Determination of Organometal Contaminants Using PTV GC–ICP-MS

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Researchers from the Université de Pau et des Pays de l’Adour, in France, have developed a large volume injection method using a programmed temperature vaporization (PTV) injector for the simultaneous determination of mercury (Hg), tin (Sn), and lead (Pb) at ultra-trace levels in natural waters using gas chromatography–inductively coupled plasma mass spectrometry (GC–ICP-MS) (1).

Mercury, tin, and lead are among the most problematic organometallic species. Their high toxicity even at trace levels and ability to bioaccumulate and bioamplify along food chains makes them dangerous when they are present in the environment. Mercury in particular is widespread in aquatic ecosystems, and has both natural and anthropogenic origins as inorganic mercury (IHg) will form monomethylmercury (MMHg) through a biomethylation process, which will then bioamplify along food chains (2,3). MMHg is a potent neurotoxin (5), whereas the toxological role of IHg is still under discussion (6).

On the other hand, tin is a common contaminant in water environments because of its historic use in anti-fouling paints, pesticide formulations, wood preservatives, and polymer additives. As a powerful biocide, organotin compounds were regularly used on marine vessels until their ban in 2008 (6). However, their sedimentary legacy still remains, with dredging activities causing issues to resurface.

Similar to tin, lead contamination stems from human activity. The use of tetraethyllead as an anti-knocking additive in gasoline was a particularly common source until it was phased out in the mid-1970s (7). However, lead continues to find its way into the environment, from runoff waters from human activities such as mineral extraction and processing, smelting and refining, power generation, battery plants, and waste disposal or incineration (8). Organolead compounds are neurotoxic in nature (9).

With ever more stringent environmental quality standards (EQS) being set, the challenge for analytical chemists to detect trace levels of compounds in water environments has become greater. In order to monitor and investigate the fate of these compounds-and their many forms-in the environment, increasingly sensitive analytical methods are required. To address this, researchers sought to develop an on-line preconcentration method using a PTV inlet in combination with GC–ICP-MS to simultaneously determine the amount of Hg, Sn, and Pb in natural water.

The reported method was found to be very sensitive and, following optimization of the PTV parameters, absolute and methodological detection limits were found to be in the pg/L level, which is below EU requirements. Using unpolluted river water samples, researchers tested the applicability of the method with all targeted compounds being quantified with very good precisions.

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