Oxytetracycline at Environmental Interfaces Studied
by Second Harmonic Generation
Patrick L. Hayes and Franz M. Geiger
Department of Chemistry, Northwestern University, Evanston IL
WMRC Symposium on PPCPs in the Illinois Environment -- April 25, 2008
Oxytetracycline
Oxytetracycline (OTC)
S
H3C CH3
OH
N
H3C OHH
H
H3C
OH
CH3
N
HCl
NH2
OH
O
OH
OH
O
Morantel
O
Mifflin et al. J. Phys. Chem. B 2006, 110, 22577.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
N
Konek et al. J. Am. Chem. Soc. 2005, 127, 15771.
Oxytetracycline
•Tetracyclines are used in humans and
cattle/poultry/swine
Oxytetracycline (OTC)
H3C CH3
OH
N
H3C OHH
H
OH
HCl
NH2
OH
O
OH
OH
O
O
•Estimated 3 million pounds of tetracyclines
used annually for growth stimulation in
livestock!
•25-75% of tetracyclines administered to
animals are excreted in the active form.
Hileman, B. “Resistance is on the Rise” Chem. Eng. News 2001, February 19, 47.
Kulshrestha, P.; Giese, R. F. Aga, D.S. Environ. Sci. Technol. 2004, 38, 4097.
Boxall, A. B. A. EMBO Reports 2004, 5, 1110.
Simon, N. S. Environ. Sci. Technol. 2005, 39, 3480.
Antibiotic Resistance in Soil Bacteria
Importance of Mobility: Case I “A Sticky Antibiotic”
Bacterium
Bacterium
Resistant
Soil
Particle
Soil
Particle
Sticky
Antibiotic
Soil
Particle
Bacterium
Localized
Soil
Particle
Antibiotic Resistance in Soil Bacteria
Importance of Mobility: Case II “A Mobile Antibiotic”
Resistant
Resistant
Soil
Particle
Resistant
Soil
Particle
Soil
Particle
Mobile
Antibiotic
Resistant
Soil
Particle
Koike et al. Appl. Envir. Microbiol. 2007, 73, 4813.
Environmental Interfaces Control Transport,
Reactivity, Bioavailability
Challenges:
•Complexity
•Separating Bulk from Surface
•Sensitivity
Soils
Pollutant Plume
Water Table
Surface
Waters
Second Harmonic Generation
Water
Fundamental
Laser Light
Second
Harmonic
Generation
(SHG)
Normalized Abs./SHG E-field (a.u.)
Second Harmonic Generation (SHG)
1.5
1.0
0.5
Quartz
Aqueous
Aqueous
UV-Vis
UV-Vis Spectrum
0.0
Nitrate
Nitrate
Surface
SHG
Spectrum
Fused
Quartz/Water
Quartz/Water
Surface
SHGSpectrum
290
300 310
320 330 340
Wavelength (nm)
Advantages:
•Surface-Specific
•Sensitivity Allows for Real-time
Monitoring of Adsorption
“Measurable” is ESHG  Nads
•Experiments Run Under Flow Conditions
Eisenthal, K. B. Chem. Rev. 1996, 96, 1343.
Shen, Y. R. “The Principles of Nonlinear Optics” John Wiley & Sons: New York, 2003.
350 360
Experimental Setup
Pulsed & Tunable Laser
SiO2
laser
PMT
Aqueous
Phase
Waste
Analyte
Water
Teflon Flow
Cell
UV-Vis
Mifflin, A.L.; Gerth, K.A.; Weiss, B.M. Geiger, F.M. J. Phys. Chem. A 2003, 107, 6212.
Mifflin, A.L.; Gerth, K.A.; Geiger, F.M. J. Phys. Chem. A 2003, 107, 9620.
Mifflin, A.L.; Musorrafiti, M.J.; Konek, C.T.; Geiger, F.M. J. Phys. Chem. B 2005, 109, 24386.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
Model Environmental Interfaces
O
Pollutant
OH
HO
O
H 3C
H
O
O
H3C
O
Si
O
O
O
Fused
Quartz
Si
O
O
O
Si
O
O
O
Si
O
O
O
Soil
Particle
9
9
O
Organic
Adlayer
O
O
Si
O
O
NH
NH
9
9
9
O
NH
O
O
16
OH
H3C
Si
O
O
O
Si
O
O
Increasing Complexity
Our Strategy:
Common Organic Motifs
R
Use synthetic chemistry to:
(1)
Isolate and study individual functional groups.
(2) Build more complex model interfaces.
OH
OH
O
O
R
O
O
CH3
R
OCH3
OH
O
Sutton, R.; Sposito, G. Environ. Sci. Technol. 2005, 39, 9009.
Al-Abadleh et al. J. Am. Chem. Soc. 2004, 126, 11126.
Gibbs-Davis, J.M.; Hayes, P.L.; Scheidt K. A.; Geiger F.M. J. Am. Chem. Soc. 2007, 129, 7175.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
R
R
N
H
O
R
R
Normalized Abs./SHG E-Filed (a.u.)
OTC Spectroscopy and
Adsorption/Desorption Trace
at
Fused Quartz/Water Interface
(pH 8)
1.2
OTC
UV-Vis
1.0
0.8
0.6
0.4
SHG OTC
Fused Quartz/Water
0.2
0.0
240
280
320
360
400
Wavelength (nm)
SHG E-Field (a.u.)
8.5
8.0
7.5
7.0
6.5
6.0
OTC
5 x 10–5 M
5.5
H2O
5.0
0
Mifflin et al. J. Phys. Chem. B 2006, 110, 22577.
500
1000
Time (s)
H2O
1500
OTC Isotherm &
The Kd Model
(pH 8)
1.2
O
OH
1.0

0.8
0.6
NH
0.4
O
0.2
9
0.0
0.0
0.2
0.4
0.6
0.8
1.0 1.2x10
-5
O
Si
O
O
Concentration (M)
Retardation Factor:
R =1+(r/n).Kd
Kd = 0.11 mL/g
Taking: (r/n) = 4 – 10 g/cm3
Rf = 1.44 - 2.1
Rf = 2, corresponds to 50%
reduction in OTC mobility relative
to water.
Langmuir, D. Aqueous Environmental Geochemistry; Prentice Hall, Inc: New Jersey, 1997.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
Mifflin et al. J. Phys. Chem. B 2006, 110, 22577.
Summary of Isotherm Experiments: Mobility
O
OH
HO
O
H
O
H3C
O

Si
O
O
O
9
Si
O
O
O
O
r
g
 10 3
n
cm
Si
O
O
O
Si
O
O
Si
O
O
O
9
9
O
NH
O
O
9
OH
O
NH
O
Si
O
O
9
O
Si
O
O
2.0
Rf
Kd (mL/g)
0.10
NH
O
16
H 3C
H3C
0.05
1.5
0.00
1.0
Mifflin et al. J. Phys. Chem. B 2006, 110, 22577.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
Predicting OTC Mobility: Surface Energy and OTC Retardation
2.0
For Hydrogen-Bonding
Surfaces, and Taking:
(r/n) = 4 -10 g/cm3
Rf
1.8
(c)
 = 49º, 9 mJ/m2
f
1.6
c
1.4
(f)
e
 = 75º, 22 mJ/m2
d
1.2
a
b
O
1.0
OH
HO
0
5
10
15
SL [mJ/m2]
20
25
O
H
O
NH
O
O
Si
O
O
(a)
Mifflin et al. J. Phys. Chem. B 2006, 110, 22577.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
O
O
Si
O
O
(b)
O
(c)
Si
O
O
(d)
O
9
9
O
NH
O
O
Si
O
O
O
NH
9
9
OH
H 3C
H3C
O
Si
O
O
(e)
9
O
Si
O
O
(f)
Predicting OTC Mobility: Surface Energy and OTC Retardation
2.0
For Hydrogen-Bonding
Surfaces, and Taking:
(r/n) = 4 -10 g/cm3
Rf
1.8
IHSS Humic Acid:
Contact Angle: 59(3)
Surface Energy: 14(1) mJ/m2
Predicted Rf: 1.4(1)
f
1.6
1.4
IHSS HA
c
e
Aldrich Humic Acid:
d
Aldrich HA
Contact Angle: 57(3)
Surface Energy: 13(1) mJ/m2
Predicted Rf: 1.3(1)
1.2
a
b
O
1.0
OH
HO
0
5
10
15
SL [mJ/m2]
20
25
O
H
O
NH
O
O
Si
O
O
(a)
Mifflin et al. J. Phys. Chem. B 2006, 110, 22577.
Hayes et al. J. Phys. Chem. C 2007, 111, 8796.
O
O
Si
O
O
(b)
O
(c)
Si
O
O
(d)
O
9
9
O
NH
O
O
Si
O
O
O
NH
9
9
OH
H 3C
H3C
O
Si
O
O
(e)
9
O
Si
O
O
(f)
Connections to Mobility
Mobile
OTC ???
2.0
Rf
1.8
OTC will tend to be less mobile in silica-rich
soils that:
f
1.6
Contain natural organic matter with a large
density of benzoic acid functional groups
•
Display high interfacial energy
e
c
1.4
•
d
1.2
a
b
1.0
0
5
10
15
SL [mJ/m2]
20
25
Acknowledgements
Professor Franz M. Geiger
Dr. Amanda Mifflin (OTC)
Dr. Julianne Gibbs-Davis
Professor Karl A. Scheidt
Geiger Group 2006
Funding: