Efficient sample preparation method based on solvent‐assisted dispersive solid‐phase extraction for the trace detection of butachlor in urine and waste water samples

In this work, an efficient sample preparation method termed solvent‐assisted dispersive solid‐phase extraction was applied. The used sample preparation method was based on the dispersion of the sorbent (benzophenone) into the aqueous sample to maximize the interaction surface. In this approach, the dispersion of the sorbent at a very low milligram level was achieved by inserting a solution of the sorbent and disperser solvent into the aqueous sample. The cloudy solution created from the dispersion of the sorbent in the bulk aqueous sample. After pre‐concentration of the butachlor, the cloudy solution was centrifuged and butachlor in the sediment phase dissolved in ethanol and determined by gas chromatography with flame ionization detection. Under the optimized conditions (solution pH = 7.0, sorbent: benzophenone, 2%, disperser solvent: ethanol, 500 μL, centrifuged at 4000 rpm for 3 min), the method detection limit for butachlor was 2, 3 and 3 μg/L for distilled water, waste water, and urine sample, respectively. Furthermore, the preconcentration factor was 198.8, 175.0, and 174.2 in distilled water, waste water, and urine sample, respectively. Solvent‐assisted dispersive solid‐phase extraction was successfully used for the trace monitoring of butachlor in urine and waste water samples.     

Disposable pipette tips extraction: Fundamentals,applications and state of the art

Disposable pipette tips extraction consists of a solid‐phase extraction in which the sorbent is poorly dispersed in a pipette tip, which allows a quick and dynamic contact between the aspirated analyte from the sample and the solid phase. It is a technique used particularly in food and forensic analysis, since it requires a small amount of sample and solvent. This article highlights the principles, advantages and disadvantages of the disposable pipette tips extraction method and reviews recent applications.     

Application of mercapto‐silica polymerized high internal phase emulsions for the solid‐phase extraction and preconcentration of trace lead(II)

A new class of solid‐phase extraction column prepared with grafted mercapto‐silica polymerized high internal phase emulsion particles was used for the preconcentration of trace lead. First, mercapto‐silica polymerized high internal phase emulsion particles were synthesized by using high internal phase emulsion polymerization and carefully assembled in a polyethylene syringe column. The influences of various parameters including adsorption pH value, adsorption and desorption solvents, flow rate of the adsorption and desorption procedure were optimized, respectively, and the suitable uploading sample volumes, adsorption capacity, and reusability of solid phase extraction column were also investigated. Under the optimum conditions, Pb²⁺ could be preconcentrated quantitatively over a wide pH range (2.0–5.0). In the presence of foreign ions, such as Na⁺, K⁺, Ca²⁺, Zn²⁺, Mg²⁺, Cu²⁺, Fe²⁺, Cd²⁺, Cl^? and NO₃^?, Pb²⁺ could be recovered successfully. The prepared solid‐phase extraction column performed with high stability and desirable durability, which allowed more than 100 replicate extractions without measurable changes of performance. The feasibility of the developed method was further validated by the extraction of Pb²⁺ in rice samples. At three spiked levels of 40.0, 200 and 800 μg/kg, the average recoveries for Pb²⁺ in rice samples ranged from 87.3 to 105.2%.     

Potential sources of background contaminants in solid phase extraction and microextraction

A study to identify the sources of background contamination from SPE, using a C-18 sorbent, and solid-phase microextraction (SPME), using a 70 microm carbowax/divinylbenzene (CW/DVB) fiber, was carried out. To determine the source of contamination, each material used in the procedure was isolated and examined for their contribution. The solid-phase column components examined were: sorbent material and frits, column housings and each solvent used to elute analytes off the column. The components examined in the SPME procedure were: SPME fiber, SPME vials, water (HPLC grade), and salt (sodium chloride) used to increase the ionic strength. The majority of the background contaminants from SPE were found to be from the SPE sorbent material and frits. The class of contaminants extracted during a blank extraction were phthalates and other plasticizers used during the manufacturing process. All had blank levels corresponding to measured concentrations below 2 ng/ mL, except for undecane, which had a concentration of 5.4 ng/mL. The most prevalent contaminants in the SPME blank procedure are 1,9-nonanediol, a mixture of phthalates and highly bis-substituted phenols. All the concentrations were below 2 ng/mL, with the exception of bis (2-ethylhexyl) phthalate, which had concentrations ranging from 5 to 20 ng/mL.     

Comparison of mouse plasma and brain tissue homogenate sample pretreatment methods prior to high‐performance liquid chromatography for a new 1,2,4‐triazole derivative with anticonvulsant activity

The focus of the study was to develop a bio‐analytical assay for a 1,2,4‐triazole derivative from plasma and brain tissue homogenate samples. The goal was to compare analytical techniques that facilitate high accuracy with simplified sample processing. In this study, commonly used standard protein precipitation and solid‐phase extraction methods utilizing C₁₈ and cartridges of Hybrid technology were compared in terms of their ability for sample pretreatment and removal of biological matrices before high‐performance liquid chromatography quantification. Fast classical reversed‐phase chromatography on a C₁₈ column paired with selective sample preparation using Hybrid solid‐phase extraction technology resulted in the most precise bio‐analytical determination of the hydrophobic 1,2,4‐triazole derivative in both biological samples studied. The obtained recovery values were above 95% with the coefficient of variation lower than 5%.     

Pressurized liquid extraction and GC‐MS analysis for simultaneous determination of seven components in Cinnamomum cassia and the effect of sample preparation

A pressurized liquid extraction and GC‐MS method was developed for simultaneous quantitative determination of the seven components, including cinnamaldehyde, copaene, cinnamic acid, coumarin, 2‐methoxycinnamaldehyde, 2‐methoxycinnamic acid and safrole in Cinnamomum cassia. The results showed that methanol and ethanol was not available for extraction of cinnamaldehyde and 2‐methoxycinnamaldehyde due to aldol reaction. The developed method was validated to be sensitive, accurate and simple, and was successfully employed for the analysis of 15 samples of C. cassia. The contents of the investigated components were significantly variant and cinnamaldehyde is the most abundant compound, but safrole was not detected in all samples.     

Green analytical chemistry in sample preparation for determination of trace organic pollutants

The principles of green chemistry are applied to not only chemical engineering and synthesis, but also increasingly analytical chemistry. We describe environment-friendly analytical techniques applied to isolate and to enrich trace organic pollutants from solid and aqueous samples. Amounts of organic solvents used in analytical laboratories are reduced by applying solventless extraction, extraction using other types of solvent, assisted solvent extraction and miniaturized analytical systems.     

The role of graphene‐based sorbents in modern sample preparation techniques

The application of graphene‐based sorbents in sample preparation techniques has increased significantly since 2011. These materials have good physicochemical properties to be used as sorbent and have shown excellent results in different sample preparation techniques. Graphene and its precursor graphene oxide have been considered to be good candidates to improve the extraction and concentration of different classes of target compounds (e.g., parabens, polycyclic aromatic hydrocarbon, pyrethroids, triazines, and so on) present in complex matrices. Its applications have been employed during the analysis of different matrices (e.g., environmental, biological and food). In this review, we highlight the most important characteristics of graphene‐based material, their properties, synthesis routes, and the most important applications in both off‐line and on‐line sample preparation techniques. The discussion of the off‐line approaches includes methods derived from conventional solid‐phase extraction focusing on the miniaturized magnetic and dispersive modes. The modes of microextraction techniques called stir bar sorptive extraction, solid phase microextraction, and microextraction by packed sorbent are discussed. The on‐line approaches focus on the use of graphene‐based material mainly in on‐line solid phase extraction, its variation called in‐tube solid‐phase microextraction, and on‐line microdialysis systems.     

Solid‐phase extraction combined with dispersive liquid–liquid microextraction for the determination of pyrethroid pesticides in wheat and maize samples

A rapid, selective and sensitive sample preparation method based on solid‐phase extraction combined with the dispersive liquid–liquid microextration was developed for the determination of pyrethroid pesticides in wheat and maize samples. Initially, the samples were extracted with acetonitrile and water solution followed phase separation with the salt addition. The following sample preparation involves a solid‐phase extraction and dispersive liquid–liquid microextraction step, which effectively provide cleanup and enrichment effects. The main experimental factors affecting the performance both of solid‐phase extraction and dispersive liquid–liquid microextration were investigated. The validation results indicated the suitability of the proposed method for routine analyze of pyrethroid pesticides in wheat and maize samples. The fortified recoveries at three levels ranged between 76.4 and 109.8% with relative standard deviations of less than 10.7%. The limit of quantification of the proposed method was below 0.0125 mg/kg for the pyrethoroid pesticides. The proposed method was successfully used for the rapid determination of pyrethroid residues in real wheat and maize samples from crop field in Beijing, China.     

Sample preparation with solid phase microextraction and exhaustive extraction approaches: Comparison for challenging cases

In chemical analysis, sample preparation is frequently considered the bottleneck of the entire analytical method. The success of the final method strongly depends on understanding the entire process of analysis of a particular type of analyte in a sample, namely: the physicochemical properties of the analytes (solubility, volatility, polarity etc.), the environmental conditions, and the matrix components of the sample. Various sample preparation strategies have been developed based on exhaustive or non-exhaustive extraction of analytes from matrices. Undoubtedly, amongst all sample preparation approaches, liquid extraction, including liquid–liquid (LLE) and solid phase extraction (SPE), are the most well-known, widely used, and commonly accepted methods by many international organizations and accredited laboratories. Both methods are well documented and there are many well defined procedures, which make them, at first sight, the methods of choice. However, many challenging tasks, such as complex matrix applications, on-site and in vivo applications, and determination of matrix-bound and free concentrations of analytes, are not easily attainable with these classical approaches for sample preparation.     

State of the art of environmentally friendly sample preparation approaches for determination of PBDEs and metabolites in environmental and biological samples: A critical review

Green chemistry principles for developing methodologies have gained attention in analytical chemistry in recent decades. A growing number of analytical techniques have been proposed for determination of organic persistent pollutants in environmental and biological samples. In this light, the current review aims to present state-of-the-art sample preparation approaches based on green analytical principles proposed for the determination of polybrominated diphenyl ethers (PBDEs) and metabolites (OH-PBDEs and MeO-PBDEs) in environmental and biological samples. Approaches to lower the solvent consumption and accelerate the extraction, such as pressurized liquid extraction, microwave-assisted extraction, and ultrasound-assisted extraction, are discussed in this review. Special attention is paid to miniaturized sample preparation methodologies and strategies proposed to reduce organic solvent consumption. Additionally, extraction techniques based on alternative solvents (surfactants, supercritical fluids, or ionic liquids) are also commented in this work, even though these are scarcely used for determination of PBDEs. In addition to liquid-based extraction techniques, solid-based analytical techniques are also addressed. The development of greener, faster and simpler sample preparation approaches has increased in recent years (2003–2013). Among green extraction techniques, those based on the liquid phase predominate over those based on the solid phase (71% vs. 29%, respectively). For solid samples, solvent assisted extraction techniques are preferred for leaching of PBDEs, and liquid phase microextraction techniques are mostly used for liquid samples. Likewise, green characteristics of the instrumental analysis used after the extraction and clean-up steps are briefly discussed.     

Magnetic molecularly imprinted polymer for the efficient and selective preconcentration of diazinon before its determination by high‐performance liquid chromatography

A molecularly imprinted polymer was selectively applied for solid‐phase extraction and diazinon residues enrichment before high‐performance liquid chromatography. Diazinon was thermally copolymerized with Fe₃O₄@polyethyleneglycol nanoparticles, methacrylic acid (functional monomer), 2‐hydroxyethyl methacrylate (co‐monomer), and ethylene glycol dimethacrylate (cross‐linking monomer) in the presence of acetonitrile (porogen) and 2,2‐azobisisobutyronitrile (initiator). Then, the imprinted diazinon was reproducibly eluted with methanol/acetic acid (9:1, v/v). The sorbent particles were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. The comprehensive study of variables through experimental design showed that the maximum performance was achieved under these conditions: pH 7, 10 mL sample volume, 15 mg sorbent, 10 min vortex time, 5 min ultrasonic time, 200 μL methanol/acetic acid (9:1, v/v) as eluent, and 5 min desorption time. Under optimized conditions, the molecularly imprinted polymer solid‐phase extraction method demonstrated a linear range (0.02–5 g/mL), a correlation coefficient of 0.997, and 0.005 g/mL detection limit.     

Miniaturized pipette‐tip‐based electrospun polyacrylonitrile nanofibers for the micro‐solid‐phase extraction of nitro‐based explosive compounds

In this study, a self‐assembly of miniaturized pipette‐tip‐based solid‐phase extraction for the simultaneous extraction of nitroaromatic compounds was developed, with electrospun polyacrylonitrile nanofibers used as sorbents. The electrospun polyacrylonitrile nanofibers were characterized by scanning electron microscopy, FTIR analysis and surface area analysis. Good linearities for the four nitroaromatic compounds (2,6‐dinitrotoluene, 2‐nitrotoluene, 3‐nitrotoluene, and 4‐nitrotoluene) were obtained in a range of 250–1000 μg/L with coefficients of determination > 0.99. The limits of detection of these analytes were between 21 and 38 μg/L. The results showed that the pipette‐tip‐based solid‐phase extraction was effective in extracting nitrotoluenes in the pH regime of environmental interest (≈ 6). The investigation also revealed that the optimum mass of electrospun polyacrylonitrile nanofibers sorbent was 15 mg and 20 aspirating/dispensing cycles gave the maximum recovery of nitrotoluenes with 200 μL acetonitrile as the best eluting solvent. Moreover, the performance of the present method was studied for the extraction and determination of nitroaromatic compounds in real environmental water samples and good recoveries ranging from 70 to 115% were found, and respective relative standard deviations of <12% were obtained.     

A review of solid phase extraction: Basic principles and new developments

Summary A review with 178 references on the basic principles and recent developments in the solid phase extraction is presented. New solid phases, chromatographic modes, experimental configurations and off-line and on-line automated devices are discussed.     

Review: Sample preparation of catecholamines and biologically active peptides by solid phase extraction

This paper reviews solid phase extraction as applied to the sample preparation of catecholamines and biologically active peptides. The mechanisms used in solidphase extraction are: non-polar, polar, ion-exchange, and covalent.     

Solid‐phase extraction of plant thionins employing aluminum silicate based extraction columns

Thionins belong to a family of cysteine‐rich, low‐molecular‐weight (～5 KDa) biologically active proteins in the plant kingdom. They display a broad cellular toxicity against a wide range of organisms and eukaryotic cell lines. Thionins protect plants against different pathogens, including bacteria and fungi. A highly selective solid‐phase extraction method for plant thionins is reported deploying aluminum silicate (3:2 mullite) powder as a sorbent in extraction columns. Mullite was shown to considerably improve selectivity compared to a previously described zirconium silicate embedded poly(styrene‐co‐divinylbenzene) monolithic polymer. Due to the presence of aluminum(III), mullite offers electrostatic interactions for the selective isolation of cysteine‐rich proteins. In comparison to zirconium(IV) silicate, aluminum(III) silicate showed reduced interactions towards proteins which resulted into superior washings of unspecific compounds while still retaining cysteine‐rich thionins. In the presented study, European mistletoe, wheat and barley samples were subjected to solid‐phase extraction analysis for isolation of viscotoxins, purothionins and hordothionins, respectively. Matrix‐assisted laser desorption/ionization time of flight mass spectroscopy was used for determining the selectivity of the sorbent toward thionins. The selectively retained thionins were quantified by colorimetric detection using the bicinchoninic acid assay. For peptide mass‐fingerprint analysis tryptic digests of eluates were examined.     

An on‐line sample pretreatment technique for the HPLC analysis of plant samples

A continuous‐flow, on‐line sample pretreatment technique using a silica gel microsyringe extractor has been developed. All steps including extraction, separation, clean‐up, and concentration occur in the microsyringe. The overall sample pretreatment process takes <10 min per sample. Different polarity chemicals in the plant sample are successively extracted and separated, and analyzed in parallel using HPLC–UV and HPLC–UV–MS/MS. Polycyclic aromatic hydrocarbons, alkylphenols, and plant hormones were determined as model compounds for nonpolar, intermediate polarity, and polar fractions, respectively. All the parameters that influence the extraction and separation efficiency of the microsyringe extractor have been optimized and evaluated. Under the optimized conditions, recoveries of target compounds ranged from 78.4 to 101.9%, the RSD was <12.8% and the square of the correlation coefficient was >0.99. Complex plant samples of Sambucus Mandshurica Kitag have been tested using this method. Fluorene, phenanthrene, pyrene, and plant hormones were detected in all the samples, and concentrations ranged from 24.2–34.9, 43.8–67.1, 25.9–29.2, and 14.5～110.8 ng/g, respectively.     

Supramolecular-based dispersive liquid-liquid microextraction: a novel sample preparation technique utilizes coacervates and reverse micelles

The present study reports a novel sample enrichment method termed supramolecular-based dispersive liquid-liquid microextraction (SM-DLLME). The SM solvent selected was made up of reversed micelles of decanoic acid dispersed in tetrahydrofuran (THF)-water. THF plays double role, not only acts as a disperser solvent but also causes self-assembly of decanoic acid. The contaminant used as a model was Malachite Green (MG). It was a cationic dye and was preconcentrated without any derivatization or ion-pair formation reaction. In SM-DLLME, the most important advantages of DLLME technique and preconcentration strategy based on the coacervation and reverse micelles have come together. Moreover, in this method, disadvantages of DLLME such as extraction capability of only hydrophobic analytes and hiring toxic and hazardous organic solvents as the extraction solvent and disadvantages of coacervation-based extraction method such as tedious, labor-intensive and time-consuming stirring procedure have been avoided. Several variables affecting the microextraction efficiency were investigated and optimized. Under the optimized conditions and preconcentration of only 5.00 mL of sample, the enhancement factor was 52, limit of detection (LOD) was 4 μg/L and relative standard deviations (RSDs) for 145 and 36 μg/L of MG in textile industry wastewater were 1.8 and 3.2%, respectively (n = 6).     

On-line coupling of sequential injection extraction with restricted-access materials and post-column derivatization for sample clean-up and determination of propranolol in human plasma

The presented paper deals with a new methodology for direct determination of propranolol in human plasma. The methodology described is based on sequential injection analysis technique (SIA) coupled with solid phase extraction (SPE) column based on restricted access materials (RAM). Special RAM column containing 30 μm polymeric material—N-vinylacetamide copolymer was integrated into the sequential injection manifold. SIA–RAM system was used for selective retention of propranolol, while the plasma matrix components were eluted with two weak organic solutions to waste.

Due to the acid–basic and polarity properties of propranolol molecule and principles of reversed-phase chromatography, it was possible to retain propranolol on the N-vinylacetamide copolymer sorbent (Shodex MSpak PK-2A 30 μm (2 mm × 10 mm)). Centrifuged plasma samples were aspirated into the system and loaded onto the column using acetonitrile–water (5:95, v/v), pH 11.00, adjusted by triethylamine. The analyte was retained on the column while proteins contained in the sample were removed to waste. Interfering endogenous substances complicating detection were washed out by acetonitrile–water (15:85), pH 11.00 in the next step. The extracted analyte was eluted by means of tetrahydrofuran–water (25:75), pH 11.00 to the fluorescence detector (emission filter 385 nm). The whole procedure comprising sample pre-treatment, analyte detection and column reconditioning took about 15 min. The recoveries of propranolol from undiluted plasma were in the range 96.2–97.8% for three concentration levels of analyte. The proposed SIA–RAM method has been applied for direct determination of propranolol in human plasma.