolve in water easily it became a several step process. To
make the stock solution we combined 1.67 grams of KBrO3 with 5.35 grams of NaBr in a 100mL
volumetric flask then added 5mL of 6M H2SO4. Since Bromine fumes are highly toxic it is
important that the flask remains in the hood at all times after the addition of H2SO4.Then we
diluted the solution by filling the rest of the flask with distilled water to 100mL mark. After
mixing our solution we heated the flask to 60 degrees Celsius but were careful not to overheat
the solution because Br vaporizes at 60 degrees Celsius. This original stock solution was deep
orange in color so in order for it to work in the spectrometer we made three 1:20 dilutions. After
diluting the solution three times the spectrometer was able to give accurate readings. We were
advised that our Bromine solutions will degrade over time so we took absorbency readings of
just the Bromine solutions so we can monitor how much it degrades over time. To help prevent
significant degradation we stored our stock solution in brown containers which helps eliminate
the effects of photo degradation.
Week Two:
We analyzed the stock solution of Bromine and decided it would be best if we made a
fresh stock solution because the original solution had degraded significantly and we had no
background spectra for concentration versus absorbance for Bromine solution. The second stock
solution we made for Bromine consisted of 5.3515 grams of NaBr and 1.6614 grams of KBrO3 .
We also made a stock solution of our sulfa drug Sulfadiazine. To make this solution we diluted
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Degrading Sulfadiazine
D. Johnson, C. Harrison
.0363 grams of Sulfadiazine to 500mL. The stock solution for our sulfa drug had a concentration
of 2.9007x10-8. We diluted the Bromine solution until it had a concentration of 4.8x10-4. We
then took absorbance readings of just Bromine and just Sulfadiazine for a background spectrum.
We mixed 5mL of bromine with 10ml of Sulfadiazine and diluted the solution to 100mL. We
took absorbance readings from the initial starting point, 5, 10, 15, 20, 30, 40, 50, and 60 minutes.
We monitored the pH overtime but did not add anything to manipulate it.
Week Three:
Since pH has a significant impact on what forms of Sulfadiazine are present we set out to
determine if degradation occurs best in acidic or basic solutions. Since we had a background
absorbance spectrum for concentration versus absorbance for Bromine we decided to use the
slightly degraded Bromine solution from the previous week and found the concentration using
this spectrum. We had to remake our solution of Sulfadiazine; we made a solution which had a
concentration of 3.54x10-4M. For our experiment we used three different dilutions of Bromine
which were 5:100, 10:100, and 50:100. For each trail 10mL of our Sulfadiazine solution was
used. To lower the pH we used 5mL of 1M HCl, to raise the pH we used 5mL of 1M NaOH. We
noticed that the majority of the degradation happens within the first 15 minutes so we took
absorbance readings at 0, 2, 5, 10, 15 ,20, 25, 30, 35, 40, 45, 50, 55, and 60 minutes.
Week Four:
We noticed in last week’s results that a pH of 2.2 had the greatest degradation so we did
further testing under acidic conditions. We had to make fresh Bromine solutions so we followed
the same steps but cut the mass and volumes in half to save on waste material. We also cut the
mass and volume in half when we made the sulfadiazine solution to eliminate excess waste. We
tested two different concentrations of Bromine which were 3.77x10-4M and 1.89x10-4M. We
used 5mL of each Bromine concentration, 5mL of 1M HCl, and 10mL of the stock sulfadiazine
solution, then diluted the mixture to 100mL and took absorbance readings at 0, 2, 5, 10, 15 ,20,
25, 30, 35, 40, 45, 50, 55, and 60 minutes. We ran additional testing on solutions containing just
Bromine and HCl to see if there was any degradation not caused by the sulfadiazine.
Week Five:
Since our Bromine solution has a shelf life of one week we did not have to make a new
Bromine stock solution, we used the spectrum we made for Bromine to determine the
concentration of the solution. We did have to make another sulfadiazine solution using the same
process as before. We carried two tests at a pH of 2.2 with Bromine concentrations of
3.77x10-4M and 1.89x10-4M using the same setup as last week. We also tested a solution with
just 5mL of 1M HCl and our Sulfadiazine solution to eliminate the possibility that degradation
was due to HCl reacting with Sulfadiazine.
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Degrading Sulfadiazine
D. Johnson, C. Harrison
Results and Data Analysis:
The first data collected came from a run with solutions of 2.9x10-5M Sulfadiazine and
4.8x10-4 Br. The pH was not controlled for this initial run, as we were just getting going and
wanted to see how the process would work. The molar ratio of Br to sulfa-drug was about 20:1
so that the bromine would be in excess. Very little separation was observed in the absorbance
curves of sulfadiazine over an hour. The concentration of sulfadiazine, based on its absorbance,
appeared to decrease a little in the first five minutes. Data points were taken at 0 and 5 minutes,
so this result could have arisen from one inaccurate measurement.
The second week, tests of three different bromine concentrations were run at high (above
12.5) and low (below 2.5) pH. All solutions had a sulfadiazine concentration of 3.54x10-5; Br
concentrations varied between 2.5x10-4 and 1.1x10-3. The bromine was still kept in excess by a
ratio around 20:1. These bromine solutions were saved from the previous week. Due to some
degradation, their concentrations were calculated by comparing their spectrum to that of a known
spectrum using Microsoft Excel. Separation appeared in the absorbance curves in the two acidic
trials of higher bromine concentration, as can be seen in Figure 3. The absorbance of given
wavelengths within the strongest absorbance range of the sulfa-drug are plotted in Figure 4. In
these graphs, the pure bromine spectrum has been subtracted from the total. The absorbance
spectrums of bromine and sulfadiazine are each plotted in Figure 2.
Figure 2
0.9
Spectrums of Pure 2.9x10-5M Sulfa
and 4.8x10-4M Bromine
0.8
0.7
Absorbance
0.6
0.5
Sufla
0.4
Br
0.3
0.2
0.1
0
200
250
300
350
wavelength (nm)
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400
450
Degrading Sulfadiazine
D. Johnson, C. Harrison
Figure 3: a)
2.5
b)
3
5.49x10-4M Br - low pH
2.5
1min.
2
7.34x10-4M Br - low pH
1min.
3min.
1.5
5min.
7min.
10min.
1
3min.
2
5min.
15min.
7min.
1.5
10min.
1
15min.
20min.
0.5
25min.
20min.
0.5
25min.
30min.
41
0
200
250
300
30min.
0
350
200
Wavelength (nm)
Absorbance
Absorbance
0.25
0.2
0.15
0.1
0.05
0
0
10
20
350
b) 7.34e-4M Br at low pH
Absorbance at 266nm
0.3
300
Wavelength (nm)
Figure 4: a) 5.486e-4M Br at low pH
0.35
250
30
40
50
time (min.)
0.48
0.47
0.46
0.45
0.44
0.43
0.42
0.41
0.4
0.39
Absorbance at 250nm
0
10
20
30
40
time (min.)
Control runs were carried out to make sure the acid (HCl) alone was not degrading the
sulfa-drug. A test was also done to make sure the acid did not degrade the spectrum of the
bromine. The spectrums did not decrease over time for either, so indeed the absorbance of the
sulfadiazine was decreasing.
Over the next two weeks, four more trials were carried out to confirm the results. Except
for one with a low concentration of bromine, all showed degradation. These data are plotted in
Figures 5-7. Again, the absorbance over time for one wavelength is plotted correspondingly in
part (b) of each figure.
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Degrading Sulfadiazine
D. Johnson, C. Harrison
Figure 5: a) Sulfadiazine concentration: 1.78x10-5M
1.4
0.25
2.41x10-4M Br at low pH
1.2
2min.
1
4min.
0.8
9min.
0.6
14min.
19min.
0.4
0.15
0.1
0.05
24min.
0.2
Absorbance at
250nm
0.2
Absorbance
Absorbance
b)
29min.
0
200
250
300
0
55min.
350
0
20
Wavelength (nm)
0.18
0.6
2min.
0.14
0.5
4min.
0.12
0.4
8min.
0.3
13min.
0.2
18min.
0.04
0.1
23min.
0.02
31min.
0
0
200
250
300
Absorbance at
260nm
0.16
Absorbance
Absorbance
b)
4.82x10-4M Br at low pH
0.7
60
Time (min.)
Figure 6: a) Sulfadiazine concentration: 1.78x10-5M
0.8
40
0.1
0.08
0.06
0
350
10
20
Time (min.)
Wavelength (nm)
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30
40
Degrading Sulfadiazine
D. Johnson, C. Harrison
Figure 7: a) Sulfadiazine concentration: 1.81x10-5M
0.6
3.77x10-4M
Br at low pH
2min.
4min.
0.4
6min.
0.3
10min.
0.2
15min.
0.1
20min.
25min.
0
200
250
300
31min.
Wavelength (nm)
Absorbance
Absorbance
0.5
b)
0.1
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
Absorbance at
250nm
0
10
20
30
40
Time (min.)
The final trial at 1.89x10-4M Br did not show any degradation. This was the lowest
concentration of bromine tested.
Our best results appeared in with 5.49x10-4M bromine; the spectrum is shown in Figure 3
(a) where good separation appeared. In Figure 4 (a), the degradation over time for this trial can
be seen at a 266nm – a wavelength where the sulfa-drug absorbs. Fitting a linear curve to this
graph using Excel gives an equation of y = -0.0043x + 0.278. According to this, the absorbance
decreases 0.0043 per minute. Figure 6 also contains some good data. A trend line fitted to the
first 18 minutes of the curve in Figure 6 (b) gives a degradation rate of 0.0074 absorbance units
per minute. This is a higher rate even though the bromine concentration is less. However, due to
the inconsistency in bromine solutions (discussed in the next section), this is not a dependable
observance.
Discussion:
The concentrations of our bromine solutions from week to week were not very consistent.
On the weeks we made solutions, we calculated the Br concentration from the ingredients.
However, the solutions degraded over the course of a week, so the weeks when we used old
solutions, they were a little less concentrated. Using the absorbance spectrum, we calculated the
concentration, but error likely resulted from this method. This reasoning is likely why we found
degradation in a solution of 2.41x10-4M Br in week 4 (figure 5a), but not one with higher
concentration of 2.56x10-4M in week 3. In week 3, the Br solution was a week old, so its
calculated concentration was probably greater than the actual.
The graphs shown in the previous section represent all of our trials that showed some sort
of degradation. The separation of the absorbance curves over time happened in the ultraviolet
spectrum. This range is where sulfadiazine absorbs light. It appears that the sulfa-drug was
broken down by bromine, but we do not know how this occurs and what the products are.
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Degrading Sulfadiazine
D. Johnson, C. Harrison
Further Work:
Further studies could be carried out to verify our data and find a more quantitative
analysis of the effects of bromine. Similar tests could be run with higher concentrations of
sulfadiazine to obtain more accurate data. At the concentrations we used, error was large from
the spectrometers due to the very small absorbance. If bromine is a viable way to remove
sulfadiazine from water, it needs to be determined if other substances are present after the
reaction. Methods may need to be developed to remove the remaining bromine from the water.
Conclusions:
After eleven trials of attempting to degrade sulfadiazine with bromine, it was found that
better results occurred at low pH. We tested neutral and high pH levels and saw no degradation
of the sulfa-drug, but with a low pH, the sulfa-drug concentrations appeared to lessen when in
solution with bromine. Our hypothesis that bromine solutions will degrade sulfadiazine was
confirmed. However, more testing is needed to quantify the effectiveness of this reaction before
it can be used on the large scale to remove sulfa-drugs from waste water.
References:
http://www.lenntech.com/processes/disinfection/chemical/disinfectants-bromine.htm
http://webpages.charter.net/kwilliams00/bcftp/docs/halides.htm
Wyllie, Graeme R. A. Chemistry 128L Laboratory Manual. Concordia College, Spring 2012.
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