Cracking the problem: Organo-phosphate flame retardants measured in wild bird eggs by LC/MS

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  • Published: Jan 23, 2012
  • Channels: HPLC
thumbnail image: Cracking the problem: Organo-phosphate flame retardants measured in wild bird eggs by LC/MS


Organo-phosphate ester flame retardants

The polybrominated flame retardants have been receiving a great deal of attention in research labs around the world due to their propensity to escape into the environment and their subsequent climb through the food chain. But there is a second class of flame retardants with an annual consumption about twice as large that also requires careful monitoring.

The organo-phosphate esters (OPs) have been used to reduce flammability since the 1960s, protecting plastic goods, solvents, electronics and other types of goods. They work by forming a protective layer of char which resists high temperatures and protects the underlying product from attack by oxygen and radiant heat, so inhibiting fire formation and increasing escape time.

Despite their widespread application worldwide, there is limited information about their environmental and health impacts. A few research groups have examined the accumulation of OPs in air, dust, water and sediments but there have been even less studies of their bioaccumulation, which could have important implications for human exposure. OPs have been found in human tissues and body fluids but their health effects are not clear.

In order to expand the inadequate knowledge of the distribution of OPs in the animal kingdom, a team of scientists based at Carleton University, Ottawa, Canada has devised a method based on LC/MS to measure the levels of OPs in lipid-rich samples. Robert Letcher, Da Chen and Shaogang Chu used chicken eggs to develop the technique before applying it to the analysis of herring gull eggs.


Interferences from apparatus used in egg extraction

The chicken eggs were spiked with deuterated tributyl phosphate as internal standard and the lipids were extracted by accelerated solvent extraction followed by solid-phase extraction. The lipids are where the OPs are stored in biological samples. The extracts were spiked with a mixture of 12 OPs for method optimisation.

The extract was injected onto a phenyl column and the OPs were separated with a gradient of methanol in aqueous formic acid before transfer to the mass spectrometer for electrospray ionisation in positive-ion mode. They were detected by selected ion monitoring using the most abundant precursor ion for each individual compound, which happened to be the protonated molecule.

The chromatograms showed adequate separation between the eluting compounds to allow their measurement without interference from each other. There were also minimal effects from the egg matrix but other interferences were found to have an influence.

When blank samples containing no OPs were analysed, measurable levels of three analytes were detected. Tris(2-chloroisopropyl) phosphate (TCPP), tris(2-chloroethyl) phosphate (TCEP) and tributyl phosphate (TBP) were all present at 0.15, 0.10 and 0.08 ng/g, respectively. The same problems had been reported for the analysis of OPs in water and sediments.

These levels are significant when compared with the amounts that were found in eggs from wild birds, so the team had to isolate their source. Every commercial silica gel and Florisil absorbent that they tested "contained considerable OP background contamination" and the commercial SPE cartridges contained TCPP and TBP. So, contamination was eliminated by avoiding plastic equipment and using solvent-rinsed glass SPE cartridges and pre-rinsed SPE silica gel.

Under these conditions, recoveries were 8-104% for 10 OPs but were lower for the two brominated analytes. The detection and quantitation limits were 0.01-0.12 and 0.06-0.20 ng/g, respectively.


Herring gull eggs widely contaminated with fire retardants

The optimised LC/MS technique was applied to the contents of 13 herring gull eggs collected from Channel-Shelter Island in Lake Huron, Canada as part of the Great Lakes Herring Gull Monitoring Program of Environment Canada.

Three OPs were consistently detected: TCPP, TCEP and tris(2-butoxyethyl) phosphate at up to 4.1, 0.6 and 2.2 ng/g respectively. Two other OPs, triphenyl phosphate and tris(1,3-dichloro-2-propyl) phosphate, were found in some samples at levels just above their detection limits.

These figures might be regarded as baseline levels, says Letcher, because the initial levels of the parent OPs could be reduced by metabolic degradation to the respective mono- and diesters. So, the actual concentrations in eggs could be greater, emphasising the need for further investigation into the bioavailability of OPs in gulls in particular and the food web in general.

This method is fast, accurate and sensitive and is particularly suitable for measuring OPs in archived and valuable wildlife samples because only 1 g of egg homogenate is needed for successful analysis. It should help to increase our knowledge of the distribution of OPs in the wild.



The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

  

Phosphate ester flame retardants have been measured in herring gull eggs by a fast and accurate LC/MS method which requires small sample sizes, an important aspect for wildlife screening

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