Christopher F. Harrington

The speciation of mercury and organomercury compounds by using high-performance liquid chromatography

Abstract No previous reviews on speciation analysis by high-performance liquid chromatography (HPLC) have dealt solely with the analysis of mercury. The analytical methods are classified on the basis of the sample matrix analysed and deal with: standards and water, marine organisms, biomedical samples and sediments. The relevant technical information, column type, mobile phase, method of detection and detection limit, is presented in tabular form for each of the sample types. The majority of methods use reversed phase chromatography, usually with a buffer, organic modifier and some form of counter ion or complexing agent. Other aspects addressed in this review include sample preparation and instrumental methods of analysis. The review covers publications from 1986 to 1999.

Bacterial degradation of arsenobetaine via dimethylarsinoylacetate.

Microorganisms from Mytilus edulis (marine mussel) degraded arsenobetaine, with the formation of trimethylarsine oxide, dimethylarsinate and methylarsonate. Four bacterial isolates from these mixed-cultures were shown by HPLC/hydride generation-atomic fluorescence spectroscopy (HPLC/HG-AFS) analysis to degrade arsenobetaine to dimethylarsinate in pure culture; there was no evidence of trimethylarsine oxide formation. Two of the isolates ( Paenibacillus sp. strain 13943 and Pseudomonas sp. strain 13944) were shown by HPLC/inductively coupled plasma-mass spectrometry (HPLC/ICPMS) analysis to degrade arsenobetaine by initial cleavage of a methyl-arsenic bond to form dimethylarsinoylacetate, with subsequent cleavage of the carboxymethyl-arsenic bond to yield dimethylarsinate. Arsenobetaine biodegradation by pure cultures was biphasic, with dimethylarsinoylacetate accumulating in culture supernatants during the culture growth phase and its removal accompanying dimethylarsinate formation during a carbon-limited stationary phase. The Paenibacillus sp. also converted exogenously supplied dimethylarsinoylacetate to dimethylarsinate only under carbon-limited conditions. Lysed-cell extracts of the Paenibacillus sp. showed constitutive expression of enzyme(s) capable of arsenobetaine degradation through methyl-arsenic and carboxymethyl-arsenic bond cleavage. The work establishes the capability of particular bacteria to cleave both types of arsenic-carbon bonds of arsenobetaine and demonstrates that mixed-community functioning is not an obligate requirement for arsenobetaine biodegradation.

Structured approach to achieving high accuracy measurements with isotope dilution inductively coupled plasma mass spectrometry

This study investigated a method for simplifying the implementation of ID-ICP-MS, to achieve high accuracy measurements. The method developed is an adaptation of an earlier methodology that utilised an iterative ‘matching’ procedure. While retaining the many advantages of this approach, we have removed the iterative component and simplified the ‘matching’ step between the spiked mass bias calibrant and the spiked sample. Based on a conventional analysis, an approximate ‘match’ (usually within 5%), was made between the spiked reference standard and the spiked sample. This provides the basis for calculating the final result using the normal IDMS equation, while retaining many of the benefits of the full ‘matching’ procedure. These benefits negate many sources of error, such as mass bias, detector dead time and characterisation of the spike material. Many common errors and necessary corrections are negated or eliminated when using the new procedure. Examples are given of the method as applied to the analysis of certified reference materials, such as waters and plastics as well as blind trial data. The accuracy achieved using this procedure, on blind trial solutions, is typically to within 1% (relative to concentration) at the 95% level of confidence.

Problems Encountered During the Development of a Method for the Speciation of Mercury and Methylmercury by High-performance Liquid Chromatography Coupled to Inductively Coupled Plasma Mass Spectrometry

A study was carried out to develop a method for the determination of methylmercury and inorganic mercury by coupling HPLC to ICP-MS. During the course of this work it was noted that the use of stainless-steel components in the HPLC system led to adsorption of the mercury compounds, which was more pronounced with mercury(II) chloride than methylmercury. In particular, the use of a stainless steel sample loop led to larger peaks for both compounds, but particularly inorganic mercury, compared with a PEEK loop. The type of loop used had no effect on the separation of these compounds on an ODS column using a mobile phase composed of 10 mM tetrabutylammonium bromide and 60% methanol. However, both of the two ODS stainless-steel columns tested adsorbed the compounds to some degree, leading to a slow bleed of mercury. The use of components made with materials other than stainless steel, e.g. , PEEK sample loops and glass-lined columns, and inclusion of a sulfur ligand in the eluent (2-mercaptoethanol) reduced these problems significantly.

THE SPECIATION OF MERCURY AND ORGANOMERCURY COMPOUNDS BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY/ATMOSPHERIC PRESSURE IONIZATION MASS SPECTROMETRY

A method for the structural confirmation of mercury (II) chloride and organomercury (II) chlorides (monomethylmercury chloride, monoethylmercury chloride and monophenylmercury chloride) employing liquid chromatography coupled to atmospheric pressure ionization mass spectrometry was developed. The chromatographic system comprised a Kromasil 100-5C18, 5μm (250 × 4.6 mm) column and a mobile phase of 2-mercaptoethanol (0.01% v/v) in methanol: water (1:1 v/v), at a flow rate of 1 mL min−1. The optimization of the API-MS conditions is discussed, together with the fragmentation patterns observed for standards. No peaks due to the molecular ion were present and the most intense peaks were due to [M + mercaptoethanol]+ or [M + 2 mercaptoethanol − H]+. The qualitative analysis of fish tissue spiked with methylmercury (II) chloride, using selected ion monitoring (SIM), is discussed.

Orthodox uncertainty budgeting for high accuracy measurements by isotope dilution inductively coupled plasma-mass spectrometry

A full uncertainty budget for the analysis of copper in dilute nitric acid solution by isotope dilution ICP-MS has been formulated and described. The budget was dominated by the contribution of the standard uncertainty of the measured isotope amount ratios of the sample blend and the blend used for mass bias correction. The contribution from other components such as weighing, isotopic composition, standard solution concentration, and dilution factors were not very significant. The accuracy of the method was demonstrated by the analysis of NIST SRM 3114 copper solution.

Atomic Spectrometry Updates: A 25-year retrospective

Members of the Atomic Spectrometry Updates Editorial Board take a look back over 25 years at how the subject of atomic spectrometry has changed, and how the review articles have developed to reflect this.

Analytical approaches to investigating metal-containing drugs.

Many pharmaceuticals contain metals, either as part of the active compound or within the formulation. They are also found in related products such as dietary supplements and toiletries. Concentrations of metals in biological fluids or tissues from patients taking these agents, are measured where there may be an adverse reaction, dose-related toxicity or for therapeutic drug monitoring. Other situations, for analysis of environmental samples include occupational exposure (manufacture, administration to patients, pharmaceutical research) or in investigations of poisoning. Highly sensitive and accurate analytical methods are now available to determine the total metal concentration in a specific sample, but also to measure the specific chemical form of the drug, a metabolite of the drug, or the drugs interaction with important cellular components, such as DNA. The use of ICP-MS to measure total metal concentrations, or HPLC coupled to ICP-MS for the more complex speciation measurements, will depend on the type of information that is required. For the investigation of the drug species present, other complementary analytical techniques such as electrospray mass spectrometry (LC-MS/MS) are required for a full structural elucidation of the analytes. In this current publication we highlight the measurement of two metal(loid) based pharmaceutical drugs for the treatment of cancer. One 4-(N-(S-glutathionylacetyl)amino) phenylarsenoxide (GSAO) containing arsenic and under investigation for the treatment of solid tumours, and the second cis-diamminedichloroplatinum (II) (cisplatin) containing platinum and widely used in the clinical setting as a front line treatment against various neplasias in particular testicular, ovarian, bladder and head and neck cancers.

UK quality assurance of blood cobalt and chromium after hip implants

In 2010 the Medicines and Healthcare Products Regulatory Agency (MHRA) issued a medical device alert recommending measurement of cobalt and chromium concentrations in blood from patients experiencing discomfort or pain associated with metal-on-metal hip prostheses.1 2 This followed concerns relating to possible adverse effects of metal released from the implants. A second alert updated the advice and …

2:Analysis of Organometal(loid) Compounds in Environmental and Biological Samples

Measurement of the different physicochemical forms of metals and metalloids is a necessary pre-requisite for the detailed understanding of an elements interaction with environmental and biological systems. Such chemical speciation data is important in a range of areas, including toxicology, ecotoxicology, biogeochemistry, food safety and nutrition. This chapter considers developments in the speciation analysis of organometallic compounds (OMCs), focusing on those of As, Hg, Se and Sn. Typically, organometallic analysis requires a chromatographic separation prior to analyte detection and gas chromatography (GC), high performance liquid chromatography (HPLC) or capillary electrophoresis (CE) can serve this purpose. Following separation, detection is achieved using element specific detectors (ESDs) such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES), atomic fluorescence spectrometry (AFS), atomic absorption spectrometry (AAS) or atmospheric pressure ionization mass spectrometry (API-MS). Techniques employing a vapor generation (VG) stage prior to detection are also discussed. Complementary structural and quantitative data may be acquired through the combination of elemental and molecular mass spectrometry. The advantages and disadvantages of the various analytical systems are discussed, together with issues related to quantification and quality management.