Investigating the potential of high-performance liquid chromatography with atmospheric pressure chemical ionization-mass spectrometry as an alternative method for the speciation analysis of organotin compounds

Review of measured concentrations of triphenyltin compounds in marine ecosystems and meta-analysis of their risks to humans and the environment

The state of scientific knowledge regarding analytical methods, environmental fate, ecotoxicity and ecological risk of triphenyltin (TPT) compounds in marine ecosystems as well as their exposure and health hazard to humans was reviewed. Since the 1960s, TPT compounds have been commonly applied as biocides for diverse industrial and agricultural purposes. For instance, they are used as active ingredients in antifouling systems on marine vessels and mariculture facilities, and as fungicides in agriculture. Due to their intensive use, contamination of coastal waters by TPT and its products of transformation has become a worldwide problem. The proportion of quantified TPT to total phenyltin compounds in the marine environment provides evidence that TPT is photodegradable in water and sediment but resistant to biotransformation. Concentrations of TPT in marine biota are consistently greater than concentrations in water and sediment, which implies potential of TPT to bioaccumulate. TPT is toxic to both marine plants and animals. The predicted no effect concentration (PNEC) for TPT, as determined by use of the species sensitivity distribution approach, is 0.64 ng L(-1). In some parts of the world, concentrations of TPT in seawater exceed the PNEC, indicating that TPT can pose risks to marine life. Although there is negligible risk of TPT to average human consumers, TPT has been detected in blood of Finnish people and the concentration was greater in fishermen who ate more seafood. It is, therefore, advocated to initiate regular monitoring of TPT in blood and breast milk of populations that consume greater amounts of seafood.

On-line solid-phase extraction coupled with liquid chromatography/electrospray ionization mass spectrometry for the determination of trace tributyltin and triphenyltin in water samples

On-line solid-phase extraction (SPE) for pre-concentration and sample cleanup is one strategy to reduce matrix effects and to simultaneously improve detection sensitivity in liquid chromatography/mass spectrometry (LC/MS). This paper describes an on-line SPE-LC/MS method for the determination of tributyltin (TBT) and triphenyltin (TPhT) at trace levels in water samples. The direct coupling of an on-line C18 pre-column to LC/MS was used to pre-concentrate TBT and TPhT at trace levels from waters and to remove interfering matrix effects. Pre-concentration was followed by separation of TBT and TPhT on a C18 column using a mobile phase containing 0.1% (v/v) HCOOH/5 mM HCOONH4 and methanol. While both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) can be interfaced with MS for the detection of TBT and TPhT, ESI-MS was preferred for this application. The calibration curve for the targets was linear in the concentration range 0.1-30 microg L(-1). The detection limit (signal-to-noise (S/N) ratio = 3) was 0.02 microg L(-1) when 3.0 mL of sample was enriched on the C18 pre-column. The recoveries of TBT and TPhT in spiked waters were from 81.0 to 101.9%. The reproducibilities for the analysis of the standard mixture (10 microg L(-1)) for TBT and TPhT were 13.1 and 5.0%, respectively. The developed method was an easy and fast way to analyze TBT and TPhT in water samples.

Determination and pharmacokinetics of a new diorganotin(IV) complex dibutyldi(4-chlorobenzohydroxamato)tin(IV) in rat plasma by a high performance liquid chromatographic method

Dibutyldi(4-chlorobenzohydroxamato)tin(IV) is a new diorganotin(IV) arylhydroxamate complex with 4-chloro-benzohydroxamic acid as ligand which shows high in vivo and in vitro antitumor activity. A high performance liquid chromatographic (HPLC) method using a Diamonsil ODS column was first validated in the pharmacokinetic studies in rat plasma. The plasma was deproteinized with methanol that contained acetanilide as the internal standard. The mobile phase was a mixture of methanol and 0.5% trifluoroacetic acid (TFA) in water (30:70) (pH 3.0). The detection wavelength was set at 238 nm. A linear curve over the concentration range 0.1-25 microg/ml (r = 0.9992) was obtained. The method was used to determine the concentration-time profiles for dibutyldi(4-chlorobenzohydroxamato)tin(IV) in the plasma after a single intravenous dose of 2, 5, and 12 mg/kg to rats. The pharmacokinetics parameter calculations and modeling were carried out using the 3p97 pharmacokinetics software. A nonlinear pharmacokinetics was found in rats at doses from 2 to 12 mg/kg. The results showed that the concentration-time curves of dibutyldi(4-chlorobenzohydroxamato)-tin(IV) in rat plasma could be fitted to two-compartment model.

Ultraviolet degradation of methyltins: elucidating the mechanism by identification of a detected new intermediary product and investigating the kinetics at various environmental conditions

The photodegradation of methyltins, as environmental pollutants, has scarcely been studied so far because of the shortage of rapid and sensitive speciation methods, even though they have very simple structures. The photodegradation of monomethyltin trichloride (MMT), dimethyltin dichloride (DMT) and trimethyltin chloride (TMT) was studied with our new developed HPLC-FPD hyphenated system, which enables rapid and sensitive detection of methyltins. The half-life times and kinetic rate constants of their degradation at different pH were calculated. The results suggest that MMT, DMT and TMT can be degraded under the UV irradiation rapidly at different pH, with a degradation rate sequence of TMT<DMT<MMT. An unknown intermediary product, which is more stable and has higher concentration at pH 8 for MMT and DMT, of methyltin photodegradation was detected for the first time. This unknown intermediary product was identified as methyloltin with electrospray mass spectrometry, and the possible mechanism was proposed based on the intermediary product. The effects of some environmental parameters such as salinity and humic acid on the degradation rate of methyltins were also investigated. Results suggest that salinity and humic acid have strong effect on their degradation, especially for TMT, which was almost never degraded in the solutions containing NaCl and humic acid.

Determination of tributyltin and 4-hydroxybutyldibutyltin chlorides in seawater by liquid chromatography with atmospheric pressure chemical ionization-mass spectrometry

A liquid chromatographic method is described for the simultaneous determination of tributyltin (TBT) and the hydroxylated intermediate 4-hydroxybutyldibutyltin (OHBuDBT). Separation was achieved in reverse phase mode on a cyanopropyl-bonded silica column under a gradient elution. Various organic solvents and additives were tested and the optimum composition of the mobile phase contained methanol, water, formic acid and tropolone as a complexing agent. Butyltin compounds were detected with an ion trap mass spectrometer interfaced to a liquid chromatograph with an atmospheric pressure chemical ionization source (LC-APCI-MS). Identification and fragmentation pattern of OHBuDBT chloride in full scan MS and MS/MS are reported for the first time using LC-APCI-MS. Gas chromatography-mass spectrometry (GC-MS) spectrum of the same compound is also reported for the first time for comparison purpose. This method allowed limits of detection (LOD) of 35 and 26 ng mL(-1) for TBT and OHBuDBT, respectively, based on successive injections of 10 microL of blank seawater extract. A liquid-liquid extraction procedure using n-hexane-ethyl acetate was developed for the simultaneous analysis of TBT and OHBuDBT chlorides in natural seawater and allowed average recoveries from 72 to 96% for the two compounds at three different spiking levels.

Preparation, preservation and application of pure isotope-enriched phenyltin species

A method combining liquid/liquid extraction and chromatographic fractionation has been developed for the preparation of pure monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TPhT), synthesized from isotope-enriched Sn metal using phenylation of SnI(4) in diethylether (DEE) followed by quenching with HBr and water. After two successive extractions of the aqueous HBr phase with DEE, >99% of both DPhT and TPhT was recovered in the combined DEE phase and 94% of the MPhT remained in the aqueous phase. The MPhT in the aqueous phase was extracted into dichloromethane. The organic phases were vaporized and the PhTs were redissolved in MeOH/water/acetic acid/sodium acetate (59/30/6/8, v/v/v/w), which was also used as storing solution. Aliquots of the two solutions containing either DPhT and TPhT or MPhT were injected into a silica-based C(18) column for isolating and purifying single species. The yields of pure MPhT, DPhT, and TPhT, each synthesized from isotope-enriched (118)Sn metal, (122)Sn metal, and (124)Sn metal, were better than 99%. After chromatographic separation, the single phenyltin compounds were mixed to prepare a spike for multiple-isotope species-specific isotope dilution (MI-SSID). MI-SSID was successfully used to determine phenyltin compounds in the certified reference material, mussel tissue BCR CRM-477. At -20 degrees C, all of the fractionated phenyltin species were stable in the storage solution for at least 197 days. When these standards were stored at 4 degrees C or 22 degrees C, 4-6% of the DPhT and TPhT degraded within 27 days. The degradation of DPhT and TPhT increased with the ionic strength and acidity of the storage solution.

Structural Analysis of Ionic Organotin(IV) Compounds Using Electrospray Tandem Mass Spectrometry

A novel electrospray ionization (ESI) mass spectrometric approach for the structure elucidation of ionic organotin(IV) compounds or complexes with weakly bonded ligands as for example monodentate carboxylates or sulfonates is proposed using both positive-ion and negative-ion ESI tandem mass spectra. The ionization mechanism of organotin(IV) compounds involves the cleavage of the most labile bond with an ionic character yielding two complementary ions, [Cat]+ and [An]-. Positively charged species containing tin atom, [Cat]+, are analyzed in the positive-ion mode and negatively charged species without the tin atom, [An]-, in the negative-ion mode. Fragmentation patterns of [C24H29N2Sn]+, [C21H22NSn]+, and [C17H30NSn]+ ions are proposed based on the detailed interpretation of MSn spectra, which is simplified by an easy recognition of characteristic tin isotopic clusters in particular fragment ions. Proposed fragmentation mechanisms are supported by comparison with MSn spectra of deuterium-labeled analogues. The applicability of this method is illustrated on two sets of organotin(IV) compounds, including seven [2,6-bis(dimethylaminomethyl)phenyl]diphenyltin(IV) derivatives with small inorganic counteranions X (Br, NO3, SCN, BF4, SeCN, CN, PF6), six organotin(IV) complexes containing two C,N-chelating ligands with azo dyes, and the identification of unknown hydrolysis products.

Speciation of organotin compounds by capillary electrophoresis: comparison of aqueous and mixed organic-aqueous systems

A capillary electrophoresis method with direct ultraviolet detection was developed for the analysis of organotin species. Despite the fact that direct detection of organotin compounds by ultraviolet absorption is difficult because most organotins possess poor chromophoric properties, the application of low wavelength (lambda = 200 nm) and mixed organic-aqueous media enabled a significant enhancement in sensitivity. A mixed organic-aqueous system (10% methanol/40% acetonitrile/50% H2O) containing acetic acid and tetrabutylammonium perchlorate formed the basis for rapid, efficient and sensitive determinations of organotin cations such as tripropyltin, tributyltin, triphenyltin and diphenyltin. The concentration limits of detection (LOD) for the four organotin compounds were in the range of 0.4-14 microM, comparable to that obtained with the most sensitive indirect UV method reported until now, and took advantage of a stable baseline, a symmetric peak shape and an absence of disturbing system peaks. The relative standard deviations (n = 7) for the relative peak time and peak area were 0.44-0.77 and 4.8-5.8%, respectively. In addition to sensitivity enhancements, the use of organic-aqueous systems instead of pure aqueous media resulted in improved selectivity and efficiency of separations.

Liquid chromatography-mass spectrometry and strategies for trace-level analysis of polar organic pollutants

Liquid chromatography-mass spectrometry using atmospheric pressure ionization (LC-API-MS) has drastically changed the analytical methods used to detect polar pollutants in water. The present status of application of this technique to organic water constituents is reviewed. The selection of the appropriate LC conditions, whether reversed-phase liquid chromatography, ion-pair chromatography, capillary electrophoresis or ion chromatography, and of the most sensitive ionization mode, electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI), depends upon the polarity and acidity of the analytes. Strongly acidic compounds such as aromatic sulfonates, sulfonated dyes, haloacetic acids, linear alkylbenzene sulfonates, aliphatic sulfonates and sulfates and complexing agents, weakly acidic compounds such as carboxylates and phenols, neutral compound classes, namely alkylphenol ethoxylates, alcohol ethoxylates and polycyclic aromatic hydrocarbons and the basic toxins, quaternary ammonium compounds and organometallic compounds are considered. The selection of the mass spectrometer depends upon the analytical task: triple-quadrupole mass spectrometers are highly suited for sensitive quantitation and for qualitative analyses, ion traps are especially suited for structure elucidation, whereas time-of-flight mass spectrometers and quadrupole time-of-flight mass spectrometers with their higher mass resolution are ideal for the determination of molecular formulas of unknown compounds and for screening purposes. While large steps have already been made, future efforts with respect to water analysis may be directed at fine-tuning the methodical arsenal for increased sensitivity and selectivity and to extend LC-MS application to transformation products.

The potential of organic (electrospray- and atmospheric pressure chemical ionisation) mass spectrometric techniques coupled to liquid-phase separation for speciation analysis

The use of mass spectrometry based on atmospheric pressure ionisation techniques (atmospheric pressure chemical ionisation, APCI, and electrospray ionisation, ESI) for speciation analysis is reviewed with emphasis on the literature published in and after 1999. This report accounts for the increasing interest that atmospheric pressure ionisation techniques, and in particular ESI, have found in the past years for qualitative and quantitative speciation analysis. In contrast to element-selective detectors, organic mass spectrometric techniques provide information on the intact metal species which can be used for the identification of unknown species (particularly with MS-MS detection) or the confirmation of the actual presence of species in a given sample. Due to the complexity of real samples, it is inevitable in all but the simplest cases to couple atmospheric pressure MS detection to a separation technique. Separation in the liquid phase (capillary electrophoresis or liquid chromatography in reversed phase, ion chromatographic or size-exclusion mode) is particularly suitable since the available techniques cover a very wide range of analyte polarities and molecular mass. Moreover, derivatisation can normally be avoided in liquid-phase separation. Particularly in complex environmental or biological samples, separation in one dimension is not sufficient for obtaining adequate resolution for all relevant species. In this case, multi-dimensional separation, based on orthogonal separation techniques, has proven successful. ESI-MS is also often used in parallel with inductively coupled plasma MS detection. This review is structured in two parts. In the first, the fundamentals of atmospheric pressure ionisation techniques are briefly reviewed. The second part of the review discusses recent applications including redox species, use of ESI-MS for structural elucidation of metal complexes, characterisation and quantification of small organometallic species with relevance to environment, health and food. Particular attention is given to the characterisation of biomolecules and metalloproteins (metallothioneins and phytochelatins) and to the investigation of the interaction of metals and biomolecules. Particularly in the latter field, ESI-MS is the ideal technique due to the softness of the ionisation process which allows to assume that the detected gas-phase ions are a true representation of the ions or ion-biomolecule complexes prevalent in solution. It is particularly this field, important to biochemistry, physiology and medical chemistry, where we can expect significant developments also in the future.

Determination of triorganotin species in water samples by liquid chromatography-electrospray-mass spectrometry

Liquid chromatography coupled to electrospray-mass spectrometry (LC-ES-MS) with positive ion detection was evaluated for the determination of tributyltin and triphenyltin in water samples using tripropyltin as internal standard. The separation was performed in the isocratic mode on a silica-based C18 column with a mobile phase containing 0.02% trifluoroacetic acid in acetonitrile-water (50:50, v/v). The optimum LC-ES-MS conditions were established and quantification was performed on the basis of the [M]+ ions. Limits of detection for standard solutions were 100 and 200 pg Sn injected for triphenyltin and tributyltin, respectively, and good reproducibility was observed. Solid-phase extraction was carried out on C18 cartridges to preconcentrate the analytes from natural water samples, with recoveries ranging from 80 to 110%. Limits of detection for SPE-LC-ES-MS were in the range of low ng l(-1), which demonstrates the suitability of the method for environmental samples.

Atmospheric pressure chemical ionization mass spectrometric and visible spectrophotometric studies of copper(I) and copper(II) complexes with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

Complexes of copper(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) formed in aqueous methanol in a wide range of pH (from acidic to alkaline) as well as copper(I)-5-Br-PADAP species formed in methanolic solutions were investigated by spectrophotometry and mass spectrometry. Pseudomolecular and fragment ions created in the atmospheric pressure chemical ionization (APCI) source confirmed the molecular masses of the complexes existing in the solvents and their structures. The structure of the Cu(II) complex with 5-Br-PADAP formed in acidic medium was proposed as CuR(R - H) (where R is the undissociated molecule of the reagent). The binding sites of the two bound reagent molecules were different: in one of them the oxygen atom of the dissociated phenolic group and the nitrogen atom from the azo (-N=N-) group took part in complex formation, whereas in the other only nitrogen atoms from the pyridyl ring and azo group were involved. The complex was stable and could not be reduced to Cu(I) species by use of standard reducing agents (ascorbic acid, hydroxylamine). In alkaline solutions the complex tended to polymerize and precipitated in media containing less than 80% of methanol. The copper(I)-5-Br-PADAP complex was extremely unstable and could be obtained (as a mixture with Cu(II) species) in media free of water or oxygen. For this complex, CuR(2) was proposed as the most probable structure. According to this proposal copper(I) reacted exclusively with nitrogen-containing binding sites and the undissociated phenolic group was not engaged in complex formation. In this system Cu(I)/Cu(II) electron transfer is very rapid, accelerated by a polar environment, e.g. in the presence of water molecules or dissolved oxygen.

Current awareness

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (6 Weeks journals - Search completed at 7th. June 2000)