Solid-phase Extraction Efficiency Research Articles

Comparison of solvent extraction and solid-phase extraction for the determination of polychlorinated biphenyls in transformer oil

Solid-phase extraction (SPE) of nine polychlorinated biphenyls (PCBs) from transformer oil samples was evaluated using octadecyl (CI8)-bonded porous silica. The efficiency of SPE of these PCBs was compared with those obtained by solvent extraction with DMSO and hexane. Average recoveries exceeding 95% for these PCBs were obtained via the SPE method using small cartridges containing 100mg of 40pm CI8-bonded porous silica. The average recovery by solvent extraction with DMSO and hexane exceeded 83%. It was concluded that the recoveries and precision for the solvent extraction of PCBs were poorer than those for the SPE.

Detection, quantification, and identification of dermorphin in equine plasma and urine by LC–MS/MS for doping control

Dermorphin is a unique opioid peptide that is 30-40 times more potent than morphine. It was misused and went undetected in horse racing until 2011 when intelligence obtained from a few North American race tracks suggested its use. To prevent such misuse, a reliable analytical method became necessary for detection and identification of dermorphin in post-race horse samples. This paper describes the first liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for such a purpose. Equine plasma and urine samples were pre-treated with ethylenediamine tetra-acetic acid and urea prior to solid-phase extraction (SPE) on Oasis MCX cartridges. Resulting eluates were dried under vacuum and analyzed by LC-MS/MS for dermorphin. The matrix effect, SPE efficiency, intra-day and inter-day accuracy and precision, and stability of the analyte were assessed. The limit of detection was 10 pg/mL in plasma and 20 pg/mL in urine, and the limit of confirmation was 20 pg/mL in plasma and 50 pg/mL in urine. Dermorphin in plasma is stable at ambient temperature, but its diastereomer is unstable. With isotopically labeled dermorphin as an internal standard, the quantification range was 20-10,000 pg/mL in plasma and 50-20,000 pg/mL in urine. The intra-day and inter-day accuracy was from 91 % to 100 % for the low, intermediate, and high concentrations. The intra-day and inter-day coefficients of variation were less than 12 %. The method differentiates dermorphin from its diastereomer. This method is very specific for identification of dermorphin in equine plasma and urine, as assessed by BLAST search and targeted SEQUEST search, and by MS/MS spectrum library search. The method has been successfully applied to analysis of samples collected following dermorphin administration to research horses and of official post-race samples.

A high-throughput LC-MS/MS method suitable for population biomonitoring measures five serum folate vitamers and one oxidation product.

Small specimen volume and high sample throughput are key features needed for routine methods used for population biomonitoring. We modified our routine eight-probe solid phase extraction (SPE) LC-MS/MS method for the measurement of five folate vitamers [5-methyltetrahydrofolate (5-methylTHF), folic acid (FA), plus three minor forms: THF, 5-formylTHF, 5,10-methenylTHF] and one oxidation product of 5-methylTHF (MeFox) to require less serum volume (150 μL instead of 275 μL) by using 96-well SPE plates with 50 mg instead of 100 mg phenyl sorbent and to provide faster throughput by using a 96-probe SPE system. Total imprecision (10 days, two replicates/day) for three serum quality control pools was 2.8-3.6% for 5-methylTHF (19.5-51.1 nmol/L), 6.6-8.7% for FA (0.72-11.4 nmol/L), and ≤11.4% for the minor folate forms (<1-5 nmol/L). The mean (±SE) recoveries of folates spiked into serum (3 days, four levels, two replicates/level) were: 5-methylTHF, 99.4 ± 3.6%; FA, 100 ± 1.8%; minor folates, 91.7-108%. SPE extraction efficiencies were ≥85%, except for THF (78%). Limits of detection were ≤0.3 nmol/L. The new method correlated well with our routine method [n = 150, r = 0.99 for 5-methylTHF, FA, and total folate (tFOL, sum of folate forms)] and produced slightly higher tFOL (5.6%) and 5-methylTHF (7.3%) concentrations, likely due to the faster 96-probe SPE process (1 vs. 5 h), resulting in improved SPE efficiency and recovery compared to the eight-probe SPE method. With this improved LC-MS/MS method, 96 samples can be processed in ~2 h, and all relevant folate forms can be accurately measured using a small serum volume.

Sensitive Determination of Bioactive Crocin Analogues in &lt;i&gt;Gardenia jasminoides&lt;/i&gt; Ellis Using SPE Prior to HPLC Analysis

In this study, the feasibility of single-walled carbon nanotubes (SWCNTs) as solid-phase extraction (SPE) adsorbent for the determination of bioactive crocin analogues in the traditional Chinese Medicine (TCM) of Gardenia Jasminoides Ellis prior to HPLC analysis was studied. Various experimental factors influencing SPE efficiency and HPLC conditions were studied. By using SWCNTs as the SPE adsorbent, the detection limit of 1.19-2.21 fmol (at S/N of 3) were achieved with the preconcentration efficiency of more than 120-folds, indicating this proposed method was very practical for increasing the sensitivity prior to HPLC analysis, and it may provides useful clue for the efficient extraction for the bioactive compounds in TCMs.

A graphene/Co3O4 nanocomposite as a new adsorbent for solid phase extraction of Pb(ii), Cu(ii) and Fe(iii) ions in various samples

A graphene-based cobalt nanocomposite (G/Co3O4) was synthesized and used for the first time as an effective adsorbent for the preconcentration of the Pb(II), Cu(II) and Fe(III) ions in environmental water and food samples prior to flame atomic absorption detection. The properties of the graphene, Co3O4 and G/Co3O4 nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, and thermal gravimetric analysis. The experimental parameters affecting the solid phase extraction efficiency for analyte ions including sample pH, adsorption and elution contact time, volume and concentration of eluting reagent, sample volume and interfering ions were examined. The adsorption capacity of the G/Co3O4 composite was found to be 58, 77 and 78 mg g−1 for Pb(II), Cu(II) and Fe(III), respectively. The quantitative elution of the adsorbed metal ions was carried out by 2 mL of 2 mol L−1 HNO3. The preconcentration factor of the method was 175. The limit of detection was found to be ≤0.81 μg L−1. The accuracy of the method was studied by analyzing certified reference material (RM 8704 Buffalo River Sediment, SRM 1568a Rice Flour and SPS-WW1 Batch 111-Wastewater) and spiked real samples. The method was applied for the separation and preconcentration of trace metal ions in tap water, wastewater, dam water, well water, kiwi and wheat samples.

A Fast and Sensitive Method for the Simultaneous Determination and Quantification of Six Anionic Surfactants in Surface Water using HILIC-ESI-MS Technique

The hydrophobic hydrocarbon chain and the polar sulfate group confer surfactant properties and enable them to beused as anionic surfactants. Anionic surfactants (AS) are known for their adverse impact on environment, particularly on aquaticecosystem. In the present study a fast, sensitive and selective method for the determination and subsequent quantification of sixanionic surfactants was developed using hydrophilic interactive liquid chromatography (HILIC) coupled to a electrospray ionization(ESI) mass spectrometer (MS), in the concentration range 15-20 μg/L. The capability of the method was establishedusing regression analysis and ANOVA. The method performance was evaluated by analyzing real time surface water spiked with1-dodecyl hydrogen sulfate at 15 μg/L. Combined efficiency of solid phase extraction and MS detection established recovery of89% in presence of natural matrix. These results point out that HILIC coupled to multistage MS procedures can be a powerfultechnique for environmental applications concerning the screening of polar contaminants.

Dynamic layer-by-layer self-assembly of multi-walled carbon nanotubes on quartz wool for on-line separation of lysozyme in egg white

The multi-walled carbon nanotubes (MWNTs) coated quartz wool (MWNTs/QW) prepared by dynamic layer-by-layer self-assembly was used as solid-phase extraction (SPE) absorbent for on-line separation and preconcentration of lysozyme in egg white. The coating procedures were performed continuously in a flow system operated by a set of sequential injection devices. The quartz wool was placed in a microcolumn forming a loose packing to guarantee the minimized flow impedance and the intimate contact between proteins and absorbent surface. Various parameters affecting SPE efficiency including the volume, pH, ionic strength and flow rate of sample and eluent were systematically studied. The feasibility of the proposed method was validated by successfully applied to the separation of lysozyme in egg white.

A novel superparamagnetic surface molecularly imprinted nanoparticle adopting dummy template: An efficient solid-phase extraction adsorbent for bisphenol A

Leakage of the residual template molecules is one of the biggest challenges for application of molecularly imprinted polymer (MIP) in solid-phase extraction (SPE). In this study, bisphenol F (BPF) was adopted as a dummy template to prepare MIP of bisphenol A (BPA) with a superparamagnetic core–shell nanoparticle as the supporter, aiming to avoid residual template leakage and to increase the efficiency of SPE. Characterization and test of the obtained products (called mag-DMIP beads) revealed that these novel nanoparticles not only had excellent magnetic property but also displayed high selectivity to the target molecule BPA. As mag-DMIP beads were adopted as the adsorbents of solid-phase extraction for detecting BPA in real water samples, the recoveries of spiked samples ranged from 84.7% to 93.8% with the limit of detection of 2.50pgmL−1, revealing that mag-DMIP beads were efficient SPE adsorbents.

Validation of the Pseudo Imprinted Microspheres for Solid-Phase Extraction of Acyclovir from Swine Tissue

The novel pseudo imprinted microspheres were synthesized by aqueous suspension polymerization using theophylline as the template and employed as a special sorbent of solid-phase extraction for selective extraction of acyclovir from swine tissue. The pseudo imprinted microspheres revealed high affinity and selectivity to acyclovir, and the matrix interferences could be efficiently eliminated, which make the extract of solid-phase extraction clean enough for HPLC analysis. The parameters that affect the extraction efficiency of solid-phase extraction were investigated, including solvent of extraction, volume of loading sample, washing and elution solvent, etc. Good linearity was obtained in a range of 0.05~15 μg/mL with correlation coefficient (r2) of 0.9991. The recoveries at three spiked levels were ranged from 91.4% to101.0% with RSD less than of 5.0%.

Application of Nanoscale Poly(divinyl-Benzene Vinylpyrrolidone) as Solid-Phase Extraction Adsorbent Prior to LC-MS-MS for the Determination of Paralytic Shellfish Poisoning Toxins in Shellfish

In the present study, the feasibility of the poly(divinyl-benzene vinylpyrrolidone) as solid-phase extraction (SPE) nanoscale adsorbent prior to LC-MS-MS method for the sensitive and selective determination of eight paralytic shellfish poisoning (PSP) (GTX1, GTX2, GTX3, GTX4, GTX5, dcGTX2, dcGTX3 and dcNEO-b) toxins in the shellfish was investigated. Various parameters affecting SPE efficiency including the eluent and its volume, and sample volume were studied. The application of the SPE can remove most of the ematrix interference compared with the conventional SPE procedure. By using slected reaction monitoring (SRM) mode in LC-MS-MS analysis, the acquired calibration curves were strictly linear (r2 &gt; 0.996) for the eight targeted analyses. The feasibility of the proposed method was finally validated by quantifing the eight PSPs in the shellfish samples (scallop, Crassostrea gigas and Ruditapes philippinarum) with the satisfitory recoveries of more than 80% with RSDs less than 10%.

Using Single-Walled Carbon Nanotubes as Solid-Phase Extraction Adsorbent for the Sensitive Determination of Amino Acid Neurotransmitters in Human Cerebrospinal Fluids

Carbon nanotubes are a kind of new carbon-based nanomaterials, which have drawn great attention in many application fields including the biomarker analysis in biomedical and clinical research. In the present study, the feasibility of single-walled carbon nanotubes (SWCNTs) as solid-phase extraction (SPE) adsorbent for the determination of amino acid neurotransmitters (AANs) (glutamic, dopamine and γ-amino-n-butyric acid) in human cerebrospinal fluids (CSFs) was investigated. Various parameters affecting SPE efficiency including the eluent and its volume, adsorbent amount and sample volume were systematically studied. The acquired calibration curves were linear (r2 &gt; 0.999) over the concentration range 10 to 500 ng per injection. By using SWCNTs as the SPE adsorbent, the detection limit of 12.9-42.5 fmol (at S/N of 3) were achieved with the preconcentration efficiency of more than 500-folds. The feasibility of the proposed method was validated by successfully applied to the measurements of ANNs in human CSFs sampled from healthy subjects and the patients with human immunodeficiency virus (HIV) infection, malignant melanoma and hypertension. This original application represents a powerful tool to study the kinetics of ANNs release by neuronal cells during neurotransmission, as well as for the understanding of the pathobiological and therapeutic basis of these remarkable molecular for diverse diseases.

Measurement of F2-isoprostanes, hydroxyeicosatetraenoic products, and oxysterols from a single plasma sample

Oxidized lipids such as F2-isoprostanes (F2-IsoPs), hydroxyeicosatetraenoic acid products (HETEs), and cholesterol oxidation products (COPs) are widely believed to be involved in multiple diseases. Usually, each product is measured individually in separate blood samples. In this study we describe a method allowing us to measure F2-IsoPs, HETEs, COPs, and arachidonate using a single sample. Plasma (1 ml) samples from healthy volunteers were diluted with heavy isotopic standards, hydrolyzed in alkali with organic solvent, and then subjected to anionic-exchange solid-phase extraction (SPE). After the SPE column was washed, hexane and hexane/ethyl acetate portions were collected and combined for COPs measurement. Thereafter the column was loaded with hexane/ethanol/acetic acid and fractions were collected for total F2-IsoPs, total HETEs, and arachidonate measurement. All compounds in the eluates were measured by gas chromatography–mass spectrometry. The efficiency of SPE and reproducibility for all compounds measured were high. Levels of total F2-IsoPs (0.45±0.26 ng/ml (n=157)), total HETEs (34.06±16.35 ng/ml (n=21)), total arachidonate (68.36±24.45 μg/ml (n=33)), and COPs (7-ketocholesterol, 12.25±6.56 ng/ml; 7β-hydroxycholesterol, 6.32±3.46 ng/ml; 7α-hydroxycholesterol, 15.06±7.06 ng/ml; 24-hydroxycholesterol, 41.39±18.22 ng/ml; and 27-hydroxycholesterol, 29.08±16.79 ng/ml (n=26)) were recorded in healthy subjects (age range 20 to 66 years; average male to female ratio 1:1).

Determination of nitrate esters in water samples: Comparison of efficiency of solid-phase extraction and solid-phase microextraction

This paper deals with comparison of efficiency of extraction techniques (solid-phase extraction, SPE and solid-phase microextraction, SPME) used for extraction of nitrate esters (ethyleneglycoldinitrate, EGDN and nitroglycerin, NG), representing the first step of the method of quantitative determination of trace concentrations of nitrate esters in water samples. EGDN and NG are subsequently determined by means of high-performance liquid chromatography with ultraviolet detection (HPLC-UV). Optimization of SPE and SPME conditions was carried out using model water samples. Seven SPE cartridges were tested and the conditions were optimized (type of sorbent, type and volume of solvent to be used as eluent). For both nitrate esters the limit of detection (LOD) and the limit of quantification (LOQ) obtained using SPE/HPLC-UV were 0.23 μg mL −1 and 0.70 μg mL −1, respectively. Optimization of SPME conditions: type of SPME fibre (four fibres were tested), type and time of sorption/desorption, temperature of sorption. PDMS/DVB (polydimethylsiloxane/divinylbenzene) fibre coating proved to be suitable for extraction of EGDN and NG. For this fibre the LOD and the LOQ for both nitrate esters were 0.16 μg mL −1 and 0.50 μg mL −1, respectively. Optimized methods SPE/HPLC-UV and SPME/HPLC-UV were then used for quantitative determination of nitrate esters content in real water samples from the production of EGDN and NG.

Relative influence of the dissolved humic material on the solid-phase extraction efficiency of pesticides from environmental water

The effect of organic matter on the solid-phase extraction (SPE) efficiency for pesticides belonging to different chemical groups (urea-derivatives, carbamates and triazines) and having different polarities, was simultaneously studied for the first time in pure and simulated water samples. SPE was carried out in precolumns packed with C18 silica or styrene-divinylbenzene copolymer PLRP-S phases on-line coupled to high performance liquid chromatography (HPLC) analysis. Retention factors in water (k'W) were estimated for 25 compounds and used for the calculation of the theoretical breakthrough volume (VbT) in pure water. Experimental breakthrough volumes (VbE) were first determined using purified and deionized water as the matrix for selected compounds having VbT < 500 mL; then, the same water with an added humic acid sodium salt (HA) at 0.4–5.6 mg/L of dissolved organic carbon (DOC) content, was used as the matrix for compounds having VbE < 500 mL in pure water. Several polar pesticides showed negative linear or logarithmic VbE curves depending on HA content; their recoveries were also determined in environmental samples having low dissolved organic carbon values, between 0.5–6.4 mg/L. A similar behavior was observed for these compounds in simulated and natural water samples, where DOC concentration and the percolated volume (Vp) mainly determine the solute recoveries values. However, the variation of recoveries as a function of DOC content could be negative or null depending on the two examined conditions (Vp lower or larger than VbE in pure water). Results demonstrated that breakthrough volume must always be considered to correctly interpret the participation of dissolved humic material on the SPE efficiency of organic micropollutants in water.

Determination of four benzodiazepine residues in pork using multiwalled carbon nanotube solid-phase extraction and gas chromatography–mass spectrometry

A solid-phase extraction (SPE)/GC-MS method using multiwalled carbon nanotubes (MWCNTs) was developed for the determination of four benzodiazepine residues including diazepam, estazolam, alprazolam and triazolam in pork. The analytes were extracted by ultrasonic assistant extraction using acetonitrile, concentrated and purified by MWCNTs packed cartridge, and determined by GC-MS. Ultrasonic extraction conditions, which included temperature, time, power, and solvent volume, were optimized. Comparative studies showed that MWCNTs were superior to C18 for the adsorption of drugs. Parameters influencing SPE efficiency, such as sample amounts, variety and volume of the eluent, were also optimized. Electron ionization (EI) operating in time program-selected ion monitoring mode (SIM) was used for GC-MS identification. The analytes were quantified with external standard calibration curve method. Lower limit of detection and quantification was obtained by the new method. Linear calibration curves were obtained in the concentration range from 10 ng/mL to 500 ng/mL for diazepam and from 20 ng/mL to 1000 ng/mL for estazolam, alprazolam and triazolam with calibration coefficients of 0.99 and above. The average recoveries for the four benzodiazepines spiked in pork were 75% to 104% and their relative standard deviations were between 1.3% and 10%. The limits of detection were 2 microg/kg for diazepam and 5 microg/kg for estazolam, alprazolam and triazolam in pork, respectively.

Influence of Suspended Clay Minerals and Humic Matter on the Solid Phase Extraction Efficiency of Selected Pesticides from Water

The purpose of this investigation was to determine the influence of humic acids (HA) and Ca-montmorillonite (CaM) on the solid-phase extraction (SPE) efficiency of atrazine, alachlor and α-cypermethrin from water samples at various pH-values. The nature and intensity of binding of the studied pesticides to CaM were determined by X-ray diffraction analysis and termogravimetric analysis (TGA) test. The studied pesticides eluted from discs were analysed by thin-layer chromatography (TLC). The effects of CaM and humic acid were generally pH-dependent and acted independently in extraction efficiency influence. Lower recovery of pesticides was observed at higher pH values when CaM was ≥0.1 g and was attributed to greater dispersion of clay, increased surface area and subsequent adsorption. Concentrations of dissolved organic carbon (DOC) in humic acid had less effect on the extraction efficiency when water was at pH 8 compared to water at pH 2, which was probably due to greater nonpolar interactions of the pesticides to the charge-neutralized humic acid molecule.

Determination of Commonly Used Herbicides in Surface Water Using Solid-Phase Extraction and Dual-Column HPLC-DAD

The present study describes the application of different solid-phase extraction techniques for the extraction, separation, and quantitative determination of 10 commonly used herbicides with different chemical structures (chlorsulfuron, diuron, bentazone, linuron, chlorpropham, fenoxoprop-ethyl, MCPA, diclofop-methyl, fluazifop-butyl, trifluraline) in water. Octadecyl (C18) Empore extraction disks, octadecyl (C18), and stryene divinylbenzene (SDB) Bond Elut Env cartridges were compared for solid-phase extraction efficiency. Herbicides were separated and quantified by reversed-phase high performance liquid chromatography with diode-array detection (HPLC-DAD) with simultaneous separation on two columns of differing polarity (C18 and CN) to confirm identification. Analytical separation was performed simultaneously on C18 and CN columns. Reanalysis of the sample extracts on a (cyano) CN column were used to confirm the identity of these compounds. Method optimization and validation parameters were presented in this work. Recoveries varied from 76.0% to 99.0% for C18 disks, from 75.1% to 100.0% for C18 cartridges, and from 54.0% to 98.0% for SDB cartridges over concentrations at 0.025–0.4 μg L−1. The limits of detection were 0.012–0.035 μg L−1.

Determination of volatile compounds in grape distillates by solid-phase extraction and gas chromatography

Solid-phase extraction (SPE) procedure on octadecylsilica (C 18) was developed for accumulation of volatile compounds from grape distillates. The procedure was optimised for final analysis by capillary gas chromatography. At mass concentrations in model solutions ranging from 0.1 to 50 mg/l solid-phase extraction recoveries of all analytes ranged from 69% for 2-phenylethanol to 102% for capric acid, with RSD values from 2 to 9%. SPE recoveries of internal standards to be added in the sample solution prior to extraction, higher alcohols 2-ethyl-1-hexanol and 1-undecanol, were 97 and 93%, respectively, with RSD values of 3%. Detection limits of analyzed compounds in model solutions ranged from 0.011 mg/l for isoamyl acetate to 0.037 mg/l for caproic acid. Method efficiency was tested in relation to acetic acid content, volume fraction of ethanol and possible matrix effects. A significant influence of matrix on SPE efficiency for geraniol, cis-2-hexen-1-ol and cis-3-hexen-1-ol was detected. For the same reason, 2-phenylethanol could not be determined by developed SPE method in samples of grape distillates. The developed solid-phase extraction method was successfully applied to determine the differences in volatile compound content in different grape distillates produced by the distillation of crushed, pressed and fermented grapes.

Optimization of the determination of deoxynivalenol in corn samples by liquid chromatography and a comparison of two clean-up principles

The determination of deoxynivalenol (DON) in corn by liquid chromatography with DAD detection was optimized. The separations were achieved on a Hypersil ODS column (100 x 4.6 mm; particle size 5 ?m) by isocratic elution (0.6 cm3/min), a mobile phase consisting of acetonitrile?water in the ratio of 16:84. UV Detection was performed at 220 nm. Linear calibration curves were constructed in the concentration range of 0.72 ? 12.00 ng/?l (equivalent to 0.29 ? 4.8 ?g/g com). The detection limit measured as the signal-to-noise ratio (3:1) was 0.16 ng/?l for DON (equivalent to 0.06 ?g/g corn). The efficiencies of two clean-up principles for crude corn extract were compared solid-phase and immunochemical extraction. The efficiency of solid-phase extraction was found to be higher, with a value of 92.7 % when MycoSep 225 columns were used, while its value was 97.6 % when self-made activated charcoal?alumina?Celite?cationic columns were used. In contrast, the efficiency of the immunochemical columns (IMA) was only 73.8%. It was also found that the self-made columns could be used at least three times in a row in that way differing from the MycoSep 225 columns, which could not be reused either with or without regeneration, as well as from the IMA columns, which had a regeneration efficiency of 53.6 %.

Optimization of solid-phase extraction using artificial neural networks in combination with experimental design for determination of resveratrol by capillary zone electrophoresis in wines

Solid-phase extraction (SPE) is often used for preconcentration of analytes from biological samples. Such an analytical step requires optimization for obtaining reliable results. Optimization in analytical chemistry is traditionally still often done with relaxation method, when an optimal value of a single variable is searched for (single variable approach (SVA)). However, if the optimized procedure is complex, there is a danger not to find the real optimum by SVA. Therefore, more advanced optimization approaches should be applied—multivariable approach (MVA). Applying MVA optimization and finding the real optimum, better experimental conditions are obtained and thus, time, chemicals and analytical procedure cost can be served. Nowadays, using artificial neural networks (ANN's) in combination with MVA is rapidly expanding. In this work, the optimization of SPE using relaxation method (SVA) and optimization by ANN's in combination with experimental design (MVA) are compared and latter approach is practically illustrated. Advantages of MVA over SVA for optimization are discussed. The prediction of the optimal SPE conditions for determination cis- and trans-resveratrol in Australian wines by capillary zone electrophoresis is described and the improvement of efficiency of SPE using MVA is confirmed.