Isaac Rodriguez Pereiro

Speciation Analysis for Organotin Compounds in Biomaterials after Integrated Dissolution, Extraction, and Derivatization in a Focused Microwave Field

Hydrolysis with acetic acid carried out in a low-power focused microwave field in the presence of sodium tetraethylborate and nonane is shown to shorten the sample preparation time for gas chromatographic determination of organotin compounds in biological materials. After a 3-min reaction time, ethyl derivatives of mono-, di-, and tributyltin, and triphenyltin are quantitatively (>95%) found in the supernatant organic phase that is injected onto a capillary GC column. Two rapid one-step analytical procedures, using flame photometric and atomic emission detection, respectively, were developed on this basis and validated by analyzing the NIES11 certified reference fish tissue.

Elemental speciation and coupled techniques—towards faster and reliable analyses

Various procedures for accelerated and simplified sample preparation and analyte introduction into a plasma source spectrometer are developed and evaluated for speciation analysis of organometallic compounds using the example of alkyl and arylmetals and cyanocobalamin analogues. The topics discussed include microwave-assisted chemistry in three phase systems (solid–liquid–liquid and solid–liquid–gas), purge and capillary trap sample preparation and fast chromatography (multicapillary GC and microparticulate stationary phase reversed-phase LC) as a sample introduction technique for MIP-AES and ICP-MS, respectively. Integration of the sample preparation and of the chromatographic separation steps into a single instrumental module (as an accessory for atomic spectrometry) is evaluated. Attention is given to the reliability of information obtained in the case when standards are not available and when the target analytes are poorly defined (speciation of Cd bound to metallothionein isoforms). The utility of a dual orthogonal approach (complementary separation and complementary detection techniques) is demonstrated.

Optimization of the coupling of multicapillary GC with ICP-MS for mercury speciation analysis in biological materials

The coupling between multicapillary gas chromatography (MCGC) and inductively coupled plasma mass spectrometry (ICP-MS) was optimized with the objective of minimizing the detection limits and time necessary for the species-selective determination of mercury compounds. The most critical parameters influencing the sensitivity were the position of the capillary inside the ICP injector, the makeup gas flow rate and the column temperature. The interface itself did not need to be heated. An absolute detection limit of 0.08 pg could be achieved and was controlled by the injection speed and the data acquisition rate of the quadrupole mass analyser. Using a previously developed automated purge-and-trap accessory, a method for the analysis of fish samples was developed and validated by the analysis of the DORM-1 and TORT-1 National Research Council of Canada (NRCC) certified reference materials. The experimental detection limit for methylmercury was 0.2 ng g –1 ; for Hg 2+ it was controlled by the reagent blank.

Determination of mercury species in fish reference materials by isothermal multicapillary gas chromatography with atomic emission detection after microwave-assisted solubilization and solvent extraction

A simple and rapid procedure for the simultaneous determination of methylmercury and Hg2+ in fish reference materials was developed. The procedure was based on a rapid (2.5 min) microwave-assisted solubilization of biomaterial with tetramethylammonium hydroxide, simultaneous quantitative ethylation–extraction of the mercury species into hexane (15 min) and flash isothermal separation (15–30 s) using a multicapillary regular column (100 cm) or a minicolumn (22 cm). The chromatographic hardware necessary for sample introduction into a microwave induced plasma was downscaled to a split injection port and a 20×20×10 cm compartment (housing the 1 m column) or a 22 cm×1 cm od thermally insulated tube (housing the minicolumn) maintained at a constant temperature and connected directly to the detector. No dilution of the GC eluent (60–120 ml min–1) with make-up gas was necessary to achieve optimum sensitivity. Detection limits (as Hg) were 0.5 pg µl–1 (20 ng g–1 dry mass) and 2 pg µl–1 (80 ng g–1 dry mass)for MeHg+ and Hg2+, respectively. The method was validated for speciation analysis for mercury in BCR 463, BCR 464 (Tuna Fish) and NRCC DORM-1 (Dogfish Mussel) certified reference materials.

Elemental Speciation Analysis by Multicapillary Gas Chromatography with Microwave-Induced Plasma Atomic Spectrometric Detection

Multicapillary column gas chromatography (MC-GC)/microwave-induced plasma atomic emission spectrometry (MIP AES) was developed for fast speciation analysis of organotin compounds in the environment. Ethylated butyltin compounds could be separated isothermally within less than 30 s (instead of ∼5-10 min) without sacrificing either the resolution or the sample capacity of conventional capillary GC with oven temperature gradient programming. Careful optimization of the pressure and temperature GC program allowed a comprehensive organotin speciation analysis including phenyltin compounds within less than 2.5 min, increasing the sample throughput 6-fold. Compatibility of MC-GC with an MIP atomic emission detector (MIP-AED) was discussed. MC-GC/MIP-AES was validated for the analysis of sediment (PACS-1 and BCR 462) and biological (NIES11) certified reference materials.

Speciation of mercury by ICP-MS after on-line capillary cryofocussing and ambient temperature multicapillary gas chromatography

An automated, small and easily mountable/demountable accessory based on a constant temperature multicapillary GC is proposed for time-resolved introduction of gaseous mercury species into an ICP-MS. The fast, narrow-band injection was achieved by cryofocussing (–80 °C) of dimethyl-, methylethyl- and diethylmercury in an 11 cm capillary housed in a steel tube prior to desorption of the species (within 3–5 s) by rapid-pulse high intensity current. The highest chromatographic resolution was achieved at ambient column temperatures; isothermal separations at higher temperatures offered increased sensitivity and speed of analysis controlled by the data acquisition rate of a quadrupole MS. The compatibility of the operating variables with the ICP ionization conditions (argon at 50–300 ml as the carrier gas) and negligible peak broadening on the column and in the ICP-MS interface allow the sensitive (limit of detection 0.15 pg) isotope-selective speciation of mercury in biological and sediment samples.

Fast Species-selective Screening for Organolead Compounds in Gasoline by Multicapillary Gas Chromatography With Microwave-induced Plasma Atomic Emission Detection

Multicapillary GC is proposed and optimized as a tool for the introduction of gasoline samples into an MIP atomic emission spectrometer for the fingerprinting and species-selective analysis for organolead additives. The coupling of multicapillary GC with MIP-AES not only allows speciation of alkyllead but is also faster than analysis for total lead in gasoline by flame AAS or ICP-AES. All five tetraalkyllead species (MenEt4–nPb,n=1–4) are baseline separated and quantified within 10 s in comparison with about 10–20 min required by conventional GC procedures. Separation is carried out in the isothermal mode but neither resolution nor sample capacity is sacrificed in comparison with conventional capillary GC with oven temperature gradient programming. The throughput reaches about 100 samples h–1. The detection limit is below 1 µg l–1 and the linearity range spans four concentration decades. The method was validated by the analysis of the NIST SRM 2715 (Lead in Fuel) reference material.

Flash Species-selective Analysis by Multicapillary Gas Chromatography with Microwave Induced Plasma Atomic Spectrometric Detection

Multicapillary column isothermal gas chromatography with element-selective detection has been shown to allow the ultra-rapid (<30 s instead of about 10 min) analysis of non-polar compounds with boiling-points of 200–300 °C, without sacrificing the resolution and efficiency of conventional capillary GC with oven temperature gradient programming. An example of speciation analysis for butyltin compounds in a PACS-1 certified reference sediment is shown.