Analysis of polar pesticides in water and wine samples by automated in-tube solid-phase microextraction coupled with high-performance liquid chromatography-mass spectrometry

Current overview and perspectives in environmentally friendly microextractions of carbamates and dithiocarbamates

Carbamates and dithiocarbamates are two classes of pesticides widely employed in the agriculture practice to control and avoid pests and weeds, hence, the monitoring of the residue of those pesticides in different foodstuff samples is important. Thus, this review presents the classification, chemical structure, use, and toxicology of them. Moreover, it was shown the evolution of liquid- and solid-phase microextractions employed in the extraction of carbamates and dithiocarbamates in water and foodstuff samples. The classification, operation mode, and application of the microextractions of liquid-phase and solid-phase used in their extraction were discussed and related to the analytical parameters and guidelines of green analytical chemistry.

Triazine-based covalent porous organic polymer for the online in-tube solid-phase microextraction of polycyclic aromatic hydrocarbons prior to high-performance liquid chromatography-diode array detection

A triazine-based covalent organic porous polymer (COP) was synthesized from the monomers 1,3,5-triphenylbenzene and tricyanogen chloride via the Friedel-Crafts reaction and characterized in detail using Brunauer-Emmett-Teller analysis, X-ray photoelectron spectroscopy, elemental analysis, and scanning electron microscopy, which confirmed that the COP had a rough surface and suitable extraction site. It was then employed in in-tube solid-phase microextraction combined with a high-performance liquid chromatography-diode array detector. The COP adsorbent was evaluated with different types of analyte, including estrogens, polycyclic aromatic hydrocarbons (PAHs), and plasticizers. The COP produced its best performance with PAHs. In order to obtain the highest extraction efficiency for PAHs, the main influential factors were optimized. Furthermore, a sensitive analytical method was established with the limits of detection of 0.004-0.010 µg L^-1, high enrichment factor of 1110-2763, and wide linear ranges (0.013-20.0 µg L^-1, 0.016-20.0 µg L^-1 and 0.033-20.0 µg L^-1). The relative standard deviation in intra-day and inter-day tests was also controlled to be within 0.3-3.1%. The proposed method was employed in the online detection of trace PAHs in real water samples, with satisfactory results obtained.

In-tube solid-phase microextraction: Current trends and future perspectives

In-tube solid-phase microextraction (IT-SPME) was developed about 24 years ago as an effective sample preparation technique using an open tubular capillary column as an extraction device. IT-SPME is useful for micro-concentration, automated sample cleanup, and rapid online analysis, and can be used to determine the analytes in complex matrices simple sample processing methods such as direct sample injection or filtration. IT-SPME is usually performed in combination with high-performance liquid chromatography using an online column switching technology, in which the entire process from sample preparation to separation to data analysis is automated using the autosampler. Furthermore, IT-SPME minimizes the use of harmful organic solvents and is simple and labor-saving, making it a sustainable and environmentally friendly green analytical technique. Various operating systems and new sorbent materials have been developed to improve its extraction efficiency by, for example, enhancing its sorption capacity and selectivity. In addition, IT-SPME methods have been widely applied in environmental analysis, food analysis and bioanalysis. This review describes the present state of IT-SPME technology and summarizes its current trends and future perspectives, including method development and strategies to improve extraction efficiency.

Fabric phase sorptive extraction followed by ultra-performance liquid chromatography-tandem mass spectrometry for the determination of fungicides and insecticides in wine

In this work, fabric phase sorptive extraction (FPSE) is investigated for the extraction and preconcentration of ultra-trace level residues of fungicides (19 compounds) and insecticides (3 species) in wine samples. Subsequently, the preconcentrated analytes are selectively determined using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Parameters affecting the efficiency and repeatability of the extraction are evaluated in depth; moreover, the proposed method is characterized in terms of linear response range, trueness, precision and limits of quantification (LOQs). The set-up of the extraction process and the type of coating were the variables exerting the most prominent effects in the repeatability and the yield of the extraction, respectively. Under optimized conditions, samples (10 mL of wine diluted with the same volume of ultrapure water) were extracted with a small amount of cellulose fabric (3 discs with 4 mm of diameter: total surface 0.38 cm²) coated with a sol-gel polyethylene glycol sorbent (sorbent amount 3.3 mg), immersed in the diluted sample, without being in direct contact with the PTFE covered magnetic stir bar. Following the overnight extraction step, analytes were quantitatively recovered using only 0.3 mL of an ACN-MeOH (80:20) mixture. Under equilibrium sampling conditions, the linear response range of the method varied from 0.2 to 200 ng mL^-1, with limits of quantification (LOQs) between 0.03 and 0.3 ng mL^-1. Relative recoveries ranged from 77 ± 6% to 118 ± 4%, and from 87 ± 4% to 121 ± 6% for red and white wines, respectively. Application of the optimized method to commercial wines demonstrated the existence of up to 9 out of 22 investigated compounds in the same wine sample. The compound identified at the highest concentration was iprovalicarb (IPR), with a value of 130 ± 9 ng mL^-1 in a commercial white wine.

Atrazine adsorption removal with nylon6/polypyrrole core-shell nanofibers mat: possible mechanism and characteristics

A functionalized nylon6/polypyrrole core-shell nanofibers mat (PA6/PPy NFM) was prepared via situ polymerization on nylon6 electrospun nanofibers mat (PA6 NFM) template and used as an adsorbent to remove atrazine from aqueous solutions. The core-shell structure of PA6/PPy NFM can be clearly proved under scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of initial solution pH and ionic strength, as well as the comparison of the adsorption capacity of functionalized (PA6/PPy NFM) and non-functionalized (PA6 NFM) adsorbent, were examined to reveal the possible adsorption mechanism. The results indicated that π-π interaction and electrostatic interaction should play a key role in the adsorption process. The kinetics and thermodynamics studies also further elucidated the detailed adsorption characteristics of atrazine removal by PA6/PPy NFM. The adsorption of atrazine could be well described by the pseudo-second-order equation. The adsorption equilibrium data was well fitted with the Freundlich isotherm model with a maximum adsorption capacity value of 14.8 mg/g. In addition, the increase of adsorption rate caused by a temperature increase could be felicitously explained by the endothermic reaction. The desorption results showed that the adsorption capacity remained almost unchanged after six adsorption/desorption cycles. These results suggest that PA6/PPy NFM could be employed as an efficient adsorbent for removing atrazine from contaminated water sources.

Microextraction techniques coupled to liquid chromatography with mass spectrometry for the determination of organic micropollutants in environmental water samples

Until recently, sample preparation was carried out using traditional techniques, such as liquid–liquid extraction (LLE), that use large volumes of organic solvents. Solid-phase extraction (SPE) uses much less solvent than LLE, although the volume can still be significant. These preparation methods are expensive, time-consuming and environmentally unfriendly. Recently, a great effort has been made to develop new analytical methodologies able to perform direct analyses using miniaturised equipment, thereby achieving high enrichment factors, minimising solvent consumption and reducing waste. These microextraction techniques improve the performance during sample preparation, particularly in complex water environmental samples, such as wastewaters, surface and ground waters, tap waters, sea and river waters. Liquid chromatography coupled to tandem mass spectrometry (LC/MS/MS) and time-of-flight mass spectrometric (TOF/MS) techniques can be used when analysing a broad range of organic micropollutants. Before separating and detecting these compounds in environmental samples, the target analytes must be extracted and pre-concentrated to make them detectable. In this work, we review the most recent applications of microextraction preparation techniques in different water environmental matrices to determine organic micropollutants: solid-phase microextraction SPME, in-tube solid-phase microextraction (IT-SPME), stir bar sorptive extraction (SBSE) and liquid-phase microextraction (LPME). Several groups of compounds are considered organic micropollutants because these are being released continuously into the environment. Many of these compounds are considered emerging contaminants. These analytes are generally compounds that are not covered by the existing regulations and are now detected more frequently in different environmental compartments. Pharmaceuticals, surfactants, personal care products and other chemicals are considered micropollutants. These compounds must be monitored because, although they are detected in low concentrations, they might be harmful toward ecosystems.

Molecular classification of pesticides including persistent organic pollutants, phenylurea and sulphonylurea herbicides

Pesticide residues in wine were analyzed by liquid chromatography–tandem mass spectrometry. Retentions are modelled by structure–property relationships. Bioplastic evolution is an evolutionary perspective conjugating effect of acquired characters and evolutionary indeterminacy–morphological determination–natural selection principles; its application to design co-ordination index barely improves correlations. Fractal dimensions and partition coefficient differentiate pesticides. Classification algorithms are based on information entropy and its production. Pesticides allow a structural classification by nonplanarity, and number of O, S, N and Cl atoms and cycles; different behaviours depend on number of cycles. The novelty of the approach is that the structural parameters are related to retentions. Classification algorithms are based on information entropy. When applying procedures to moderate-sized sets, excessive results appear compatible with data suffering a combinatorial explosion. However, equipartition conjecture selects criterion resulting from classification between hierarchical trees. Information entropy permits classifying compounds agreeing with principal component analyses. Periodic classification shows that pesticides in the same group present similar properties; those also in equal period, maximum resemblance. The advantage of the classification is to predict the retentions for molecules not included in the categorization. Classification extends to phenyl/sulphonylureas and the application will be to predict their retentions.

QSPR prediction of chromatographic retention times of pesticides: partition and fractal indices

The high-performance liquid-chromatographic retentions of red-wine pesticide residues are modeled by structure-property relationships. The effect of different types of features is analyzed: geometric, lipophilic, etc. The properties are fractal dimensions, partition coefficient, etc., in linear and nonlinear correlation models. Biological plastic evolution is an evolutionary perspective conjugating the effect of acquired characters and relations that emerge among the principles of evolutionary indeterminacy, morphological determination and natural selection. It is applied to design the co-ordination index that is used to characterize pesticide retentions. The parameters used to calculate the co-ordination index are the molar formation enthalpy, molecular weight and surface area. The morphological and co-ordination indices barely improve the correlations. The fractal dimension averaged for non‑buried atoms, partition coefficient, etc. distinguishes the pesticide molecular structures. The structural and constituent classification is based on nonplanarity, and the number of cycles, and O, S, N and Cl atoms. Different behavior depends on the number of cycles.

High-performance liquid chromatography with paired ion electrospray ionization (PIESI) tandem mass spectrometry for the highly sensitive determination of acidic pesticides in water

A novel method based on the paired ion electrospray ionization (PIESI) mass spectrometry has been developed for determination of acidic pesticides at ultratrace levels in surface and ground waters. The proposed approach provides greatly enhanced sensitivity for acidic pesticides and overcomes the drawbacks of the less sensitive negative ion mode ESI-MS. The limits of detection (LODs) of 19 acidic pesticides were evaluated with four types of dicationic ion-pairing reagent (IPR) in both single ion monitoring (SIM) and selected reaction monitoring (SRM) mode. The LOD of 19 pesticides obtained with the use the optimal dicationic ion-pairing reagent ranged from 0.6pg to 19pg, indicating the superior sensitivity provided by this method. The transition pathways for different pesticide-IPR complexes during the collision induced dissociation (CID) were identified. To evaluate and eliminate any matrix effects and further decrease the detection limits, off-line solid-phase extraction (SPE) was performed for DI water and a river water matrix spiked with 2000ng L(-1) and 20ng L(-1) pesticides standards respectively, which showed an average percent recovery of 93%. The chromatographic separation of the acidic pesticides was conducted by high-performance liquid chromatography (HPLC) using a C18 column (250mm×2.1mm) in the reversed phase mode using linear gradient elution. The optimized HPLC-PIESI-MS/MS method was utilized for determination of acidic pesticide at ng L(-1) level in stream/pond water samples. This experimental approach is 1-3 orders of magnitude more sensitive for these analytes than other reported methods performed in the negative ion mode.

Determination of pesticide residues in wine by membrane-assisted solvent extraction and high-performance liquid chromatography-tandem mass spectrometry

The determination of pesticides in food products is an essential issue to guarantee food safety and minimise health risks of consumers. A protocol based on membrane-assisted solvent extraction and liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) that allows the determination of 18 pesticides in red wine at minimum labour effort for sample preparation was developed and validated. Ten millilitres of wine were extracted using 100 μL of toluene filled in a non-porous polyethylene membrane bag which is immersed in the wine sample. After 150 min extraction under stirring, an aliquot of the extraction solution is analysed using HPLC-MS/MS. The limits of quantification ranged from 3 ng/L for Pirimicarb to 1.33 μg/L for Imidacloprid. Quantification by matrix-matched calibration provided relative standard deviations ≤16 % for most of the target pesticides. The linearity of calibration was given over three to four orders of magnitude, which enables the reliable measurement of a broad range of pesticide concentrations, and for each target pesticide, the sensitivity of the protocol meets the maximum residue levels set by legislations at least for wine grapes. Good agreement of results was found when the new method was compared with a standard liquid-liquid extraction protocol. In five wine samples analysed, Carbendazim and Metalaxyl were determined at micrograms per litre concentrations, even in some of the organic wines. Tebuconazol and Cyprodinitril were determined at lower abundance and concentration, followed by Spiroxamin and Diuron.

Molecularly imprinted polymer for analysis of trace atrazine herbicide in water

A molecularly imprinted polymer (MIP) for atrazine was synthesized by non-covalent method. The binding capacity of MIP was 1.00 mg g(-1) polymer. The selectivity and recovery were investigated with various pesticides which are mostly, found in the environment, for both similar and different chemical structure of atrazine. The competitive recognition between atrazine and structurally similar compounds was evaluated and it was found that the system provided highest recovery and selectivity for atrazine while low recovery and selectivity were obtained for the other compounds. The highest recovery was obtained from MIP compared with non-imprinted polymer (NIP), a commercial C(18) and a granular activated carbon (GAC) sorbent. The method provided high recoveries ranged from 94 to 99% at two spiked levels with relative standard deviations less than 2%. The lower detection limit of the method was 80 ng L(-1). This method was successfully applied for analysis of environmental water samples.