Microextraction Technique Research Articles

Liquid-phase microextraction of polycyclic aromatic hydrocarbons: A review

Abstract Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds comprised of two or more fused benzene rings, which arise from the incomplete combustion of organic materials. These compounds have been of concern as carcinogens and mutagens for the past 50-60 years. Lately, they are also receiving attention as endocrine-disrupting chemicals. Therefore, proper analytical methods are required for sampling and analyzing these compounds. In response to problems associated with the conventional methods like solid-phase extraction (SPE) and liquid-liquid extraction (LLE), many studies have focused on the miniaturization of different sample preparation techniques. In this regard, the use of different types of liquid phase microextraction (LPME) techniques has increased significantly during the recent few decades. LPME techniques are advantageous because they use single-step sample preparation and have shown a greater sensitivity, selectivity, and efficiency than the conventional methods. In addition, these techniques have good potential for automation, to reduce the time and cost of analysis. This review focuses on the most important configurations of LPME including single‐drop microextraction (SDME), hollow-fiber liquid-phase microextraction (HF-LPME), and dispersive liquid-liquid microextraction (DLLME) techniques used for the sampling and determination of PAHs in different samples, along with their cons and pros, as well as their prospects.

Miniaturized extraction method for analysis of synthetic opioids in urine by microextraction with packed sorbent and liquid chromatography—tandem mass spectrometry

Synthetic opioids are responsible for numerous overdoses and fatalities worldwide. Currently, fentanyl and its analogs are also mixed with heroin, cocaine and methamphetamine, or sold as oxycodone, hydrocodone and alprazolam in counterfeit medications. Microextraction techniques became more frequent in analytical toxicology over the last decade. A method to simultaneously quantify nine synthetic opioids, fentanyl, sufentanil, alfentanil, acrylfentanyl, thiofentanyl, valerylfentanyl, furanylfentanyl, acetyl fentanyl and carfentanil, and two metabolites, norfentanyl and acetyl norfentanyl, in urine samples by microextraction with packed sorbent (MEPS) and liquid chromatography—tandem mass spectrometry (LC-MS/MS) was developed and validated. A multivariate optimization was performed to establish the number and speed (stroke) of draw-eject sample cycles and the extraction solvent. The best extraction condition was eight draw-eject sample cycles, with a velocity of 3.6 µL/sec and acetonitrile as elution solvent. Linearity was achieved between 1 to 100 ng/mL, with a limit of detection (LOD) of 0.1 ng/mL and limit of quantification (LOQ) of 1 ng/mL. Imprecision (% relative standard deviation) and bias (%) were less than 12.8% and 5.7%, respectively. The method had good specificity and selectivity when challenged with 10 different matrix sources and 36 pharmaceuticals and drugs of abuse at concentrations of 100 or 500 ng/mL. The method was successfully applied to authentic urine samples. MEPS was an efficient semi-automatic extraction technique, requiring small volumes of organic solvents (640 µL) and sample (200 µL). The cartridges can be cleaned and reused (average of 150 sample extractions/barrel inside and needle).

Ionic liquid functionalized zinc oxide nanorods for solid-phase microextraction of aflatoxins in food products

Aflatoxins (AFs) in food and agricultural products pose serious health hazards to consumers. As a result, exports are restricted and farmers lose much needed income. One major challenge faced in controlling AFs in developing countries in particular is lack of simple and cost-effective methods of analysis. To address this problem, a solid-phase microextraction (SPME) technique was developed based on 1-hexyl-3-methylimidazolium hexafluorophosphate functionalized zinc oxide nanorods for the extraction of AFB1, AFB2, AFG1 and AFG2 in food products prior to HPLC analysis. The SPME was performed using 10 mg of the adsorbent at pH 7 and vortexing for 1 min at 500 rpm, and desorbed by sonication for 2 min in 1 mL acetonitrile. The technique showed excellent linearity (correlation coefficients, ≥0.997). LOD and LOQ were determined respectively to be 0.07 and 0.73 μg/kg for AFB1, 0.01 and 0.12 μg/kg for AFB2, 0.04 and 0.44 μg/kg for AFG1 and 0.02 and 0.18 μg/kg for AFG2. The intra- and inter-day relative standard deviations were in the ranges of 3.9–4.7% and 6.9–8.4%, respectively. The acquired recovery of blank samples of the pepper and groundnut samples spiked with mixed analytes at 5 and 10 μg/kg spiking levels were in the range of 88.6–99.8%. The SPME was employed for the analysis of the considered analytes from real chili pepper and processed groundnut samples. Overall, the technique is easy, fast, cost-effective and environmentally friendly and can be used for the analysis of AFs in various food and agricultural products.

The Effect of Plant Water Status on the Chemical Composition of Pistachio Nuts (Pistacia vera L. Cultivar Bianca)

Pistachio nuts are worldwide appreciated for their chemical and organoleptic profiles. There are several studies on the influence of irrigation on pistachio productivity, whereas there are little available data on the influence on nut quality. In this study we characterized some qualitative traits of pistachio nuts cultivar Bianca in Mediterranean environment and how plant water status affected them. Water status had a positive and significant influence on the chlorophylls content, nuts from less stressed trees showed higher values of chlorophyll a (14.7 mg/100 g) and b (21.1 mg/100 g) compared than more stressed trees (9.3 and 11.5 mg/100 g for a and b, respectively). Solid phase microextraction technique in headspace followed by gas chromatography/mass spectrometry (HS-SPME GC/MS) identified seventeen different compounds with terpenes being the major class of volatiles; the most abundant were α-Pinene (range 26.2–35 μg/g), D-Limonene (2.8–3.3 μg/g), 2-Carene (1.8–3 μg/g) and β-Myrcene (0.6–1.4 μg/g). Overall, we found higher level of terpenes in less stressed trees and for α-Pinene and β-Myrcene differences were significant. The fatty acid composition analysis revealed oleic acid (70.1–71.1%), linoleic acid (13.5–14.4%) and palmitic acid (9.6–9.8%) as the most abundant compounds, but tree water status did not influence their concentration. Overall, the data reported proved that supplemental irrigation contributes to increase pistachio nut quality.

Ultra-trace Cr preconcentration in honey samples by magnetic ionic liquid dispersive liquid-liquid microextraction and electrothermal atomic absorption spectrometry

An analytical method based on the dispersive liquid-liquid microextraction (DLLME) technique, using a magnetic ionic liquid (MIL) as an extraction phase, was developed for ultra trace Cr determination in honey samples. The elemental detection was performed by electrothermal atomic absorption spectrometry (ETAAS). In the developed method both centrifugation and complexation of the analyte were not required. The Cr(III) species was extracted by the MIL trihexyl(tetradecyl)phosphonium ([P6,6,6,14]FeCl4) after the formation of [CrCl2(H2O)4]Cl. The MIL phase was separated by a magnetic rod, diluted in CHCl3 and Cr was determined by ETAAS. Under optimized experimental conditions, an extraction efficiency of 98% and a sensitivity enchancement factor of 105 were achieved. A detection limit (LOD) of 5 ng L−1 Cr and relative standard deviation of 3.5% (at 50 ng L−1 Cr and n = 10) were obtained. Also, the linear range of the calibration curve was from 15 ng L−1 to 180 ng L−1. The method was applied for Cr determination in honey samples of different shades.

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples.

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

Enhancement of volatile profiling using multiple-cumulative trapping solid-phase microextraction. Consideration on sample volume

In the present work, the performance of the multiple-cumulative trapping headspace solid-phase microextraction technique used in the headspace linearity range and saturated headspace was investigated and compared, with the ultimate goal of maximizing the fingerprinting information extractable using a cross-sample comparison algorithm for olive oil quality assessment. It was highlighted as the use of 0.1 g of olive oil provides comparable or even better profiling than 1.5 g at a little expense of sensitivity. However, the use of multiple-cumulative-solid-phase microextraction, along with the correct sample volume, improved not only the overall sensitivity but significantly burst the level of information for cross-sample studies.

Dispersive Liquid-Liquid Microextraction for the Extraction of Polycyclic Aromatic Hydrocarbons in Apple Juice

Polycyclic aromatic hydrocarbons (PAHs) are hazardous and persistent organic pollutants that usually exist at low concentrations in the environment. In this study, dispersive liquid-liquid microextraction (DLLME) technique coupled with high performance liquid chromatography-fluorescence detection (HPLC-FD) was optimized for the analysis of selected PAHs, namely phenanthrene (PHE), fluoranthene (FLA) and benzo[a]pyrene (BaP) in apple juice. Under the optimal extraction conditions (the mixture of 200 µL of acetone and 50 µL of 1-octanol was applied to extract the selected PAHs for 1 min), the DLLME-HPLC-FD showed excellent linearity over the concentration range of 5 to 200 µg/L for both PHE and FLA, and 0.01 to 5 µg/L for BaP with correlation coefficients, r ≥ 0.9956. The method offered ultra-trace detection of selected PAHs in the range of 0.002 to 0.5 µg/L, and negligible matrix effects in determining selected PAHs with relative recovery average within the range of 92.6 to 109.6% in apple juice. The advantages of applying this method for the extraction of PAHs include rapidity, simple operation, as well as small consumption of organic extraction solvent, which is beneficial for routine analysis.

Landing microextraction sediment phase onto surface enhanced Raman scattering to enhance sensitivity and selectivity for chromium speciation in food and environmental samples

The current study explores the first full mode liquid microextraction technique coupled with surface-enhanced Raman spectroscopy (SERS), and has been successfully applied for chromium speciation in food and environmental matrices. Herein, chromium as chlorochromate anion [CrO3Cl]− and the cationic rhodamine 6G [RG]+ dye has been extracted in organic phase as a complex ion associate [RG+.CrO3Cl−.nS]org at pH ≤ 1.0. Afterwards, the extracted phase was deposited on the surface of the nano-flower shaped silver nanoparticles substrate and the SERS response was monitored against the reagent blank at 1505 cm−1. Substrate characterizations, reaction mechanism assignment, stoichiometry, speciation, analytical applications, selectivity and validation were performed. The analytical procedure exhibits a detection limit of 0.03 µg L−1 under the optimized experimental conditions. The accuracy of the proposed strategy was validated by inductively coupled plasma optical emission spectrometry method using student's t- and F tests at 95% confidence.

Optimization of a solid-phase microextraction technique for chloro‑ and nitro- substituted aromatic compounds using design of experiments

A rapid and sensitive direct immersion solid-phase microextraction (SPME) technique for the analysis of seven chloro (Cl-) and nitro (NO2-) substituted anilines, toluenes, and nitrobenzenes from small volume (1.5 mL) aqueous samples was optimized for gas chromatography using Design of Experiments (DoE). Screening of the SPME factors was performed by a fractional factorial DoE, and the optimization of influential factors was achieved with a central composite multi-response surface DoE. Extraction time, pre-SPME agitation speed, extraction temperature, and desorption temperature were identified as significant factors and their values were set using a desirability function that maximized the extraction of the seven target analytes. Extraction time and agitation speed showed significant interactions for most analytes (α = 0.05). The relative standard deviations (RSDs) for within-day and between-day analyses were below 8%, suggesting that the method was repeatable and reproducible. The obtained limits of detection were in the low μg/L range (1–10) using a Flame Ionization Detector, far below what is needed for industrial contaminated sites (usually >1 mg/L). The optimized SPME method increased the analyte concentration up to 2–3 orders of magnitude compared with direct GC injection. The optimized SPME method was applied to two groundwater samples from a contaminated site in which the concentrations of three of the target analytes were ranged from 0.06 to 9.42 mg/L with RSDs <11%. When the concentrations of the target analytes in the sample matrix were higher than 0.5 mg/L, a competition for the SPME extraction sites was observed where analytes with higher affinity for the fiber material replaced the analytes with lower affinity. As a result, dilution of highly contaminated samples is recommended. This study provided for the first time an analytical method for the quantification of frequently co-occurring contaminants from the chloro‑ and nitro- substituted aniline, toluene, and nitrobenzene families.

Application of liquid-phase microextraction to the analysis of plant and herbal samples.

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. 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. 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. 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.

Correction to: Bioanalytical Applications of Microextraction Techniques: A Review of Reviews

In the original publication, the phrase “Liquid phase” in Table 1 column 1 was included in the wrong line. The phrase needs to be included in row 13 in front of LPME.

Ultrasound-assisted hydrophobic deep eutectic solvent based solid-liquid microextraction of Sudan dyes in spice samples.

An environmentally friendly, simple method was carried out with the help of an ultrasonic assisted solid-liquid microextraction technique using a new deep eutectic solvent (DES) for the extraction and determination of Sudan dyes (I-IV) in spice samples. In this method, parameters affecting the optimization were researched and optimized such as DES composition, DES volume, ultrasonic time, temperature and, centrifuge time. The analytical performance of the developed method was quite satisfactory, the R2 values were higher than 0.9989, and the limits of quantification were <1.17μgg-1. Two different concentrations (10-50μgg-1) were spiked to Chili peppers, paprika, cumin and sumac spices for the applicability and accuracy of the developed microextraction method. Some of these spices were found to contain Sudan I and IV dyes. The recovery values for spiked samples were found to be between 85.55% and 99.29% and relative standard deviations were found to be <3.17% when using a 10μgg-1 Sudan dyes concentration. The results showed that the developed method can be successfully applied for extraction and determination of Sudan dyes in spice samples.

Identification and quantification of volatile toxic compounds in tequila

Nitrosoamines (NAms), methanol and furfural are toxic compounds that are frequently found in low concentrations in alcoholic beverages and food products. NAms such as Nitrosodimethylamine, Nitrosodiethylamine, Nitrosodibutylamine, Nitrosopiperidine and Nitrosopyrrolidine are considered cancerogenic and mutagenic compounds whereas furfural and methanol can lead in skin cancer and eye damage respectively. Therefore, in this work these compounds were analyzed in tequila (white, rested and aged), which is an important and highly consumed beverage. The technique of headspace solid-phase micro-extraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used for its simplicity, speed, high precision and its environmental friendliness. The influence of the important extraction parameters such as temperature (Teq), equilibrium time (teq), extraction time and ionic strength was evaluated through a factorial analysis. The quantification was carried out using the standard additions method. In order to validate the methodology, the limits of detection and quantification were determined. Amongst the NAms, the NDBA was the only NAm detected in all the tequila samples studied. The maximum concentrations found of NDBA, furfural and methanol were 7.33 µg/L, 0.95 mg/100 mL anhydrous alcohol and 132.51 mg/100 mL anhydrous alcohol. These amounts were within the limits considered safe for human consumption by the Environmental Protection Agency and Mexican norms.

Bioanalytical Applications of Microextraction Techniques: A Review of Reviews

Sample preparation is a critical step in the separation of target analytes from complex matrices, which can influence the reliability and accuracy of the resulting analysis. Recent trends in sample preparation techniques are directed toward the automation and online coupling of sample preparation units, miniaturization, high efficiency, low costs, and reducing or eliminating solvent consumption. Microextraction techniques (METs) have all these advantages over conventional extraction methods. Thus, the application of METs in the analysis of different analytes from biological samples has increased significantly in recent years. Over time, many review articles have been written, which focus on the advantages, applications, and advances of these techniques for the analysis of various compounds in biological matrices. This paper presents a review of publications pertaining to the application of different types of METs in the analysis of biological samples along with their different aspects and a discussion of their future.

Hollow fiber–liquid phase microextraction method based on a new deep eutectic solvent for extraction and derivatization of some phenolic compounds in beverage samples packed in plastics

The present study describes a sensitive, efficient, and easy approach for isolation, enrichment, and derivatization some phenolic compounds in the beverage samples packed in plastic bottles. The sample preparation method is based on a hollow fiber–liquid phase microextraction technique using a deep eutectic solvent. The enriched analytes are determined by gas chromatography–mass spectrometry. For this purpose, a new deep eutectic solvent composed of 8–hydroxyquinoline and pivalic acid is synthesized and used as an extraction solvent. The solvent is mixed with chloroacetyl chloride as a derivatization agent and filled into a hollow fiber segment containing an iron wire within the lumen. The prepared stir bar (hollow fiber) is stirred into the sample solution in which sodium chloride is dissolved to increase ionic strength of the solution. Temperature of the solution is adjusted at 50 °C to improve efficiency of the extraction/derivatization procedure. Under optimum conditions, the introduced method indicated high enhancement (1652–3265) and enrichment (1085–1256) factors, low limits of detection (9–22 ng L−1) and quantification (29–76 ng L−1), good linearity (r2 ≥ 0.9950), and satisfactory repeatabilities. Finally, the proposed method was applied in analysis of the analytes in the various beverage samples packed in plastic packages.

Deep eutectic-based vortex-assisted/ultrasound-assisted liquid-phase microextractions of chromium species

In the present work, vortex-assisted liquid-phase microextraction (VA-LPME) and ultrasound-assisted liquid-phase microextraction (UA-LPME) techniques were used for the speciation of chromium (Cr3+/Cr6+) followed by their determination using flame atomic absorption spectrometry. 1-(2-Pyridylazo)-2-naphthol (PAN) was used as a chelating agent to form a hydrophobic complex with Cr3+; then, it was extracted by choline chloride–phenol mixture, as an extraction solvent. A solution of 1.0 mol L−1 ascorbic acid was used as a reducing agent to convert Cr6+ to Cr3+ (total chromium), and the concentration of Cr6+ was determined from the subtraction of Cr3+ form total chromium. The efficiency of two microextraction techniques was compared in terms of type and amount of extraction solvent, type and volume of extraction solvent, pH of solution, volume of tetrahydrofuran (THF), and extraction time. Based on the obtained results, the extraction recoveries of VA-LPME and UA-LPME techniques are 52% and 60%, respectively. Therefore, UA-LPME is superior technique than VA-LPME. By optimizing different parameters affecting the recovery percentage (RP) of Cr3+, the calibration curve was depicted in the concentration range of 1.5–375.0 ng mL−1 Cr3+ with a correlation coefficient of 0.9937. The limit of detection was 0.4 ng mL−1, and the relative standard deviation (RSD%) for seven replicate analyses of 50.0 µg L−1 of Cr3+ was 3.6%. Finally, the UA-LPME method was successfully applied for the determination of Cr species in different food and water samples.

Determination of Three Estrogens in Environmental Water Samples Using Dispersive Liquid-Liquid Microextraction by High-Performance Liquid Chromatography and Fluorescence Detector

In this work the dispersive liquid-liquid microextraction technique (DLLME) is presented as an important alternative to the classical extraction methods and was used to extract and concentrate estrogens’ before its quantification by HPLC in environmental water samples. For the evaluation of the analytical methodology, the following conditions were used: sample volume 8 mL, extraction solvent 200 μL of chlorobenzene, and dispersive solvent 2000 μL of acetone. The enrichment factor (EF) was 140 for estrone, 202 for 17β-estradiol (E2), and 199 for 17α-ethinylestradiol (EE2). Limit of detection was 20 ng L−1 for E1, 3.1 ng L−1 for E2, and 2.7 ng L−1 for EE2. Repeatability and intermediate reproducibility presented values of relative standard deviation lower than 10%. Finally, recovery tests were performed to evaluate the water matrices’ effects on the extraction performance, resulting in recoveries between 76 and 110% in surface water and between 84 and 109% in wastewater.

Sample matrix influence on microdrop hold-up in single drop microextraction

Abstract Single drop microextraction has become a widespread liquid/liquid microextraction technique owing to its simplicity, high preconcentration factor and low consumption of organic solvents in the extraction due to direct introduction of the very low volume of extract into the analytical system. Crucial features ensuring excellent repeatability of single drop microextraction include: solvent volume, solvent type, sample agitation, salts addition, and pH. The influence of sample quality on the microdrop volume and agitation type was studied. Effect of the sample matrix, such as water, acid content samples (orange juice), sample containing alcohol (plum brandy) and protein content sample (milk), on the microdrop hold-up was also investigated. For water analysis, several organic solvents such as chloroform, dichloromethane, tetrachloromethane, tetrachloroethane and chlorobenzene were tested; last three mentioned were suitable for SDME experiments. For milk samples analysis, chlorobenzene microdrop was found to be optimal; advantage of salt addition has been reported. For orange samples, 1:10 dilution was suggested with stable microdrop volumes (toluene) of up to 6 µL for lower stirring rates (100 rpm and 250 rpm). For alcohol-content samples, the change of alcohol percentage of real-life samples had to be considered. A strong influence of the matrix quality on the microdrop stability has been proven.

Direct Analysis of Psilocin and Muscimol in Urine Samples Using Single Drop Microextraction Technique In-Line with Capillary Electrophoresis.

The fully automated system of single drop microextraction coupled with capillary electrophoresis (SDME-CE) was developed for in-line preconcentration and determination of muscimol (MUS) and psilocin (PSC) from urine samples. Those two analytes are characteristic active metabolites of Amanita and Psilocybe mushrooms, evoking visual and auditory hallucinations. Study analytes were selectively extracted from the donor phase (urine samples, pH 4) into the organic phase (a drop of octanol layer), and re-extracted to the acidic acceptor (background electrolyte, BGE), consisting of 25 mM phosphate buffer (pH 3). The optimized conditions for the extraction procedure of a 200 µL urine sample allowed us to obtain more than a 170-fold enrichment effect. The calibration curves were linear in the range of 0.05–50 mg L−1, with the correlation coefficients from 0.9911 to 0.9992. The limit of detections was determined by spiking blank urine samples with appropriate standards, i.e., 0.004 mg L−1 for PSC and 0.016 mg L−1 for MUS, respectively. The limits of quantification varied from 0.014 mg L−1 for PSC and 0.045 mg L−1 for MUS. The developed method practically eliminated the sample clean-up step, which was limited only to simple dilution (1:1, v/v) and pH adjustment.