Trace Analysis Of Organic Compounds Research Articles

Development of a novel and useful methodology for the simultaneous analysis of multiclass contaminants in bovine fat.

The instrumental development of tandem mass spectrometers fosters the actual trend in the trace analysis of organic compounds to the development of methods that allow the analysis of contaminants of the most diverse origin in a single analytical sample. The multiclass methods are aligned with the Who's One Health initiative while accomplishing the concepts of green chemistry. However, there are few reports of wide scope multiclass methods for the analysis of contaminants in this matrix. In this work, a method for the simultaneous determination of 62 compounds in bovine fat, was developed and validated following DG-SANTE/11813/2021 guidance. Liquid nitrogen milled fat was extracted with toluene and acetonitrile. Then a clean-up in a cryogenic bath, followed by dispersive solid phase extraction was performed. Residue determination was done using liquid chromatography for 44 compounds and gas chromatography for 18 compounds, both coupled to tandem mass spectrometry in MRM mode. The method was first developed and validated for two ectoparasiticides, then the scope was expanded for the analysis of 13 veterinary drugs and 49 pesticides. Recovery percentages were in the range of 60-134%, high matrix effect was observed in 50% of the scope of the method. Most compounds presented limits of quantification of 10 μg kg-1 in compliance with international requirements. The method was applied to monitor 49 commercial samples to evaluate its performance. Eighty percent of samples contained ethion and 10% had fluazuron, both within MRLs, highlighting the need for proper withdrawal times.

Exploration of Extraction and Separation Techniques for Routine Trace Analysis of Organic Compounds in Water: Dispersive Liquid-Liquid Microextraction vs Liquid-Liquid Extraction

Dispersive liquid-liquid microextraction (DLLME) was compared to liquid-liquid extraction (LLE) in terms of the methods’ abilities to analyze samples and ultimately to provide information to an analyst. A simple method of relative quantification by compound class approximation was introduced and its validity tested, while the merits of comprehensive gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS) were exhibited on multiple sets of locally obtained environmental water samples. 20 classes of compounds were effectively identified by the DLLME-GC×GC-TOFMS protocol proposed. The limits of detection (LOD) of the protocol ranged between 17 and 377 times lower than the conventional protocol designed for targeted total extractable hydrocarbon (TEH) and total petroleum hydrocarbon (TPH) analysis, with LODs of selected compounds between 0.08 and 1.0 µg/L. Relative quantification shows promising results and was used for quantification of non-targeted analytes within real samples. This quantification method will be used to inform future work to be implemented in industrial environmental analysis.

Miniature time-of-flight mass analyzer for use in combination with a compact highly-repetitive femtosecond laser ionization source

In most cases, a molecular ion is observed in femtosecond laser ionization mass spectrometry, which provides information concerning the molecular weight of the analyte. However, the Ti:sapphire laser currently used as the ionization source is costly and involves special skills for operation and maintenance, which prevents its practical use in many applications. In this study, we report on the development of a miniature time-of-flight mass analyzer with a flight tube length of 65 mm for use in combination with a compact highly-repetitive (120–560 kHz) femtosecond Yb laser and a time-correlated single ion counting system. The fundamental beam (1030 nm) was converted into ultraviolet beams emitting at 343, 257, and 206 nm, which was utilized as an efficient two-photon ionization source. A mass resolution of 670 was achieved for the molecular ion of chlorobenzene, the minimum time for measuring a mass spectrum being 0.1 s. This mass spectrometer was used in the on-site real-time monitoring of products appeared by the combustion of plastic, some nerve agent analogs, and an explosive in the air. The interference arising from nitrogen and oxygen in the air was suppressed, since they require nonresonant four- and three-photon ionizations, respectively. The mass spectrometer was combined with a gas chromatograph and used for the comprehensive analysis of polycyclic aromatic hydrocarbons, suggesting its potential advantage for use in the practical trace analysis of organic compounds in the environmental and forensic sciences.

Magnetic Solid-Phase Extraction of Organic Compounds Based on Graphene Oxide Nanocomposites.

Graphene oxide (GO) is a chemical compound with a form similar to graphene that consists of one-atom-thick two-dimensional layers of sp2-bonded carbon. Graphene oxide exhibits high hydrophilicity and dispersibility. Thus, it is difficult to be separated from aqueous solutions. Therefore, functionalization with magnetic nanoparticles is performed in order to prepare a magnetic GO nanocomposite that combines the sufficient adsorption capacity of graphene oxide and the convenience of magnetic separation. Moreover, the magnetic material can be further functionalized with different groups to prevent aggregation and extends its potential application. Until today, a plethora of magnetic GO hybrid materials have been synthesized and successfully employed for the magnetic solid-phase extraction of organic compounds from environmental, agricultural, biological, and food samples. The developed GO nanocomposites exhibit satisfactory stability in aqueous solutions, as well as sufficient surface area. Thus, they are considered as an alternative to conventional sorbents by enriching the analytical toolbox for the analysis of trace organic compounds.

Trace analysis of organic compounds in foods with surface-enhanced Raman spectroscopy: Methodology, progress, and challenges.

Surface-enhanced Raman spectroscopy (SERS) provides a potential solution for rapid analysis of trace compounds such as residual pesticides, naturally occurred toxicants, banned or restricted drugs, and food additives in complex food matrices. In this review, the basic principles of SERS and general approaches to successfully apply SERS in food analysis are covered from an applications perspective. The key steps including substrate selection and evaluation, sample preparation and simplification, spectral collection, and data analysis during the development of SERS methods for food analysis are summarized, together with the discussion of typical underlying technical barriers or major challenges of these methods and their applications. Future directions in successfully applying SERS technology as a routine analytical approach to solve real-world food problems are analyzed. This comprehensive review summarizes the recent progress on theory, application, and scope of SERS for food analysis, providing a basic understanding of the technology; more importantly, key methodology, potential pitfalls, and possible solutions during the development of rapid SERS methods based on authors' years of SERS experience are shared with researchers in the field.

Paul H. Chen

Paul H. Chen, 80, died on Jan. 3, 2017, in Seattle. “Paul, a devoted Christian with great integrity, was an analytical chemist specialized in gas chromatography/mass spectrometry analysis of trace organic compounds in environmental pollutions. He worked as head of mass spectrometry for Philip Morris Research Center (1968), as a professor at National Yang-Ming University in Taiwan (1976), and as a visiting professor at Indiana University. He joined the Behavioral and Neurological Toxicology Lab at the National Institute of Environmental Health Sciences in Research Triangle Park (1983). He also worked as a group leader at QST Environmental in Gainesville, Florida (1985). He worked for the US Environmental Protection Agency (USEPA) in Athens, Georgia, until his retirement in 2000. He had 43 publications and received numerous awards, including the USEPA Bronze Medal.”—Melissa G. Chen, wife Most recent title: Chemist, US Environmental Protection Agency Education: BS, chemical engineering, Cheng Kung University...

Development of a single format membrane assisted solvent extraction-molecularly imprinted polymer technique for extraction of polycyclic aromatic hydrocarbons in wastewater followed by gas chromatography mass spectrometry determination

A technique that combines membrane assisted solvent extraction and molecularly imprinted polymer into a single step format has been successfully developed and evaluated for the extraction of the 16 US-EPA priority polycyclic aromatic hydrocarbons in wastewater samples followed by determination using gas chromatography coupled with time of flight mass spectrometry. The technique involves placing the polymer particles into a hydrophobic polypropylene membrane bag which is in contact with an aqueous donor phase. The technique was optimized for various parameters that include presence of an organic modifier in the donor phase, stirring rate and extraction time. The optimum conditions were 25% of dimethyl sulfoxide as an organic modifier and stirring at 1000 rpm for 120 min. The limits of detection using the technique were in the 0.01–0.45 ng mL−1 range. Linearity values determined in the 10–1 000 ng mL−1 calibration range were all above 0.9972. Extraction efficiencies of the sixt analytes calculated as averages for three spiking concentrations ranged from 62.8 to 96.8% (RSD = 3.1–12.3%). The optimized method was tested for the extraction of polycyclic aromatic hydrocarbons in wastewater samples in the presence of surrogate standards. The developed method showed great reproducibility with inter day repeatability values ranging from 0.6 to 24.9%. The analytes were quantified in the nanogram level showing that the developed technique is a viable alternative in the analysis of trace organic compounds in complex aqueous samples.

One-pot synthesis of zeolitic imidazolate framework-8/poly (methyl methacrylate-ethyleneglycol dimethacrylate) monolith coating for stir bar sorptive extraction of phytohormones from fruit samples followed by high performance liquid chromatography-ultraviolet detection

In this work, zeolitic imidazolate framework-8 (ZIF-8)/poly (methyl methacrylate-ethyleneglycol dimethacrylate) (MMA-EGDMA) composite monolith was in situ synthesized on stir bar by one-pot polymerization. Compared with the neat monolith, ZIF-8/poly(MMA-EGDMA) composite monolith has larger surface area and pore volume. It also exhibits higher extraction efficiency for target phytohormones than poly(MMA-EGDMA) monolith and commercial polyethylene glycol (PEG) coated stir bar. Based on it, a method of ZIF-8/poly(MMA-EGDMA) monolith coated stir bar sorptive extraction (SBSE)-high performance liquid chromatography-ultraviolet detection (HPLC-UV) was established for the analysis of five phytohormones in apple and pear samples. The developed method exhibited low limits of detection (0.11–0.51μg/L), wide linear range (0.5–500μg/L) and good recoveries (82.7–111%), which demonstrated good application potential of the ZIF-8/monolith coated stir bar in trace analysis of organic compounds.

Direct Analysis of Organic Compounds in Liquid Using a Miniature Photoionization Ion Trap Mass Spectrometer with Pulsed Carrier-Gas Capillary Inlet.

A miniature ion trap mass spectrometer with capillary direct sampling and vacuum ultraviolet photoionization source was developed to conduct trace analysis of organic compounds in liquids. Self-aspiration sampling is available where the samples are drawn into the vacuum chamber through a capillary with an extremely low flow rate (less than 1 μL/min), which minimizes sample consumption in each analysis to tens of micrograms. A pulsed gas-assisted inlet was designed and optimized to promote sample transmission in the tube and facilitate the cooling of ions, thereby improving instrument sensitivity. A limit of detection of 2 ppb could be achieved for 2,4-dimethylaniline in a methanol solution. The sampling system described in the present study is specifically suitable for a miniature photoionization ion trap mass spectrometer that can perform rapid and online analysis for liquid samples. Graphical Abstract ᅟ.

A Simple Method for the Evaluation of the Pulse Width of an Ultraviolet Femtosecond Laser Used in Two-Photon Ionization Mass Spectrometry

A simple method was proposed for on-site evaluation of the pulse width of an ultraviolet femtosecond laser coupled with a mass spectrometer. This technique was based on measurement of a two-photon ionization signal in mass spectrometry by translation of the prism in the pulse compressor of the femtosecond laser. The method was applied to optical pulses that were emitted at wavelengths of 267, 241, and 219 nm; the latter two pulses were generated by four-wave Raman mixing using the third harmonic emission of a Ti:sapphire laser (267 nm) in hydrogen gas. The measurement results show that this approach is useful for evaluation of the pulse width of the ultraviolet femtosecond laser used in mass spectrometry for trace analysis of organic compounds.

Rapid analysis of trace organic compounds in water by automated online solid-phase extraction coupled to liquid chromatography–tandem mass spectrometry

A fully automated online solid-phase extraction (SPE) with directly coupled liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for analysis of 34 trace organic compounds in diverse water matrices has been developed. The current method offers several advantages over traditional offline SPE methods including low sample volume (1.7mL), decreased solvent use, higher throughput, and increased reproducibility. The method uses simultaneous positive and negative ESI for analysis of all compounds in one injection, which reduces cycle time (extraction+analysis) to <15min. Method optimization included testing different online SPE cartridges, mobile phase compositions, and flow rates. The method detection limits (MDLs) ranged from 0.1 to 13.1ng/L with 80% of the compounds having an MDL <5ng/L. Matrix spike recoveries in three different water qualities were evaluated and ranged from 61.2% to145.1% with 95% of the recoveries ranging between 70–130%. As part of the method validation studies, linearity (0.9911–0.9998), intra-day variability (1.0–10.4%), inter-day variability (1.0–11.9%), and matrix effects were also assessed. The use of 26 isotopically-labeled standards increased the reliability of the method while retention time locking and use of two transitions for most compounds increased the specificity. The applicability of the method was tested on samples across treatment points from two wastewater plants, a septic tank, surface water and groundwater.

Chemometric optimization of derivatization reactions prior to gas chromatography–mass spectrometry analysis

Derivatization is a methodological technique that can be used to make an organic compound more suitable for qualitative and/or quantitative analysis (e.g. pharmaceuticals). However, many analysts try to avoid this analytical procedure as it is time-consuming and labour-intensive. On the other hand, an inter-laboratory study demonstrated that with regard to sensitivity and measurement uncertainty, gas chromatography coupled to mass-spectrometry was superior to liquid chromatography coupled to mass spectrometry for the trace analysis of organic compounds in matrices of greater complexity. In our previous paper (Kumirska et al., J. Chemometr. 25 (2011) 636–643) we suggested using principal component analysis (PCA) to optimize the derivatization of six compounds (5 oestrogenic steroids and diethylstilbestrol) prior to GC–MS analysis. In the present work we applied a highly sophisticated model – 24 pharmaceuticals derived from six classes of drugs. The efficiency of different derivatization reactions was evaluated by PCA and compared with that obtained from cluster analysis (CA), the latter method being applied in this context for the first time. Derivatization using N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and 1% trimethylchlorosilane (TMCS) in pyridine and ethyl acetate (2:1:1, v/v/v) for 30min at 60°C was found to be optimal. The SPE-GC–MS method was also validated and successfully applied to the analysis of selected pharmaceuticals in wastewater and surface waters in Poland.

Impact of dry weather discharges on annual pollution from a separate storm sewer in Toulouse, France

The city of Toulouse with its separate sewer system is ideal for studying stormwater. However, during dry weather, the storm sewer also discharges water into the environment, and it is the impact of these discharges on annual pollution from storm sewer that is the object of this study.Samples have been taken from the outlets of two storm drains located in heavily and moderately urbanized areas. Sampling has been undertaken during wet weather and during dry weather between January 2010 and February 2011. Three dry weather and two wet weather samples have been taken every three months and from each outlet. The overall pollution parameters have been analyzed (chemical oxygen demand, biological oxygen demand, total nitrogen, ammonium, nitrate, total phosphorus, suspended solid matter, volatile suspended matter, pH, conductivity, turbidity). Characterization has been completed by analysis of trace organic compounds: polycyclic aromatic hydrocarbons, total hydrocarbons, methyl tert-butyl ether, diethylhexylphthalate, nonylphenols, hormones (estradiol, ethinylestradiol). For certain parameters, the results obtained did not conform to legislative requirements concerning discharge into the natural environment. Correlations between these parameters have been studied, and identified between several of them using principal component analysis. The most important correlation observed was between conductivity and concentration in total phosphorus for one of the outlet. Results showed that dry weather had an impact on annual pollution load from separate storm sewer and that level of urbanization was also a factor. The effect of season has been studied but no significant impact was found.

Reference Samples for Ultra Trace Analysis of Organic Compounds on Substrate Surfaces

Reference samples were produced for development, benchmarking and comparison of analytical techniques based on mass spectroscopy as TD-GCMS and TOF-SIMS and x-ray analysis as TXRF-NEXAFS. Organic contaminants representing plasticizers, disinfectants and flame retardants were chosen. The contaminants were selected with respect to reliable detection using the above analytical techniques. The stability of the reference samples produced with dethylphtalate, triclosane, and tetrabrombisphenol A on silicon stripes or wafers with a diameter of 200 mm was found to be approx. 10 days. The comparison of the techniques showed that the mass spectroscopy methods allowed reliable qualification of organic surface contamination. TD-GCMS quantifies and identifies the volatile organic compounds whereas TXRF quantifies the carbon contamination, especially the non-volatile, on sample surfaces.

New Advances in Large-Volume Injection Gas Chromatography-Mass Spectrometry

Gas chromatography-mass spectrometry (GC-MS) with large-volume injection (LVI) is a well-known analytical technique with high sensitivity and specificity, which has been widely used in the identification and quantitation of organic compounds, especially at very low concentrations. This review paper summarizes the new advances of LVI-GC-MS since 2000 and includes the currently available large volume injectors and GC-MS techniques, the sample preparation techniques used with LVI-GC-MS, and the applications of LVI-GC-MS in the analysis of trace organic compounds in a variety of sample matrices.

Problems of PAH quantification by GC–MS method using isotope-labelled standards

The gas chromatography–mass spectrometry (GC–MS) system is presently routinely used in environmental analysis of trace organic compounds. With the use of a MS-detector, stable isotope-labelled materials’ analogous of the native analyte are convenient internal standard. They can be used for tracing and compensating analytes’ losses during the particular stages of analytical procedure, such as cleaning or diluting, and variations in instrument settings and sensitivity. However, the stage of quantitative analysis is connected with numerous problems that result from the necessity of obtaining reliable results of determination.In this article, problems connected with the quantitative analysis of polycyclic aromatic hydrocarbons in sediment samples using GC–MS system were raised.The aim of conducted work was to assess the influence of the following factors on the results obtained: calibration of the GS–MS system, internal standard addition technique and the amount of internal standard added.

Trends and recent applications of matrix solid-phase dispersion

Matrix solid-phase dispersion (MSPD) is a sample-preparation technique with increasing acceptance in trace analysis of organic compounds using chromatographic and electro-driven separation techniques. It has been applied to the extraction and fractionation of a large number of substances from solid, semi-solid, and liquid matrices. Low sample and solvents consumption, straightforward application, and reduced cost, and its ability to simultaneously perform extraction and clean-up in a single step, are some of its major advantages. This review attempts to provide an updated, concise and critical overview on the latest trends and applications of MSPD, placing emphasis on comparison of its performance with that of other techniques, besides focusing on practical features to take into account depending on the nature of the sample and the properties of the analytes. Achievements, advantages, and limitations are discussed. The paper also highlights future challenges to be faced.

Ultraviolet femtosecond laser ionization mass spectrometry

For this study, multiphoton ionization/mass spectrometry using an ultraviolet (UV) femtosecond laser was employed for the trace analysis of organic compounds. Some of the molecules, such as dioxins, contain several chlorine atoms and have short excited-state lifetimes due to a "heavy atom" effect. A UV femtosecond laser is, then, useful for efficient resonance excitation and subsequent ionization. A technique of multiphoton ionization using an extremely short laser pulse (e.g., <10 fs), referred to as "impulsive ionization," may have a potential for use in fragmentation-free ionization, thus providing information on molecular weight in mass spectrometry.

Fiber-packed needle for dynamic extraction of aromatic compounds

A fiber-packed needle was developed as a novel extraction device for gas-chromatographic analysis of trace organic compounds in aqueous samples. In the extraction device, a bundle of the polymer-coated filaments as the sorbent material was longitudinally packed into a specially designed needle. The extraction was made by pumping the aqueous sample solution into the needle extraction device, and the subsequent desorption process was carried out with a flow of desorption solvent through the needle in a heated gas chromatograph injector. The needle device showed an excellent thermal stability for repeated use without any deterioration of extraction performance, and no carryover effect was observed after the optimization of the desorption conditions. Additionally, the extraction efficiency of the fiber-packed needle could be enhanced by optimizing the number of packed filaments. The selectivity for various compounds could be also tuned using an appropriate combination of the fibrous medium and the coating polymer. The relative standard deviation for run to run was from 3.88 to 4.55% (n = 5), and that for needle to needle was 7.21% (n = 3), clearly suggesting a good repeatability of the needle extraction technique developed. Upon successful optimization of the extraction conditions, a rapid extraction of trace organic compounds from an aqueous sample matrix was successfully demonstrated, where each extraction process was completed within 10 min.

Solid‐Phase Room‐Temperature Phosphorescence

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