Solid-phase Extraction Approach Research Articles

Development of Al-MOF based pipette-tip solid-phase extraction approach for detection of fluoroquinolones in animal innards

Residues of fluoroquinolones (FQs) have been identified as a threat to food safety, highlighting the need for effective detection methods in food samples. This study utilized a hydrothermal synthesis method to create Al-based metal-organic framework (Al-MOF) for pipette-tip solid-phase extraction of FQs in food matrices. Coupled with HPLC-FLD, a novel sample pretreatment method for simultaneous detection of three FQs was developed, demonstrating good linearity (1−500 ng/g) with R2 values ranging from 0.9990 to 0.9998. Limits of detection and quantification were found to be 0.15−0.25 ng/g and 1.0−2.0 ng/g, respectively, with the relative standard deviations below 9.3 %. The extraction method showed promising results in animal liver and kidney samples, with a recovery rate of 75.2−103.6 %. Overall, this simple, rapid, and efficient method offers a valuable approach for analyzing trace levels of FQs in complex matrices.

Development of a NiFe2O4 covalent organic framework based magnetic solid-phase extraction approach for specific capture of quinolones in animal innards prior to UHPLC–Q–Orbitrap HRMS detection

This study aimed to present a selective and effective method for analyzing quinolones (QNs) in food matrix. Herein, a NiFe2O4-based magnetic sodium disulfonate covalent organic framework (NiFe2O4/COF) was prepared using a simple solvent-free grinding method, and was adopted as a selective adsorbent for magnetic solid phase extraction of QNs. Coupled with UHPLC–Q–Orbitrap HRMS, an efficient method for simultaneous detection of 18 kinds of QNs was established. The method exhibited good linearity (0.01–100 ng g−1), high sensitivity (LODs ranging from 0.0011 to 0.0652 ng g−1) and precision (RSDs below 9.5%). Successful extraction of QNs from liver and kidney samples was achieved with satisfactory recoveries ranging from 82.2% to 108.4%. The abundant sulfonate functional groups on NiFe2O4/COF facilitated strong affinity to QNs through electrostatic and hydrogen bonding interactions. The proposed method provides a new idea for the extraction of contaminants with target selectivity.

Tailored covalent organic framework with phosphorylation for boosting typical actinide adsorption under acidic conditions

Uranium and plutonium are typical actinides tightly associated with nuclear fuel cycle. In this work we rationally design and fabricate a phosphonic group-decorated covalent organic framework, TzDa-Phos, for highly selective removal of uranium [U(VI)] and plutonium [Pu(IV)]. The saturation adsorption capacity for U(VI) can reach 394 mg/g at pH 4.0, and even maintains 40 mg/g in 1–4 M HNO3 solutions. The distribution coefficient of Pu(IV) with TzDa-Phos is recorded up to 9.7 × 103 mL/g at 3 M HNO3. The excellent adsorption performance of TzDa-Phos for U(VI) and Pu(IV) is reasonably attributed to phosphonic groups decorated in TzDa. Specifically, the strong complexation of PO with uranium nitrate species (e.g., UO2(NO3)+, UO2(NO3)20) is indicated at high acidities, in contrary to the coordination of P-O− with uranium at pH 4.0 as evidenced by FT-IR, XPS and EXAFS analyses. This work provides a promising adsorbent to recover uranium and plutonium from various wastewaters via a solid-phase extraction approach.

Performance critical comparison of offline SPE, online SPE, and direct injection for the determination of CECs in complex liquid environmental matrices

Sample preparation for the analysis of organic micropollutants in wastewater samples is commonly carried out by solid-phase extraction (SPE) procedures, which involve different manual laboratory operations. This conventional approach requires several hours of counter labour and entail the use of a lot of disposable material, and the subsequent contaminated non-recyclable plastic-residue production. In contrast, by coupling and automatizing the pre-treatment to the instrumental analysis most of that burden erases, sample size gets miniaturized and, thus, storage becomes freed-up. Even lab counters get cleared off from sample pre-treatment apparatus. However, method performance could get alter as a trade-off. This paper presents the results from a study in which methodology, including SPE online-coupled to UHPLC-MS/MS chromatography, was developed for multi-residue (58) determination of veterinary and pharmaceutical drugs in urban and piggery wastewater (influent and effluent to wastewater treatment plants (WWTPs)). Similarly, the direct injection (DI) of large volumes (hundreds of µL) of same matrix samples into the chromatographic system was optimized too. The performance of both automated methods was statistically compared with the classical off-line SPE. As dealing with trace analysis, suitable injection volumes for the alternative approaches were selected on the premise of low limits of quantification (MLQs). Under the selected conditions, validation parameters such as linearity range, method quantification limits, peak shape and carry over were determined. Usually more than 50 % of the analytes showed MLQs below 50 ng/L, for all matrices and methodologies, especially for DI. Real wastewater samples from a local urban WWTP and farm were analysed with all three tested methodologies. Determined concentrations and removal rates were statistically compared and turned out being quite similar. However, analysis under offline SPE and DI approaches provided a larger amount of information as they reached lower MLQs. Offline-SPE provided the worst precision among all.

Goat milk-derived short chain peptides: Peptide LPYV as species-specific characteristic and their versatility bioactivities by MOF@Fe3O4@GO mesoporous magnetic-based peptidomics

Goat milk as an ideal substitute for human milk has not been sufficiently explored. An in-situ synthesized MOF@Fe3O4@GO was demonstrated as a magnetic mesoporous adsorbent for efficiently enriching short chain peptides (SCPs) in milk compared with the routine solid phase extraction approach with graphite carbon black or C18 as the packing material in terms of the number of enriched SCPs and data stability. A total of 61 and 126 SCPs were identified and quantified in bovine milk (0.09–89.34 μg L−1) and goat milk (10.5–1267.06 μg L−1), respectively, and peptide LPYV can be used as a potential marker for adulteration of goat milk. Relative high expression of chymotrypsin and pepsin by EnzymePredictor analysis could partially elaborate the reason of the abundance of SCPs in goat milk. Compared with bovine milk, further bioinformatics analysis indicated that goat milk could own higher nutritional value because of relative higher concentrations (>1 mg/L) of SCPs (LLV, FL, LVYP) with confirmed bioactivities including angiotensin-converting enzyme (ACE) inhibitor, antioxidant, dipeptidylpeptidase (DPP) III and DPP IV inhibitor, etc. Overall, this study opened a novel avenue for understanding versatility benefit of dairy products from a perspective of SCPs by using a developed MOF@Fe3O4@GO mesoporous magnetic-based peptidomics.

Speciation of trace amounts of Sb(III) and Sb(V) in environmental water using inductively coupled plasma mass spectrometry after magnetic solid-phase extraction with rGO/Fe3O4.

We developed an approach of magnetic dispersive solid-phase extraction (MSPE) based on magnetic graphene nanocomposite rGO/Fe3O4 for the determination of trace Sb(III) and Sb(V) using inductively coupled plasma mass spectrometry (ICP-MS). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the sorbent. The adsorption behavior of Sb(III) and Sb(V) on rGO/Fe3O4 was investigated. The results showed that the adsorption capacity of Sb(V) was nearly zero at pH = 9, while Sb(III) could be well adsorbed on rGO/Fe3O4. The magnetic SPE parameters including pH, adsorbent dosage, eluent type, and volume were optimized. The detection limit of Sb(III) under ideal conditions was 6 ng L-1, and the relative standard deviation was 7.6% (c = 1 g L-1, n = 7). The technique was used to identify Sb(III) at trace levels in environmental water samples, and its validity was examined by recovery experiments and the examination of an approved reference material.

Employing a Carbon-Based Nanocomposite as a Diffusive Solid-Phase Extraction Adsorbent for Methamphetamine for Therapeutic Purposes

Due to the obvious minimal doses of drugs in biological matrices as well as the societal difficulties caused by methamphetamine usage, methamphetamine identification is critical in clinical and forensic laboratories. Because of their simple and inexpensive production procedure, as well as their excellent selectivity and sensitivity, polymeric carbon-based nanocomposites are strong contenders for the diffusive solid-phase extraction approach. The diffusive solid-phase extraction absorbent nanographene oxide polypyrrole composite was produced and used to recover methamphetamine from a complicated urine substrate. The generated NGPPC was fully characterized, and the significant extracting parameters have been explored using the one-parameter-at-a-time strategy. NGOPC is being used to extract methamphetamine using a urine medium with high efficiency. The NGPPC synthesizing procedure was easy, and the extraction method will demonstrate good repeatability. Moreover, the practical and efficient synthesis process stimulates the use of carbon-based compounds in various extraction procedures. As for detecting and quantifying equipment, HPLC monitors are being used. 300 mL methanol, 7 min extracting and desorption duration, 5000 mixing frequency, urinary pH value of 20, 40 mg adsorption, and 5 mL amount of urine were the optimal extraction variables. Following tracing the calibration graph, the method’s linear ranges were determined to be 40-600 ng/ml. The detection limits (LOD) and quantitation limits (LOQ), correspondingly, were 10 and 35.80 ng/mL. The proposed methodology seemed to have a detection range of 9 ng/mL. The suggested approach’s applicability in numerous characterization and medical facilities was proven by the examination of addicted subjects using the proposed technique. For successful extraction of methamphetamine using biological urine samples, the carbon-based adsorbent was being used as diffusive solid-phase extraction adsorption.

Triple-stage Quadrupole Mass Spectrometer to Determine Ubiquitously Present Per- and Polyfluorinated Alkyl Substances in Drinking Water at Part Per Trillion Levels Using Solid Phase Extraction Approach.

An accurate analytical method was developed to determine selected per- and polyfluorinated alkyl substances (PFAS) at the level of parts per trillion (ppt or ng/L) in drinking water. The method included a concentration step using solid phase extraction (SPE) approach in combination with a liquid chromatography-tandem mass spectrometry system (LC-MS/MS). This method was optimized and validated for the common PFAS contaminants in drinking water. An initial demonstration of capability was established with an acceptable initial calibration, minimum reporting limit (MRL), limit of detection (LOD), initial demonstration of low system background, and initial demonstration of precision (IDP). Isotopically labeled internal standards were used for quantification. Surrogate standards were used to monitor method performance. The current method will help in better understanding of PFAS crisis by providing an efficient measurement of PFAS in water. In this study, the recoveries of four surrogates were between 84 and 113%, and calculated limit of detection (DL) and minimum reporting limits (MRL) were generally 1.0-3.0 and 5-10 ng/L, respectively.

Automated Optimized Synthesis of [18F]FLT Using Non-Basic Phase-Transfer Catalyst with Reduced Precursor Amount.

3′-deoxy-3′-[18F]fluorothymidine ([18F]FLT) is a positron emission tomography (PET) tracer useful for tumor proliferation assessment for a number of cancers, particularly in the cases of brain, lung, and breast tumors. At present [18F], FLT is commonly prepared by means of the nucleophilic radiofluorination of 3-N-Boc-5′-O-DMT-3′-O-nosyl thymidine precursor in the presence of a phase-transfer catalyst, followed by an acidic hydrolysis. To achieve high radiochemical yield, relatively large amounts of precursor (20−40 mg) are commonly used, leading to difficulties during purification steps, especially if a solid-phase extraction (SPE) approach is attempted. The present study describes an efficient method for [18F]FLT synthesis, employing tetrabutyl ammonium tosylate as a non-basic phase-transfer catalyst, with a greatly reduced amount of precursor employed. With a reduction of the precursor amount contributing to lower amounts of synthesis by-products in the reaction mixture, an SPE purification procedure using only two commercially available cartridges—OASIS HLB 6cc and Sep-Pak Alumina N Plus Light—has been developed for use on the GE TRACERlab FX N Pro synthesis module. [18F]FLT was obtained in radiochemical yield of 16 ± 2% (decay-corrected) and radiochemical purity >99% with synthesis time not exceeding 55 min. The product was formulated in 16 mL of normal saline with 5% ethanol (v/v). The amounts of chemical impurities and residual solvents were within the limits established by European Pharmacopoeia. The procedure described compares favorably with previously reported methods due to simplified automation, cheaper and more accessible consumables, and a significant reduction in the consumption of an expensive precursor.

Polyamidoamine dendrimer-functionalized silica nanocomposite with polydopamine coating for dispersive micro solid-phase extraction of benzoylurea insecticides in water samples

近年来,由农药残留导致的环境污染问题已引起社会的广泛关注,开发便捷高效的分析方法对农药残留进行检测和监测十分必要。研究设计并成功制备了聚多巴胺涂敷的聚酰胺-胺树状分子功能化的二氧化硅复合材料(SiO2-PAMAM-PDA),并采用透射电镜对其进行表征。开发了以此复合材料为吸附剂的分散微固相萃取方法(D-μ-SPE),并结合高效液相色谱对水基质中的4种苯甲酰脲类杀虫剂(BUs)残留进行了富集检测。多巴胺结构中含有丰富的苯环、氨基及羟基,可与目标物形成氢键、π-π相互作用,从而增强了材料对苯甲酰脲的萃取能力。对吸附剂用量、萃取时间等可能影响萃取效率的条件进行了单因素优化。在最优条件下,该方法的线性范围在10~500 μg/L之间,根据3倍信噪比(S/N)计算所得的检出限(LOD)为1.1~2.1 μg/L,回收率为82.8%~94.1%,相对标准偏差(RSD)为2.1%~8.0%。将建立的方法与已报道的以苯甲酰脲作为目标物的方法进行了对比,发现方法样品用量及萃取剂用量均较少,且所需前处理时间较短,有机溶剂消耗也较少,为苯甲酰脲类农药的检测提供了更快速、绿色的选择。为评估所开发方法的实际样品适用性,将其应用于3种河水样品中4种苯甲酰脲类杀虫剂的分析检测,所得回收率及RSD分别为69.5%~99.4%和0.2%~9.5%,表明此方法在实际样品中同样具有较高的准确性和精密度。

Magic extraction: solid-phase extraction and analytical pyrolysis to study polycyclic aromatic hydrocarbon and polychlorinated biphenyls in freshwater

Polycyclic aromatic hydrocarbons and polychlorinated biphenyls are commonly categorized as persistent organic pollutants. In order to analyze these pollutants, customized stationary phases are increasingly being developed and synthesized for solid-phase extraction. In this work, we tested a new solventless solid-phase extraction approach based on the use of a Magic Chemisorber® (Frontier Lab) which consists of a bead-covered polydimethylsiloxane stationary phase with a thickness of 500 µm. These devices are directly immersed into aqueous samples and then introduced into a pyrolysis–gas chromatography-mass spectrometry system equipped with a cryofocusing system for the thermal desorption and analysis of the adsorbed species. Our new method performs better than the most recent solid-phase extraction devices, with limits of detection lower than 2.7 ng/L and limits of quantification lower than 9.0 ng/L. The method was tested on standard compounds and on an environmental sample, showing the potential to characterize other chemical species besides the persistent organic pollutants, such as phthalate plasticizers and antioxidants.

Magnetic silicon carbide nanocomposite as a sorbent in magnetic dispersive solid phase extraction followed by dispersive liquid–liquid microextraction in the gas chromatographic determination of pesticides

A magnetic silicon carbide nanocomposite based-magnetic dispersive solid phase extraction approach using aspiration/dispersion cycles was proposed. Several pesticides including diazinon, ametryn, chlorpyrifos, hexaconazole, diniconazole, tebuconazole, and triticonazole were extracted by this method from different samples. The analytes were extracted by a few mg of the prepared nanocomposite from the sample solution. The sample solution and adsorbent contact area was increased by performing aspiration/dispersion cycles. The nanocomposite particles were separated from sample solution using a neodymium magnet. Then an appropriate volume of an organic solvent was added onto the nanocomposite particles to desorb the analytes. Then, the obtained eluate was utilized in the next microextraction method to achieve high sensitivity and enrichment factor. Gas chromatography equipped with mass spectrometry was used for determination of the extracted analytes. Validation values considering ICH protocol illustrated that limits of detection and quantification were within the ranges of 0.06–0.33 and 0.19–1.0 ng mL−1. Good precision (relative standard deviations ≤ 7.0 %), acceptable linearity (r2 ≥ 0.992), high enrichment factors (600–850), extensive linear ranges, and acceptable extraction recoveries (60–85 %) were obtained. This approach was done on different real samples and chlorpyrifos and diazinon were determined in some of them.

Synthesis and application of magnetic surface molecularly imprinted polymers in selective solid-phase extraction of epoxy triglyceride from deep frying oil

As the major oxidized triglycerides (ox-TGs), epoxy triglyceride is one of the toxic polar components from deep frying oil. However, the conventional methods are difficult to separate epoxy triglyceride from other ox-TGs due to their similar molecular and structures. To address the problem, a novel magnetic solid-phase extraction approach based on a surface molecularly imprinted polymers was developed. The polymers coated on Fe3O4 nanoparticles (Fe3O4@MIPs) were synthesized and used as highly selective sorbents for capture epoxy triglyceride from deep frying oil. They have high adsorption capacity (58.3 mg/g), stable equilibrium adsorption time (60 min) and excellent specificity. This method had a satisfactory linear relationship in the range of 0.2–10 mg/L (R2 = 0.997), and the detection limit of epoxy triglyceride was 0.0599 mg/L. Results indicated that Fe3O4@MIPs could not only specifically separate epoxy triglycerides, but also provided a potent idea for the separation of other ox-TGs from deep frying oil.

Experimental and density functional theory studies during a new solid phase extraction of phenolic compounds from wastewater samples prior to GC–MS determination

In this work a commercial polymer-based dispersive solid phase extraction approach has been used in phenolic compounds extraction from wastewater samples. In the extraction procedure, firstly the sorbent (polyvinylpyrrolidone) forms a homogenous solution with aqueous phase contacting the analytes and then its solubility was decreased by adding sodium chloride which leads to its dispersion into the aqueous solution as tiny particles. During this step, the investigated phenolic compounds were adsorbed onto the polymer. Then, a deep eutectic solvent synthesized from choline chloride and alpha-terpineol was used for elution of the compounds from the polymer surface. Optimization of the effective factors showed that the subsequent conditions are suitable for extraction of the analytes: sorbent (polyvinylpyrrolidone) amount, 125 mg; sample solution pH, 4; NaCl concentration, 20%, w/v; and desorption solvent volume, 75 µL. Acceptable figures of merit consist of limits of detection and quantification in the ranges of (0.13–0.36 ng/mL and 0.43–1.2 ng/mL, relative standard deviations ≤ 6%, and extraction recovery and enrichment factor in the ranges of 60–92% and 80–122 were obtained. The powers of the interactions between the studied chemical species were analyzed with the help of Conceptual Density Functional Theory calculations and important quantum chemical parameters related to the chemical reactivity. The obtained theoretical data were in a good agreement with experimental observations.

Solid-Phase Extraction Approaches for Improving Oligosaccharide and Small Peptide Identification with Liquid Chromatography-High-Resolution Mass Spectrometry: A Case Study on Proteolyzed Almond Extract.

Reverse-phase solid-phase extraction (SPE) is regularly used for separating and purifying food-derived oligosaccharides and peptides prior to liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. However, the diversity in physicochemical properties of peptides may prevent the complete separation of the two types of analytes. Peptides present in the oligosaccharide fraction not only interfere with glycomics analysis but also escape peptidomics analysis. This work evaluated different SPE approaches for improving LC-MS/MS analysis of both oligosaccharides and peptides through testing on peptide standards and a food sample of commercial interest (proteolyzed almond extract). Compared with conventional reverse-phase SPE, mixed-mode SPE (reverse-phase/strong cation exchange) was more effective in retaining small/hydrophilic peptides and capturing them in the high-organic fraction and thus allowed the identification of more oligosaccharides and dipeptides in the proteolyzed almond extract, with satisfactory MS/MS confirmation. Overall, mixed-mode SPE emerged as the ideal method for simultaneously improving the identification of food-derived oligosaccharides and small peptides using LC-MS/MS analysis.

Preparation of polydopamine-functionalized mesoporous silica-coated core/shell magnetic nanocomposite for efficiently extracting five amphetamine-type stimulants from wastewater followed by UPLC-MS/MS determination

Wastewater-based epidemiology (WBE) was a near-real-time monitoring strategy for illegal drugs. However, solid-phase extraction (SPE) widely used in WBE was time-consuming and labor-intensive to extract ultra-trace target compounds from wastewater. In this study, a convenient magnetic solid-phase extraction (MSPE) approach based on newly designed and synthesized polydopamine functionalized core-shell magnetic mesoporous silica (Fe3O4@nSiO2@mSiO2@PDA) nanocomposite was synthesized and firstly utilized for simultaneously extracting five amphetamine-type stimulants (ATSs) from wastewater samples. Subsequently, ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method coupled with optimal MSPE was developed for determination of ultra-trace ATSs in wastewater. The validation results indicated a favorable linearity ranging from 1 to 200 ng L−1, low limit of detection (0.5–2.5 ng L−1), and qualified recovery (95.1–106.6%) and repeatability (0.6–6.2%). In addition, the Fe3O4@nSiO2@mSiO2@PDA nanoparticles could be reused for at least ten times without significant loss of the adsorption efficiencies of ATSs. Finally, the MSPE-UPLC-MS/MS method was successfully applied to real wastewater samples with the results that the preparation procedure was shrunk from 2 h to 30 min without obvious decline of extraction efficiency compared with the SPE. Hence, based on merits of the novel Fe3O4@nSiO2@mSiO2@PDA nanocomposite, the proposed method is convenient and reliable for determination of ATSs in wastewater.

Facile Separation of PEGylated Liposomes Enabled by Anti-PEG scFv

PEGylated nanocarriers have gained increasing attention due to reduced toxicity and enhanced circulation compared with free drugs. According to guidances of drug regulatory departments worldwide, it is crucial to determine free and liposomal drug concentrations; however, the conventional used separation methods including dialysis, ultrafiltration, and solid-phase extraction (SPE) have drawbacks of time-consuming, drug leakage, environmental pollution or error bias of trace level drug. Here we developed a facile PEG-scFv-based separation method combined with HPLC to quantify free doxorubicin (DOX) and liposomal DOX in plasma. Anti-PEG single chain variable fragment antibody (PEG-scFv) was adopted to sediment PEGylated liposomes by simple incubation and low speed centrifugation. Compared to SPE, it demonstrated sufficient accuracy and sensitivity to evaluate free and liposomal DOX with intact liposomes. Therefore, it can serve as an alternative approach of SPE, which is suitable for quality assessment and pharmacokinetics evaluation of PEGylated liposomal drugs and possible other PEGylated nanocarriers.

Salt-induced homogenous solid phase extraction of hydroxylated metabolites of polycyclic aromatic hydrocarbons from urine samples using a deep eutectic solvent as an elution solvent prior to HPLC-FLD analysis

A novel solid phase extraction approach named homogenous dispersive solid phase extraction was introduced for the simultaneous extraction/preconcentration of four polycyclic aromatic hydrocarbons hydroxylated metabolites from urine samples. The method was done by dissolving a water-miscible organic polymer in urine and a homogenous phase was obtained. Then, by adding NaCl the sorbent was re-precipitated in the solution bulk as tiny particles and the analytes are adsorbed onto the sorbent. Hence, the sorbent was separated and the analytes on the surface of particles were separated by choline chloride: butyric acid deep eutectic solvent and determined by HPLC-FLD. The effective parameters were optimized by central composite design and the following conditions were obtained: sample solution pH, 4; polyvinylpyrrolidone amount, 63 mg; sodium chloride concentration, 20% w/v; and choline chloride:butyric acid deep eutectic solvent volume, 87 µL. After optimization, the method was validated and broad linear ranges and low limits of detection (14–28 ng/L) and quantification (49–96 ng/L) were obtained. Acceptable enrichment factors (85–109), extraction recoveries (74–96%), and adequate percision (RSDs ≤ 6.2%) were obtained. Finally, the introduced method was effectively applied for measurement of the studied chemical compounds in urine samples obtained from tobacco smokers.

Effect of operating variables on the separation of radiostrontium from aqueous matrices with ion-selective solid-phase extraction systems

Radiostrontium (r-Sr: 90Sr) is one of the primary fission products in nuclear power plants and generates liquid radioactive waste when intermixed to the aqueous matrix. Therefore, separation or preconcentration of r-Sr from the aqueous matrices is necessary for environmental monitoring or nuclear forensics. The solid-phase extraction (SPE) approach is prevalently used for r-Sr isolation and to design matrix-specific methods, while generalized SPE-assisted operating protocols are not proposed by far. In the current work, four different SPEs, namely AnaLig Sr-01, Eichrom Sr, Triskem TK100, and Eichrom DGA, were evaluated for selective separation of Sr from aqueous matrices. Operating variables, e.g., solution acidity, washing solvent, eluent-type or volume, loading or elution flow-rate, were varied to optimize the SPEs performance. The objective was to ascertain the operating variables for maximum Sr-separation yield from aqueous environmental samples with the SPEs mentioned above. In addition, the Sr-separation efficiency of SPEs was evaluated by calculating the separation factor (SFSr/M) between Sr and interfering elements to r-Sr (M = Ca, Mg, Ba, or Y), and the Sr-retention capacity of the SPEs was determined. Finally, the optimized operating variables for the evaluated SPEs were used to construct protocols for r-Sr separation from aqueous matrices. Real 90Sr contaminated aqueous samples from the Chernobyl nuclear power plant cooling pond were treated by those protocols, and the results are validated comparing with the IAEA-recommended classical protocol. All the SPEs were able to isolate Sr at varying extents from matrices at the optimum conditions, even at much higher contents of interfering elements. Eichrom Sr or AnaLig Sr-01 showed better Sr-retention capability among the SPEs, while Triskem TK100 showed superiority over other SPEs regarding Sr-selectivity.

Determination of chlorothalonil metabolites in soil and water samples

Pesticide metabolites are frequently detected in groundwater at concentrations often exceeding those of their parent pesticides. A well-known example is the metabolites of chlorothalonil, a non-systematic, broad spectrum fungicide. Some of the chlorothalonil metabolites occur frequently and at elevated concentrations in groundwater, which is why the use of chlorothalonil was recently banned in the European Union. To estimate the long-term evolution of the concentration of the chlorothalonil metabolites in groundwater after this ban, it is important to know if metabolite residues in soil and unsaturated zone can affect the concentrations in groundwater. We developed and validated a method for the determination of 5 chlorothalonil metabolites in soil (R471811, R417888, SYN507900, SYN548580 and R611968), including those which are frequently detected in groundwater. The developed protocols, based on a solid phase extraction approach (for R471811, R417888, SYN507900, SYN548580) or a QuEChERS approach (for R611968) followed by UHPLC-MS/MS analysis, provided excellent sensitivity (LOQ of 0.5 µg/kg for all metabolites), precision (RSD<10 % at low, medium and high concentrations) and accuracy (84-115 %). In addition, we developed a simple but highly sensitive (LOQ of 5-10 ng/L) direct-injection method for the analysis of these 5 metabolites in water to compare their occurrence in soil and groundwater. The application of these methods to agricultural soil samples and groundwater samples showed that the detection frequency of the 5 chlorothalonil metabolites in soil and groundwater seems to be inversed and dependent on their sorption coefficient. The latter might control the amount of the chlorothalonil metabolites which is retained in the soil or which leaches towards groundwater. Our results provide insights to estimate the retention of the different chlorothalonil metabolites in soil and unsaturated zone and therefore, to assess the influence of the soil and unsaturated zone on the long-term concentration evolution of these metabolites in groundwater.