Hollow fiber microextraction: a new hybrid microextraction technique for trace analysis.

A new hybrid microextraction technique (hollow fiber microextraction) is presented that uses the main concepts and advantages of the modern miniaturized devices used for trace analysis. This novel analytical approach uses devices made of polypropylene membranes (10.0 mm long and 0.6 mm internal diameter) in which convenient organic solvents are embedded that promote fast kinetics during the enrichment process, using the floating sampling technology concept. An innovative analytical cycle is also proposed by use of low-cost disposable devices during the microextraction stage together with a user-friendly ("single liquid desorption step") back-extraction stage in compliance with green analytical chemistry principles. To evaluate the performance of the proposed technique, 18 polycyclic aromatic hydrocarbons (PAHs) were used as model compounds and were monitored by gas chromatography coupled with mass spectrometry. Under optimized experimental conditions, assays performed on 25 mL aqueous samples spiked with the PAHs at trace level yielded average recoveries between (14.5 ± 8.2)% (dibenzo[a,h]anthracene) and (90.4 ± 8.4)% (benzo[a]anthracene) with use of a device in which n-nonane had been embedded. Low detection limits were also achieved (2.50-6.00 ng L-1), as well as good linear dynamic ranges (20.00-2000.00 ng L-1), with suitable coefficients of determination (r2 > 0.9905) and appropriate precision (relative standard deviation below 15%). By use of the standard addition method, the proposed hybrid microextraction technique had remarkable performance to monitor PAHs at the ultratrace level in several types of matrices, including surface water, wastewater, soil, tea, and fish liver samples. From the data obtained, the new hybrid hollow fiber microextraction technique proved to be user-friendly, eco-friendly, cost-effective, and very competitive for routine work. In short, the novel microextraction technique proposed herein is a remarkable alternative to other well-established microextraction techniques for ultratrace analysis of emerging compounds in real matrices. Graphical abstract Innovative analytical procedure for hollow fiber microextraction (HFµE). GC gas chromatography, LD liquid desorption.

Bar adsorptive microextraction technique - application for the determination of pharmaceuticals in real matrices.

In the present work, bar adsorptive microextraction using miniaturized devices (7.5 × 3.0 mm) coated with suitable sorbent phases, combined with microliquid desorption (100 µL) followed by high-performance liquid chromatography with diode array detection (BAµE-µLD/HPLC-DAD), is proposed for the determination of trace level of six pharmaceuticals (furosemide, mebeverine, ketoprofen, naproxen, diclofenac and mefenamic acid) in environmental water and urine matrices. By comparing ten distinct sorbent materials (five polymeric and five activated carbons), the polymer P5 proved to be the most suitable to achieve the best selectivity and efficiency. The solvent volume minimization in the liquid desorption stage demonstrated remarkable effectiveness, being more environmentally friendly, and simultaneously increased the microextraction enrichment factor two-fold. Assays performed through BAµE(P5, 0.9 mg)-µLD(100 µL)/HPLC-DAD on 25 mL of ultrapure water samples spiked at the 4.0 µg/L level yielded average recoveries ranging from 91.4% (furosemide) to 101.0% (ketoprofen) with good precision (RSD < 10.6%), under optimized experimental conditions. The analytical performance showed convenient detection limits (25.0 - 120.0 ng/L), good linear dynamic ranges (0.1 to 24.0 µg/L), appropriate determination coefficients (r 2 > 0.9983), and excellent repeatability through intraday (RSD < 10.4%)) and interday (RSD < 10.0%) assays. By using the standard addition methodology, the application of the present analytical approach on environmental waters and urine samples revealed the occurrence of trace levels of some pharmaceuticals. The solvent minimization during the back-extraction step associated with the miniaturization of BAµE devices proved to be a very promising analytical technology for static microextraction analysis. Graphical abstract BAµE operating under the floating sampling technology for the determination of pharmaceuticals in aqueous media.

Combining stir-bar sorptive extraction and large volume injection-gas chromatography-mass spectrometry for the determination of benzotriazole UV stabilizers in wastewater matrices.

Stir-bar sorptive extraction and liquid desorption followed by large volume injection-gas chromatography coupled to mass spectrometry under selected ion monitoring mode acquisition (SBSE-LD/LVI-GC-MS(SIM)) was applied for the determination of six benzotriazole UV stabilizers (Tinuvin P, Allyl-bzt, Tinuvin 320, Tinuvin 326, Tinuvin 327 and Tinuvin 328) in wastewater matrices. Parameters affecting the performance of extraction and desorption steps were thoroughly evaluated using uni- and multivariate optimization strategies, based on the use of experimental factorial designs. Assays performed with stir bars, coated with 24 µL of polydimethylsiloxane, on 25 mL of ultra-pure water samples spiked at the 0.5 ng/mL level, yielded recoveries ranging from 47.9±1.4% (Tinuvin P) to 103.1±3.6% (Tinuvin 326), under optimized experimental conditions. When applied to complex matrices (e.g. wastewater), the methodology showed also excellent linear dynamic ranges (0.02-10.00 ng/mL) for the six benzotriazole UV stabilizers studied with correlation coefficients higher than 0.9970, limits of quantification in between 0.004 and 0.015 ng/mL, suitable repeatability (RSD<12.7%) and reproducibility (RSD<4.5%). The application of the proposed methodology to urban sewage waters from Spain and Portugal wastewater plants revealed the presence of low contents of some benzotriazole UV stabilizers.

Influence of salt stress on essential oil yield and composition of lemon grass (Cymbopogon schoenanthus L. Spreng. ssp. Laniger (Hook) Maire et Weil).

Cymbopogon is an aromatic plant valued for its citrus scent aroma. In this article, the effect of saline irrigation water on yield and quality of Cymbopogon schoenanthus L. was evaluated. Compounds of essential oils were identified by gas chromatography-mass spectrometry and/or (13)C-NMR spectroscopy. Results showed that the growth of the aerial part was not affected at a concentration of 50 mmol NaCl. Under salt stress, the content of major chemical compounds was affected differently by the treatment level.

Analysis of the volatiles emitted by whole flowers and isolated flower organs of the carob tree using HS-SPME-GC/MS.

The volatiles emitted by fresh whole flowers and isolated flower organs of male, female, and hermaphrodite carob trees (Ceratonia siliqua L.; Leguminosae) were analyzed by headspace solid-phase microextraction followed by capillary gas chromatography and mass spectrometry. The headspace of carob flowers is mainly constituted of high amounts of monoterpenes and sesquiterpenes, and more than 25 compounds were identified. The gender and cultivar affected both the qualitative profile and the relative abundances of the volatiles of whole flowers and isolated floral organs. Linalool and its derivatives (cis-linalool furan oxide, 2,2,6-trimethyl-3-keto-6-vinyltetrahydropyran, cis-linalool pyran oxide, and trans-linalool furan oxide), alpha-pinene, and alpha-farnesene were the dominant volatiles. Female flowers had a higher diversity of volatile compounds than males and hermaphrodites, but a lower abundance of the major ones. Similarly, the floral scent of female flowers of cv. Mulata had a higher content of volatiles but a lower abundance of the major ones, when compared to cv. Galhosa. In each of the three gender types of flowers, the nectary disks seemed to be the major source of volatiles.