Emerald Coast Surfrider takes the helm on local Gulf DOS water testing

Tony D'eramo, Emerald Coast Surfrider board member and marine biologist takes water samples on July 10. Photo courtesy Michael Sturdivant

Organization hopes to enlighten on water health, seeks public support

With concerns of the oil and dispersant’s effects reaching the Florida Panhandle shores, both surfers and beach goers are anxious to know if it is safe to enter the Gulf of Mexico.

Local surfing organization, Emerald Coast Surfrider Foundation started going the extra mile on July 10 to acquire a specific testing called DOS (details below).

The DOS test checks for the chemical compounds present in dispersant and can serve as an indicator of its presence. As of yet, no federal Environmental Protection Agency tests for DOS have been reported for Florida.

“We want to surf and know if the water is safe,” Michael Sturdivant said as he explained the motivation behind Surfrider to use the organization’s limited funds to do this specific testing.

“The earlier tests for dispersants had been looking for alcohol and ethanol associated with dispersants but according to the labs we spoke with, these would rarely show in any test as they evaporate very quickly” Mike said in referring to the EPA’s tests.

“I am not completely certain that these tests will be more accurate, but with multiple reports of illness in our surfing community, we must move forward and at least try to provide this vital health information. We asked the DEP, state, and county to do this over a month ago and they have been very slow to respond,” Sturdivant said.

Surfrider took samples from Okaloosa Island Pier, Miramar Beach at Pompano Joes, Blue Mountain Beach and Seaside on July 10. It takes two weeks for the results.

“We would like to test for other substances like oil, vanadium, benzene, and others, but our budget is very small, Sturdivant continued.

Each test cost $350.00, and with four tests in one day, Emerald Coast Surfrider will soon deplete their organization’s funds, and  are seeking contributions to help offset the costs of the tests.

Emerald Coast Surfrider is a local non-profit organization and is funded entirely by donations. Anyone interested in helping out can contact Surfrider at http://www.surfrideremeraldcoast.org/

Links to local water testing results from EPA and DEP:

http://www.epa.gov/bpspill/water.html

http://www.dep.state.fl.us/deepwaterhorizon/water.htm#walton


The lab Surfrider is using is located in Kelso Washington. It is the same lab that is processing DOS samples for the EPA.  This lab also handled much of the testing for the Exxon Valdez disaster (Columbia Analytical Services, Inc.)

Analytical Testing for Corexit Dispersants Used in the Gulf Spill by www.caslab.com

The analysis of various sample matrices including seawater, sediment, and tissue to determine concentrations of Corexit dispersants used in the Gulf spill requires the use of one or more of the components in the dispersant as a tracer. The primary active ingredient (i.e., the primary surfactant) in the Corexit products is Dioctyl Sulfosuccinate Sodium Salt (DOS). The other primary ingredients function as carriers until the dispersant is applied. At that point, the lighter fractions evaporate and the water soluble component(s) dissolve in the seawater and rapidly dissipate.

As indicated in the structure shown below, DOS has two R groups, each an identical branched octyl, or bis(2-ethylhexyl) group. The R groups give the compound its ability to disperse non-polar compounds (e.g., components of the Gulf oil from the Deepwater Horizon well). The other portions of the molecule are two ester linkages with a common carbon between them (linking one R-ester group with the other R´-ester group). Another key to the behavior of the surfactant is the sulfonic acid group that is substituted on the common carbon linking the two ester groups.

Sulfonic acid is a strong acid, readily dissociable in water. The compound is added to the Corexit dispersants as the sodium salt, so once it is released into an aqueous medium, it ionizes to leave a fully charged sulfonate. This, with help from the carbonyls in the ester linkages providing hydrogen bonds with water, enables the molecule to be miscible with water when carrying petroleum hydrocarbon (i.e., bonded via partial charges with the R groups).

The full charge overcomes the resistance of water repelling the non-polar hydrocarbon material. Thus, the effectiveness of the surfactant is realized as the complex specie dissolves.

However, much of the dispersant remains affixed to relatively large fragments of petroleum material (evidenced by preliminary analytical testing at Columbia Analytical Services, Inc.) and drifts with the material until washing ashore, sinking, biodegrading, or encountering some other fate.

Analytical Challenge:
The key to the analysis is twofold:
Separation (i.e., extraction) from seawater, oil, sediment, and possibly tissue is the challenge. (Note: The analysis for DOS in tissue might not be applicable. Instead, metabolites of DOS may end up being the targeted species if data shows DOS is readily metabolized by fish, mollusks, crustaceans, benthic organisms, mammals, etc.). Analysis by Liquid Chromatography w/Tandem Mass Spectrometry (LC/MS/ MS)

Chemical separations to isolate DOS from the sample matrix must be performed prior to determination by LC/MS/MS. The determination in seawater is relatively easy when taking advantage of the anionic character of DOS. Anion exchange resin is used to separate DOS from the salt matrix prior to instrumental analysis, followed by elution using an appropriate solvent.

The analysis of sediment and tissue requires a preliminary solvent extraction followed by separation of DOS via ion exchange treatment. For sediment, DOS must be manipulated into a relatively polar solvent for the ion exchange treatment to function effectively. If relatively large amounts of petroleum material are present, the chemical separation is more complex, as the petroleum:DOS specie requires complete dissolution to assure quantitative results. Thus, DOS must be taken from a non-polar solvent to a polar solvent prior to ion exchange treatment.

Determinations of DOS in tissue introduce at least two more significant considerations. The first is whether a direct solvent extraction of homogenized tissue will yield quantitative removal of DOS. Perhaps a mild alkaline digestion will be necessary to allow efficient solvent extraction.

The other, bigger, question is related to the fate of DOS once ingested. The compound is likely metabolized after ingestion, thus, the metabolites become the target compounds of the analysis (i.e.,new tracers for Corexit dispersants). No work has been done to date for DOS in tissue at Columbia Analytical Services, Inc., nor has a literature search revealed any significant investigation in this area, to date. Further research is required to identify the fate of DOS after ingestion by various organisms.

Once DOS has been isolated in an appropriate solvent, the analysis is performed by LC/MS/MS. Due to superior selectivity and sensitivity, coupled with the fact that DOS lends itself best to liquid chromatography, LC/MS/MS is the most appropriate choice of instrumentation. The tandem mass spectrometers allow a determination relatively free of matrix interferences. The initial electrospray ionization (“soft” ionization) simply removes a proton from DOS to produce a parent ion and is followed by a second ionization that   produces a daughter ion. The combination of the two ionizations and subsequent mass filtering serves to remove interference by selectively allowing only ions specific to the target compound to reach the detector. The result is high selectivity, as well as high signal: background.

A typical reporting limit for seawater is 0.1 ng/ml.
Nomenclature:
Abbreviation = DOS
Dioctyl Sulfosuccinate Sodium Salt
Bis(2-ethylhexyl)sulfosuccinate Sodium Salt
Di(2-ehthylhexyl) Sodium Sulfosuccinate
Docusate Sodium
Structure:
Solubility:
Soluble in water.
Freely soluble in alcohol (MeOH, EtOH), glycerol, carbontetrachloride, acetone, xylene.
Very soluble in combinations of water and water-miscible organic solvents.
Stable in acid and neutral solutions.
Hydrolysis occurs under alkaline conditions.
Uses:
Cosmetics
Pharmaceuticals
Foods
Active Surfactant in Corexit 9500 and Corexit EC9527A

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