Solid-phase Extraction Extraction Research Articles

B-286 Single Experiment, Single Plate Solid Phase Extraction (SPE) Optimization using 47 Drug Analytes as an Example

Abstract Background SPE of biological matrices isolates analytes of interest from interfering matrix components that can affect LC-MS/MS quantitation. Optimal SPE conditions are dependent upon the sample matrix and analyte properties and typically require multiple experiments to determine optimal conditions for SPE extraction. Here, a 96-well method development plate was utilized to streamline method development for a panel of 47 clinical research drug analytes: 14 antipsychotics, 22 antidepressants and 11 anticonvulsants. Methods An SPE plate with four polymeric sorbents: reversed phase (X), strong and weak cation-exchange and weak anion-exchange mixed-mode phases (X-C, X-CW and X-AW) was used. The 47 drugs analytes were extracted on all four sorbents using three sets of conditions: acidic pretreatment/wash (aq) with basic elution (AB), neutral pretreatment/wash (aq) with neutral elution (NN), and basic pretreatment/wash (aq) with acidic elution (BA). A 50/50 methanol/water wash was also included. Elution used neutral or pH adjusted ethyl acetate/isopropanol or methanol/acetonitrile. A reagent blank, matrix blank, extracted serum samples spiked post-elution (n=2), and spiked serum (n=4) were extracted on each sorbent using each set of conditions. Optimal conditions were determined by calculating absolute percent recovery for each analyte. Results Recovery for antipsychotics was 85-97% using X-CW-AB, except Chlorpromazine (59%). It had better recovery (80%) using X-AB. Recovery for the antidepressants was 75-112% using X-C-AB, except Bupropion (35%) and Selegiline (10%). Bupropion had better recovery (83% and 95%) using X or X-CW and BA. Selegiline had better recovery using X, X-CW and X-AW with BA (83-92%). Anticonvulsants comprise zwitterionic, sulfonamides, neutral, acidic, and basic compounds with widely varying pKa and polarity. Targeting a single method for these analytes is difficult. The best recovery for anticonvulsants used X-CW-AB with several exceptions. Lacosamide, Felbamate, and Levetiracetam are neutral and among the most polar analytes and had 7-31% recovery under all SPE conditions tested. Zwitterionic Gabapentin and Pregabalin had 50-53% recovery from X-CW and X-C sorbents. The stronger protic elution (ammoniated methanol/acetonitrile vs ethyl acetate/isopropanol ) improved solubility for complete elution. Oxcarbazepine had 37% recovery from X-CW-AB, but recovery was 71% under BA conditions. Neutral, polar Zonisamide and Topiramate (Sulfonamide compounds) recovery was 25-26% using X-CW-AB. However, recovery was better (47% and 83%) under NN conditions, suggesting the analytes didn’t undergo complete elution from the X-CW sorbent. A stronger elution solvent would improve recovery from X-CW. Conclusions Most antipsychotics were recovered with X-CW-AB. Most antidepressants could be extracted using X-C-AB. Some analytes had higher recovery using hydrophobic interaction (X) SPE. A single mixed-mode SPE two-step elution protocol using a stronger elution solvent may be feasible. Anticonvulsants had mixed results. Some would require a stronger elution solvent. Some could be included in the other two panels to maximize recovery, but some had low recovery under all conditions tested. The method development plate screened 12 SPE methods for 47 analytes in a single experiment, greatly reducing the time and labor required to identify the best sorbent and starting conditions for SPE extraction optimization for drug analysis. This workflow could be implemented for other SPE method development projects.

Polymer inclusion membrane for the extraction of oxytetracycline from milk prior to aptamer-based biosensing

Aptamer-based sensing may suffer from severe limitations when applied to complex biological and food samples. To alleviate the interference of matrix elements, we propose the use of a polymer inclusion membrane (PIM) as a simple, yet effective sample clean-up tool prior to aptamer-based sensing. As a proof-of-concept, Aliquat 336 anion exchanger was incorporated into a plasticized cellulose acetate membrane to transport oxytetracycline (OTC) from raw milk into an aqueous NaCl acceptor solution. Efficient transport has been ensured by adding a chelating agent to the raw milk and adjusting the pH to alkaline. The amount of extracted OTC was determined as a function of time and acceptor phase NaCl concentration. The extracted amount was proportional to the raw milk OTC concentration in the investigated 0.22–2.2 µM range. Circular dichroism spectroscopy was used to examine the conformation of an OTC-binding aptamer to evaluate if PIM extracts are compatible with aptamer-based biosensors. Solid phase extraction (SPE) was used as a reference sample pre-treatment technique. The aptamer retained its native conformation in the PIM extract, contrary to the SPE extract, and responded to the presence of OTC. Consequently, the PIM-based extraction is adaptable to aptasensor constructs. Besides its simplicity, it offers a cheaper and greener alternative to other sample preparation procedures.

Sample Preparation Techniques for Growth-Promoting Agents in Various Mammalian Specimen Preceding MS-Analytics.

The misuse of growth-promoting drugs such as beta-2 agonists and steroids is a known problem in farming and sports competitions. Prior to the analysis of biological samples via liquid chromatography (LC)-mass spectrometry (MS) or gas chromatography (GC)-MS, sufficient sample preparation is required to reliably identify or determine the residues of drugs. In practice, broad screening methods are often used to save time and analyze as many compounds as possible. This review was conceptualized to analyze the literature from 2018 until October 2023 for sample preparation procedures applied to animal specimens before LC- or GC-MS analysis. The animals were either used in farming or sports. In the present review, solid phase extraction (SPE) was observed as the dominant sample clean-up technique for beta-2 agonists and steroids, followed by protein precipitation. For the extraction of beta-2 agonists, mixed-mode cation exchanger-based SPE phases were preferably applied, while for the steroids, various types of SPE materials were reported. Furthermore, dispersive SPE-based QuEChERs were utilized. Combinatory use of SPE and liquid-liquid extraction (LLE) was observed to cover further drug classes in addition to beta-2 agonists in broader screening methods.

A-080 Overcoming Challenges of Equilibrium Dialysis-Based Free Thyroxine Measurements

Abstract Background Thyroid function tests are widely used to detect diseases of the thyroid. Concerns about the accuracy and reliability of free thyroxine (FT4) measurements have been stated by the clinical laboratory community. To address these concerns, CDC established a reference measurement procedure (RMP) for FT4 based on equilibrium dialysis (ED). ED-based methods have advantages over traditional direct immunoassays. As with all analytical methods, factors affecting accuracy and reliability of ED-based methods need identification and understanding. To investigate potential sources of error, the CDC FT4 RMP was used to evaluate T4 stability at different of storage conditions, adsorption of FT4 to common labware surfaces, and the effect of dialysis membrane materials on the measured FT4 in serum. Methods FT4 was measured in serum using the IFCC RMP (1). FT4 was separated from the protein-bound form during the equilibrium dialysis step of the RMP. Dialysates were spiked with internal standard (13C6-T4) and the analyte was further isolated by C18 solid phase extraction (SPE) and liquid-liquid extraction (LLE) in ethyl acetate prior to injection on an UHPLC system coupled with a triple quadrupole mass spectrometer. Bracketed calibration and primary reference materials were used to determine FT4 concentration in serum. This procedure was used to evaluate stability of serum FT4 during storage at −70 to 5 °C. Short- and long-term T4 stability of calibrator solutions at −70 °C to ambient temperature and the extent of adsorption of T4 calibrator solutions to the commonly used labware surfaces were evaluated. Furthermore, the suitability of 4 different dialysis membranes was assessed. In addition, three alternatives to the currently used SPE and LLE extraction steps were tested: LLE using cyclohexane and ethyl acetate, LLE with ethyl acetate, and supported liquid extraction with cyclohexane and ethyl acetate. Results T4 calibrator solution was stable in 1.7% ammonium hydroxide in ethanol for at least 2.9 years at −70 °C and up to 7 days at ambient temperature. Exposure of various calibrator solutions such as T4 in ethanol, ethanol with 1.7% ammonium hydroxide, 10% acetonitrile with 0.1% formic acid to common labware resulted in up to 10.1% loss of the analyte. FT4 in serum and T4 in dialysates and extracts were stable at −70 to 5 °C. Use of alternative dialysis membranes resulted in up to −8.8% mean bias to the reference membranes. Recoveries of the analyte using four extraction methods were 85.4%–95.0%. None of the tested extraction conditions significantly changed the results obtained with the original FT4 RMPs. Conclusion Although FT4 RMP must strictly adhere to the ED conditions described for the RMP, other parts of the sample preparation procedures can deviate from the originally published procedure. Careful selection of procedure for calibrator solvents, dialysis membranes, labware, and storage conditions is required to ensure accurate and reproducible FT4 measurements.

Small volatile lipophilic molecules induced belowground by aphid attack elicit a defensive response in neighbouring un-infested plants.

In pioneering studies on plant-aphid interactions, we have observed that Vicia faba plants infested by aphids can transmit signals via the rhizosphere that induce aboveground defence in intact, neighbouring plants. The aphid parasitoid Aphidius ervi is significantly attracted towards intact broad bean plants grown in a hydroponic solution previously harbouring Acyrtosiphon pisum-infested plants. To identify the rhizosphere signal(s) possibly mediating this belowground plant-plant communication, root exudates were collected using Solid-Phase Extraction (SPE) from 10-day old A. pisum-infested and un-infested Vicia faba plants hydroponically grown. To verify the ability of these root exudates to trigger defence mechanisms against the aphids we added them to V. fabae plants grown in hydroponic solution, and tested these plants in the wind-tunnel bioassay to assess their attractiveness towards the aphids' parasitoids A. ervi. We identified three small volatile lipophilic molecules as plant defence elicitors: 1-octen-3-ol, sulcatone and sulcatol, in SPE extracts of A. pisum-infested broad bean plants. In wind tunnel assays, we recorded a significant increase in the attractiveness towards A. ervi of V. faba plants grown in hydroponic solution treated with these compounds, compared to plants grown in hydroponic treated with ethanol (control). Both 1-octen-3-ol and sulcatol have asymmetrically substituted carbon atoms at positions 3 and 2, respectively. Hence, we tested both their enantiomers alone or in mixture. We highlighted a synergistic effect on the level of attractiveness towards the parasitoid when testing the three compounds together in respect to the response recorded against them singly tested. These behavioural responses were supported by the characterization of headspace volatiles released by tested plants. These results shed new light on the mechanisms underlying plant-plant communication belowground and prompt the use of bio-derived semiochemicals for a sustainable protection of agricultural crops.

Compound-Specific Carbon, Hydrogen, and Nitrogen Isotope Analysis of Nitro- and Amino-Substituted Chlorobenzenes in Complex Aqueous Matrices.

Compound-specific isotope analysis (CSIA) is an established tool to study the fate of legacy groundwater contaminants but is only emerging for nonconventional contaminants, e.g., nitro- and amino-substituted chlorobenzenes that are widely used as industrial feedstock and the target of this work. To date, CSIA of the target compound groups used special combustion interfaces and the potential matrix interferences in environmental samples has not been assessed. We validated CSIA methods for δ13C, δ2H, and δ15N of four analytes from each chemical group and developed a solid-phase extraction (SPE) method to minimize matrix interferences during preconcentration of complex aqueous samples. The SPE recovery was >80% and the method quantification limits of SPE-CSIA for δ13C, δ2H, and δ15N were 0.03-0.57, 1.3-2.7, and 3.4-10.2 μM aqueous-phase concentrations, respectively, using 2 L of spiked MQ water. The SPE-CSIA procedure showed negligible isotope fractionation for δ13C (≤0.5‰), δ15N (≤0.5‰), and δ2H (≤5‰ for nitroaromatics and ≤10‰ for aminoaromatics). In addition, solvent evaporation, water sample storage up to 7 months, and SPE extract storage for 1.5 years did not change analytes' δ13C signatures beyond ±0.5‰. However, to avoid significant δ2H and δ15N fractionation of aminoaromatics, cartridge breakthrough should be avoided and SPE preconcentration must be conducted at pH > pKa + 2. Application of the method at a contaminated site showed excellent precision, at ≤0.3‰ for C and N, and ≤1.5‰ for H. The methods validated here now allow the use of multielement CSIA to track the environmental fate of nitro- and amino-substituted chlorobenzenes in complex aqueous samples.

Development of chromatographic techniques connected with corona and tandem mass spectrometry detection systems for determination of amoxicillin in bovine milk

A new determination method for analysis of antibiotic amoxicillin (AMS) in milk samples was proposed. For isolation of the studied compound solid phase extraction (SPE) and salting-out assisted liquid-liquid extraction (SALLE) were used. The optimal parameters of isolation processes were chosen and matrix effect was evaluated. The liquid chromatographic techniques connected with corona detector (HPLC-CAD) and tandem mass spectrometry system (LC-MS/MS) were used for determination of amoxicillin in SPE and SALLE extracts, respectively. The developed procedures were validated for linearity and precision. The proposed method showed good intra-day and inter-day precision with relative standard deviation values ranging from 1.6% to 4.2%. Limit of detection for SALLE-LC-MS/MS method of AMS determination was lower than the maximum residue limit (MRL: 4 μg kg -1) for amoxicillin in milk samples. The elaborated methods were applied for the monitoring of amoxicillin in different milk samples from regional dairies.

Ternary water–organic solvent mixtures used for insecticide SPE extraction and analysis with acetylcholinesterase biosensor

Few biosensors are reported for usage in combination with the organic solvent due to their negative impact on the enzymes. The usage of ternary water–organic solvent mixtures in combination with acetylcholinesterase biosensors allows to increase the useable total content of organic solvents with minimum negative effects to a higher content in comparison with a single organic solvent in water. The combination of acetonitrile/ethanol/water has a smaller negative effect on both enzyme activity and inhibition by insecticides in comparison with acetonitrile/methanol/water mixtures. The insecticides were eluted from solid-phase extraction (SPE) columns with a binary mixture of organic solvents acetonitrile/ethanol in 1/3 ratio and subsequently analysed with an acetylcholinesterase biosensor and the optimum total content of organic solvents of 12%. The analytical method allows the analysis of complex samples with improved selectivity and at improved limits of detection for chlorpyrifos-oxon and carbofuran analysis in river waters and soil samples. The usage of mixtures of organic solvents in combination with enzymes is an interesting approach that allows working with a higher total content of organic solvents than each individual solvent.

Optimization of Solid-Phase Extraction of a Degradation Product of Novichok (A234) and Its Application to Environmental Samples.

There have been no detailed investigations regarding solid-phase-extraction (SPE) optimization and screening for the degradation products of ethyl (1-(diethylamino)ethylidene)phosphoramidofluoridate (A234) in various environmental samples. Therefore, as a first step in the selective SPE of the degradation products of A234, we optimized the SPE adsorption and extraction parameters for the A234 degradation product ethylhydrogen (1-(diethylamino)ethylidene)phosphoramidate (cpd 1). Among various SPE cartridges, the Si cartridge (500 mg, 3 mL) selectively extracted cpd 1 using an elution volume of 4 mL of 25% H2O in acetonitrile, which eliminated most interference without cpd 1 loss during loading and washing. In addition, the sorbent capacity is also critical in the adsorption of cpd 1. The Si cartridge (500 mg, 3 mL) retained cpd 1 in the concentration range 1-10 µg/mL. The linearity of detector response of cpd 1 in deionized H2O was studied in the range of 1.0-100 ng/mL and showed good linearity with γ2 ranging from 0.9979 to 0.996. The limits of detection for cpd 1 are 10 ng/mL in the product-scan mode and 100 ng/mL in the full-scan mode. Also, after we optimized the SPE method, we validated the precision and accuracy of the Si-cartridge extraction method in real soil samples with diverse concentrations. The precision ranged from 2.5% to 5.3%. This newly developed SPE is applicable to the analysis of a degradation product of Novichok A234 in various environmental matrices, such as water, soil and sand, in the Organization for the Prohibition of Chemical Weapons (OPCW) proficiency test and unknown samples collected from suspected sites.

Volatile Analysis of Wuliangye Baijiu by LiChrolut EN SPE Fractionation Coupled with Comprehensive GC×GC-TOFMS.

Wuliangye baijiu is one of the most famous Chinese liquors with a protected geographical indication. This study used LiChrolut® EN-based solid-phase extraction (SPE) and fractionation combined with comprehensive two-dimensional chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) to unveil its volatile composition. The volatiles were isolated with LiChrolut® EN-based SPE and traditional liquid-liquid extraction (LLE). The neutral/basic fractions from LLE and the SPE were fractionated on a LiChrolut® EN SPE column and analyzed by comprehensive GC×GC-TOFMS. Compared with LLE, more esters and alcohols were detected in the SPE-based extraction. The SPE fractionation and GC×GC-TOFMS analysis resulted in the identification of about 500 volatile compounds in more than 3000 peaks of the Wuliangye baijiu. The approach simplifies the complex baijiu composition into functional group-based fractions for reliable identification and analysis. This study provided a confidence volatile identification approach for Chinese baijiu based on the SPE fractionation GC×GC-TOFMS.

Assessing Performance of Wastewater Treatment Using in Vitro Cell-based Assays.

Bioanalytical tools, namely in vitro bioassays, can be employed in tandem with chemical analyses to assess the efficacy of wastewater treatment and the potential for adverse effects from the discharges of wastewater into receiving waters. In the present study, samples of untreated wastewater (i.e., influent) and treated wastewater (i.e., effluent) were collected from two wastewater treatment plants and a wastewater treatment lagoon to investigate potential differences in treatment performance. In addition, grab samples of surface water were collected downstream of the lagoon discharge to evaluate the water quality in the receiving stream. After solid-phase extraction (SPE) using ion exchange columns for basic/neutral and acidic compounds, respectively, the extracts were analyzed for a suite of 16 indicator compounds. The two SPE extracts were combined for analysis of biological responses in four in vitro cell-based bioassays. The concentrations of several indicator compounds, including the estrogens, 17β-estradiol (E2) and 17α-ethinylestradiol (EE2), were below the limits of detection. However, androstenedione and estrone were detected in several influent samples. The concentrations of these steroid hormones and some of the other indicator compounds declined during treatment, but acesulfame K, carbamazepine, trimethoprim and DEET persisted in the effluent. The MTS-CellTiter 96® AQueous One Solution Cell Proliferation Assay (MTS) indicated that cell viability was not affected by exposure to the extracts. The Qiagen Nuclear Receptors 10-Pathway Reporter Array indicated that several cellular pathways were upregulated, with the greatest upregulation observed with the estrogen receptor (i.e., induction ratios of12 to 47) and the liver X receptor (i.e., induction ratios of10 to 45). The ERα CALUX assay indicated that estrogenic activity was lower in effluents compared to influents, but the expected improved removal of estrogenic activity during nitrification was not observed. The results of the Nrf2 Luciferase Luminescence Assay indicated a lower oxidative stress in the effluent samples, except for the lagoon. Overall, the present study further demonstrates that bioassays provide complementary information to chemical analyses and offer a way to assess treatment performance, even when target contaminants are not detected. There are thus advantages to using a combination of chemical analyses and in vitro bioassays to monitor the treatment efficiency of wastewater treatment plants and to predict the potential impacts of wastewater discharges into receiving waters.

Simultaneous enantioselective analysis of illicit drugs in wastewater and surface water by chiral LC-MS/MS: A pilot study on a wastewater treatment plant and its receiving river.

An enantioselective method for quantifying amphetamine-type chiral illicit drugs (CIDs) in wastewater and surface water was developed, validated, and applied to samples from a wastewater treatment plant (WWTP) and its effluent-receiving river in Beijing, China. Water samples were subjected to solid-phase extraction (SPE) and then quantified via liquid chromatography-tandem mass spectrometry. The enantioseparation of CIDs was performed with a CHIRALPAK CBH column. Chromatographic parameters, including mobile phase composition and flow rates, were tested to identify the satisfactory enantiomeric resolution. The SPE method was optimized by evaluating variables, including SPE cartridge types, extraction solvents, and solvent volumes. The Oasis HLB sorbent showed good performance with recoveries exceeding 60% and matrix effects ranging from-19.6% to 26.6% for most target enantiomers, except for norephedrine (NE), in three different aquatic matrixes. The established method was superior to previously reported methods and had a low limit of detection, low limit of quantification, and short runtime (<45min). The repeatability and reproducibility of the method reached 19.1% and 17.8%, respectively. The method was successfully utilized to monitor the daily variations in CIDs in the influent, effluent, and effluent-receiving river of a WWTP in Beijing over 1 week. The common occurrence of 1R,2S-(-)-ephedrine (1R,2S-(-)-EPH), 1S,2S-(+)-pseudoephedrine (1S,2S-(+)-PEPH), R-(-)-methamphetamine (METH), and S-(+)-METH in wastewater samples was observed. Ephedrines (1R,2S-(-)-EPH and 1S,2S-(+)-PEPH) were the most abundant CIDs in the influent, effluent, upstream, and downstream samples with concentrations of 725.8±181.2ng/L, 22.9±4.9ng/L, 12.96±0.79ng/L, and 11.6±6.7ng/L, respectively. METH was detectable in most water samples and was present in excess in S-enantiomer form in the influent and in R-enantiomer form in the effluent and surface water. R-(-)-MDMA was detected at a concentration of up to 2.4ng/L in the influent. The metabolites norketamine (NK), amphetamine(AMP), MDA, and NE were not detected in water samples given the low concentration of their parent drugs.

Benzoxazine Porous Organic Polymer as an Efficient Solid-Phase Extraction Adsorbent for the Enrichment of Chlorophenols from Water and Honey Samples.

Porous organic polymers have gained great research interest in the field of adsorption. A benzoxazine porous organic polymer (BoxPOP) constructed from p-phenylenediamine, 1,3,5-trihydroxybenzene and paraformaldehyde was fabricated and explored as an adsorbent for solid-phase extraction (SPE) of four chlorophenols from water and honey samples. Under the optimized SPE conditions, the response linearity for the analysis of the SPE extract of the chlorophenols by high performance liquid chromatography-diode array detector was observed in the range of 0.2-40.0ngmL-1 for water samples and 5.0-400.0ngg-1 for honey samples. The method detection limits of the analytes were 0.06-0.08ngmL-1 for water samples and 1.5-2.0ngg-1 for honey samples. The recoveries of the analytes from fortified water and honey samples ranged from 84.8 to 119.0% with the relative standard deviations below 8.4%. The results indicate that the prepared BoxPOP is an effective adsorbent for the chlorophenols. The established method provides an alternative approach for the determination of chlorophenols in real samples.

Magnetic Solid-Phase Extraction (MSPE) Using Magnetite-Based Core-Shell Nanoparticles with Silica Network (SiO2) Coupled with GC-MS/MS Analysis for Determination of Multiclass Pesticides in Water.

For the analysis of pesticide residues in water samples, various extraction techniques are available. However, liquid-liquid extraction (LLE) and solid-phase extraction (SPE) are most commonly used. LLE and SPE extraction techniques each have their own disadvantages. The aim of the study was to develop an environment-friendly multi-residue method for determination of multiclass pesticides in environmental water samples (ground water, agricultural field/irrigation run-off water, etc.). The magnetic solid-phase extraction (MSPE) technique using surface-fabricated magnetic nano-particles was used for extraction of water samples, followed by quantification by gas chromatography tandem mass spectrometry. The developed multi-residue method was validated in terms of linearity, LOD, LOQ, recovery, and repeatability. Recovery data were obtained at the spiking concentration level of 1, 5, and 10 µg/L, yielding recoveries in the range of 70-120%. Overall, non-polar pesticides from all the groups, i.e., synthetic pyrethroid, organophosphorus, organochlorine, herbicides, and fungicides, show acceptable recovery percentages. Good linearity (r2 value ≥ 0.99) was observed at the concentration range of 0.5-100 µg/L. RSD values were found ≤ 18.8. The study shows that the method is specific, rapid, and low cost, as well as having a good linearity and recovery; thus, this method is applied in routine purposes for the analysis of pesticide residue in real water samples. Due to better adsorption ability, permeability, and magnetic separability, the functionalized nano-particles were found effective in the enrichment of 22 multiclass pesticides including organo-phosphorus, organo-chlorine, synthetic pyrethroid, herbicides, and fungicides.

Highly efficient porous sorbent derived from asphalt for the solid-phase extraction of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are generated primarily during the incomplete combustion of organic matter and are ubiquitous environmental pollutants. For the first time, in this study, a mesoporous carbon derived from asphalt with high surface area (2300 m²g−1 with an average of 1.2 cm³ g−1) was utilized as a sorbent for the solid-phase extraction (SPE) of several PAHs in tap water samples. The factors influencing the extraction capability of the new material were investigated and the optimum conditions were determined to be as follows: Sample volume - 200 mL, no adjustment of sample pH, and sorbent amount - 50 mg. Under the most favorable SPE conditions, with gas chromatography-mass spectrometric analysis, the method exhibited a linear range of 0.5-50 μgL−1 with limits of detection between 0.004 and 0.026 μgL−1. The recoveries obtained from spiked tap water samples spiked at 1 μgL−1 and 5 μgL−1, were in the range 86.7-98.2% with relative standard deviations of <9%. The method was also applied to tap water samples collected from the local environment. The concentrations of PAHs detected ranged between 0.13 and 48 μgL−1. The reusability of the sorbent was tested with five consecutive SPE extraction, and no carryover of analytes was observed.

A comparative and simultaneous analysis of indoxyl sulfate and sodium butyrate in human plasma by SPE and HPLC methods for kidney patients

A comparison of high-performance liquid chromatography (HPLC) and solid-phase extraction (SPE) methods is carried out for the simultaneous analysis of indoxyl sulfate and sodium butyrate in plasma using Phenyl (250 × 4.6 mm; 5 µm) and SunShell (150 × 4.6 mm, 2.6 µm) columns with mobile phases ammonium acetate (20 mM)-ACN (95:5, v/v) and water-ACN (90:10), respectively. The values of the retention, separation and resolution factors for indoxyl sulfate and sodium butyrate were 3.1, 1.29 and 2.0 with phenyl and 1.0, 1.55 and 1.60 with SunShell columns. The values of the theoretical plates were in the range of 650 to 1600 while the tailing factors were 0.98 to 1.0. The limits of the detection and quantification of sodium butyrate and indoxyl sulfate were 0.1–1.9 and 0.43–9.2 µg with these columns. The hydrogen bondings and π-π interactions were responsible for the separation of these molecules. The multi-wall carbon nanotubes (MWCNTs) served as a good sorbent in SPE extraction. The developed SPE and HPLC methods were quick, robust, exact and economic for the analysis of indoxyl sulfate and sodium butyrate. The reported SPE and HPLC methods can be useful to determine the reported molecules in plasma.

Elecrtospun methacrylic acid‐modified polystyrene nanofiber as solid phase adsorbent for preconcentration of methyl green from aqueous samples

AbstractThis research describes the development of a new design of electrospun nanosorbent, polystyrene/methacrylic acid nanofibers (PS/MAA NFs), for the extraction and preconcentration of Methyl green (MG) from aqueous samples via solid phase extraction (SPE). The experimental parameters affecting the SPE extraction efficiency including sample flow rate through the sorbent, ionic strength and pH of the sample solution, weight of sorbent, volume and type of eluent were investigated, and optimized. Under the optimum conditions (40 ml of 1 mg/L MG, pH: 5, sample flow rate: 2 ml/min, 0.1 g PS/MAA NFs and eluting solvent: 3 ml MeOH), the calibration curve was linear in the MG concentration range of 25–1,000 μg/L. The limit of detection and enhancement factor of the proposed method, for extraction from 40 ml sample solution, were obtained as 10 μg/L and 8.3, respectively. MG dye was extracted from different real samples (urban, mineral and river waters) using the proposed adsorbent and the results showed that PS/MAA NFs were suitable for preconcentration and determination of trace amount of methyl green in wastewater samples.

Quantification of cylindrospermopsin, anatoxin-a and homoanatoxin-a in cyanobacterial bloom freshwater using direct injection/SPE coupled with UPLC-MS/MS

Analytical methods based on direct injection (DI) and solid phase extraction (SPE) coupled with ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) were developed for the determination of anatoxin-a (ATX-a), cylindrospermopsin (CYN), and homoanatoxin-a (HATX-a) in freshwater samples impacted with cyanobacterial blooms. The presence of CYN in freshwater samples was detected and quantified based on direct injection method, while ATX-a and HATX-a could be determined by both DI and SPE-based methods. Matrix effects (ME) on the signal intensity of the cyanotoxins were systematically evaluated for both direct injection and SPE extract samples. CYN, ATX-a, and HATX-a suffered a significant suppression during UPLC-MS/MS. The selection of internal standards (ISs) for compensating/correcting the losses of target cyanotoxins during sample preparation and matrix effects in UPLC-MS/MS analyses were systematically evaluated. Acetaminophen-d4 (an isotopically labelled acetaminophen) is a suitable internal standard for correcting the ME on the signal intensity of ATX-a and HATX-a, while the use of L-phenylalanine-d5 or caffeine-d9 as IS for correcting ME of these toxins was not efficient, as expected. The method detection limit (MDL) for the target cyanotoxins ranged from 0.6 to 15 ng/L, which is sensitive enough to detect the presence of these toxins in cyanobacterial bloom freshwater. The developed methods were successfully applied for routine monitoring of the occurrence of these cyanotoxins in a local water body. Monitoring results depicted that ATX-a, CYN and HATX-a were ubiquitously detected in water samples, at concentrations ranging from 70 to 24,600 ng/L.

An automated solid phase extraction procedure for lipid biomarker purification and stable isotope analysis

Effective recovery and high purity of lipid biomarkers are essential for compound-specific stable isotope analysis in a variety of fields ranging from hydrocarbon research, paleoclimatology, food and drug analysis and medicine. Solid-phase extraction (SPE) is the most common method for purifying organic compounds from complex mixtures. SPE constitutes the most labor-intensive part of laboratory work often limiting the number of samples that can be analyzed. Reliable, easy-to-use, automated methods could increase sample throughput as well as reproducibility. Here we introduce such a method using a Gilson ASPEC GX-271 system and test the separation quality, reproducibility, and efficiency in comparison to a classical manual SPE lipid purification procedure. Using multiple extractions of the same natural soil sample we show that the automated SPE is comparable in overall quality and slightly superior in reproducibility to a manual SPE. We demonstrate that stable hydrogen isotope measurements of n-alkanes purified using an automated SPE extraction showed significantly lower standard errors. Furthermore, the unattended operation of the system eases the purification of large sample sets. Generally, the automated SPE using the Gilson ASPEC GX-271 for lipid biomarker separation provides qualitatively and quantitatively accurate and reproducible results with more efficient purification of compounds than the manual method.

Detection and quantitation of ecdysterone in human serum by liquid chromatography coupled to tandem mass spectrometry

The polyhydroxylated phytosteroid ecdysterone is present in various plants (e.g. spinach). It is widely marketed as the active component of dietary supplements, due to its reported health and performance promoting effects. For evaluation of its actual bioavailability, a fast and sensitive method was developed, optimized and validated for human serum. Instrumental analysis was performed utilizing liquid chromatography-tandem mass spectrometry with positive electrospray ionization and acquisition in multiple reaction mode. Solid phase extraction and dilute-and-inject (following protein precipitation) were tested to isolate ecdysterone from human serum. Both methods were compared in the light of the preset analytical target profile. The limit of detection (LOD) and quantitation (LOQ) for ecdysterone in human serum after SPE extraction corresponded to 0.06 ng/mL and 0.14 ng/mL, respectively, meeting the requested sensitivity of the method. The assay was linear over the range of 0.10 ng/mL to 20.83 ng/mL. As expected, the sensitivity of the SPE method was better than that of the dilute-and-inject procedure, which did not allow for quantitation of all post administration serum samples.Accuracy (relative error; %) and precision (coefficient of variation; %), were both within acceptance criteria (<15%).The developed method was successfully applied to a ten week intervention study conducted in young men performing regular resistance training. Different doses of supplements containing ecdysterone from spinach extract have been administered during the study and the quantitation of ecdysterone in serum samples has been successfully conducted. Ecdysterone could be quantified in all post-administration samples using solid phase extraction (SPE) for sample pretreatment.