Preparation and examination of monolithic in-needle extraction (MINE) device for the direct analysis of liquid samples

Combination of extraction and chromatographic techniques opens NEW possibilities in sample preparation area. Macroporous poly(styrene-divinylbenzene) (PS-DVB) monoliths were prepared by in situ polymerization in stainless steel needles. The surface of stainless steel needle was modified earlier by the silane coupling agent. Monolithic materials located inside needles were used as the in-needle extraction device. Scanning electron microscope (SEM) images were obtained for nine monoliths. Spectra of prepared materials were also performed with the use of two techniques: Attenuated Total Reflectance (ATR) and Fourier Transform Infrared Spectroscopy (FTIR). The new monolithic in-needle extraction (MINE) devices were used in the preparation of a series of test water samples for chromatographic analysis. The extraction of phenolic compounds from water samples was carried out by pumping liquid samples through the MINE device. Obtained results indicate a high efficiency of in-needle extraction systems based on monolithic materials. Breakthrough volume and the sorption efficiency of prepared monolithic in-needle extraction devices were determined experimentally. The achieved recovery was close to 90%, and determined LOQ values varied between 0.4 and 6 μg.     

Pipette‐tip solid‐phase extraction using cetyltrimethylammonium bromide enhanced molybdenum disulfide nanosheets as an efficient adsorbent for the extraction of sulfonamides in environmental water samples

Surfactant cetyltrimethylammonium bromide enhanced molybdenum disulfide was used as an adsorbent in pipette‐tip solid‐phase extraction for the pretreatment of sulfonamides in environmental water samples. The factors affecting the extraction recoveries of the analytes, including the sample pH value, amount of sorbent, type and volume of eluent solution, and salt concentration were optimized. This pipette‐tip solid‐phase extraction method demonstrated good linearity (0.05–10.0 µg/L) with a coefficient of determination of 0.9984–0.9996, limit of detection (0.2–0.4 ng/L) and limit of quantitation (0.5–1.0 ng/L), good analyte recoveries (76–91), and acceptable limit of quantitation (<10%) under the optimized conditions. These results indicated that the proposed method was a good tool for monitoring sulfonamides in environmental water samples.     

Selective solid phase extraction and preconcentration of trace mercury(II) with poly-allylthiourea packed columns

A new method for selective solid-phase extraction and preconcentration of trace mercury(II) from aqueous solution was developed by using poly-allylthiourea as a new extractant. The procedure is based on the retention of analyte in the form of thiourea complex on a mini column of polymer resin. The effects of pH, eluent type, eluent concentration, sample volume, sample flow rate, and foreign ions on the recovery of the analyte were investigated using model solutions. At optimal pH value, the extraction capacity of the new sorbent was 1.13 mmol g^?1. The adsorption behavior of mercury(II) on the sorbent can be described by a Langmuir adsorption isotherm equation. The method was validated by analyzing a certified reference material with the results being in agreement with those quoted by manufacturers. The method was applied to the determination of trace inorganic mercury(II) in natural water samples and vegetables with satisfactory results.     

Solid-phase extraction based on multi-walled carbon nanotube (MWCNT) sorbents combined with bio-coacervation extraction for the determination of atrazine from water samples followed by HPLC analysis

In this study, combined technique of solid-phase extraction based on multi-walled carbon nanotubes with bio-coacervation extraction (SPE-MWCNT-BCAE) has been developed as a new sample preparation method for the determination of atrazine from water samples. The proposed method involves two steps: analyte enrichment on the solid sorbent and subsequently elution of the analyte by an appropriate solvent. Multi-walled carbon nanotubes (MWCNTs) were used as the sorbent. They have high specific surface area, nano-scale structure and high diffusion rate. The second step is based on the use of bioaggregates for analyte re-enrichment, which consists of biosurfactants and ionic liquid. This method follows the principles of green chemistry. Parameters affecting the extraction efficiency were optimized. Under optimum conditions, the enrichment factor was 176. The linear dynamic range (LDR) and limit of detection (LOD) were 2–100 µg L^?1 and 0.66 µg L^?1, respectively. The relative standard deviation (RSD) for six replicate measurements was 3.8%. The method was applied to the determination of ultratrace levels of atrazine in environmental water samples with satisfactory results.     

Method development for the analysis of N-nitrosodimethylamine and other N-nitrosamines in drinking water at low nanogram/liter concentrations using solid-phase extraction and gas chromatography with chemical ionization tandem mass spectrometry

N-nitrosodimethylamine (NDMA) is a probable human carcinogen of concern that has been identified as a drinking water contaminant. U.S. Environmental Protection Agency Method 521 has been developed for the analysis of NDMA and 6 additional N-nitrosamines in drinking water at low ng/L concentrations. The method uses solid-phase extraction with coconut charcoal as the sorbent and dichloromethane as the eluent to concentrate 0.50 L water samples to 1 mL. The extracts are analyzed by gas chromatography-chemical ionization tandem mass spectrometry using large-volume injection. Method performance was evaluated in 2 laboratories. Typical analyte recoveries of 87-104% were demonstrated for fortified reagent water samples, and recoveries of 77-106% were demonstrated for fortified drinking water samples. All relative standard deviations on replicate analyses were < 11%.     

Role of Hansen solubility parameters in solid phase extraction

The sorbent–eluent systems combined from eight polymeric sorbents and seven solvents as eluents were used for the extraction of phenol and its oxidation products from water samples. The individual interactions between sorbents, eluents and analytes were characterized by Hansen solubility parameters. Principal components analysis (PCA) was used for revealing the dominant interactions (dispersive, polar, and hydrogen bonding type) in sorbent–analyte–eluent systems. The importance of solubility parameters was also determined by a novel procedure based on sum of ranking differences (SRD). Although PCA and ranking by SRD are based on different principles and calculations, they have provided very similar results. The recovery in a given system has been predicted from the magnitudes of mutual interactions (sorbent–analyte, sorbent–eluent, analyte–eluent) by multiple linear regression.     

Application of a thiourea‐containing task‐specific ionic liquid for the solid‐phase extraction cleanup of lead ions from red lipstick,pine leaves,and water samples

Here, task‐specific ionic liquid solid‐phase extraction is proposed for the first time. In this approach, a thiourea‐functionalized ionic liquid is immobilized on the solid sorbent, multiwalled carbon nanotubes. These modified nanotubes packed into a solid‐phase extraction column are used for the selective extraction and preconcentration of ultra‐trace amounts of lead(II) from aqueous samples prior to electrothermal atomic absorption spectroscopy determination. The thiourea functional groups act as chelating agents for lead ions retaining them and so, give the selectivity to the sorbent. Elution of the retained ions can be performed using an acidic thiourea solution. The effects of experimental parameters including pH of the aqueous solution, type and amount of eluent, and the flow rates of sample and eluent solutions on the separation efficiency are investigated. The linear dependence of absorbance of lead on its concentration in the initial solution is in the range of 0.5–40.0 ng/mL with the detection limit of 0.13 ng/mL (3s_b/m, n = 10). The proposed method is applicable to the analysis of red lipstick, pine leaves, and water samples for their lead contents.     

The evaluation of different sorbents for the preconcentration of phenoxyacetic acid herbicides and their metabolites from soils

A procedure using alkaline extraction, solid-phase extraction (SPE) and HPLC is developed to analyze the polar herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) together with their main metabolites in soils. An ion-pairing HPLC method is used for the determination as it permits the baseline separation of these highly polar herbicides and their main metabolites. The use of a highly cross-linked polystyrene-divinylbenzene sorbent (PS-DVB) gives the best results for the analysis of these compounds. This sorbent allows the direct preconcentration of the analytes at the high pH values obtained after quantitative alkaline extraction of the herbicides from soil samples. Different parameters are evaluated for the SPE preconcentration step. The high polarity of the main analytes of interest (2,4-D and MCPA) makes it necessary to work at low flow rates (< or =0.5 mL min(-1)) in order for these compounds to be retained by the PS-DVB sorbent. A two stage desorption from the SPE sorbent is required to obtain the analytes in solvents that are appropriate for HPLC determination. A first desorption with a 50:50 methanol:water mixture elutes the most polar analytes (2,4-D, MCPA and 2CP). The second elution step with methanol permits the analysis of the other phenol derivatives. The humic and fulvic substances present in the soil are not efficiently retained by PS-DVB sorbents at alkaline pH's and so do not interfere in the analysis. This method has been successfully applied in the analysis of soil samples from a golf course treated with a commercial product containing esters of 2,4-D and MCPA as the active components.     

疏水整体柱在线固相萃取与高效液相色谱-串联质谱联用测定牛肝中5种阿维菌素类药物残留

建立了牛肝中5种阿维菌素类药物残留的疏水整体柱在线固相萃取结合高效液相色谱-串联质谱测定的方法。以疏水的聚(甲基丙烯酸丁酯-乙二醇二甲基丙烯酸酯)整体柱(10 mm×2.1 mm)作为固相萃取介质,考察了上样流动相和洗脱流速对阿维菌素类药物的萃取效果,优化了梯度洗脱流动相的种类及质谱条件。方法在1~100 μg/L范围内线性关系良好(r>0.995),定量限为5 μg/kg。在5、10、50、100 μg/kg添加水平的回收率为77.4%~98.4%,日内和日间相对标准偏差分别为4.46%~8.03%和4.79%~8.68%,并且该柱反复使用400次后未发现萃取效率降低。结果表明,该整体柱对牛肝中5种阿维菌素类药物能够有效萃取,并且可以重复使用。该方法简单,自动化程度高,可应用于常规阿维菌素类药物残留分析。     

Multi-residue determination of organophosphorus and organochlorine pesticides in environmental samples using solid-phase extraction with cigarette filter followed by gas chromatography-mass spectrometry

A solid‐phase extraction (SPE) method was developed to extract 14 pesticides simultaneously from environment samples using cigarette filter as the sorbent before gas chromatography‐mass spectrometry (GC‐MS) analysis. Parameters influencing the extraction efficiency, such as the sample loading flow rate, eluent and elution volume, were optimized. The optimum sample loading rate was 3 mL/min, and the retained compounds were eluted with 6 mL of eluent at 1 mL/min under vacuum. Good linearity was obtained for all the 14 pesticides (r²>0.99) from 0.1 to 20 μg/L for water and from 2 to 400 μg/kg for soil samples. The detection limits (signal‐to‐noise=3) of the proposed method ranged from 0.01 to 0.20 μg/L for water samples and from 0.42 to 6.95 μg/kg for soil samples. The developed method was successfully applied for determination of the analytes in real environmental samples, and the mean recoveries ranged from 76.4 to 103.7% for water samples and from 79.9 to 105.3% for soil samples with the precisions (relative standard deviation) between 2.0 and 13.6%.     

Molecularly imprinted polymers for on-line preconcentration by solid phase extraction of pirimicarb in water samples

The synthesis and performance of a molecularly imprinted polymers (MIPs) as a selective solid phase extraction sorbent for the preconcentration of the carbamate pirimicarb from water samples is described. The MIP was prepared using pirimicarb as the template, methacrylic acid as the functional monomer and ethylene glycol dimethacrylate as the cross-linking monomer, and using chloroform as the solvent. The detection of pirimicarb was carried out by differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE) in 0.1 mol l⁻¹ HCl. Solvents of different polarities were checked for the polymer synthesis, and different experimental variables (sample pH, selection of the eluent used, eluent volume, analyte and eluent flow rates and sample volume) associated with the rebinding/extraction process were optimised. For a 25 ml sample, the process took about 13 min and resulted in a nominal enrichment factor of 50 (eluent MeOH:H₂O:HAc, 7:2:1; 0.5 ml) for pirimicarb. A limit of detection of 4.1 μg l⁻¹ was obtained, and a good reproducibility of the measurements using different MIP microcolumns was found. Furthermore, the MIP selectivity was evaluated by checking several substances with similar and different molecular structures to that of pirimicarb. As an application, pirimicarb was determined in water samples of diverse origin which were spiked at a concentration level of 71.5 μg l⁻¹.     

Separation and determination of ciprofloxacin in seawater,human blood plasma and tablet samples using molecularly imprinted polymer pipette‐tip solid phase extraction and its optimization by response surface methodology

By synthesizing a molecular imprinted polymer as an efficient adsorbent, ciprofloxacin was micro‐extracted from seawater, human blood plasma and tablet samples by pipette‐tip micro solid phase extraction and determined spectrophotometrically. Response surface methodology was applied with central composite design to build a model based on factors affecting on microextraction of ciprofloxacin; including volume of eluent solvent, number of extraction cycles, number of elution cycles, and pH of sample. Other factors that affect extraction efficiency, such as type of eluent solvent, volume of sample, type, and amount of salt were optimized with one‐variable‐at‐a‐time method. Under optimum extraction condition, pH of sample solution was 7.0, volume of eluent solvent (methanol) was 200 µL, volume of sample solution was 10 mL, and the number of extraction and elution cycles was five and seven, respectively, amount of Na₂SO₄ (as salt) and MIP (as sorbent) were optimized at 150 and 2 mg, respectively. The linear range of the suggested method under optimum extraction factors was 5–150 µg/L with a limit of detection of 1.50 µg/L for the analyte. Reproducibility of the method (as relative standard deviation) was better than 7%.     

Nitrogen doped nano porous graphene as a sorbent for separation and preconcentration trace amounts of Pb,Cd and Cr by Ultrasonic assisted in‐syringe dispersive micro solid phase extraction

Nitrogen doped nano porous graphene was used as an efficient sorbent in solid‐phase extraction process for simultaneous separation and pre‐concentration of metal ions lead (II), cadmium(II), and chromium(III)) in biological samples. Ultrasonic assisted in‐syringe dispersive micro solid phase extraction coupled with micro sampling atomic absorption spectrometry was utilized for the determination of metal ions. Nitrogen doped nano porous graphene was synthesized as a nano sorbent by chemical vapour deposition method. Methane and aniline were used as carbon and nitrogen sources. The characterization of sorbent was performed by field emission scanning electron microscope, transmission electron microscopy, atomic force microscope, fourier transform infrared, chemical element analysis and raman analysis. Effective parameters on the extraction efficiency such as pH, sorbent dosage, eluent volume and eluent concentration were optimized by central composite design and desirability function. Experimental results indicate that the optimal conditions for this extraction were pH = 6.4, 1.42 mg of sorbent, 100 μL of eluent, and 0.84 mol L^‐1 of eluent concentration. The detection limits are as low as 1.5, 0.3 and 0.9 μg L^‐1 for lead, cadmium, and chromium, respectively. The intra‐day precisions were 3.6, 4.38 and 2.94 and Inter‐day precision were 4.83, 5.26 and 4.52 for lead, cadmium, and chromium, respectively. Method performance was investigated by determination of mentioned heavy metals in complicated biological matrixes such as human plasma, urine and saliva samples with good recoveries.     

Determination of dodecanol and ethoxylated fatty alcohols from environmental samples using diatomaceous earth as a green sorbent for solid‐phase extraction

This study describes the use of diatomaceous earth during solid‐phase extraction as an efficient sorbent for separation and concentration of dodecanol and ethoxylated dodecanol containing 1–9 ethoxyl groups. The efficiency of different eluents was evaluated for model samples which allowed to select methanol and chloroform for tests with river water samples. During model experiments, it was observed that the recovery rates of specific compounds in the studied mixture were influenced by the character of the solvent used for desorption. Hydrophobic compounds, such as dodecanol and ethoxylated dodecanol with 1–3 ethoxyl groups, were eluted by chloroform with 100% efficiency. In case of the remaining compounds, which were more hydrophilic, a 97% recovery rate was achieved during elution with methanol. Such dependencies were not observed in case of river water samples, as the results obtained for both studied sorbent‐eluent systems were comparable. In both variants the recovery of dodecanol and ethoxylated dodecanol containing 1–9 ethoxyl groups ranged from 33 to 99%.     

The Use of Ultrasound in pipette‐tip solid‐phase extraction based on CuS@ZnS@Fe3O4‐CNTs for pre‐concentration of tartrazine in water samples

This paper report a novel strategy for synthesis and application of CuS@ZnS@Fe₃O₄‐CNTs composite which has great potentials as artificial receptor for tartrazine trapping due to its ultrahigh surface area and functionality which is related to application of electrochemical route. A durable and economical pipette‐tip CuS@ZnS@Fe₃O₄‐CNTs nano‐composite miniaturized solid phase extraction coupled with UV‐Vis spectrophotometry was developed for clean‐up and determination of tartrazine from various water samples. Undoubtedly, presence of mild‐intensity/frequency ultrasound irradiation played a key role for reducing consumption of eluent volume by broking hydrogen bonds between retained analyte and sorbent. The influence of factors including pH, sorbent dosage, sonication time and eluent volume were investigated and optimum conditions were obtained using experimental design methodology. Under optimized conditions, good extraction efficiencies for the analyte were obtained with no matrix interference in the subsequent UV‐Vis. Good linearity for tartrazine in the range of 20‐5000 ng mL^‐1 with correlation coefficients of R² ≥ 0.99 and low detection limit close to 4.76 ng mL^‐1 reveals high applicability of method for trace analysis.     

Solid phase extraction method for the separation and determination of chromium(III) in the presence of chromium(VI) using silica gel modified by N,N'-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine

N,N'-bis-(α-methylsalicylidene)-2,2-dimethyl-1,3-propanediimine (SBTD) modified silica gel was prepared and used as sorbent for solid phase extraction of Cr(III) ions from aqueous solution. This sorbent showed a high sorption affinity for Cr(III) while recovery of Cr(VI) was very low. The analyte ion retained on the column was eluted with 1 mol L(-1) HNO(3). The chromium ion in the eluent was determined by graphite furnace atomic absorption spectrometry. The effects of different parameters such as pH, eluent type and volume, Schiff's base concentration, sample and eluent flow rate, interfering ions and adsorbent amount were investigated.     

Magnetic solid-phase extraction to preconcentrate trace amounts of gold (III) using nickel ferrite magnetic nanoparticles

In this research, nickel ferrite (NiFe₂O₄) magnetic nanoparticles were synthesised by a simple method and applied as sorbent for magnetic solid-phase extraction of trace amounts of Au(III) from water samples. Detection in this technique was performed by flame atomic absorption spectrometry. The effects of sample pH, amount of sorbent, extraction time, desorption solvent and its volume on the extraction process were optimised. The effects of interfering ions on the recovery of the analyte were also evaluated in model solutions. The best results were obtained at pH 6.5 with 5 mL of eluent solution (0.1 mol L^?1 sodium thiosulphate) and an extraction time of 30 min. Under optimal conditions, the sorption capacity was 34.6 mg g^?1. Also, enhancement factor (for 100 mL of sample solution) was found to be 19.3. The calibration graph was linear in the range of 4.4–800.0 µg L^?1 gold concentration and the limit of detection was 1.32 µg L^?1. The relative standard deviation of the method (for n = 8) was 1.57%. The method was successfully applied to the extraction of Au(III) from water samples.     

Hydrophobic polymer monoliths as novel phase separators: Application in continuous liquid–liquid extraction systems

Hydrophobic macroporous polymer monoliths are shown to be interesting materials for the construction of “selective solvent gates”. With the appropriate surface chemistry and porous properties the monoliths can be made permeable only for apolar organic solvents and not for water. Different poly(butyl methacrylate-co-ethylene dimethacrylate) (BMA-EDMA) and poly(styrene-co-divinylbenzene) (PS-DVB) monoliths prepared with tailored chemistries and porosities were evaluated for this purpose. After extensive characterization, the PS-DVB monoliths were selected due to their higher hydrophobicity and their more suitable flow characteristics. BMA-EDMA monoliths are preferred for mid-polarity solvents such as ethyl acetate, for which they provide efficient separation from water. Breakthrough experiments confirmed that the pressures necessary to generate flow of organic solvents through PS-DVB monoliths were substantially lower than for water. A phase separator was constructed using the monoliths as the flow selector. This device was successfully coupled on-line with a chip-based continuous liquid–liquid-extraction (LLE) system with segmented flow. Efficient separation of different solvents was obtained across a wide range of flow rates (0.5–4.0 mL min⁻¹) and aqueous-to-organic flow ratios (β = 1–10). Good robustness and long life-time were also confirmed. The suitability of the device to perform simple, cheap, and reliable phase separation in a continuous LLE system prior to gas-chromatographic analysis was proven for some selected real-life applications.     

Application of Nylon6/Polypyrrole core–shell nanofibres mat as solid-phase extraction adsorbent for the determination of atrazine in environmental water samples

A novel solid-phase extraction (SPE) system, based on a new sorbent of Nylon6/Polypyrrole (PA6/PPy) core–shell nanofibres mat and a new packing format of SPE disks, is presented in this paper. A series of related parameters that may affect the efficiency, such as the kind of eluent and its volume, the amount of nanofibres mat, ionic strength, pH of the sample, flow rate of the sample and volume of the sample, have been investigated systematically. Under the optimised conditions, the target analyte in 10 mL water samples can be completely extracted by a 3.0 mg PA6/PPy nanofibres mat and easily eluted by 400 µL acetonitrile. Around 20 µL elution was injected directly to HPLC-UV for determination, without further concentration. Besides, the nanofibres mat could be repeatedly used up to six cycles. Satisfactory linearity was achieved in the range of 0.1–40.0 ng/mL with a correlation coefficient of 0.9999. The limit of detection (LOD) (3 S/N) was 0.03 ng/mL, which could meet the determination requirements of atrazine as per the European Union legislation, US. Safe Drinking Water Act and the State Environmental Protection Administration of China. The simple, effective and economic method was proposed for the determination of atrazine in environmental water at trace level. The recoveries ranged from 94.73 to 114.92%, with relative standard deviations (RSDs) of 2.5–4.2%, and were obtained from tap water and lake water samples with atrazine at 2.0 ng/mL, suggesting the actual feasibility of the proposed method in environmental water samples.     

Sponge-nested polymer monoliths: Versatile materials for the solid-phase extraction of bisphenols

Polymer monoliths are promising materials for sample preparation due to their high porosity, pH stability, and simple preparation. The use of melamine formaldehyde foams has been reported as an effective support to prepare highly robust silica and polymer monoliths. Herein, divinylbenzene monoliths based on a 50:50 (%, w/w) crosslinker/porogen ratio have been nested within a melamine-formaldehyde sponge, resulting in monoliths with a surface area higher than 400 m²/g. The extraction performance of these monoliths was evaluated for the extraction of endocrine-disrupting bisphenols from aqueous solutions. We evaluated for the first time the versatility of sponge-nested polymer monoliths by comparing three different extraction modes (vortex mixing, magnetic stirring, and orbital shaking). Vortex mixing showed a comparable recovery of bisphenols (39%–81%) in a shorter extraction time (30 min, instead of 2 h). In addition, the robustness of the sponge-nested polymer monoliths was demonstrated for the first time by reshaping a larger monolithic cube (0.125 cm³) into four smaller pieces (4 × 0.03125 cm³) leading to a 16%–21% increase in extraction efficiency. This effect was attributed to an increase in the effective contact area with the sample, obtaining a higher analyte extraction capacity.