Applications of solid‐phase micro‐extraction with mass spectrometry in pesticide analysis

Pesticides, widely applied in agriculture, can produce a variety of transformation products and their continuous use causes deleterious effects to ecosystem. Efficient and sensitive analytical techniques for enrichment and analysis of pesticides samples are highly required. Compared with other extraction methods, solid‐phase micro extraction is a solvent free, cost effective, robust, versatile, and high throughput sample preparation technique, especially for the analysis of pesticides from complicated matrices. Coupling of solid‐phase micro extraction with gas chromatography and mass spectrometry and liquid chromatography–mass spectrometry has been extensively applied in pesticide analysis. On the other hand, in recent years, combination of fast separation using solid‐phase micro extraction and rapid detection using ambient mass spectrometry is providing highly efficient pesticide screening. This article summarizes the applications of solid‐phase micro extraction coupled to mass spectrometry for pesticides analysis.     

Mass‐spectrometry‐based lipidomics

Lipids, which have a core function in energy storage, signalling and biofilm structures, play important roles in a variety of cellular processes because of the great diversity of their structural and physiochemical properties. Lipidomics is the large‐scale profiling and quantification of biogenic lipid molecules, the comprehensive study of their pathways and the interpretation of their physiological significance based on analytical chemistry and statistical analysis. Lipidomics will not only provide insight into the physiological functions of lipid molecules but will also provide an approach to discovering important biomarkers for diagnosis or treatment of human diseases. Mass‐spectrometry‐based analytical techniques are currently the most widely used and most effective tools for lipid profiling and quantification. In this review, the field of mass‐spectrometry‐based lipidomics was discussed. Recent progress in all essential steps in lipidomics was carefully discussed in this review, including lipid extraction strategies, separation techniques and mass‐spectrometry‐based analytical and quantitative methods in lipidomics. We also focused on novel resolution strategies for difficult problems in determining C=C bond positions in lipidomics. Finally, new technologies that were developed in recent years including single‐cell lipidomics, flux‐based lipidomics and multiomics technologies were also reviewed.     

Perry G. Wang (Ed.): Monolithic chromatography and its modern applications

Organic micropollutants such as pharmaceuticals, perfluorinated compounds (PFCs), and pesticides, are important environmental contaminants. To obtain more information regarding their presence in marine organisms, an increasing demand exists for reliable analytical methods for quantification of these micropollutants in biotic matrices. Therefore, we developed extraction procedures and new analytical methods for the quantification of 14 pesticides, 10 PFCs, and 11 pharmaceuticals in tissue of marine organisms, namely blue mussels (Mytilus edulis). This paper presents these optimized analytical procedures and their application to M. edulis, deployed at five stations in the Belgian coastal zone. The methods consisted of a pressurized liquid extraction and solid-phase extraction (SPE) followed by ultra high-performance liquid chromatography coupled to triple quadrupole mass spectrometry for pharmaceuticals and pesticides, and of a liquid extraction using acetonitrile and SPE, followed by liquid chromatography coupled to time-of-flight mass spectrometry for PFCs. The limits of quantification of the three newly optimized analytical procedures in M. edulis tissue varied between 0.1 and 10 ng g(-1), and satisfactory linearities (≥0.98) and recoveries (90-106%) were obtained. Application of these methods to M. edulis revealed the presence of five pharmaceuticals, two PFCs, and seven pesticides at levels up to 490, 5, and 60 ng g(-1), respectively. The most prevalent micropollutants were salicylic acid, paracetamol, perfluorooctane sulfonate, chloridazon, and dichlorvos.     

Pesticides in water and the performance of the liquid-phase microextraction based techniques. A review

The control of pesticides in surface, drinking and groundwater is nowadays a real necessity. In the European Community, their concentration must comply with the established parametric and environmental quality standards (EQSs). Regarding the new legislation, this article updates the information concerning the monitoring of pesticides and the technical specifications for their measurement in water samples where ultra-sensitive analytical methods are required. For some compounds, like pesticides, there is still a need to improve the performance of the existing methods. High sensitive techniques like gas chromatography tandem mass spectrometry (GC–MS/MS) and liquid chromatography coupled with mass spectrometry (LC–MS) have been developed. However, for most of the substances present at trace and ultra-trace levels the extraction and preconcentration steps are so far essential for their detection. Advances at a micro scale have been made and different types of microextractions are being developed. Liquid-phase microextraction (LPME) is an example. The study of this technique has increased in the last years and some innovations have been recently reported for pesticides water analysis. This article reviews the new developed LPME-based techniques and compares its performance with the analytical specifications established for pesticides water monitoring. The results show that LPME-based techniques can be a promising tool to improve the nowadays performance of methods used in pesticides water control.     

Comparison of different cleanup procedures for oil crops based on the development of a trace analytical method for the determination of pyraclostrobin and epoxiconazole

The effects of different cleanup procedures in removing high‐molecular‐mass lipids and natural colorants from oil‐crop extracts, including dispersive solid‐phase extraction, low‐temperature precipitation and gel permeation chromatography, were studied. The pigment removal, lipid quantity, and matrix effects of the three cleanup methods were evaluated. Results indicated that the gel permeation chromatography method is the most effective way to compare the dispersive solid‐phase extraction and low‐temperature precipitation. Pyraclostrobin and epoxiconazole applied extensively in oil‐crop production were selected as typical pesticides to study and a trace analytical method was developed by gel permeation chromatography and ultra high performance liquid chromatography with tandem mass spectrometry. Average recoveries of the target pesticides at three levels (10, 50, and 100 μg/kg) were in the range of 74.7–96.8% with relative standard deviation values below 9.2%. The limits of detection did not exceed 0.46 μg/kg, whereas the limits of quantification were below 1.54 μg/kg and much lower than maximum residue limit in all matrices. This study may provide the essential data for optimizing the analytical method of pesticides in oil‐crop samples.     

Sample treatment and determination of pesticide residues in fatty vegetable matrices: A review

A demanding task in pesticide residue analysis is yet the development of multi-residue methods for the determination of pesticides in vegetables with relatively high fat content (i.e. edible oils and fatty vegetables). The separation of pesticides and other chemical contaminants from high-fat food samples prior to subsequent steps in the analytical process is yet a challenging issue to which much effort in method development has being applied. This review addresses the main sample treatment methodologies for pesticide residue analysis in fatty vegetable matrices. Even with the advent of advanced hyphenated techniques based on mass spectrometry these complex fatty matrices usually require extensive sample extraction and purification. Current methods involve the use of one or the combination of some of the following techniques for both the sample extraction and clean-up steps: liquid-liquid partitioning, solid-phase extraction (SPE), gel-permeation chromatography (GPC), matrix solid-phase dispersion (MSPD), etc. An overview of methods developed for these contaminants in fatty vegetables matrices is presented. Sample extraction and purification techniques are discussed and their most recent applications are highlighted. This review emphasizes that sample preparation is a critical step, but also the determination method is, and cannot be treated separately from sample treatment. In recent years, the appearance and use of new, more polar pesticides has fostered the development of liquid chromatography/mass spectrometry (LC-MS) besides gas chromatography. The main features of LC-MS for the analysis of multi-class pesticides in fatty vegetable samples will be also underlined, with an emphasis on the multi-class, multi-residue strategy and the difficulties associated.     

Multiresidue determination of 114 multiclass pesticides in flue‐cured tobacco by solid‐phase extraction coupled with gas chromatography and tandem mass spectrometry

A sensitive and robust multiresidue method for the simultaneous analysis of 114 pesticides in tobacco was developed based on solid‐phase extraction coupled with gas chromatography and tandem mass spectrometry. In this strategy, tobacco samples were extracted with acetonitrile and cleaned up with a multilayer solid‐phase extraction cartridge Cleanert TPT using acetonitrile/toluene (3:1) as the elution solvent. Two internal standards of different polarity were used to meet simultaneous pesticides quantification demands in the tobacco matrix. Satisfactory linearity in the range of 10–500 ng/mL was obtained for all 114 pesticides with linear regression coefficients higher than 0.994. The limit of detection and limit of quantification values were 0.02–5.27 and 0.06–17.6 ng/g, respectively. For most of the pesticides, acceptable recoveries in the range of 70–120% and repeatabilities (relative standard deviation) of <11% were achieved at spiking levels of 20, 100, and 400 ng/g. Compared with the reported multiresidue analytical method, the proposed method provided a cleaner test solution with smaller amounts of pigments, fatty acids as well as other undesirable interferences. The development and validation of the high sensitivity, high selectivity, easy automation, and high‐throughput analytical method meant that it could be successfully used for the determination of pesticides in tobacco samples.     

High‐performance liquid chromatography with diode‐array detection cotinine method adapted for the assessment of tobacco smoke exposure

Smoking is considered to be one of the main risk factors for cancer and other diseases and is the second leading cause of death worldwide. As the anti‐tobacco legislation implemented in Europe has reduced secondhand smoke exposure levels, analytical methods must be adapted to these new levels. Recent research has demonstrated that cotinine is the best overall discriminator when biomarkers are used to determine whether a person has ongoing exposure to tobacco smoke. This work proposes a sensitive, simple and low‐cost method based on solid‐phase extraction and liquid chromatography with diode array detection for the assessment of tobacco smoke exposure by cotinine determination in urine. The analytical procedure is simple and fast (20 min) when compared to other similar methods existing in the literature, and it is cheaper than the mass spectrometry techniques usually used to quantify levels in nonsmokers. We obtained a quantification limit of 12.30 μg/L and a recovery of over 90%. The linearity ranges used were 12–250 and 250–4000 μg/L. The method was successfully used to determine cotinine in urine samples collected from different volunteers and is clearly an alternative routine method that allows active and passive smokers to be distinguished.     

Investigating aroma diversity combining purge‐and‐trap,comprehensive two‐dimensional gas chromatography,and mass spectrometry

Headspace gas chromatography is frequently used for aroma profiling thanks to its ability to naturally exploit the volatility of aroma compounds, and also to provide chemical information on sample composition. Its main advantages rely on simplicity, no use of solvent, amenability to automation, and the cleanliness of the extract. In the present contribution, the most effective sampling (dynamic extraction), separation (multidimensional gas chromatography), and detection (mass spectrometry) techniques for untargeted analysis are exploited in combination, showing their potential in unraveling aroma profiles in fruit beers. To complete the overall analytical process, a neat workflow for data analysis is discussed and used for the successful characterization and identification of five different beer flavors (berries, cherry, banana, apple, and peach). From the technical viewpoint, the coupling of purge‐and‐trap, comprehensive two‐dimensional gas chromatography, and mass spectrometry makes the global methodology unique, and it is for the first time discussed. A (low‐)flow modulation approach allowed for the full transfer into the second dimension with mass‐spectrometry compatible flow (< 7 mL/min), avoiding the need of splitting before detection and making the overall method sensitive (1.2–5.2‐fold higher signal to noise ratio compared to unmodulated gas chromatography conditions) and selective.     

Influence of matrix on suitability of four methods for organochlorine pesticide analysis in waters

The monitoring of organochlorine pesticides has raised a great concern in the last years due to their toxicity (some of them are carcinogenic and endocrine disruptor compounds) and persistence. European Directive 2008/105/EC establishes very restrictive levels for organochlorine pesticides in surface waters. Therefore, simple, fast, highly sensitive and low cost analytical methods are required to detect and quantify these pollutants in water. In the present work, four procedures for extraction and determination are proposed and compared for the analysis of 28 organochlorine pesticides in tap, surface and sea waters. The suitability of each method of analysis was evaluated for each kind of water. The extraction methods proposed were: two solid-phase extraction methods using C₁₈ laminar disk and Oasis HLB cartridges, a solid-phase microextraction procedure using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, and a micro liquid–liquid extraction procedure using ethyl acetate as solvent. Determination of pesticides was performed by large volume on-column injector-gas chromatography-electron capture detection (LVOCI-GC-ECD), splitless-GC-ECD and GC-MS (mass spectrometry). All methods present a good sensitivity with method detection limits lower than 10?ng?L^?1, good accuracy with recoveries between 75 and 120% (with some exceptions) and good precision (relative standard deviations <15%), according to the Commission Decision 2002/657/EC criteria. The advantages and disadvantages of each method are discussed in terms of the green chemistry principles, the figures of merit and the matrix effect. This work tries to be a useful guidance for routine and control analysis laboratories.     

Rapid analysis of pesticide residues in drinking water samples by dispersive solid‐phase extraction based on multiwalled carbon nanotubes and pulse glow discharge ion source ion mobility spectrometry

An analytical method based on dispersive solid‐phase extraction with a multiwalled carbon nanotubes sorbent coupled with positive pulse glow discharge ion mobility spectrometry was developed for analysis of 30 pesticide residues in drinking water samples. Reduced ion mobilities and the mass–mobility correlation of 30 pesticides were measured. The pesticides were divided into five groups to verify the separation capability of pulse glow discharge in mobility spectrometry. The extraction conditions such as desorption solvent, ionic strength, conditions of adsorption and desorption, the amounts of multiwalled carbon nanotubes, and solution pH were optimized. The enrichment factors of pesticides were 5.4‐ to 48.7‐fold (theoretical enrichment factor was 50‐fold). The detection limits of pesticides were 0.01～0.77 μg/kg. The linear range was 0.005–0.2 mg/L for pesticide standard solutions, with determination coefficients from 0.9616 to 0.9999. The method was applied for the analysis of practical and spiked drinking water samples. All results were confirmed by high‐performance liquid chromatography with tandem mass spectrometry. The proposed method was proven to be a commendably rapid screening qualitative and semiquantitative technique for the analysis of pesticide residues in drinking water samples on site.     

Determination of organophosphorus pesticides by gas chromatography with mass spectrometry using a large‐volume injection technique after magnetic extraction

A fast and efficient method was developed for the extraction and determination of organophosphorus pesticides in water samples. Organophosphorus pesticides were extracted by solid‐phase extraction using magnetic multi‐walled carbon nanotubes and determined by gas chromatography with ion‐trap mass spectrometry. Parameters affecting the extraction were investigated. Under optimum conditions of the method, 10 mg magnetic multi‐walled carbon nanotubes were added into 10 mL sample. After 2 min, adsorbent particles settled at the bottom of test tube with a magnet. After removing aqueous supernatant, the analytes were desorbed with acetonitrile. Then, 70 μL of acetonitrile phase was injected into the gas chromatography and mass spectrometry system that had an ion‐trap analyzer. To achieve high sensitivity, the large‐volume‐injection technique was used with a programmed temperature vaporization inlet, and the ion‐trap mass spectrometer was operated in single ion storage mode. Under the best conditions, the enrichment factors and extraction recoveries were in the range of 113–124 and 74–103%, respectively. The limits of detection were between 3 and 15 ng/L, and the relative standard deviations were < 10%. This method was successfully used for the determination of organophosphorus pesticides in dam water, lagoon water, and river water samples with good reproducibility and recovery.     

Gas purge microsyringe extraction for quantitative direct gas chromatographic-mass spectrometric analysis of volatile and semivolatile chemicals

Sample pretreatment before chromatographic analysis is the most time consuming and error prone part of analytical procedures, yet it is a key factor in the final success of the analysis. A quantitative and fast liquid phase microextraction technique termed as gas purge microsyringe extraction (GP-MSE) has been developed for simultaneous direct gas chromatography-mass spectrometry (GC-MS) analysis of volatile and semivolatile chemicals without cleanup process. Use of a gas flowing system, temperature control and a conventional microsyringe greatly increased the surface area of the liquid phase micro solvent, and led to quantitative recoveries of both volatile and semivolatile chemicals within short extraction time of only 2 min. Recoveries of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and alkylphenols (APs) determined were 85-107%, and reproducibility was between 2.8% and 8.5%. In particular, the technique shows high sensitivity for semivolatile chemicals which is difficult to achieve in other sample pretreatment techniques such as headspace-liquid phase microextraction. The variables affecting extraction efficiency such as gas flow rate, extraction time, extracting solvent type, temperature of sample and extracting solvent were investigated. Finally, the technique was evaluated to determine PAHs, APs and OCPs from plant and soil samples. The experimental results demonstrated that the technique is economic, sensitive to both volatile and semivolatile chemicals, is fast, simple to operate, and allows quantitative extraction. On-site monitoring of volatile and semivolatile chemicals is now possible using this technique due to the simplification and speed of sample treatment.     

Liquid extraction surface analysis (LESA) of food surfaces employing chip‐based nano‐electrospray mass spectrometry

An automated surface‐sampling technique called liquid extraction surface analysis (LESA), coupled with infusion nano‐electrospray high‐resolution mass spectrometry and tandem mass spectrometry (MS/MS), is described and applied to the qualitative determination of surface chemical residues resulting from the artificial spraying of selected fresh fruits and vegetables with representative pesticides. Each of the targeted pesticides was readily detected with both high‐resolution and full‐scan collision‐induced dissociation (CID) mass spectra. In the case of simazine and sevin, a mass resolution of 100 000 was insufficient to distinguish the isobaric protonated molecules for these compounds. When the surface of a spinach leaf was analyzed by LESA, trace levels of diazinon were readily detected on the spinach purchased directly from a supermarket before they were sprayed with the five‐pesticide mixture. A 30 s rinse under hot running tap water appeared to quantitatively remove all remaining residues of this pesticide. Diazinon was readily detected by LESA analysis on the skin of the artificially sprayed spinach. Finally, incurred pyrimethanil at a level of 169 ppb in a batch slurry of homogenized apples was analyzed by LESA and this pesticide was readily detected by both high‐resolution mass spectrometry and full‐scan CID mass spectrometry, thus showing that pesticides may also be detected in whole fruit homogenized samples. This report shows that representative pesticides on fruit and vegetable surfaces present at levels 20‐fold below generally allowed EPA tolerance levels are readily detected and confirmed by the title technologies making LESA‐MS as interesting screening method for food safety purposes. Copyright © 2011 John Wiley & Sons, Ltd.     

Fast Multi‐residue Screening for 84 Pesticides in Tea by Gas Chromatography with Dual‐tower Auto‐sampler,Dual‐column and Dual Detectors

A fast multi‐residue screening method for determining pesticides in tea is described. Pesticides are extracted from tea with acetone and methylene chloride, then enriched and cleaned up with solid phase extraction (SPE) prior to gas chromatographic determination. The fast screening is achieved by a gas chromatograph system equipped with dual‐column, dual‐tower auto‐sampler and both electron capture detector (ECD) and flame photometric detector (FPD). Optimal conditions are investigated for the prospective pesticides including column selection, detection mode, the retention behaviors, quantitative calibration, as well as the recoveries and repeatability of pesticides from tea samples. Under the optimal conditions, with the FPD‐P detector accompanied CP‐SIL 13CB column, 48 pesticides can be separated well and detected within 38 min; and with a DB‐5 column, 35 ECD‐detectable pesticides can be separated and detected within 46 min. The recoveries of 84 pesticides in tea samples are 65–120% with 0.34–16% RSD for spiking 0.02–3.0 mg/kg standard species. Because of the thermal instability of most pesticides, direct cold extraction of pesticides from a tea sample is recommended. The proposed method provided a very fast and efficient procedure to screen 84 pesticides from a complicated tea sample matrix.     

Rapid quantification of pharmaceuticals and pesticides in passive samplers using ultra high performance liquid chromatography coupled to high resolution mass spectrometry

The presence of both pharmaceuticals and pesticides in the aquatic environment has become a well-known environmental issue during the last decade. An increasing demand however still exists for sensitive and reliable monitoring tools for these rather polar contaminants in the marine environment. In recent years, the great potential of passive samplers or equilibrium based sampling techniques for evaluation of the fate of these contaminants has been shown in literature. Therefore, we developed a new analytical method for the quantification of a high number of pharmaceuticals and pesticides in passive sampling devices. The analytical procedure consisted of extraction using 1:1 methanol/acetonitrile followed by detection with ultra-high performance liquid chromatography coupled to high resolution and high mass accuracy Orbitrap mass spectrometry. Validation of the analytical method resulted in limits of quantification and recoveries ranging between 0.2 and 20 ng per sampler sheet and between 87.9 and 105.2%, respectively. Determination of the sampler-water partition coefficients of all compounds demonstrated that several pharmaceuticals and most pesticides exert a high affinity for the polydimethylsiloxane passive samplers. Finally, the developed analytical methods were used to measure the time-weighted average (TWA) concentrations of the targeted pollutants in passive samplers, deployed at eight stations in the Belgian coastal zone. Propranolol, carbamazepine and seven pesticides were found to be very abundant in the passive samplers. These obtained long-term and large-scale TWA concentrations will contribute in assessing the environmental and human health risk of these emerging pollutants.     

Improved sample preparation of glyphosate and methylphosphonic acid by EPA method 6800A and time‐of‐flight mass spectrometry using novel solid‐phase extraction

The employment of chemical weapons by rogue states and/or terrorist organizations is an ongoing concern in the United States. The quantitative analysis of nerve agents must be rapid and reliable for use in the private and public sectors. Current methods describe a tedious and time‐consuming derivatization for gas chromatography–mass spectrometry and liquid chromatography in tandem with mass spectrometry. Two solid‐phase extraction (SPE) techniques for the analysis of glyphosate and methylphosphonic acid are described with the utilization of isotopically enriched analytes for quantitation via atmospheric pressure chemical ionization–quadrupole time‐of‐flight mass spectrometry (APCI‐Q‐TOF‐MS) that does not require derivatization. Solid‐phase extraction‐isotope dilution mass spectrometry (SPE‐IDMS) involves pre‐equilibration of a naturally occurring sample with an isotopically enriched standard. The second extraction method, i‐Spike, involves loading an isotopically enriched standard onto the SPE column before the naturally occurring sample. The sample and the spike are then co‐eluted from the column enabling precise and accurate quantitation via IDMS. The SPE methods in conjunction with IDMS eliminate concerns of incomplete elution, matrix and sorbent effects, and MS drift. For accurate quantitation with IDMS, the isotopic contribution of all atoms in the target molecule must be statistically taken into account. This paper describes two newly developed sample preparation techniques for the analysis of nerve agent surrogates in drinking water as well as statistical probability analysis for proper molecular IDMS. The methods described in this paper demonstrate accurate molecular IDMS using APCI‐Q‐TOF‐MS with limits of quantitation as low as 0.400 mg/kg for glyphosate and 0.031 mg/kg for methylphosphonic acid. Copyright © 2012 John Wiley & Sons, Ltd.     

Acid interferences in atomic spectrometry: analyte signal effects and subsequent reduction

When considering elemental analysis by atomic spectrometry techniques (e.g. flame atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry), the sample is normally introduced as a solution. In many instances an acid is present in that solution, as a result of previous sample preparation steps, analyte stabilization procedures, etc. Therefore, acids are among the most common matrices involved in spectroscopic analysis. The effect of the acid on the different stages taking place during the whole analytical process has been reviewed. Attention has been paid to the three techniques mentioned above. The results summarized here reveal the crucial role that acids play in atomic spectrometry, being one of the most important sources of interferences suffered by these techniques. In the last part of this bibliographic survey, the methods found for correction of the acid effect are mentioned and briefly described.     

Determination of multi‐pesticide residue in tobacco using multi‐walled carbon nanotubes as a reversed‐dispersive solid‐phase extraction sorbent

A multi‐pesticide residue determination method based on a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method using multiwalled carbon nanotubes as reversed‐dispersive solid‐phase extraction material was validated in 37 representative pesticides in tobacco. Determination was performed using liquid chromatography with tandem mass spectrometry in multiple reaction monitoring mode. Three major types of tobacco leaf samples, namely, flue‐cured, burley, and oriental tobacco were studied and compared. Three factors (extraction time, external diameter, and amount of extraction material used) that could affect the performance of multi‐walled carbon nanotubes were investigated. Optimization of sample preparation and determination allowed recoveries between 70.8 and 114.8% for all 37 pesticides with < 20.0% relative standard deviations at three spiking levels of 20, 50, and 200 μg/kg. The limits of quantification and limits of detection for the 37 pesticides ranged within 0.46–28.57 and 0.14–8.57 μg/kg at a signal‐to‐noise ratio of 10 and 3, respectively.