LC-MS Applications for Environmental Analysis

Simultaneous Determination of Oil

Dispersants in Seawater and Crude Oil by

LC and Tandem MS

Cesar E. Ramirez,

1,2

Sudha Rani Batchu,

and Piero R. Gardinali

1,2

Department of Chemistry and Biochemistry, Florida International University, Miami, FL

Southeast Environmental Research Center, Florida International University, Miami, FL

Application Note 586

Key Words

Environmental analysis, oil spill, Corexit

, Deepwater Horizon, Gulf of

Mexico, seawater

Goal

To develop a liquid chromatography with tandem mass spectrometry

(LC-MS/MS) method capable of simultaneously detecting and quantifying

DOSS and 2-butoxyethanol in a single chromatographic run without

preconcentration or cleanup steps. This method can serve as a tool to

track Corexit

after its usage in oil spills and determine if Corexit EC9527A

was employed.

Introduction

On April 20, 2010 the

Deepwater Horizon

(MC-252) oil

platform caught fire and sank in the Gulf of Mexico,

creating a large release of oil and gas from the riser pipe

and uncapped well head. Efforts to contain and clean up

the spill included heavy use of oil dispersants both above

and below the surface. The dispersants Corexit EC9500A

and Corexit EC9527A (formerly Corexit 9500 and

Corexit 9527, produced by Nalco, Naperville, IL) were

approved for use in the Gulf of Mexico oil spill by the

U.S. Environmental Protection Agency (EPA).

At least

1.8 million gallons of dispersants were applied during the

response and recovery process.

Corexit EC9500A was the

main product used in that effort.

Figure 1. Satellite view of oil slick in the Gulf of Mexico on May 24,

2010

According to available material safety data sheets, the

components of Corexit EC9500A are dioctyl

sulfosuccinate sodium salt (DOSS) (10–30% w/w),

hydrotreated light petroleum distillates (10–30% w/w),

and propylene glycol (1–5% w/w).

Corexit EC9527A

contains mainly 2-butoxyethanol (30–60% w/w) and

DOSS (10–30% w/w).

These mixtures of solvents and

surfactants reduce the interfacial tension between water

and oil, facilitating the breakup of the oil into tiny droplets

that are easily dispersed by wind and wave action.

The

structures of 2-butoxyethanol and DOSS are shown in

Figure 2.

Figure 2. 2-butoxyethanol and dioctyl sulfosuccinate (DOSS), the

main components of Corexit formulations

Although Corexit formulations have been found to have

only low-to-moderate toxicity to most aquatic species,

tracking these formulations in the environment is still a

priority because much of their fate is still not well

understood.

The large amounts of Corexit used in the

Gulf of Mexico gave rise to the need for an analytical

method capable of detecting its presence in seawater even

when large dilution factors are expected.

2-butoxyethanol is of interest because it is found only in

Corexit EC9527A. Despite the fact that a variety of other

sources can contribute to its presence in coastal areas,

chronic background environmental concentrations of

2-butoxyethanol are expected to be low because of its

high miscibility in water and its fast biodegradation

(half-life of 1–4 weeks) in environmental waters.

2-Butoxyethanol

Dioctyl sulfosuccinate

Image from NASA/GSFC, MODIS Rapid Response

and demis.nl