Catching the elusive persistent and mobile organic compounds: Novel sample preparation and advanced analytical techniques

Persistent and Mobile Organic Compounds (PMOCs) are emerging pollutants in the environment that have only been rarely detected in previous years due to the lack of analytical techniques available for their analysis. These compounds, being very polar, are able to spread through the surface waters, and reach groundwaters and drinking water sources. The challenges in the analysis of these compounds in water include their poor extraction efficiencies from environmental matrices and weak retention in conventional chromatographic columns. As a result, the toxicity and environmental fate of PMOCs are largely unknown. This review will examine recent developments in sorbent and chromatographic column technologies, and other sample preparation strategies that will enable analysis of PMOCs and advance our knowledge on their fate and transport in the environment. In addition, analysis of these compounds in water via liquid chromatography with tandem mass spectrometry (LC–MS/MS) are discussed in this review.     

Enantioselective simultaneous analysis of selected pharmaceuticals in environmental samples by ultrahigh performance supercritical fluid based chromatography tandem mass spectrometry

In order to assess the true impact of each single enantiomer of pharmacologically active compounds (PACs) in the environment, highly efficient, fast and sensitive analytical methods are needed. For the first time this paper focuses on the use of ultrahigh performance supercritical fluid based chromatography coupled to a triple quadrupole mass spectrometer to develop multi-residue enantioselective methods for chiral PACs in environmental matrices. This technique exploits the advantages of supercritical fluid chromatography, ultrahigh performance liquid chromatography and mass spectrometry. Two coated modified 2.5 μm-polysaccharide-based chiral stationary phases were investigated: an amylose tris-3,5-dimethylphenylcarbamate column and a cellulose tris-3-chloro-4-methylphenylcarbamate column. The effect of different chromatographic variables on chiral recognition is highlighted. This novel approach resulted in the baseline resolution of 13 enantiomers PACs (aminorex, carprofen, chloramphenicol, 3-N-dechloroethylifosfamide, flurbiprofen, 2-hydroxyibuprofen, ifosfamide, imazalil, naproxen, ofloxacin, omeprazole, praziquantel and tetramisole) and partial resolution of 2 enantiomers PACs (ibuprofen and indoprofen) under fast-gradient conditions (<10 min analysis time).     

Enantiomeric fraction determination of chiral drugs in environmental samples using chiral liquid chromatography and mass spectrometry

When it was recognized that chiral drug residues have stereospecific toxicity towards environmental organisms the attention given to enantiomeric fraction determination of chiral drugs in the environment increased. Among various analytical techniques, chiral liquid chromatography (LC) coupled with mass spectrometry (MS) has been widely used due to its simplicity, wide applicability and high sensitivity. In this review, we aim to provide a comprehensive overview and comparison of the types of chiral stationary phases, elution modes and MS detection techniques employed and address the advances and limitations. The impact of the mobile phase composition on enantioseparation and MS detection are discussed based on the different methods developed. In addition, diverse applications for the enantiomeric fraction determination of chiral drugs in environmental matrices using chiral LC and MS are discussed in depth.     

Enantioseparation and determination of dufulin enantiomers in cucumber and soil by chiral liquid chromatography–tandem mass spectrometry

A simple and rapid method for enantioselective determination of dufulin in cucumber and soil was developed by liquid chromatography with tandem mass spectrometry. The enantiomers were separated on a Superchiral S‐OD chiral cellulose tris(3,5‐dimethylphenylcarbamate) column at 20°C, with a mixture of acetonitrile and water (0.1% formic acid; 52:48, v/v) as mobile phase at a flow rate of 0.65 mL/min. The pretreatment conditions were optimized using an orthogonal test, and the optimized method showed good linearity and sensitivity. The limits of detection and limits of quantification of two dufulin enantiomers were 0.006 and 0.02 mg/kg, respectively. The average recoveries of S‐enantiomer and R‐enantiomer in cucumber and soil were 80.61–99.83% and 80.97–102.96%, respectively, with relative standard deviations of 1.30–9.72%. The method was successfully applied to determine dufulin in real cucumber and soil samples. The results demonstrate that the method could facilitate further research on the differences between individual dufulin enantiomers with respect to metabolites and environmental fate and finally help reveal the complex interactions that exist between dufulin, humans and the environment.     

Overview of Analytical Methodologies for Dioxin Analysis

Abstract

Poly(chlorinated) dibenzo‐p‐dioxins and dibenzofurans (PCDDs/PCDFs) are persistent organic pollutants which are globally distributed in practically all environmental compartments and which exert a broad spectrum of toxic and biochemical effects. Humans are exposed to these compounds mainly through the diet with food of animal origin usually being the predominant source.

Multiple step isolation and clean up procedures are necessary to determine trace levels of these analytes in complex environmental and biological samples. This article reviews some of the recent developments in the extraction procedures, such as SFE, PLE, HS‐SPME, MAE, SCWE, ASE; clean‐up areas and instrumental analysis of dioxins in biological/environmental samples. Due to its specificity and sensitivity gas chromatography coupled with high resolution mass spectrometry (GC–HRMS), high‐resolution gas chromatography high‐resolution mass spectrometry (HRGC‐HRMS), or GC‐MS/GC techniques have been extensively applied to environmental, medicinal, and biological studies.     

High‐performance liquid chromatographic separations of stereoisomers of chiral basic agrochemicals with polysaccharide‐based chiral columns and polar organic mobile phases

The separation of the stereoisomers of 23 chiral basic agrochemicals was studied on six different polysaccharide‐based chiral columns in high‐performance liquid chromatography with various polar organic mobile phases. Along with the successful separation of analyte stereoisomers, emphasis was placed on the effect of the chiral selector and mobile phase composition on the elution order of stereoisomers. The interesting phenomenon of reversal of enantiomer/stereoisomer elution order function of the polysaccharide backbone (cellulose or amylose), type of derivative (carbamate or benzoate), nature, and position of the substituent(s) in the phenylcarbamate moiety (methyl or chloro) and the nature of the mobile phase was observed. For several of the analytes containing two chiral centers all four stereoisomers were resolved with at least one chiral selector/mobile phase combination.     

Case of enantiomer impurity identification by normal-phase chiral high-performance liquid chromatography with optical rotation and mass spectrometric detection

An impurity produced in the synthesis of compound I is separated and identified as its enantiomer II using normal-phase chiral high-performance liquid chromatography (HPLC) with UV absorbance, optical rotation (OR) and mass spectrometric (MS) detection. The results show that the impurity II and compound I have equal and opposite specific rotations, identical MS spectra and the same MS-MS fragmentation pattern, as required for enantiomers. The procedures presented demonstrate a novel combination of methods for enantiomer identification and characterization that do not require the preparation of individual enantiomer markers or even the racemic mixture, thus reducing the need for additional synthetic work.     

Enantioselective separation and pharmacokinetic dissipation of cyflumetofen in field soil by ultra‐performance convergence chromatography with tandem mass spectrometry

Little data on the enantioselective separation of cyflumetofen exists, despite the fact that such data are essential to the assessment of the fate and potential toxic effects of cyflumetofen enantiomers. To address this issue, a simple and sensitive method for the enantioselective determination of cyflumetofen enantiomers in soil has been established using ultra performance convergence chromatography tandem triple quadrupole mass spectrometry. The effects of the chiral stationary phases, mobile phase, auto backpressure regulator pressure, column temperature, flow rate of the mobile phase, and compensation pump solvent were evaluated. The proposed method was applied to the study of the pharmacokinetic dissipation of cyflumetofen stereoisomers in soil under greenhouse conditions. The estimated half‐life of cyflumetofen isomers ranged from 12.2 to 13.6 days, and statistically significant enantioselective degradation was observed. This study not only demonstrates that there is an efficient and sensitive method for cyflumetofen enantioseparation, but also provides the first experimental evidence of the pharmacokinetic dissipation of cyflumetofen stereoisomers in the environment.     

Limitations of mass spectrometric methods for the characterization of polydisperse materials

This paper is a review of work on the characterization of coal liquids and petroleum residues and asphaltenes over several decades in which various mass spectrometric methods have been investigated. The limitations of mass spectrometric methods require exploration in order to understand what the different analytical methods can reveal about environmental pollution by these kinds of samples and, perhaps more importantly, what they cannot reveal. The application of mass spectrometry to environmental problems generally requires the detection and determination of the concentration of specific pollutants released into the environment by accident or design. The release of crude petroleum or coal liquids into the environment can be detected and tracked during biodegradation processes through specific chemicals such as alkanes or polyaromatic hydrocarbons (PAHs). However, petroleum asphaltenes are polydisperse materials of unknown mass range and chemical structures and, therefore, there are no individual chemicals to detect. It is necessary to determine methods of detection and the ranges of mass of such materials. This can only be achieved through fractionation to reduce the polydispersity of the initial sample. Comparison of mass spectrometric results with results from an independent analytical method such as size‐exclusion chromatography with a suitable eluent is advisable to confirm that all the sample has been detected and mass discrimination effects avoided. Copyright © 2010 John Wiley & Sons, Ltd.     

Enantioseparations using cellulose tris(3,5-dichlorophenylcarbamate) during high-performance liquid chromatography with analytical and capillary columns: potential for screening of chiral compounds

The appropriate selection of the mobile phase facilitated the use cellulose tris(3,5-dichlorophenylcarbamate (CDCPC) as a chiral stationary phase (CSP) during high-performance liquid chromatography (HPLC). A preliminary evaluations of this material indicated its very high chiral resolving ability toward many analytes of different chemical and pharmacological groups. Some chemicals and drugs containing two centers of chirality were also successfully resolved into all possible stereoisomers. The applicability of CDCPC for enantioseparations in capillary liquid chromatography was also shown giving promising prospects for the screening of novel biologically active compounds (which may be also synthesized based on combinatorial strategies) for their enantiomeric composition.     

高效液相色谱-串联质谱法结合多糖衍生物手性固定相拆分氰戊菊酯

建立了以多糖衍生物为手性固定相的高效液相色谱-串联质谱(HPLC-MS/MS)直接拆分氰戊菊酯对映体的方法。在反相液相色谱条件下,考察了手性固定相的种类、流动相组成、柱温、流速对氰戊菊酯4个立体异构体分离的影响。同时,利用热力学方法对氰戊菊酯的立体异构体与固定相之间的色谱保留和分离的热力学机理进行了探讨。结果表明:采用Lux Cellulose-3(纤维素-三(4-甲基苯甲酸酯))手性色谱柱,在以流动相为乙腈-水(5 mmol/L甲酸铵)=(55:45,V:V)流速0.4 mL/min,柱温30℃的条件下,可在14 mins内实现氰戊菊酯4个立体异构体的基线分离。拓展了HPLC-MS/MS在菊酯类手性农药对映体分离及检测上的应用。     

环境中手性污染物对映体分析方法的研究进展

手性污染物对映体尽管具有相似的物理化学性质,但在环境中的吸附、转移、降解等过程往往存在一定差异。生态安全问题与人类健康密切相关,因此,对手性环境污染物进行对映体水平上的分离分析是十分重要的研究课题。目前,国内外对环境中的手性污染物已开展了相关研究,然而全面评述相关分析测定方法的新进展鲜有报道。本文主要对环境中手性污染物的种类以及近5年环境中手性污染物的分析检测技术如液相色谱-质谱联用法、气相色谱-质谱联用法、毛细管电泳法、超临界流体色谱-质谱联用法等进行了归纳、综述和展望,为后续手性污染物的分析检测提供依据和参考。     

Enantiomer discrimination by mass spectrometry: noncovalent interactions of an N-derivatized dipeptide with various cinchona alkaloid derivatives and comparison with enantioselective liquid-phase separations

The enantiomer discrimination properties of cinchona alkaloid derived chiral selectors (CSs) towards a dipeptide analyte are examined by electrospray ionization mass spectrometry. The complexes formed between the CSs and the analyte enantiomers owing to various noncovalent interactions are analyzed and the magnitudes of enantiomer discrimination are determined from the complexes mass spectrometric intensities. The influence of different structural features of the CSs on enantioselectivity is discussed. The enantiomer discrimination results obtained by mass spectrometry are compared with those from related liquid chromatography enantiomer separations. A certain coherence between the chromatographic and mass spectrometric enantioselectivities could be established and the enantiomer discrimination patterns, i.e., the relative binding strengths, were identical for the two techniques. Thus, the use of mass spectrometry as a screening tool in the development of new CSs for chromatographic applications seems feasible.     

Modern developments in gas chromatography-mass spectrometry-based environmental analysis

Gas chromatography coupled with mass spectrometry (GC–MS) continues to play an important role in the identification and quantification of organic contaminants in environmental samples. GC–MS is one of the most attractive and powerful techniques for routine analysis of some ubiquitous organic pollutants due to its good sensitivity and high selectivity and versatility. This paper presents an overview of recent developments and applications of the GC–MS technique in relation to the analysis in environmental samples of known persistent pollutants and some emerging contaminants. The use of different mass analysers such as linear quadrupole, quadrupole ion-trap, double-focusing sectors and time-of-flight analysers is examined. The advantages and limitations of GC–MS methods for selected applications in the field of environmental analysis are discussed. Recent developments in field-portable GC–MS are also examined.     

Recently developed GC/MS and LC/MS methods for determining NSAIDs in water samples

Pharmaceuticals have become major targets in environmental chemistry due to their presence in aquatic environments (following incomplete removal in wastewater treatment or point-source contaminations), threat to drinking water sources and concern about their possible effects to wildlife and humans. Recently several methods have been developed for the determination of drugs and their metabolites in the lower nanogram per litre range, most of them using solid-phase extraction (SPE) or solid-phase microextraction (SPME), derivatisation and finally gas chromatography mass spectrometry (GC-MS), gas chromatography tandem mass spectrometry (GC-MS/MS) and liquid chromatography electrospray tandem mass spectrometry (LC-ES/MS/MS). Due to the elevated polarity of non-steroidal anti-inflamatory drugs (NSAIDs), analytical techniques based on either liquid chromatography coupled to mass spectrometry (LC-MS) and gas chromatography coupled to mass spectrometry (GC-MS) after a previous derivatisation step are essential. The most advanced aspects of current GC-MS, GC-MS/MS and LC-MS/MS methodologies for NSAID analysis are presented.     

酚类环境雌激素的分析研究进展

环境中分布或残留的化学物质对人类和野生动物的内分泌系统的不良影响已引起广泛关注。在已发现的数十种环境内分泌干扰物中，壬基苯酚、辛基苯酚、双酚A和2，4－二氯酚等以其相似的结构特征和类雌激素活性逐渐被划分为一类新的分析研究对象，称为酚类环境雌激素。本文综述了这些物质的主要来源和分布及其分析测定的研究进展，重点评述了一些新的分析技术如基体固相分散萃取法（MSPD）、分子印迹聚合物法（MIP）、荧光分子传感法（FMS）和生物识别－化学分析联用法等在上述物质的分析测定中的应用。比较了GC－MS和LC－MS等手段用于分析此类物质的优势和各自的局限性，并展望了这一领域未来的研究发展趋势。本文引用文献共54篇。     

LC/MS study of the UV filter hexyl 2‐[4‐(diethylamino)‐2‐hydroxybenzoyl]‐benzoate (DHHB) aquatic chlorination with sodium hypochlorite

The fate of modern personal care products in the environment is becoming a matter of increasing concern because of the growing production and assortment of these compounds. More and more chemicals of this class are treated as emerging contaminants. Transformation of commercially available products in the environment may result in the formation of a wide array of their metabolites. Personal care products in swimming pools and in drinking water reservoirs may undergo oxidation or chlorination. There is much data on the formation of more toxic metabolites from original low toxicity commercial products. Therefore, reliable identification of all possible transformation products and a thorough study of their physicochemical and biological properties are of high priority. The present study deals with the identification of the products of the aquatic chlorination of the hexyl 2‐[4‐(diethylamino)‐2‐hydroxybenzoyl]‐benzoate ultraviolet filter. High‐performance liquid chromatography/mass spectrometry (HPLC/MS) and HPLC/MS/MS with accurate mass measurements were used for this purpose. As a result, three chlorinated transformation products were identified. Copyright © 2013 John Wiley & Sons, Ltd.     

Antibodies as Tailor-Made Chiral Selectors: an Interdisciplinary Approach to Enantiomer Separation and Detection

 It has long been known that the configurational isomers of biologically active compounds, e.g., nutrients, pesticides, and drugs, may exhibit different activities in a chiral environment such as the human body. Although the majority of drugs presently in development are chiral, analytical and preparative methods for the quantitative determination and purification of stereoisomers still lag behind. One reason is that commonly used chiral selectors for the direct resolution of enantiomers are not tailor-made for a specific analyte. The identification of suitable selectors for a particular pair of enantiomers still requires considerable experimentation and is generally demanding with regard to material, time and labor. The rational design of chiral host molecules, therefore, represents a challenge in facilitating enantiomer analysis. In this article, we describe how a combination of techniques ranging from organic synthesis to molecular biology yields antibodies of predetermined specificity and stereoselectivity that can be used as tailor-made chiral selectors for the chromatographic separation of enantiomers and their sensitive detection in immunosensors.     

Mass spectrometry applied to the analysis of estrogens in the environment

Environmental analytical chemistry has recently changed focus from analysis of non-polar, persistent contaminants (e.g. polychlorinated biphenyls and dioxins) to more polar and labile compounds that interfere with biological processes. For example, natural and synthetic estrogens and their metabolites have been detected in sewage treatment plant effluents at nanogram/liter concentrations that are similar to those at which both total sex reversal and intersex (containing both testes and ova) is induced in fish exposed to these compounds in laboratory experiments. The development of techniques for the analysis of natural and synthetic estrogens in biological fluids (i.e. serum and urine) has been a priority in the biomedical field. However, the recent recognition that estrogen hormones are contaminants in the environment that may contribute to endocrine disruption has focused attention on the need for highly sensitive and specific techniques that are applicable for trace analysis in complex environmental matrices. Three optimized mass spectrometric protocols have been developed for the determination and quantitation of steroid hormones in environmental matrices using gas chromatography/tandem mass spectrometry (GC/MS/MS), liquid chromatography/mass spectrometry selected ion monitoring, (LC/MS - SIM) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The advantages and disadvantages of each method are presented.