Sample handling strategies for the determination of persistent trace organic contaminants from biota samples

Even after emergence of most advanced instrumental techniques for the final separation, detection, identification and determination of analytes, sample handling continues to play a basic role in environmental analysis of complex matrices. In fact, sample preparation steps are often the bottleneck for combined time and efficiency in many overall analytical procedures. Thus, it is not surprising that, in the last two decades, a lot of effort has been devoted to the development of faster, safer, and more environment friendly techniques for sample extraction and extract clean up, prior to actual instrumental analysis. This article focuses on the state of the art in sample preparation of environmental solid biological samples dedicated to persistent organic pollutants (POPs) analysis. Extraction techniques such as Soxhlet extraction, sonication-assisted extraction, supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), pressurised liquid extraction (PLE) and matrix solid-phase dispersion (MSPD) are reviewed and their most recent applications to the determination of POPs in biota samples are provided. Additionally, classical as well as promising novel extraction/clean-up techniques such as solid phase microextraction (SPME) are also summarized. Finally, emerging trends in sample preparation able to integrate analytes extraction and their adequate clean-up are presented.     

Trends in speciation analysis of vanadium in environmental samples and biological fluids--a review

A comprehensive review is presented addressing recent trends in the speciation and determination of vanadium in environmental and biological sample matrices, including important analytical aspects such as sample clean up, pre-concentration and method development. Methodology based on both separation and spectroscopic techniques for the determination of vanadium speciation is discussed. A brief outline of analytical principles, together with an overview of the recent developments and applications of vanadium speciation determination is included. The newer methods for detecting metal ions including hyphenated spectroscopic techniques and sample preparation schemes are also discussed.     

Atomic spectrometric methods for the determination of metals and metalloids in automotive fuels - A review

Gasoline, diesel, ethanol and more recently also biodiesel are the four types of fuel used for automobile, truck and other transportation vehicle. The presence of metallic and metalloid species in automotive fuels is undesirable, except in the form of additives in order to improve specific characteristics of the fuel. Metallic or metalloid elements may derive from the raw product, such as nickel and vanadium in petroleum-based fuel or phosphorus in biodiesel, or they may be introduced during production and storage, such as copper, iron, nickel and zinc in case of petroleum-based fuel and alcohol or sodium and potassium in the case of biodiesel. The most famous additive to fuel is undoubtedly lead, the use of which has been banned or drastically reduced now in many countries of the world. The problems related to the trace element content may be economic, such as fuel degradation and poisoning of automotive catalysts, and/or environmental, such as the emission of metal compounds to the atmosphere. The analytical methods that have been developed for metal and metalloid quantification in automotive fuel are reviewed in this article. The main atomic spectrometric techniques used for trace metal and metalloid determination in fuels, particularly atomic absorption spectrometry with flames, graphite furnaces and with chemical vapor generation, and inductively coupled plasma coupled with optical emission and mass spectrometry are presented, including the different sample preparation procedures proposed for these techniques.     

Analytical methods for the determination of fluoroquinolones in solid environmental matrices

We present a critical review of the analytical procedures proposed in the past decade for the determination of fluoroquinolones (FQs) by chromatographic methods in solid environmental matrices. We emphasize the overall analytical procedure, from sampling to final detection. We devote special attention to sample preparation, highlighting the problems involved in the analysis of real complex matrices, mainly soil, sediment, manure and sludge. We compare the different extraction techniques in terms of efficiency, time taken and environmental impact, pointing out advantages and drawbacks. We provide an overview on the role of photochemistry in the degradation of FQs in soils and sediments, and we underline the central position of analytical chemistry in environmental monitoring because FQs are emerging pollutants.     

Analytical methods for determination of free metal ion concentration, labile species fraction and metal complexation capacity of environmental waters: A review

Different experimental approaches have been suggested in the last few decades to determine metal species in complex matrices of unknown composition as environmental waters. The methods are mainly focused on the determination of single species or groups of species.The more recent developments in trace elements speciation are reviewed focusing on methods for labile and free metal determination.Electrochemical procedures with low detection limit as anodic stripping voltammetry (ASV) and the competing ligand exchange with adsorption cathodic stripping voltammetry (CLE-AdCSV) have been widely employed in metal distribution studies in natural waters. Other electrochemical methods such as stripping chronopotentiometry and AGNES seem to be promising to evaluate the free metal concentration at the low levels of environmental samples. Separation techniques based on ion exchange (IE) and complexing resins (CR), and micro separation methods as the Donnan membrane technique (DMT), diffusive gradients in thin-film gels (DGT) and the permeation liquid membrane (PLM), are among the non-electrochemical methods largely used in this field and reviewed in the text. Under appropriate conditions such techniques make possible the evaluation of free metal ion concentration.     

Comparison of Methods for the Preparation of Sewage Sludge Samples Prior to the Spectrophotometric Determination of Phosphorus

Abstract

Three procedures for the preparation of sewage sludge samples prior to the colorimetric determination of phosphorus as “molybdenum blue” were evaluated. Using samples of the US EPA's municipal digested sludge as a reference material, sulfuric acid/ammonium persulfate digestion, muffle furnace ignition followed by extraction of the ash with hydrochloric acid, and direct extraction of the sewage sludge with sodium bicarbonate solution were compared in terms of phosphorus recovery as determined by colorimetric measurements. On the basisof phosphorus recovery, the samples prepared by muffle furnace ignition/hydrochloric acid extraction of the ash showed the best accuracy and precision. This procedure was also superior in terms of the time and effort expended in the preparation of the sewage sludge samples.     

Analytical methods for antifouling booster biocides determination in environmental matrices: A review

Since the discovery of their toxicity to aquatic environments, antifouling booster biocides (ABBs) have been widely researched and detected at trace levels in diverse environmental compartments including water, sediment, and, less frequently, biota. Hence, the reliable assessment of environmental risks posed by ABBs requires the development of analytical methods sufficiently robust, accurate, and precise for the simultaneous trace-level determination of ABBs. Herein, we summarize outstanding sample preparation procedures for the analysis of main ABBs in environmental matrices, describing techniques ranging from traditional extraction methods to novel miniaturized and micro-extraction ones, which have recently received much attention due to their reduced number of steps, low operational cost, and greater respect for the environment. The main applied chromatographic-based methods coupled to different detection techniques are also addressed. Despite the recent development of numerous ABBs determination methods, this topic continues to draw attention because of the lack of standardization among methods, despite legislation set up maximum standards levels for selected ABBs, and the need to monitor ABB transformation products for a reliable ecological risk assessment.     

Microextraction methods for the determination of phthalate esters in liquid samples: A review

1,2‐Benzenedicarboxylic acid esters, commonly referred to as phthalate esters, form a group of compounds that are mainly used as plasticizers in polymers. Because phthalate esters are not chemically bound to the plastics, they can be released easily from products and migrate into the food or water that comes into direct contact. Due to their widespread use, they are considered as ubiquitous environmental pollutants. Phthalate esters are regarded as endocrine disrupting compounds by means of their carcinogenic effect. Phthalate esters can be analyzed by gas chromatography or high‐performance liquid chromatography, however, their sensitivity and selectivity limit their direct use for determination of phthalates at very low level of concentrations exist in environmental samples with complex matrices. Therefore a sample pretreatment prior to their analysis is necessary. In this review, the historical development and overview of sample preparation methodologies have briefly been discussed and a comprehensive application of these methods in combination with different analytical techniques for preconcentration and determination of phthalate esters in various matrices have been summarized. Finally, a critical comparison of the different approaches in terms of enrichment factors achieved, extraction efficiency, precision, selectivity and simplicity of operation is provided.     

Antimony in the environment as a global pollutant: a review on analytical methodologies for its determination in atmospheric aerosols

This review summarizes and discusses the research carried out on the determination of antimony and its predominant chemical species in atmospheric aerosols. Environmental matrices such as airborne particulate matter, fly ash and volcanic ash present a number of complex analytical challenges as very sensitive analytical techniques and highly selective separation methodologies for speciation studies. Given the diversity of instrumental approaches and methodologies employed for the determination of antimony and its species in environmental matrices, the objective of this review is to briefly discuss the most relevant findings reported in the last years for this remarkable element and to identify the future needs and trends. The survey includes 92 references and covers principally the literature published over the last decade.     

Sample pretreatment techniques for oligopeptide analysis from natural sources

The analysis of oligopeptides in samples of food, tissues, and body fluids attracts considerable attention. The complexity of such samples requires efficient sample preparation (i.e., concentration and cleanup) procedures to remove interfering endogenous compounds and inorganic or organic salts. The methods of sample pretreatment that enable effective and selective isolation and/or preconcentration of oligopeptides from complex sample matrices have been reviewed. In each case, examples of application were presented and discussed, taking into account selectivity, enrichment, method automation, cleanup, and environmental aspects of the developed methods.     

Evaluation of the use of microwave oven systems for the digestion of environmental samples

In most chemical analyses for inorganic determinations in environmental matrices the sample is physically destroyed by dissolution, calcination etc. These digestion procedures have to be validated in order to ensure that no contamination and/or losses have occurred which could affect the accuracy of the final results obtained; this validation can be made by using certified reference materials (CRMs).In the recent past, microwave digestion procedures have been developed and have been shown to offer the benefits of rapid sample preparation and reduced contamination risks; however, an incomplete dissolution was suspected in some cases, e.g. in interlaboratory exercises, for the analysis of organic matrices.The aim of this study was to test microwave digestion procedures for different environmental CRMs and to evaluate the suitability of these methods for the determination of some trace elements. The effects of chemical species (As, Hg and Se-species) on the total element recovery after digestion are discussed.     

The determination of trace elements in crude oil and its heavy fractions by atomic spectrometry

A literature review on the determination of trace elements in crude oil and heavy molecular mass fractions (saturates, aromatics, resins and asphaltenes) by ICP-MS, ICP OES and AAS is presented. Metal occurrences, forms and distributions are examined as well as their implications in terms of reservoir geochemistry, oil refining and environment. The particular analytical challenges for the determination of metals in these complex matrices by spectrochemical techniques are discussed. Sample preparation based on ashing, microwave-assisted digestion and combustion decomposition procedures is noted as robust and long used. However, the introduction of non-aqueous solvents and micro-emulsions into inductively coupled plasmas is cited as a new trend for achieving rapid and accurate analysis. Separation procedures for operationally defined fractions in crude oil are more systematically applied for the observation of metal distributions and their implications. Chemical speciation is of growing interest, achieved by the coupling of high efficiency separation techniques (e.g., HPLC and GC) to ICP-MS instrumentation, which allows the simultaneous determination of multiple organometallic species of geochemical and environmental importance.     

Determination of pesticide transformation products: A review of extraction and detection methods

Pesticides are widely applied and they can produce a variety of transformation products (TPs), through different pathways and mechanisms. Nowadays there is a growing interest related to the determination of pesticide TPs in several matrices (environmental, food and biological samples), due to these compounds can be more toxic and persistent than parent compounds, and some of them can be used as markers of exposure to different pesticides. Although solid-phase extraction (SPE) is mainly used for the extraction of TPs, alternative techniques such as solid-phase microextraction (SPME) and liquid-phase extraction (LPE) can be used. These TPs are mainly determined by liquid chromatography (LC) due to the recent developments in this technique, especially when it is coupled to mass spectrometry (MS) detectors, allowing the determination of known and/or unknown TPs. Furthermore, MS is a very valuable tool for the structural elucidation of unknown TPs. This review discusses all phases of analytical procedure, including sample treatment and analysis, indicating the main problems related to the extraction of TPs from several matrices due to their high polarity, as well as the different alternatives found for the simultaneous determination of parent compounds and TPs, using chromatographic techniques coupled to MS detection.     

Determination of metallo-cyanides by capillary electrophoresis after concentration on supported liquid membranes

A method for the determination of traces of metallo-cyanide complexes by capillary zone electrophoresis is described. The suitability of preconcentration procedures based on supported liquid membranes in a flow system is investigated. Methyltrioctylammonium chloride in dibutyl ether is used as the active component of the membrane liquid. Due to ion-pairing mechanisms enrichment factors ranging from 50 to 600 can be achieved for cyanide complexes of Fe(II), Fe(III), Ni, Co, Pd, Pt, Cr, Au and Ag. The final capillary electrophoretic separation of the metallo-cyanides is performed off-line with a phosphate-triethanolamine buffer at pH 8.5 as the carrier electrolyte. Its separation selectivity and compatibility with the preconcentration procedure are optimized by addition of hexamethonium bromide, sodium perchlorate and sodium cyanide. Detection limits in the low nmol range can be achieved by direct UV detection at 214 nm. An approach for the analysis of free and labile cyanide is discussed which involves the conversion of these species into the nickel cyanide complex. Applications in the fields of environmental monitoring and industrial process control are possible.     

Determination of phosphorus in natural waters: A historical review

The aim of this paper is to introduce a virtual special issue that reviews the development of analytical approaches to the determination of phosphorus species in natural waters. The focus is on sampling and sample treatment, analytical methods and quality assurance of the data. The export of phosphorus from anthropogenic activities (from diffuse and point sources) can result in increased primary production and eutrophication, and potentially the seasonal development of toxic algal blooms, which can significantly impact on water quality. Therefore the quantification of phosphorus species in natural waters provides important baseline data for studying aquatic phosphorus biogeochemistry, assessing ecosystem health and monitoring compliance with legislation.     

Membrane-based microextraction techniques in analytical chemistry: A review

The use of membrane-based sample preparation techniques in analytical chemistry has gained growing attention from the scientific community since the development of miniaturized sample preparation procedures in the 1990s. The use of membranes makes the microextraction procedures more stable, allowing the determination of analytes in complex and “dirty” samples. This review describes some characteristics of classical membrane-based microextraction techniques (membrane-protected solid-phase microextraction, hollow-fiber liquid-phase microextraction and hollow-fiber renewal liquid membrane) as well as some alternative configurations (thin film and electromembrane extraction) used successfully for the determination of different analytes in a large variety of matrices, some critical points regarding each technique are highlighted.     

Sample preparation with solid phase microextraction and exhaustive extraction approaches: Comparison for challenging cases

In chemical analysis, sample preparation is frequently considered the bottleneck of the entire analytical method. The success of the final method strongly depends on understanding the entire process of analysis of a particular type of analyte in a sample, namely: the physicochemical properties of the analytes (solubility, volatility, polarity etc.), the environmental conditions, and the matrix components of the sample. Various sample preparation strategies have been developed based on exhaustive or non-exhaustive extraction of analytes from matrices. Undoubtedly, amongst all sample preparation approaches, liquid extraction, including liquid–liquid (LLE) and solid phase extraction (SPE), are the most well-known, widely used, and commonly accepted methods by many international organizations and accredited laboratories. Both methods are well documented and there are many well defined procedures, which make them, at first sight, the methods of choice. However, many challenging tasks, such as complex matrix applications, on-site and in vivo applications, and determination of matrix-bound and free concentrations of analytes, are not easily attainable with these classical approaches for sample preparation.     

Carbon nanotubes as solid-phase extraction sorbents prior to atomic spectrometric determination of metal species: A review

New materials have significant impact on the development of new methods and instrumentation for chemical analysis. From the discovery of carbon nanotubes in 1991, single and multi-walled carbon nanotubes – due to their high adsorption and desorption capacities – have been employed as sorption substrates in solid-phase extraction for the preconcentration of metal species from diverse matrices. Looking for successive improvements in sensitivity and selectivity, in the past few years, carbon nanotubes have been utilized as sorbents for solid phase extraction in three different ways: like as-grown, oxidized and functionalized nanotubes. In the present paper, an overview of the recent trends in the use of carbon nanotubes for solid phase extraction of metal species in environmental, biological and food samples is presented. The determination procedures involved the adsorption of metals on the nanotube surface, their quantitative desorption and subsequent measurement by means of atomic spectrometric techniques such as flame atomic absorption spectrometry, electrothermal atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry/mass spectrometry, among others. Synthesis, purification and types of carbon nanotubes, as well as the diverse chemical and physical strategies for their functionalization are described. Based on 140 references, the performance and general properties of the applications of solid phase extraction based on carbon nanotubes for metal species atomic spectrometric determination are discussed.     

Developments in the Determination of Organophosphorus Pesticides

Abstract

In this paper, a review is given of some recent developments in organophosphorus pesticides residue methodology. Enrichment on XAD-resins or C₁₈ bonded phases, clean-up by gel permeation and determination by high-performance liquid chromatography (HPLC) with specific detectors can be considered as the major fields of development in the past years.

Despite of the progress made, there is still a further need for procedures which reduce handling time, e.g. by automation, and/or increase specificity of the HPLC determination in matrices of practical interest, such as food, animal and human tissues and environmental samples.     

Perspectives of analysis of carcinogenic and mutagenic metals in biological samples

There is a continuing need to assess the status of exposure to humans of the carcinogenic and/or mutagenic metals in both biological and environmental samples to better ensure that current or past exposures do not entail unacceptable health risks or to detect potentially excessive exposure before the appearance of adverse health effects. In order to more readily evaluate both the extent of exposure and trends of human exposure as well as the bioavailability, bioaccumulation and transport of these elements and their compounds, sensitive analytical procedures are required for their determination of the various oxidative states (as well as their organic derivatives) in complex matrices such as those found in both environmental and biological samples. The major objective of this overview is to highlight the more recent trends and state-of-the-art methodologies for the determination and speciation of arsenic, selenium, cadmium, chromium and nickel in human and animal tissues while concomitantly noting germane aspects of their bioavailability and interactions. Aspects of biological monitoring of the above elements will be stressed due to their potential utility in augmenting diverse epidemiologic and occupational health studies.