Speciation of trimethyllead in rainwater by gas chromatography-mass spectrometry after ethylation with sodium tetraethylborate comparison with other alkylation methods

Multielemental speciation analysis of organometallic compounds of mercury, lead and tin in natural water samples by headspace-solid phase microextraction followed by gas chromatography–mass spectrometry

The development of a simple and rapid multielemental speciation method is described with the ultimate goal to simultaneously determine various organometallic compounds of mercury, lead and tin (inorganic mercury, methylmercury, trimethyllead, triethyllead, monobutyl-, dibutyl- and tributyltin) in natural water samples. The analytical method consists on the ethylation with NaBEt4, simultaneous headspace-solid phase microextraction (HS-SPME) of the derivatives and final gas chromatographic-mass spectrometric (GC-MS) analysis. After optimization of important process parameters, like SPME fiber coating, extraction time and extraction temperature, the analytical characteristics were evaluated. Detection limits in the low ng l(-1) level, linearity over three orders of magnitude and repeatability in the range of 3-20% were achieved for all compounds under study. The accuracy of the method in terms of average percentage recovery of the compounds in spiked river water and seawater samples was better than 90%. Finally, application of the proposed method to real natural aqueous samples enabled the simultaneous determination of all the compounds under study in seawater samples obtained from the marina area of Gijón (Asturias, Spain).

Speciation of inorganic lead and ionic alkyllead compounds by GC/MS in prescreened rainwaters

A simple and novel screening method for lead compounds in environmental waters is proposed. The analytes, in an acetic medium, are sorbed on a C60 fullerene column as diethyldithiocarbamate complexes and subsequently eluted with isobutyl methyl ketone (IBMK), the lead being determined by flame atomic absorption spectrometry. The screening method acts as filter and indicates whether the target analytes are present above or below the detection limit of the method (0.5 ng/mL), giving no false positives. Positive samples were speciated by GC/MS, using a flow system similar to that of the screening method. Lead(II) and ionic di- and trialkyllead are derivatized with a Grignard reagent. Both methods use similar chemical and flow variables except for the eluent, IBMK in the screening method and n-hexane in the speciation method. The GC/MS speciation method is very sensitive; it exhibits a linear range of 0.02-5 ng/mL, and detection limits of 1-4 ng/L are achieved. Also, its repeatibility, as RSD, is less than 6%. The method was applied to the speciation of Pb2+ and di- and trialkyllead in positive prescreened rainwater samples from three different urban areas.

Analytical potential of fullerene as adsorbent for organic and organometallic compounds from aqueous solutions

In this work, the analytical potential of C60 fullerene as a sorbent for organic and organometallic compounds from aqueous solutions was studied for the first time. Fullerene adsorbs many types of organic substances (e.g., N-methylcarbamates, phenols, polycyclic aromatic hydrocarbons, amines) with efficiencies that depend on the nature of the compound concerned and never exceed 60%. Conventional sorbents such as XAD-2 or polyurethane foam are more efficient than C60 for this purpose. Organometallic compounds (viz. metalocenes and organoleads) are quantitatively adsorbed on C60 via the formation of neutral complexes or chelates; the adsorption constant is dramatically increased by the use of classical reagents such as pyrrolidinedithiocarbamate or diethyldithiocarbamate. A complementary comparative study on the adsorption of organometallic complexes on RP-C18 and silica gel 100, among others, showed C60 to be superior as sorbent. All experiments in this work were carried out by using continuous flow configurations and gas chromatography-atomic absorption spectrometry techniques.

Electrospray mass spectrometry of trimethyllead and triethyllead with in-tube solid phase microextraction sample introduction

A study of positive ionization electrospray mass spectrometry (ES-MS) was performed on trimethyllead (TML) and triethyllead (TEL). The system consisted of in-tube solid phase microextraction (SPME) coupled directly to an electrospray mass spectrometer. Fragmentation patterns of compounds were observed by applying different fragmentation voltages. High voltages produced sufficient fragmentation to elucidate the dissociation of the trialkyllead compounds. Electrospray mass spectrometry has been shown to be a suitable detection system for organolead speciation. Applying fragmentation energy programming, it might be possible to obtain in parallel the molecular and atomic signals of lead compounds. Copyright 1999 John Wiley & Sons, Ltd.