Anionic Surfactant Detection

In Aqueous Environments

John RaiaChem 4101

December 9th, 2011

The ProblemIn the Deep Water Horizon catastrophe that occurred

Spring of 2010, over 1 million gallons of an undisclosed mixture of sulfonated anionic surfactants (Corexit®) were sprayed across the oil spill site to act as an oil dispersant agent.

Some specific anionic surfactants have known toxicities for various marine species (especially green algae, sea turtles, and dolphins). They are also known to have severe respiratory and digestive issues in humans are suspected causers of human endocrine disruption.

Over time the migration of the surfactants could effect ecological systems many miles away from where they were originally introduced. §

§ Kerr, R. A. A Lot of Oil on the Loose, Not So Much to Be Found. Science 2010, 329, 734-735.

HypothesisIt is crucial to be able to identify specific anionic

surfactants that are still present in aqueous environments.

Since migration of surfactants throughout aqueous sources is an issue, quick and effective methods of sampling, detection and characterizing surfactants is essential.

By monitoring the deaths of migrating aquatic species (i.e. dolphins and sea turtles) found around coastal shores, a direct correlation to the presence of anionic surfactants in water in that area hopefully can be made, and the contents can be analyzed both quantitatively and qualitatively. º

ºNelson, Karen. One year later, Gulf oil disaster claims, questions unsettled http://www.duluthnewstribune.com/event/article/id/196672/ (accessed October 16th, 2011)

Classification of Anionic Surfactant Species

Dioctyl Sodium Sulfosuccinate (DOSS)*

• 444.216 Da• CAS #: 577-11-7 • Molecular Formula: C20H37NaO7S• MP: 153–157 °C

• Soaps : CnH2n+1COO-X

• Alkyl Sulfates (AS) • Linear Alkylbenzene

Sulfonates (LAS) and Secondary Alkyl

Sulfonates (SAS) : Cn Hn+1SO3-X

• Alkylether Sulfates (AES): CnH2+l-(OCH2CH2)n-OSO3X

• Fluorinated: CnH2n-1OPO(OH)O-X

Classifications1

Approx. 1 million gallons of sulfonated surfactant mixture

dispersed in 6.43 E 17 gallons of marine water. (detection limit from

1ppt to 3ppm) º*Sigma-Aldrich. <http://www.sigmaaldrich.com/catalog/ProductDetail.do?D7=0&N5=SEARCH_CONCAT_PNO%7CBRAND_KEY&N4=D201170%7CALDRICH&N25=0&QS=ON&F=SPEC >(accessed Oct 26, 2011).

Other standards for comparison can be

purchased accordingly

Sampling and Extraction Sampling

Costal regions Beached migrating aquatic species with known toxicities

Sampled radially, with constant distance Positive sampling for anionic surfactants should be resampled

at varying depths

• Solid Phase Extraction (C18 cartridge)2

100 mL sample

of seawater

Condition w/ MeOH and

H2O

Frozen with 4% formaldehyde until

analysis

Possible Separation MethodsMethod Advantages DisadvantagesCapillary electrophoresis2 • Reduced demand for

organic solvents • Short time for analysis• Easy to carry out

• Large sample volumes would be hard to quantitatively analyze LOD without painstaking sample prep

Gas Chromatography3 • Can be paired with tandem MS

• Lower concentrations of single analyte can be measured

• Lower limit of detection compared to HPLC

• Limit capability for compounds with low volatility

• Derivitization of analyte is necessary

• Apparatus is complicated and can be more expensive than HPLC

HPLC (Reverse Phase)1,5,6,7 • All groups of anionic surfactants can be analyzed

• Low volatile analyte can be determined

• Various methods of detection are available for coupling

• Costly analysis (very pure solvents)

• Expensive equipment• Produces toxic wastes

Possible Detection MethodsMethod Advantages Disadvantages

UV-Vis† • Quick• Inexpensive

• Limited usage with specific conjugated surfactants (e.g. LAS)

• AS and AES must be coupled with conjugating dyes to emit detectable wavelength

Mass Spec1 • provides specific information about MW and structure

• Specific tailoring for analyte in question

• Many options (Ion Trap, Triple Quad, TOF… etc.)

• Expensive• Many parameters

for consideration• Destruction of

sample

† Yuxiu A. et al. Soft Matter. 2011, 7, 6873.

Method of Choice: HPLC-MS

http://www.forumsci.co.il/HPLC/system.gif

Reversed Phase Column (C18) Gradient elution for lowering time of detection

Ion Trap Mass SpecAtmospheric Ionization Source with ESI

Full scan mode Fragmentations from 75 to 800 m/z

LOD – 0.00021 ug/L (1ppt = 1 ug/L)1

EquipmentColumn: LiChristopher

100 RP-18 (Merck)(9)

250mm x 2mm and 3um particle diameter

HPLC- Ion Trap MS (5)

Atmospheric pressure Chemical Ionization

Negative Ion Quadrupole Mode LCQ Fleet Ion Trap Mass

Spectrometer from ThermoScientific

Example Data(4)

ConclusionThe methods that were proposed allow not

only for the detection and presence anionic surfactants at low limits of detection that are needed for the study of anionic surfactants in the gulf, but also allow for differentiation of homologues as long as a standard comparison is present.

References (1) Olkowska, E.; Polkowska, Ż.; Namieśnik, J. Analytics of surfactants in the

environment: problems and challenges. Chem. Rev. 2011, 111, 5667-5700. ( (2) Riu, J.; Eichhorn, P.; Guerrero, J. A.; Knepper, T. P.; Barceló, D. Determination of

linear alkylbenzenesulfonates in wastewater treatment plants and coastal waters by automated solid-phase extraction followed by capillary electrophoresis–UV detection and confirmation by capillary electrophoresis–mass spectrometry. Journal of Chromatography A 2000, 889, 221-229.

(3) Alzaga, R.; Peña, A.; Ortiz, L.; Marıa Bayona, J. Determination of linear alkylbenzensulfonates in aqueous matrices by ion-pair solid-phase microextraction–in-port derivatization–gas chromatography–mass spectrometry. Journal of Chromatography A 2003, 999, 51-60.

(4) Lara-Martín, P. A.; Gómez-Parra, A.; González-Mazo, E. Simultaneous extraction and determination of anionic surfactants in waters and sediments. Journal of Chromatography A 2006, 1114, 205-210.

(5) Petrovic, M. Determination of anionic and nonionic surfactants, their degradation products, and endocrine-disrupting compounds in sewage sludge by liquid chromatography/mass spectrometry. Anal. Chem. 2000, 72, 4560.

(6) Poppe, A. Negative-ion mass spectrometry. X. A spurious [CH5]- ion: problems with negative chemical-ionization quadrupole instrument. Org. Mass Spectrom. 1986, 21, 59.

(7) Boiani, J. Spectator ion indirect photometric detection of aliphatic anionic surfactants separated by reverse-phase high-performance liquid chromatography. Anal. Chem. 1987, 59, 2583.

(8) An, Y.; An, Y. Disassembly-driven colorimetric and fluorescent sensor for anionic surfactants in water based on a conjugated polyelectrolyte/dye complex. Soft matter 2011, 7, 6873.

(9) LiChrospher® 100 RP-18 and RP-18 Endcapped | Merck Chemicals International http://www.merck-chemicals.com/lichrospher-100-rp-18-and-rp-18-endcapped/c_DMOb.s1LSAoAAAEWsOAfVhTl (accessed 11/11/2011, 2011).