Simple and rapid determination of N6‐(Δ2‐isopentenyl)adenine,zeatin, and dihydrozeatin in plants using on‐line cleanup liquid chromatography coupled with hybrid quadrupole‐Orbitrap high‐resolution mass spectrometry

A simple and rapid method was developed for the determination of three free cytokinins, namely, N⁶‐(Δ²‐isopentenyl)adenine, zeatin, and dihydrozeatin, in plants using TurboFlow on‐line cleanup liquid chromatography combined with hybrid quadrupole‐Orbitrap high‐resolution mass spectrometry. The samples were extracted using acetonitrile, and then the extract was purified on a C₁₈‐p column, in which the sample matrix was removed and the analytes were retained. Subsequently, the analytes were eluted from the extraction column onto the analytical column (Hypersil Gold C₁₈ column) prior to chromatographic separation and hybrid Q‐Orbitrap detection using the targeted‐MS² scan mode. The linearity was satisfactory with a correlation coefficient of >0.999 at concentrations ranging from 5–5000 pg/mL. The limits of quantification for the analytes ranged from 4.2–5.2 pg/mL. The intra‐ and inter‐day average recoveries of analytes fortified at three levels ranged from 85.4–108.2%, and the intra‐ and inter‐day relative standard deviations ranged from 4.04–8.57%. The method was successfully applied for the determination of free cytokinins in different tissue samples of Oryza sativa and Arabidopsis thaliana.     

Determination of 252–302 Da and tentative identification of 316–376 Da polycyclic aromatic hydrocarbons in Standard Reference Materials 1649a Urban Dust and 1650b and 2975 Diesel Particulate Matter by accelerated solvent extraction–HPLC-GC-MS

We have assessed and compared the extraction recoveries of polycyclic aromatic hydrocarbons (PAHs) with molecular weights of 252, 276, 278, 300 and 302 from diesel particulate matter (PM) and urban air particles using ultrasonically assisted extraction and accelerated solvent extraction methods, and evaluated the effects of sample and treatment parameters. The results show that accelerated solvent extraction can extract PAHs more efficiently from diesel PM than ultrasonically assisted extraction. They also show that PAHs are more difficult to extract from diesel PM than from urban air particles. Using toluene and maximum instrumental settings (200 °C, 3,000 psi and five extraction cycles) with 30-min static extraction times > 85% of the analytes were estimated to be extracted from the diesel particles, but four extraction cycles with just 5-min static extraction times under these conditions seem to be sufficient to extract > 95% of the analytes from the urban air particles. The accelerated solvent extraction method was validated using the Standard Reference Materials (SRM) 1649a, Urban Dust, and SRM 2975 and SRM 1650a, Diesel Particulate Matter, from the US National Institute of Standards and Technology (NIST). PAH concentrations determined by on-line high-performance liquid chromatography–gas chromatography–mass spectrometry (HPLC-GC-MS) following the developed accelerated solvent extraction method were generally higher than the certified and reference NIST values and concentrations reported in the literature (e.g. the estimated concentration of benzo[a]pyrene in SRM 2975 was 15-fold higher than the NIST-certified value), probably because the extraction recoveries were higher than in previous studies. The developed accelerated solvent extraction method was used to analyse high molecular (HMW) weight PAHs (MW > 302) in the investigated SRMs, and more than 170 (SRM 1649a), 80 (SRM 1650b) and 60 (SRM 2975) potential high molecular weight PAHs were tentatively identified in them, with molecular weights (depending on the SRM sample analysed) of 316, 326, 328, 340, 342, 350, 352, 366, 374 and 376. This is, to our knowledge, the first study to tentatively report PAHs with molecular weights of 316, 326, 328, 342, 350, 352, 366 and 376 in diesel particulate matter. GC-MS chromatograms obtained in selected ion monitoring mode (extracted ions for the abovementioned m/z) and full-scan mass spectra of tentatively identified high molecular weight PAHs are shown in the Electronic supplementary material. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Application of dispersive liquid–liquid microextraction and reversed phase-high performance liquid chromatography for the determination of two fungicides in environmental water samples

Dispersive liquid–liquid microextraction (DLLME) has been developed for the extraction and preconcentration of diethofencarb (DF) and pyrimethanil (PM) in environmental water. In the method, a suitable mixture of extraction solvent (50 µL carbon tetrachloride) and dispersive solvent (0.75 mL acetonitrile) are injected into the aqueous samples (5.00 mL) and the cloudy solution is observed. After centrifugation, the enriched analytes in the sediment phase were determined by HPLC-VWD. Different influencing factors, such as the kind and volume of extraction and dispersive solvent, extraction time and salt effect were investigated. Under the optimum conditions, the enrichment factors for DF and PM were both 108 and the limit of detection were 0.021 ng mL^?1 and 0.015 ng mL^?1, respectively. The linear ranges were 0.08–400 ng mL^?1 for DF and 0.04–200 ng mL^?1 for PM. The relative standard deviation (RSDs) were both almost at 6.0% (n = 6). The relative recoveries from samples of environmental water were from the range of 87.0 to 107.2%. Compared with other methods, DLLME is a very simple, rapid, sensitive (low limit of detection) and economical (only 5 mL volume of sample) method.     

Microwave-Assisted Ionic Liquid Extraction of n-Alkanes and Isoprenoid Hydrocarbons from Petroleum Source Rock

Microwave-assisted ionic liquid extraction (MAILE) has been investigated for the extraction of n-alkanes and isoprenoid hydrocarbons from petroleum source rock and the conditions for maximum yield of the analytes were determined. An aqueous solution of an ionic liquid, 1-butyl-3-methylimidazolium bromide (BmimBr), was employed as the extracting medium. The results showed that the concentration of ionic liquid, extraction time and extraction temperatures have effects on extraction yields of aliphatic hydrocarbons with optimal conditions at: 3.0 mol L⁻¹ ionic liquid solution, 30 min and 120 °C, respectively. The extraction yields of all the n-alkanes and acyclic isoprenoid hydrocarbons were much higher using microwave-assisted ionic liquid extraction than with Soxhlet extraction and accelerated solvent extraction. There were good correlations of the diagnostic geochemical ratios calculated from the gas chromatographic (GC) data of MAILE, Soxhlet extraction and accelerated solvent extraction. The results of this study show that MAILE is an efficient and green analytical preparatory technique for geochemical evaluation of petroleum source rock.

     

Determination of 43 polycyclic aromatic hydrocarbons in air particulate matter by use of direct elution and isotope dilution gas chromatography/mass spectrometry

We are reporting a method for measuring 43 polycyclic aromatic hydrocarbons (PAH) and their methylated derivatives (Me-PAHs) in air particulate matter (PM) samples using isotope dilution gas chromatography/high-resolution mass spectrometry (GC/HRMS). In this method, PM samples were spiked with internal standards, loaded into solid phase extraction cartridges, and eluted by dichloromethane. The extracts were concentrated, spiked with a recovery standard, and analyzed by GC/HRMS at 10,000 resolution. Sixteen ¹³C-labeled PAHs and two deuterated Me-PAHs were used as internal standards to account for instrument variability and losses during sample preparation. Recovery of labeled internal standards was in the range of 86–115%. The proposed method is less time-consuming than commonly used extraction methods, such as sonication and accelerated solvent extraction (ASE), and it eliminates the need for a filtration step required after the sonication extraction method. Limits of detection ranged from 41 to 332 pg/sample for the 43 analytes. This method was used to analyze reference materials from the National Institute of Standards and Technology. The results were consistent with those from ASE and sonication extraction, and these results were also in good agreement with the certified or reference concentrations. The proposed method was then used to measure PAHs on PM_2.5 samples collected at three sites (urban, suburban, and rural) in Atlanta, GA. The results showed distinct seasonal and spatial variation and were consistent with an earlier study measuring PM_2.5 samples using an ASE method, further demonstrating the compatibility of this method and the commonly used ASE method.      

GC/MS analysis of water-soluble organics in atmospheric aerosol: optimization of a solvent extraction procedure for simultaneous analysis of carboxylic acids and sugars

The main goal of the present study was to develop a procedure for the simultaneous GC/MS analysis of a wide range of water-soluble organic compounds (WSOCs, mainly dicarboxylic acids and sugars) in atmospheric aerosol as chemical markers of atmospheric processes. The response surface methodology, including central composite design, was applied to systematically investigate and optimize the operating conditions of a solvent extraction method as the most widely used procedure for determining WSOCs in particulate matter (PM) samples. A solvent mixture of methanol/dichloromethane (90:10) and a volume of 10 ml were the optimum conditions that permit the simultaneous analysis of 30 target WSOCs, including dicarboxylic acids and sugars. Recoveries and limits of detection were determined for a standard mixture containing target analytes, and they varied from 79 to 103 % and 0.3 to 1 ng?m^?3, respectively. The optimized procedure was used for the analysis of field PM filters and demonstrated its feasibility in detecting several important environmental WSOCs.     

An international round-robin study for the analysis of particulate semi-volatile organics by thermal desorption gas chromatography mass spectrometry

Thermal desorption gas chromatography mass spectrometry (TD-GC/MS) is becoming more commonly used for the quantification and identification of organic compounds in particulate matter (PM), including ambient and source PM such as diesel particulate matter (DPM). It has been proven as an alternative to the traditional solvent extraction (SE) method and liquid injection gas chromatograph mass spectrometry (LI-GC/MS). However, little information is available on how different types of TD-GC/MS systems compare to each other for analysis of real-world PM samples or to direct LI-GC/MS for analysis of PM components in a test solution. To address this, CanmetENERGY Characterization Laboratory initiated a round robin with the participation of 10 laboratories worldwide. Three sample types were analysed: (i) a test solution with a suite of pure compounds commonly found in PM, analysed by TD-GC/MS and LI-GC/MS; (ii) a DPM sample, analysed by TD-GC/MS and SE; and (iii) an ambient PM sample, analysed by TD-GC/MS. The first part of the study showed good overall performance and comparability between the different TD-GC/MS systems and LI-GC/MS method for the analysis of PM components in a test solution, with some variability of results due to system types and parameters used, concentration of calibration standards, and whether or not an internal standards was used. The analysis of the DPM sample showed greater variability between laboratories and methods as many PM components were present near the detection limit and matrix effects particularly affected the TD-GC/MS analysis of heavier n-alkanes. In the last part of the study, for the analysis of an ambient PM sample by TD-GC/MS, the analysis of variance showed good comparison between labs for polycyclic aromatic hydrocarbons (94% non-significant), but slightly lower for n-alkanes (68%) and biomarkers (57%).     

Application of direct thermal desorption gas chromatography time-of-flight mass spectrometry for determination of nonpolar organics in low-volume samples from ambient particulate matter and personal samplers

Direct thermal desorption and in-situ derivatization thermal desorption methods in conjunction with gas chromatography time-of-flight mass spectrometry have been characterized and evaluated for analysis of trace components from filters loaded with ambient particulate matter (PM). The limits of quantification were in the range of 7–24 pg for n-alkanes, 20 pg for hopanes, and 4–22 pg for polycyclic aromatic hydrocarbons (PAH). The limit of quantification was defined as the minimum amount of substance that conforms to the minimum distinguishable signal plus 9 times the standard deviation of this background signal from PM-loaded filters. The method has been successfully applied to low-volume samples from ambient PM collected with stationary and personal samplers. Stationary samples were collected in winter 2008 and 2010 in Augsburg, Germany. Sample aliquots of 0.2-0.3 m3 from stationary sampling were analyzed. High diurnal variation in concentration and source contribution was found especially during periods with low wind speed and low mixing layer height. High contributions of solid fuel combustion (wood and coal) were found in evening and nighttime samples, leading to peak PAH concentrations at midnight more than 10 times higher than at noon. Finally, the method was applied to samples collected by means of a personal sampler, i.e. a micro aethalometer, in Xi’an, China. Quantitative data on n-alkanes, hopanes, and PAH were obtained from sample volumes of 17 and 24 l. The impact of different sources such as vehicular and biogenic emissions could be distinguished.     

Determination of Methylamines and Methylamine-N-oxides in Particulate Matter Using Solid Phase Extraction Coupled with Ion Chromatography

Currently, the concentrations of methylamines in fine particulate matter (PM) are most often measured by aerosol time-of-flight mass spectrometry. A novel method for identification and determination of methylamines and methylamine-N-oxides in fine particles based on solid phase extraction (SPE) coupled with ion chromatography (IC) was developed. The experimental conditions including SPE conditions and chromatographic conditions were optimized. The quartz filter loaded with particulate matter (PM) samples was ultrasonically extracted with 20 mL of methanol and water (1:3, V/V) and the extraction process was repeated twice. After extraction, a total of 60 mL of extraction solvent was dropped into the extraction equipment for SPE. The Agilent AccuBond C₁₈ was chosen for enriching the methylamine, dimethylamine, trimethylamine and trimethylamine-N-oxide in fine particles. Under the optimum conditions, the target species on Agilent AccuBond C₁₈ were washed by 0.5 mL of acetonitrile solution and then concentrated (2 mL) before injecting into IC for analysis. A PRP X-200 (250 mm × 4 mm i.d.) was used for separation of analytes at 25 °C. The mobile phase was a mixture of 3% (V/V) acetonitrile solution and 5 mM nitric acid with the flow rate of 1 mL min^–1. The four aliphatic amine species were fully resolved and completely separated within 30 min. The linearity of the four compounds ranged from 0.45 μg kg^–1 to 1000 μg kg^–1 with precisions of 2%–4% and detection limits of 0.002–0.003 μg m^–3. The recoveries of the four aliphatic amine species in real PM samples were higher than 90%. This method was successfully applied in the analysis of real fine PM samples collected in Beijing. The concentrations of trimethylamine and methylamine-N-oxides were in the range of (0.01 ± 0.001) μg m^–3–(0.08 ± 0.002) μg m^–3 and (0.05 ± 0.001) μg m^–3–(0.14 ± 0.002) μg m^–3 for Beijing dust and haze PM samples, respectively.     

Determination of five polar herbicides in water samples by ionic liquid dispersive liquid-phase microextraction

A simple, rapid and efficient ionic liquid based on dispersive liquid-phase microextraction (IL-DLPME) method was developed for the determination of three triazine and two phenylurea herbicides in water samples. IL (1-hexyl-3-methylimidazolium hexafluorophosphate [C₆MIM][PF₆]) that dispersed completely into the water solution under controlled temperature was used as the extraction solvent. The analytes were easily concentrated into the ionic liquid phase. This technique combined the process of extraction and concentration of the analytes into one step and avoided use of the more common, toxic organic solvents. The factors affecting the extraction efficiency such as the IL volume, sample pH, extraction time, centrifugal time, dissoluble temperature and ionic strength were optimized. The extracts were analyzed by high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD). Under the optimized conditions, recoveries (50.5–109.1%) were obtained for the target analytes in water samples. The calibration curves were linear and the correlation coefficient ranged from 0.9947 to 0.9973 in the concentration levels of 5–100 μg L^?1. The relative standard deviations (RSDs, n?=?5) were 6.80–10.78%. The limit of detections (LODs) for the five polar herbicides were between 0.46 μg L^?1 and 0.89 μg L^?1.     

Selective determination of estrogenic compounds in water by microextraction by packed sorbents and a molecularly imprinted polymer coupled with large volume injection-in-port-derivatization gas chromatography-mass spectrometry

A fully automated protocol consisting of microextraction by packed sorbents (MEPS) coupled with large volume injection-in-port-derivatization-gas chromatography–mass spectrometry (LVI-derivatization-GC–MS) was developed to determine endocrine disrupting compounds (EDCs) such as alkylphenols, bisphenol A, and natural and synthetic hormons in river and waste water samples. During method optimization, the extraction parameters as ion strength of the water sample, the MEPS extraction regime, the volume of organic solvent used for the elution/injection step, the type of elution solvents and the selectivity of the sorbents were studied. For optimum in-port-derivatization, 10 μL of the derivatization reagent N,O-bis(trimethylsilyl)triufloroacetamide with 1% of trimethylchlorosilane (BSTFA + 1% TMCS) was used. 17β-Estradiol-molecularly imprinted polymer (MIP) and silica gel (modified with C-18) sorbents were examined for the enrichment of the target analytes from water samples and the obtained results revealed the high selectivity of the MIP material for extraction of substances with estrogen-like structures. Recovery values for most of the analytes ranged from 75 to 109% for the C18 sorbent and from 81 to 103% for the MIP material except for equilin (on C18 with only 57–66% recovery). Precision (n = 4) of the entire analysis protocol ranged between 4% and 22% with both sorbents. Limits of detection (LODs) were at the low ng L⁻¹ level (0.02–87, C18 and 1.3–22, MIP) for the target analytes.     

High Temperature Steam Extraction for the Determination of Aliphatic Hydrocarbons in Petroleum Source Rock

A simple method for the extraction of hydrocarbons from petroleum source rock by high temperature steam was investigated and the conditions for maximum yield were determined. The results showed that the temperature and kinetic rates have significant effects. The optimum temperature for the extraction of n-alkanes and isoprenoid hydrocarbons from sedimentary organic rocks was 250 °C. The optimum extraction time for lower and medium molecular weight n-alkanes was 20 min, while the higher molecular weight alkanes were exhaustively extracted after 50 min. The yields of the analytes were much higher with using the high temperature steam extraction than Soxhlet extraction. The recoveries of the n-alkanes for GC–MS analysis from the extractant water by SPME with a PDMS fibre ranged from 90 to 100% and most of the compounds were above 93%.

     

Comparison of hot Soxhlet and accelerated solvent extractions with microwave and supercritical fluid extractions for the determination of polycyclic aromatic hydrocarbons and nitrated derivatives strongly adsorbed on soot collected inside a diesel particulate filter

Several methods of extraction were optimized to extract polycyclic aromatic hydrocarbons (PAHs), their nitrated derivatives and heavy n-alkanes from a highly adsorptive particulate matter resulting from the combustion of diesel fuel in a diesel engine. This particular carbonaceous particulate matter, collected at high temperatures in cordierite diesel particulate filters (DPF), which are optimized for removing diesel particles from diesel engine exhaust emissions, appeared extremely refractory to extractions using the classical extracting conditions for these pollutants. In particular, the method of accelerated solvent extraction (ASE) is described in detail here. Optimization was performed through experimental design to understand the impact of each factor studied and the factors’ possible interactions on the recovery yields. The conventional extraction technique, i.e., Soxhlet extraction, was also carried out, but the lack of quantitative extractions led us to use a more effective approach: hot Soxhlet. It appeared that the extraction of the heaviest PAHs and nitroPAHs by either the optimized ASE or hot Soxhlet processes was far from complete. To enhance recovery yields, we tested original solvent mixtures of aromatic and heteroaromatic solvents. Thereafter, these two extraction techniques were compared to microwave-assisted extraction (MAE) and supercritical fluid extraction (SFE). In every case, the only solvent mixture that permitted quantitative extraction of the heaviest PAHs from the diesel soot was composed of pyridine and diethylamine, which has a strong electron-donor character. Conversely, the extraction of the nitrated PAHs was significantly improved by the use of an electron-acceptor solvent or by introducing a small amount of acetic acid into the pyridine. It was demonstrated that, for many desirable features, no single extraction technique stound out as the best: ASE, MAE or SFE could all challenge hot Soxhlet for favourable extractions. Consequently, the four optimized extraction techniques were performed to extract the naturally polluted diesel soot collected inside the DPF. Comparisons with the NIST standard reference material SRM 1650b showed that the soot collected from the DPF contained 50% fewer n-alkanes, and also markedly lower levels of PAHs (44 less concentrated) than SRM 1650b, and that the ratio of nitroPAHs to PAHs was increased. These results were attributed to the high temperatures reached inside the particulate filter during sampling runs and to the contribution of the catalytic DPF to aromatic and aliphatic hydrocarbons abatement.     

High Temperature Steam Extraction for the Determination of Aliphatic Hydrocarbons in Petroleum Source Rock

A simple method for the extraction of hydrocarbons from petroleum source rock by high temperature steam was investigated and the conditions for maximum yield were determined. The results showed that the temperature and kinetic rates have significant effects. The optimum temperature for the extraction of n-alkanes and isoprenoid hydrocarbons from sedimentary organic rocks was 250 °C. The optimum extraction time for lower and medium molecular weight n-alkanes was 20 min, while the higher molecular weight alkanes were exhaustively extracted after 50 min. The yields of the analytes were much higher with using the high temperature steam extraction than Soxhlet extraction. The recoveries of the n-alkanes for GC–MS analysis from the extractant water by SPME with a PDMS fibre ranged from 90 to 100% and most of the compounds were above 93%.     

Novel mode of liquid‐phase microextraction: A magnetic stirrer as the extractant phase holder

In the present study, a novel configuration of liquid‐phase microextraction was proposed, in which a magnetic stirrer with a groove was used as the extractant phase holder. It was termed as magnetic stirrer liquid‐phase microextraction. In this way, the stability of the organic solvent was much improved under high stirring speed; the extraction efficiency was enhanced due to the enormously enlarged contact area between the organic solvent and aqueous phase. The extraction performance of the magnetic stirrer liquid‐phase microextraction was studied using chlorobenzenes as the probe analytes. A wide linearity range (20 pg/mL to 200 ng/mL) with a satisfactory linearity coefficient (r² > 0.998) was obtained. Limits of detection ranged from 9.0 to 12.0 pg/mL. Good reproducibility was achieved with intra‐ and inter‐day relative standard deviations <4.8%. The proposed magnetic stirrer liquid‐phase microextraction was simple, environmentally friendly and efficient; compared to single‐drop microextraction, it had obvious advantages in terms of reproducibility and extraction efficiency. It is a promising miniaturized liquid‐phase technology for real applications.     

Chemometrics assisted dispersive liquid–liquid microextraction for quantification of seven UV filters in urine samples by HPLC‐DAD

In the present study, dispersive liquid–liquid microextraction followed by high performance liquid chromatography‐diode array detection has been developed as simple, rapid, accurate, and efficient sample preparation method for simultaneous determination of seven organic UV filters in urine samples. The influence of the main effects as well as their interactions was studied through a 2^(6–2) fractional factorial design. The candidate parameters were: type and volume of dispersant and extraction solvents, sample pH, and salt concentration. Under final optimal conditions, the analytes were extracted from 5 mL of samples by addition of 0.5 mL of acetonitrile (dispersing solvent) containing 70 μL of carbon tetrachloride (extraction solvent), without modifying the pH of the solution and applying the (+1) level of salt concentration (10% w/v NaCl). The assay was linear (R² > 0.997), relative recoveries ranged from 86.9 up to 97.3% and the LOQs between 3 and 45 ng mL^?1 were obtained. The intra‐ and interday RSDs were lower than 5 and 8% at the middle point of the linear range, respectively. The proposed method was successfully applied to different volunteer urine samples and it was shown that the extraction efficiency was not affected by the type of urine samples.     

Ultra-trace determination of aquaculture chemotherapeutants and degradation products in environmental matrices by LC-MS/MS

Two of the most common products currently used to control parasitic sea lice in fin fish aquaculture, salmon in particular, are Slice® and AlphaMax®. Emamectin benzoate (EB) is the active ingredient in Slice® and deltamethrin is the active ingredient in AlphaMax®. Several analytical methods have been developed for the determination of the active ingredients in these products but these have been focused on specific matrices and lack the sensitivity and versatility required in environmental monitoring. Here we present a validated, versatile, and simple analytical method for the determination of EB, its desmethyl degradation product (AB), and deltamethrin in a wide range of environmental matrices (sea water, marine sediment, and tissue). Sediments and tissues were extracted by accelerated solvent extraction (ASE®) and sample cleanup was achieved by solid phase extraction (SPE) while sea water was extracted using SPE disks. Analyte identification and quantification was based on liquid chromatography tandem mass spectrometry (LC-MS/MS) instrumentation with electrospray ionization, and multiple reaction monitoring (MRM). Method detection limits for the target analytes was in the parts per trillion (pg?g^?1) level for tissue and sediment and parts per quadrillion (pg?L^?1) for water. Except for deltamethrin in sea water, method performance in terms of analyte recoveries was better than 60%, and the method precision was RSD<20%. The method was used to determine EB and AB concentrations in water, sediment and prawn tissue samples collected near salmon aquaculture sites treated with Slice®. A distinct concentration gradient was observed in the immediate vicinity (within 50 to 100?m radius) of the salmon aquaculture sites where EB was detected at low ng?g^?1 levels for tissue (EB ranged from 0.041 to 3.0?ng?g^?1) and sediment (EB ranged from 0.051 to 35?ng?g^?1) and pg?L^?1 levels (EB ranged from 3 to 209?pg?L^?1) for water samples.     

Silicone discs as disposable enrichment probes for gas chromatography-mass spectrometry determination of UV filters in water samples

This work describes an effective, low solvent consumption and affordable sample preparation approach for the determination of eight UV filters in surface and wastewater samples. It involves sorptive extraction of target analytes in a disposable, technical grade silicone disc (5 mm diameter × 0.6 mm thickness) followed by organic solvent desorption, large volume injection (LVI), and gas chromatography-mass spectrometry determination. Final working conditions involved overnight extraction of 100-mL samples, containing 10% of methanol, followed by analytes desorption with 0.2 mL of ethyl acetate. The method provides linear responses between the limits of quantification (from 0.003 to 0.040 ng mL⁻¹) and 10 ng mL⁻¹, an intra-day precision below 13%, and low matrix effects for surface, swimming pool, and treated sewage water samples. Moreover, the extraction yields provided by silicone discs were in excellent agreement with those achieved using polydimethylsiloxane-covered stir bars. Several UV filters were found in surface and sewage water samples, with the maximum concentrations corresponding to octocrylene.     

Determination of fungicides in sediments using a dispersive liquid–liquid microextraction procedure based on solidification of floating organic drop

A dispersive liquid–liquid microextraction procedure based on solidification of floating organic droplet has been investigated for the determination of fungicides (cyprodinil, difenoconazole, myclobutanil, and spiroxamine) in sediments by HPLC with diode array detection. In the overall extraction process, the extraction solvents can be separated easily from the sample solution, and the experiment time was shortened. Moreover, several parameters such as the type and volume of the extraction solvent and dispersive solvent, centrifugal speed, extraction time, and salt effect that affect the extraction efficiencies of the target fungicides were studied and optimized. Under the optimized conditions, the LOD for the target analytes were in the range of 0.1–0.5 μg/g. Satisfactory recoveries of the target analytes in the sediment samples were 81.00–99.00%, with RSDs (n = 5) that ranged from 1.8 to 6.5%. Finally, the simple, sensitive, and environmentally friendly method was successfully applied to determine the target fungicides in actual sediment samples.     

Optimisation of the extraction of polycyclic aromatic hydrocarbons and their nitrated derivatives from diesel particulate matter using microwave-assisted extraction

Pressurised microwave-assisted extraction was used to extract a complex mixture containing polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs and heavy n-alkanes from a particularly refractory carbonaceous material resulting from the combustion in a diesel engine. A second-order central composite design was used to determine the optimal conditions of extraction in terms of time, temperature, volume and nature of extracting solvent from spiked diesel soots. To begin, methylene chloride, tetrahydrofuran and chloroform were tested for extracting the spiked diesel particulates; however, the nature of these solvents was not really an influential factor. Volume was the most influential factor and was kept at a medium level to enhance the extraction of heavy PAHs without introducing an important dilution factor. Temperature and time were not influential as main factors but interacted with the other factors. Finally, high temperature and duration associated with a medium volume of methylene chloride were better for the extractions. After this optimisation, five-ring and six-ring PAHs were nevertheless not satisfactorily desorbed. Other solvents were therefore tested. Only aromatic ones, and particularly heterocyclic aromatic solvents, managed to desorb the heaviest PAHs. Pyridine, with its both aromatic and its basic character, was the most successful solvent. Desorption was even complete with an addition of 17% of diethylamine into pyridine. So, using MAE, we succeeded in extracting quantitatively, from the spiked refractory diesel soot surface, two-ring to six-ring PAHs, heavy n-alkanes and short nitrated PAHs. However, heavy nitrated PAHs were better extracted with a small addition of acetic acid (1%) into pyridine instead of a basic cosolvent.