Microextraction
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INTRODUCTION: The analysis of plant and herbal samples is a challenging task for analytical chemists due to the complexity of the matrix combined with the low concentration of analytes. In recent years different liquid-phase microextraction (LPME) techniques coupled with a variety of analytical equipment have been developed for the determination of both organic and inorganic analytes. OBJECTIVE: Over the past few years, the number of research papers in this field has shown a markedly growing tendency. Therefore, the purpose of this review paper is to summarise and critically evaluate research articles focused on the application of LPME techniques for the analysis of plant and herbal samples. RESULTS: Due to the complex nature of the samples, the direct application of LPME techniques to the analysis of plants has not often been done. LPME techniques as well as their modalities have been commonly applied in combination with other pretreatment techniques, including a solid-liquid extraction technique supported by mechanical agitation or auxiliary energies for plant analysis. Applications and the most important parameters are summarised in the tables. CONCLUSION: This review summarises the application of the LPME procedure and shows the major benefits of LPME, such as the low volume of solvents used, high enrichment factor, simplicity of operation and wide selection of applicable detection techniques. We can expect further development of microextraction analytical methods that focus on direct sample analysis with the application of green extraction solvents while fully automating procedures for the analysis of plant materials.
- MeSH
- mikroextrakce kapalné fáze * MeSH
- rostliny MeSH
- rozpouštědla MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Two operational modes for Lab-In-Syringe automation of direct-immersion single-drop microextraction have been developed and critically compared using lead in drinking water as the model analyte. Dithizone was used in the presence of masking additives as a sensitive chromogenic complexing reagent. The analytical procedure was carried out inside the void of an automatic syringe pump. Normal pump orientation was used to study extraction in a floating drop of a toluene-hexanol mixture. Placing the syringe upside-down allowed the use of a denser-than-water drop of chloroform for the extraction. A magnetic stirring bar was placed inside the syringe for homogenous mixing of the aqueous phase and enabled in-drop stirring in the second configuration while resulting in enhanced extraction efficiency. The use of a syringe as the extraction chamber allowed drop confinement and support by gravitational differences in the syringe inlet. Keeping the stirring rates low, problems related to solvent dispersion such as droplet collection were avoided. With a drop volume of 60 µL, limits of detection of 75 nmol L-1 and 23 nmol L-1 were achieved for the floating drop extraction and the in-drop stirring approaches, respectively. Both methods were characterized by repeatability with RSD typically below 5%, quantitative analyte recoveries, and analyte selectivity achieved by interference masking. Operational differences were critically compared. The proposed methods permitted the routine determination of lead in drinking water to be achieved in less than 6 min.
A simple analytical workflow is described for gas chromatographic-mass spectrometry (GC-MS)-based metabolomic profiling of protic metabolites, particularly amino-carboxylic species in biological matrices. The sample preparation is carried out directly in aqueous samples and uses simultaneous in situ heptafluorobutyl chloroformate (HFBCF) derivatization and dispersive liquid-liquid microextraction (DLLME), followed by GC-MS analysis in single-ion monitoring (SIM) mode. The protocol involves ten simple pipetting steps and provides quantitative analysis of 132 metabolites by using two internal standards. A comment on each analytical step and explaining notes are provided with particular attention to the GC-MS analysis of 112 physiological metabolites in human urine.
- MeSH
- analýza moči metody MeSH
- biologické markery moč MeSH
- fluorokarbony chemie MeSH
- formiáty chemie MeSH
- lidé MeSH
- metabolomika metody MeSH
- mikroextrakce kapalné fáze metody MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Pomocí mikroextrakce do pevné fáze (SPME) a plynové chromatografie byly v souboru 137 mikrobiologicky positivních i negativních klinických exsudátů stanoveny profily těkavých karboxylových kyselin (VFA). Zatímco aerobní bakterie poskytovaly málo charakteristické profily s malým obsahem nižších kyselin nebo byly chromatograficky negativní, poskytovaly anaerobní bakterie profily s větším obsahem vyšších kyselin. Ve 20,4 % exsudátů umožnila tato metoda během 15 minut detekci mikrobů nenalezených kultivačním vyšetřením, pravděpodobně nesporolujících anaerobů. Jejich bližší charakterizace je touto metodou v důsledku nestandardních podmínek jejich růstu možná jen orientačně.
The volatile fatty acid (VFA) patterns were determined in 137 microbiologically positive and negative clinical exudates using solid phase microextraction (SPME) and gas chromatography. The aerobic bacteria yielded less distinctive patterns with small content of lower acids, whereas patterns of anaerobes contained larger amounts of higher acids. The method made it possible to detect within 15 minutes bacteria, probably non-sporulating anaerobes, in 20,4 % of exudates false-negative by cultivation. Only tentative characterisation of these bacteria was possible due to the poorly defined conditions of their growth.
- MeSH
- aerobní bakterie izolace a purifikace metabolismus MeSH
- anaerobní bakterie izolace a purifikace metabolismus MeSH
- chromatografie plynová využití MeSH
- exsudáty a transsudáty mikrobiologie MeSH
- finanční podpora výzkumu jako téma MeSH
- kyseliny karboxylové analýza MeSH
- lidé MeSH
- Check Tag
- lidé MeSH
Breast milk analysis provides useful information about acute newborn exposure to harmful substances, such as psychoactive drugs abused by a nursing mother. Since breast milk represents a complex matrix with large amounts of interfering compounds, a comprehensive sample pre-treatment is necessary. This work focuses on determination of amphetamines and synthetic cathinones in human breast milk by microextraction techniques (liquid-phase microextraction and electromembrane extraction), and their comparison to more conventional treatment methods (protein precipitation, liquid-liquid extraction, and salting-out assisted liquid-liquid extraction). The aim of this work was to optimize and validate all the extraction procedures and thoroughly assess their advantages and disadvantages with special regard to their routine clinical use. The applicability of the extractions was further verified by the analysis of six real samples collected from breastfeeding mothers suspected of amphetamine abuse. The membrane microextraction techniques turned out to be the most advantageous as they required low amounts of organic solvents but still provided efficient sample clean-up, excellent quantification limit (0.5 ng mL-1), and good recovery (81-91% and 40-89% for electromembrane extraction and liquid-phase microextraction, respectively). The traditional liquid-liquid extraction as well as the salting-out assisted liquid-liquid extraction showed comparable recoveries (41-85% and 63-88%, respectively), but higher quantification limits (2.5 ng mL-1 and 5 ng mL-1, respectively). Moreover, these methods required multiple operating steps and were time consuming. Protein precipitation was fast and simple, but it demonstrated poor sample clean-up, low recovery (56-58%) and high quantification limit (5 ng mL-1). Based on the overall results, microextraction methods can be considered promising candidates, even for routine laboratory use.
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Direct analysis of complex samples is demonstrated by the at-line coupling of hollow fiber liquid-phase microextraction (HF-LPME) to capillary electrophoresis (CE). The hyphenation of the preparative and the analytical technique is achieved through a 3D-printed microextraction device with an HF located in a sample vial of a commercial CE instrument. The internal geometry of the device guides the CE separation capillary into the HF and the CE injection of the HF-LPME extract is performed directly from the HF lumen. The 3D-printing process ensures uniform dimensions of the devices, their constant position inside the sample vial, and excellent repeatability of the HF-LPME as well as the CE injection. The devices are cheap (∼0.01 €) and disposable, thus eliminating any possible sample-carryover, moreover, the at-line CE analysis of the extract is performed fully autonomously with no need for operator's intervention. The developed HF-LPME/CE-UV method is applied to the determination of acidic drugs in dried blood spot and wastewater samples and is characterized by excellent repeatability (RSD, 0.6-9.6%), linearity (r2, 0.9991-0.9999), enrichment (EF, 29-97), sensitivity (LOD, 0.2-3.4 μg/L), and sample throughput (7 samples/h). A further improvement of selected characteristics of the analytical method is achieved by the at-line coupling of HF-LPME to capillary isotachophoresis (ITP) with electrospray ionization-mass spectrometry (ESI-MS). The HF-LPME/ITP-ESI-MS system facilitates enhanced selectivity, matrix-free analytical signals, and up to 34-fold better sensitivity due to the use of ESI-MS detection and additional on-capillary ITP preconcentration of the HF-LPME extracts.
We have developed a new microextraction technique for equilibrium, non-exhaustive analyte preconcentration from aqueous solutions into organic solvents lighter than water. The key point of the method is application of specially designed and optimized bell-shaped extraction device, BSED. The technique has been tested and applied to the preconcentration of selected volatile and semi volatile compounds which were determined by gas chromatography/mass spectrometry in spiked water samples. The significant parameters of the extraction have been found using chemometric procedures and these parameters were optimized using the central composite design (CCD) for two solvents. The analyte preconcentration factors were in a range from 8.3 to 161.8 (repeatability from 7 to 14%) for heptane, and 50.0-105.0 (repeatability from 0 to 5%) for tert-butyl acetate. The reproducibility of the technique was within 1-8%. The values of limits of detection and determination were 0.1-3.3 ng mL(-1) for heptane and 0.3-10.7 ng mL(-1) for tert-butyl acetate. The new microextraction technique has been found to be a cheap, simple and flexible alternative to the common procedures, such as SPME or LLME. This BSED-LLME technique can also be combined with other separation methods, e.g., HPLC or CE.
- MeSH
- chemické látky znečišťující vodu analýza izolace a purifikace MeSH
- design vybavení MeSH
- mikroextrakce kapalné fáze přístrojové vybavení metody MeSH
- minerální vody analýza MeSH
- pitná voda analýza MeSH
- plynová chromatografie s hmotnostně spektrometrickou detekcí metody MeSH
- reprodukovatelnost výsledků MeSH
- voda analýza MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
- práce podpořená grantem MeSH
A simple and rapid method for the determination of the methylene blue active substances assay based on in-syringe automation of magnetic stirring-assisted dispersive liquid-liquid microextraction was developed. The proposed method proved to be valid for the determination of anionic surfactant in waste, pond, well, tap, and drinking water samples. Sample mixing with reagents, extraction and phase separation were performed within the syringe of an automated syringe pump containing a magnetic stirring bar for homogenization and solvent dispersion. The syringe module was used upside-down to enable the use of chloroform as an extraction solvent of higher density than water. The calibration was found to be linear up to 0.3mg/L using only 200 µL of solvent and 4 mL of sample. The limits of detection (3σ) and quantification (10σ) were 7.0 µg/L and 22 µg/L, respectively. The relative standard deviation for 10 replicate determinations of 0.1mg/L SBDS was below 3%. Concentrations of anionic surfactants in natural water samples were in the range of 0.032-0.213 mg/L and no significant differences towards the standard method were found. Standard additions gave analyte recoveries between 95% and 106% proving the general applicability and adequateness of the system to MBSA index determination. Compared to the tedious standard method requiring up to 50 mL of chloroform, the entire procedure took only 345 s using 250-times less solvent.
- MeSH
- automatizace * MeSH
- biotest metody MeSH
- chemické látky znečišťující vodu analýza MeSH
- injekční stříkačky MeSH
- limita detekce MeSH
- magnetismus * MeSH
- methylenová modř analýza MeSH
- mikroextrakce kapalné fáze metody MeSH
- povrchově aktivní látky analýza MeSH
- rozpouštědla chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
