S1 Supporting Information A Combined Experimental and Molecular ...
Supporting Information A Combined Experimental and Molecular Simulation Investigation of the Individual Effects of Corexit Surfactants on the Aerosolization of Oil Spill Matter Zenghui Zhang,1,* Paria Avij,1,* Matt J. Perkins,2 Thilanga P. Liyana-Arachchi,3 Jennifer A. Field,2 Kalliat T. Valsaraj1 and Francisco R. Hung1,4,†,‡ 1
Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA 2 Department of Environmental & Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA 3 Department of Chemistry, University of Florida, Gainesville, FL 32611, USA 4 Center for Computation & Technology, Louisiana State University, Baton Rouge, LA 70803, USA S.1. Methods: Experimental determination of ejection rates of n-alkanes (C10-C29, done at LSU) Chemicals and standards. The Louisiana Sweet Crude Oil was supplied by the BP Gulf Coast Restoration Organization (Houston, TX, USA). Details of the surrogate oil properties are available directly from the BP Gulf Coast Restoration Organization.1 Dioctyl Sodium Sulfosuccinate (DOSS) with 99% purity was obtained from Pfaltz & Bauer (Waterbury, CT, USA). Sorbitan monooleate (Span 80) with 60.6% purity was purchased from Sigma Aldrich (St. Louis, MO, USA). Sodium chloride (99.8%) for preparing salt solution (3.5% w/w) was purchased from Fisher Scientific (Fair Lawn, NJ, USA). Ethyl acetate (HPLC grade), used as a solvent for alkane analysis, was purchased from EMD Millipore (Billerica, MA, USA. Reference Standard solutions for alkanes, methyl octanoate, methyl decanoate, methyl arachidate, and methyl octacosanoate were gained from Sigma Aldrich (St. Louis, MO, USA). Anhydrous sodium sulfate, used for dehydration, was purchased from Mallinckrodt Chemicals (St. Louis, MO, USA). All chemicals were used as received without further purification. The mixtures of oil and surfactants were prepared at room temperature. The surfactant was added drop by drop to the oil while stirring the mixture for 15 min. Sample collection and gas chromatography. Samples were collected from two methods: (1) isokinetic sampling nozzle, and (2) electrostatic precipitator (ESP; Ionic Spore Trap, DS Scientific, Baton Rouge, LA, USA). In nozzle collection, both vapors and particles were collected isokinetically by constant mass-flow air-sampling nozzle for 15 min in duplicate. These vapors and particles were collected in a bubbler filled with ethyl acetate and dried over sodium sulfate. The dehydrated solutions were injected into the GC-MS/GC-FID and analyzed for their alkane content. In ESP collection, only the particulate matter was collected *
Equal contribution To whom correspondence should be addressed ‡ Current address: Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA. E-mail: [email protected]; Telephone: 617-373-2989 †
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on an aluminum target in duplicate. Each target was placed in a mixture of deionized water and ethyl acetate. Ethyl acetate dissolved the organic fraction of collected material while deionized water dissolved salt particles. The organic fraction was dehydrated over sodium sulfate and analyzed by GC-MS to obtain its alkane content.1 Blank samples were collected before injection of oil/surfactant into the reactor to ensure that all the alkanes and surfactant components found in aerosolized samples were truly arisen from the injection of organic matter into the reactor, not due to impurities that remained in the reactor from previous experiments. For alkane analysis by GC-FID, Agilent 5890 GC-FID system was used and the injection of 1 µL made with the injector at 300ºC in splitless mode. The flow of the UHP Helium through a GC column (DB-1HT, 30 m × 250 µm × 0.1 µm) was set at the constant pressure of 120 kPa. The oven program was at 50ºC for 1.4 min, ramp at 20ºC/min until 350ºC, then hold for 3 min.1 The concentration of alkanes was determined from external calibration standards with a calibration range of 0.01 to 93.60 ng/µL. For alkane analysis by GC-MS, Agilent 6890 GC-MS system was used and the injection of 1 µL made with the injector at 300ºC in splitless mode. The flow of the UHP Helium through a GC column (HP-5msUI, 30 m × 250 µm × 0.25 µm) was set at the linear velocity of 36 cm s-1. The oven program was at 50ºC for 5 min, ramp at 10ºC/min until 300ºC, then hold for 24 min. Methyl decanoate, Methyl arachidate and Methyl octacosanoate were used as internal standards for quantification. Quantitation ions for detection of alkanes were at a m/z of 57 and 85 and the internal standard compounds at a m/z of 74 and 87.1 Also, standards for calibration were used in each batch of experimental samples to control the performance of the GC-MS/GC-FID analysis. Calculation of ejection rates for alkanes. The mean ejection rate of alkanes was calculated as the mean of duplicate measurements for volatile and intermediate volatile compounds (C10-C19). For semi-volatile alkanes (C20-C29), the ejection rate was calculated by pooling the ejection rates obtained from experiments conducted using Nozzle sampling (n = 2) and experiments collected using ESP (n = 2) collection mechanisms. S.2. Methods: Experimental determination of ejection rates of the Corexit surfactants DOSS and Span 80 (done at OSU) Chemicals and standards. Standards of solid bis-(2-ethylhexyl) sodium sulfosuccinate (DOSS, 98.1% purity) and Span 80 (70.5% purity) were obtained from Sigma Aldrich (Saint Louis, MO). A standard of 13C4–DOSS was provided by Ed Furlong and James Gray of the United States Geological Survey National Water Quality Laboratory (Denver, CO) that had been synthesized by Cambridge Isotope Laboratories, Inc (Andover, MA). MS-grade methanol and isopropanol were purchased from Fisher Scientific (Pittsburg, PA). Laboratory 18-MΩ, deionized (DI) water was obtained by an in-house Millipore Synergy unit with an LC-Pak polisher (EMD Millipore Corp, Billerica, MA). High purity ammonium acetate was purchased from Sigma Aldrich. All glassware was baked at 400 oC for 12 h prior to use. Sample dilution and liquid chromatography. Samples were stored at -20 °C until analysis. S2
Samples were diluted 0 to 100 fold and chromatographic separation of the surfactant components of Corexit was performed on an Agilent 1100 (Agilent Technologies, Inc., Santa Clara, CA) as described by Place et al.,2 with minor modifications. Briefly, the post purge guard column was replaced with an Agilent EC-C8 or a Proshell 120 EC-C18 guard column (4.6 mm ID, 5 mm length, 2.7µm particle size) to accommodate higher backpressure. The analytical column was replaced with a 30 mm Agilent XDB C8 or C18 analytical column to accommodate faster run times (4.6 mm ID, 20 mm length, 3.5mm particle size; Agilent, Santa Clara, CA). A C18 system was used for the analysis of DOSS and C8 system was used for the analysis of the nonionic surfactants. Mobile phase A consisted of 0.5 mM NH4OAc in water and mobile phase B was 100 percent acetonitrile. The initial mobile phase condition was 97.5 percent ammonium acetate in water at a flow rate of 1.0 mL min-1. The initial condition was held for 5.6 minutes to flush the non-volatile salts to waste. By 6.1 min the percent acetonitrile was increased to 50 percent. The percent acetonitrile was further increased to 66 and 97.5 percent by 9.6 and 10.1 minutes respectively, prior to returning to the 2.5 percent by 13.6 minutes. This initial condition was then held for an additional 7.4 minutes for a total run time of 20 minutes. The timing of the main-pass by-pass valve switching and divert valve switching, as described by Place et al.,2 was adjusted to reflect changes in the flow rate and gradient. Also, during the analysis of the nonionic surfactants, the mobile phase was directed through an Agilent thermostatted column compartment (G1316A) and heated to 40 °C. Tandem mass spectrometry (MS/MS). Tandem quadrupole mass spectrometric detection was performed using a Waters Micromass Quattro mass spectrometer or a Waters Aquity Tandem Quadrupole mass spectrometer (Framingham, MA) as described by Place et al.,2 with minor modification to the mass spectrometric acquisition of Span 80. Span 80 was detected using Multiple reaction monitoring (MRM) in positive ionization mode. The sodiated species of the molecular ion of Span 80 was monitored using a single transition (m/z 455455). A fragment ion could not be found in high abundance for Span 80. Fragmentation was not perused because sodium-adducted compounds have been reported to yield low abundance fragment ions.3,4 A separate analysis was performed for Span 80 in which only Span 80 was detected at the detector (as opposed to Place et al., where Span 80, Tween 80, and Tween 85 were monitored over the same acquisition window), which increased the total scan time for Span 80, increasing sensitivity. DOSS and the 13C4 DOSS internal standard were detected by MRM in negative ionization mode. The molecular ion to sulfonate ion transition (m/z 42181) was used to quantify DOSS and a second transition (m/z 421227) was used to confirm DOSS. A single transition was used to quantify the 13C4-DOSS internal standard (m/z 42581). Calibration and quality control. Calibration curves consisted of at least 5 standards and required a correlation coefficient of 0.99 or greater to be used for quantification. All calibration curves were 1/× weighted, and standards whose calculated concentrations were beyond 20% of the intended concentration were removed from the calibration curve calculation. Calibration curves spanned from the lower limit of quantification to the upper limit of quantification: for DOSS (0.2-25 µg L-1) and Span80 (60-300 µg L-1). Each calibration standard was made in a mixture of Instant Ocean salt mix (IO) and isopropanol S3
(IPA) (approximately 35 ppt salinity; 75 percent IO-25 percent IPA) and spiked to give a final concentration of 500 ng L-1 13C4–DOSS. Blank and check standards2111 were used for quality control purposes. Blanks consisted IO-IPA solutions. Check standards consisted IO-IPA spiked with 500 ng L-1 DOSS and 80000 ng L-1 of Span 80. Blank and check standards were run every eight samples. Blanks were required to yield analyte signals below the limit of detection (LOD). Check standards for DOSS were required to yield a calculated concentration within 20% of the spiked concentration and Span 80 were required to yield a calculated concentration within 35% of the spiked concentration in order for the aerosol sample data to be considered quantitative. Calculation of ejection rates for DOSS and Span 80. The mean ejection rate of DOSS was calculated by pooling the ejection rates obtained from experiments conducted using Nozzle sampling (n = 3) and experiments collected using ESP (n = 2) collection mechanisms. The mean ejection rate of Span 80 was calculated by pooling the ejection rates obtained from experiments conducted using Nozzle sampling (n = 2) and experiments collected using ESP (n = 2) collection mechanisms. The pooling of the DOSS and Span 80 data is justified because neither DOSS nor Span 80 is expected in the vapor phase. Nozzle sampling collects both particulate and vapor phase materials while ESP collects only particle materials. Additionally, the reproducibility of ejection rates for DOSS and Span 80 regardless of sampling mechanism provides additional confidence in the reasonableness of this assumption.
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S.3. Additional model details: Span 80 Table S1. Atomic charges in Span 80. See Figure S1 for nomenclature of atoms in a molecule of Span 80. Representative Gromacs files (input, topology and coordinates) are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at doi:10.7266/N73R0QW8 Name C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 O19 O20 C21 C22 O23 H24 C25 O26 C27 C28 O29 H30 C31 O32 H33
Atomic charges 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.400 -0.400 -0.250 0.250 0.608 -0.836 0.475 -0.010 -0.441 0.139 0.313 -0.680 0.418 0.247 -0.641 0.408
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Figure S1. Nomenclature of atoms in a Span 80 molecule
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S.4. Additional simulation results: PMF calculations
Figure S2. Simulation snapshots illustrating the ‘extended’ configurations observed between C15/C30 (black) and DOSS (green) / Span 80 (red) during our PMF calculations. Here the center of mass of the molecules of interest is constrained to be at the values of z coordinate indicated in the figures. First row: C15 near an air/seawater interface that is bare (left) or S7
coated with 12 molecules of DOSS (center) or Span 80 (right). Second row: C30 near an air/seawater interface that is bare (left) or coated with 12 molecules of DOSS (center) or Span 80 (right). Third row: DOSS near an air/seawater interface that is bare (left) or coated with 16 molecules of C15 (center) or C30 (right). Fourth row: Span 80 near an air/seawater interface that is bare (left) or coated with 16 molecules of C15 (center) or C30 (right).
References (1) F. S. Ehrenhauser; P. Avij; X. Shu; V. Dugas; I. Woodson; T. Liyana-Arachchi; Z. Zhang; F. R. Hung; Valsaraj, K. T. Bubble bursting as an aerosol generation mechanism during an oil spill in the deep-sea environment : Laboratory experimental demonstration of the transport pathway. Environ. Sci.: Processes Impacts 2014, 16, 65-73. (2) Place, B. J.; Perkins, M. J.; Sinclair, E.; Barsamian, A. L.; Blakemore, P. R.; Field, J. A. Trace analysis of surfactants in Corexit oil dispersant formulations and seawater. Deep Sea Research Part II: Topical Studies in Oceanography 2014. (3) Grimalt, S.; Pozo, Ó. J.; Marín, J. M.; Sancho, J. V.; Hernández, F. Evaluation of different quantitative approaches for the determination of noneasily ionizable molecules by different atmospheric pressure interfaces used in liquid chromatography tandem mass spectrometry: abamectin as case of study. Journal of the American Society for Mass Spectrometry 2005, 16, 1619-1630. (4) Pozo, O. J.; Deventer, K.; Van Eenoo, P.; Delbeke, F. T. Efficient approach for the comprehensive detection of unknown anabolic steroids and metabolites in human urine by liquid chromatography-electrospray-tandem mass spectrometry. Analytical chemistry 2008, 80, 1709-1720.
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Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70803, USA 2 Department of Environmental & Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA 3 Department of Chemistry, University of Florida, Gainesville, FL 32611, USA 4 Center for Computation & Technology, Louisiana State University, Baton Rouge, LA 70803, USA S.1. Methods: Experimental determination of ejection rates of n-alkanes (C10-C29, done at LSU) Chemicals and standards. The Louisiana Sweet Crude Oil was supplied by the BP Gulf Coast Restoration Organization (Houston, TX, USA). Details of the surrogate oil properties are available directly from the BP Gulf Coast Restoration Organization.1 Dioctyl Sodium Sulfosuccinate (DOSS) with 99% purity was obtained from Pfaltz & Bauer (Waterbury, CT, USA). Sorbitan monooleate (Span 80) with 60.6% purity was purchased from Sigma Aldrich (St. Louis, MO, USA). Sodium chloride (99.8%) for preparing salt solution (3.5% w/w) was purchased from Fisher Scientific (Fair Lawn, NJ, USA). Ethyl acetate (HPLC grade), used as a solvent for alkane analysis, was purchased from EMD Millipore (Billerica, MA, USA. Reference Standard solutions for alkanes, methyl octanoate, methyl decanoate, methyl arachidate, and methyl octacosanoate were gained from Sigma Aldrich (St. Louis, MO, USA). Anhydrous sodium sulfate, used for dehydration, was purchased from Mallinckrodt Chemicals (St. Louis, MO, USA). All chemicals were used as received without further purification. The mixtures of oil and surfactants were prepared at room temperature. The surfactant was added drop by drop to the oil while stirring the mixture for 15 min. Sample collection and gas chromatography. Samples were collected from two methods: (1) isokinetic sampling nozzle, and (2) electrostatic precipitator (ESP; Ionic Spore Trap, DS Scientific, Baton Rouge, LA, USA). In nozzle collection, both vapors and particles were collected isokinetically by constant mass-flow air-sampling nozzle for 15 min in duplicate. These vapors and particles were collected in a bubbler filled with ethyl acetate and dried over sodium sulfate. The dehydrated solutions were injected into the GC-MS/GC-FID and analyzed for their alkane content. In ESP collection, only the particulate matter was collected *
Equal contribution To whom correspondence should be addressed ‡ Current address: Department of Chemical Engineering, Northeastern University, Boston, MA 02115, USA. E-mail: [email protected]; Telephone: 617-373-2989 †
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on an aluminum target in duplicate. Each target was placed in a mixture of deionized water and ethyl acetate. Ethyl acetate dissolved the organic fraction of collected material while deionized water dissolved salt particles. The organic fraction was dehydrated over sodium sulfate and analyzed by GC-MS to obtain its alkane content.1 Blank samples were collected before injection of oil/surfactant into the reactor to ensure that all the alkanes and surfactant components found in aerosolized samples were truly arisen from the injection of organic matter into the reactor, not due to impurities that remained in the reactor from previous experiments. For alkane analysis by GC-FID, Agilent 5890 GC-FID system was used and the injection of 1 µL made with the injector at 300ºC in splitless mode. The flow of the UHP Helium through a GC column (DB-1HT, 30 m × 250 µm × 0.1 µm) was set at the constant pressure of 120 kPa. The oven program was at 50ºC for 1.4 min, ramp at 20ºC/min until 350ºC, then hold for 3 min.1 The concentration of alkanes was determined from external calibration standards with a calibration range of 0.01 to 93.60 ng/µL. For alkane analysis by GC-MS, Agilent 6890 GC-MS system was used and the injection of 1 µL made with the injector at 300ºC in splitless mode. The flow of the UHP Helium through a GC column (HP-5msUI, 30 m × 250 µm × 0.25 µm) was set at the linear velocity of 36 cm s-1. The oven program was at 50ºC for 5 min, ramp at 10ºC/min until 300ºC, then hold for 24 min. Methyl decanoate, Methyl arachidate and Methyl octacosanoate were used as internal standards for quantification. Quantitation ions for detection of alkanes were at a m/z of 57 and 85 and the internal standard compounds at a m/z of 74 and 87.1 Also, standards for calibration were used in each batch of experimental samples to control the performance of the GC-MS/GC-FID analysis. Calculation of ejection rates for alkanes. The mean ejection rate of alkanes was calculated as the mean of duplicate measurements for volatile and intermediate volatile compounds (C10-C19). For semi-volatile alkanes (C20-C29), the ejection rate was calculated by pooling the ejection rates obtained from experiments conducted using Nozzle sampling (n = 2) and experiments collected using ESP (n = 2) collection mechanisms. S.2. Methods: Experimental determination of ejection rates of the Corexit surfactants DOSS and Span 80 (done at OSU) Chemicals and standards. Standards of solid bis-(2-ethylhexyl) sodium sulfosuccinate (DOSS, 98.1% purity) and Span 80 (70.5% purity) were obtained from Sigma Aldrich (Saint Louis, MO). A standard of 13C4–DOSS was provided by Ed Furlong and James Gray of the United States Geological Survey National Water Quality Laboratory (Denver, CO) that had been synthesized by Cambridge Isotope Laboratories, Inc (Andover, MA). MS-grade methanol and isopropanol were purchased from Fisher Scientific (Pittsburg, PA). Laboratory 18-MΩ, deionized (DI) water was obtained by an in-house Millipore Synergy unit with an LC-Pak polisher (EMD Millipore Corp, Billerica, MA). High purity ammonium acetate was purchased from Sigma Aldrich. All glassware was baked at 400 oC for 12 h prior to use. Sample dilution and liquid chromatography. Samples were stored at -20 °C until analysis. S2
Samples were diluted 0 to 100 fold and chromatographic separation of the surfactant components of Corexit was performed on an Agilent 1100 (Agilent Technologies, Inc., Santa Clara, CA) as described by Place et al.,2 with minor modifications. Briefly, the post purge guard column was replaced with an Agilent EC-C8 or a Proshell 120 EC-C18 guard column (4.6 mm ID, 5 mm length, 2.7µm particle size) to accommodate higher backpressure. The analytical column was replaced with a 30 mm Agilent XDB C8 or C18 analytical column to accommodate faster run times (4.6 mm ID, 20 mm length, 3.5mm particle size; Agilent, Santa Clara, CA). A C18 system was used for the analysis of DOSS and C8 system was used for the analysis of the nonionic surfactants. Mobile phase A consisted of 0.5 mM NH4OAc in water and mobile phase B was 100 percent acetonitrile. The initial mobile phase condition was 97.5 percent ammonium acetate in water at a flow rate of 1.0 mL min-1. The initial condition was held for 5.6 minutes to flush the non-volatile salts to waste. By 6.1 min the percent acetonitrile was increased to 50 percent. The percent acetonitrile was further increased to 66 and 97.5 percent by 9.6 and 10.1 minutes respectively, prior to returning to the 2.5 percent by 13.6 minutes. This initial condition was then held for an additional 7.4 minutes for a total run time of 20 minutes. The timing of the main-pass by-pass valve switching and divert valve switching, as described by Place et al.,2 was adjusted to reflect changes in the flow rate and gradient. Also, during the analysis of the nonionic surfactants, the mobile phase was directed through an Agilent thermostatted column compartment (G1316A) and heated to 40 °C. Tandem mass spectrometry (MS/MS). Tandem quadrupole mass spectrometric detection was performed using a Waters Micromass Quattro mass spectrometer or a Waters Aquity Tandem Quadrupole mass spectrometer (Framingham, MA) as described by Place et al.,2 with minor modification to the mass spectrometric acquisition of Span 80. Span 80 was detected using Multiple reaction monitoring (MRM) in positive ionization mode. The sodiated species of the molecular ion of Span 80 was monitored using a single transition (m/z 455455). A fragment ion could not be found in high abundance for Span 80. Fragmentation was not perused because sodium-adducted compounds have been reported to yield low abundance fragment ions.3,4 A separate analysis was performed for Span 80 in which only Span 80 was detected at the detector (as opposed to Place et al., where Span 80, Tween 80, and Tween 85 were monitored over the same acquisition window), which increased the total scan time for Span 80, increasing sensitivity. DOSS and the 13C4 DOSS internal standard were detected by MRM in negative ionization mode. The molecular ion to sulfonate ion transition (m/z 42181) was used to quantify DOSS and a second transition (m/z 421227) was used to confirm DOSS. A single transition was used to quantify the 13C4-DOSS internal standard (m/z 42581). Calibration and quality control. Calibration curves consisted of at least 5 standards and required a correlation coefficient of 0.99 or greater to be used for quantification. All calibration curves were 1/× weighted, and standards whose calculated concentrations were beyond 20% of the intended concentration were removed from the calibration curve calculation. Calibration curves spanned from the lower limit of quantification to the upper limit of quantification: for DOSS (0.2-25 µg L-1) and Span80 (60-300 µg L-1). Each calibration standard was made in a mixture of Instant Ocean salt mix (IO) and isopropanol S3
(IPA) (approximately 35 ppt salinity; 75 percent IO-25 percent IPA) and spiked to give a final concentration of 500 ng L-1 13C4–DOSS. Blank and check standards2111 were used for quality control purposes. Blanks consisted IO-IPA solutions. Check standards consisted IO-IPA spiked with 500 ng L-1 DOSS and 80000 ng L-1 of Span 80. Blank and check standards were run every eight samples. Blanks were required to yield analyte signals below the limit of detection (LOD). Check standards for DOSS were required to yield a calculated concentration within 20% of the spiked concentration and Span 80 were required to yield a calculated concentration within 35% of the spiked concentration in order for the aerosol sample data to be considered quantitative. Calculation of ejection rates for DOSS and Span 80. The mean ejection rate of DOSS was calculated by pooling the ejection rates obtained from experiments conducted using Nozzle sampling (n = 3) and experiments collected using ESP (n = 2) collection mechanisms. The mean ejection rate of Span 80 was calculated by pooling the ejection rates obtained from experiments conducted using Nozzle sampling (n = 2) and experiments collected using ESP (n = 2) collection mechanisms. The pooling of the DOSS and Span 80 data is justified because neither DOSS nor Span 80 is expected in the vapor phase. Nozzle sampling collects both particulate and vapor phase materials while ESP collects only particle materials. Additionally, the reproducibility of ejection rates for DOSS and Span 80 regardless of sampling mechanism provides additional confidence in the reasonableness of this assumption.
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S.3. Additional model details: Span 80 Table S1. Atomic charges in Span 80. See Figure S1 for nomenclature of atoms in a molecule of Span 80. Representative Gromacs files (input, topology and coordinates) are publicly available through the Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC) at doi:10.7266/N73R0QW8 Name C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 O19 O20 C21 C22 O23 H24 C25 O26 C27 C28 O29 H30 C31 O32 H33
Atomic charges 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.400 -0.400 -0.250 0.250 0.608 -0.836 0.475 -0.010 -0.441 0.139 0.313 -0.680 0.418 0.247 -0.641 0.408
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Figure S1. Nomenclature of atoms in a Span 80 molecule
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S.4. Additional simulation results: PMF calculations
Figure S2. Simulation snapshots illustrating the ‘extended’ configurations observed between C15/C30 (black) and DOSS (green) / Span 80 (red) during our PMF calculations. Here the center of mass of the molecules of interest is constrained to be at the values of z coordinate indicated in the figures. First row: C15 near an air/seawater interface that is bare (left) or S7
coated with 12 molecules of DOSS (center) or Span 80 (right). Second row: C30 near an air/seawater interface that is bare (left) or coated with 12 molecules of DOSS (center) or Span 80 (right). Third row: DOSS near an air/seawater interface that is bare (left) or coated with 16 molecules of C15 (center) or C30 (right). Fourth row: Span 80 near an air/seawater interface that is bare (left) or coated with 16 molecules of C15 (center) or C30 (right).
References (1) F. S. Ehrenhauser; P. Avij; X. Shu; V. Dugas; I. Woodson; T. Liyana-Arachchi; Z. Zhang; F. R. Hung; Valsaraj, K. T. Bubble bursting as an aerosol generation mechanism during an oil spill in the deep-sea environment : Laboratory experimental demonstration of the transport pathway. Environ. Sci.: Processes Impacts 2014, 16, 65-73. (2) Place, B. J.; Perkins, M. J.; Sinclair, E.; Barsamian, A. L.; Blakemore, P. R.; Field, J. A. Trace analysis of surfactants in Corexit oil dispersant formulations and seawater. Deep Sea Research Part II: Topical Studies in Oceanography 2014. (3) Grimalt, S.; Pozo, Ó. J.; Marín, J. M.; Sancho, J. V.; Hernández, F. Evaluation of different quantitative approaches for the determination of noneasily ionizable molecules by different atmospheric pressure interfaces used in liquid chromatography tandem mass spectrometry: abamectin as case of study. Journal of the American Society for Mass Spectrometry 2005, 16, 1619-1630. (4) Pozo, O. J.; Deventer, K.; Van Eenoo, P.; Delbeke, F. T. Efficient approach for the comprehensive detection of unknown anabolic steroids and metabolites in human urine by liquid chromatography-electrospray-tandem mass spectrometry. Analytical chemistry 2008, 80, 1709-1720.
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