On-line Solid-phase Extraction Liquid Research Articles

Thyroid Hormone Metabolites Quantified in Pup and Adult Rat Cerebellum, Cortex and Whole-Brain Samples Using an Automated Online SPE-LC-MS/MS Method.

Changes in thyroid hormone (TH) levels in rat brain at early developmental stages are correlated with adverse effects on offspring development. To characterize the ability of substances to interfere with the TH concentrations in, e.g., rat brain, it is essential to know the mean TH concentrations in this tissue under control conditions. In this publication, an online solid-phase extraction (SPE) liquid chromatography (LC) tandem mass spectrometry (MS/MS) method was validated and used to measure TH metabolites (T4, T3, rT3, T2 and T1) in the brains of untreated rats. Data on TH concentrations in the whole brain and separate data from the cerebellum and the cortex are shown. The corresponding samples were gathered from young rats at postnatal days (PND) 4 and 21/22 and from adult rats. The results show inter alia the high accuracy and precision of the method, and LOQs of 0.02 ng/mL were determined for T1, T2 and rT3 and of 0.15 ng/mL for T3 and T4. Technical variability is low, as shown by the relative standard deviations of 7.5-20%. For our rat model, we found that T4, T3 and T2 concentrations rise from PND4 to PND21, whereas the rT3 concentration decreases; as well as there is no statistical difference between TH concentrations in the male and female rat brain. This method is suitable to analyze TH metabolites in the brain and build up a database of historical TH concentrations in control rats. Together, this yields a robust diagnostic tool to detect potentially adverse disturbances of TH homeostasis in the most vulnerable anatomic structure.

Porous polymer monoliths with complementary retention mechanisms for online solid-phase extraction liquid chromatography to determine lysozyme in egg white

Porous polymer monoliths with complementary retention mechanisms for online solid-phase extraction liquid chromatography to determine lysozyme in egg white

Development, validation, and use of a monitoring method for fipronil and its metabolites in chicken eggs by QuEChERS with online-SPE-LC-Q/Orbitrap analysis.

The residues of fipronil and its metabolites in chicken eggs pose a threat to human health, so regular monitoring is necessary. However, the pretreatments of the existing detection methods are complex and time-consuming. A simple and streamlined pretreatment method is needed to improve the detection efficiency. A rapid, efficient, and facile approach employing QuEChERS with online solid-phase extraction liquid chromatography tandem Q-Exactive Orbitrap high resolution mass spectrometry (online-SPE-LC-HRMS) was established and evaluated for the determination of fipronil, fipronil-desulfinyl, fipronil-sulfone and fipronil-sulfide in chicken eggs. An improved sample preparation technique combining QuEChERS and online-SPE was developed. Negative targeted ion fragmentation scanning (t-MS2 ) and targeted-selected ion monitoring (t-SIM) of the HRMS were adopted to identify and quantify the target analytes. The proposed pretreatment method took a few steps in < 13 min to achieve excellent recoveries and negligible interference. High selectivity was acquired with the adoption of Q/Orbitrap HRMS. The LOQ of the analytes was 2.5 μg kg-1 , meeting the detection requirements of the MRL enacted by the Codex Alimentarius Commission (CAC), Japan and USA for the sum of fipronil and its metabolites. Extraction recoveries at three spiked concentration levels were within 84.56-93.84% with RSD ≤ 5.87%. The established method is efficient and easy to operate and displays satisfactory LOQs, recoveries, accuracy and precision. This approach serves as a reference method for monitoring eggs while providing potential solutions for fipronil determination in more complicated matrices.

Liquid chromatography-tandem mass spectrometry analysis of delamanid and its metabolite in human cerebrospinal fluid using protein precipitation and on-line solid-phase extraction

The penetration of the antituberculosis drug delamanid into the central nervous system is not established. The distribution of delamanid and its major metabolite, DM-6705, into the cerebrospinal fluid requires investigation. A liquid chromatography-tandem mass spectrometry method for the quantification of delamanid and DM-6705 in human cerebrospinal fluid was developed and validated. The calibration range for both analytes was 0.300 – 30.0 ng/mL. The deuterium-labelled analogue of delamanid (delamanid-d4) and OPC-14714 were used as internal standards for delamanid and DM-6705, respectively. Samples were processed by protein precipitation followed by on-line solid-phase extraction and high-performance liquid chromatography on an Agilent 1260 HPLC system. A Phenomenex Gemini-NX C18 (5.0 µm, 50 mm × 2.0 mm) analytical column was used for on-line solid-phase extraction, and a Waters Xterra MS C18 (5.0 µm, 100 mm × 2.1 mm) analytical column for chromatographic separation using gradient elution, at a flow rate of 300 µL/min. The total run time was 7.5 min. Analytes were detected by multiple reaction monitoring on an AB Sciex 5500 triple quadrupole mass spectrometer at unit mass resolution, with electrospray ionization in the positive mode. Accuracy and precision were assessed over three independent validation batches. Extraction recoveries were more than 98% and were consistent across the analytical range. Both analytes in CSF exhibited non-specific adsorption to polypropylene tubes. The method was used to analyse cerebrospinal fluid samples from patients with pulmonary tuberculosis in an exploratory pharmacokinetic study.

Speed it up: How temperature drives toxicokinetics of organic contaminants in freshwater amphipods.

The acceleration of global climate change draws increasing attention towards interactive effects of temperature and organic contaminants. Many studies reported a higher sensitivity of aquatic invertebrates towards contaminant exposure with increasing or fluctuating temperatures. The hypothesis of this study was that the higher sensitivity of invertebrates is associated with the changes of toxicokinetic processes that determine internal concentrations of contaminants and consequently toxic effects. Therefore, the influence of temperature on toxicokinetic processes and the underlying mechanisms were studied in two key amphipod species (Gammarus pulex and Hyalella azteca). Bioconcentration experiments were carried out at four different temperatures with a mixture of 12 exposure relevant polar organic contaminants. Tissue and medium samples were taken in regular intervals and analysed by online solid-phase extraction liquid chromatography high-resolution tandem mass spectrometry. Subsequently, toxicokinetic rates were modelled and analysed in dependence of the exposure temperature using the Arrhenius equation. An exponential relationship between toxicokinetic rates versus temperature was observed and could be well depicted by applying the Arrhenius equation. Due to a similar Arrhenius temperature of uptake and elimination rates, the bioconcentration factors of the contaminants were generally constant across the temperature range. Furthermore, the Arrhenius temperature of the toxicokinetic rates and respiration was mostly similar. However, in some cases (citalopram, cyprodinil), the bioconcentration factor appeared to be temperature dependent, which could potentially be explained by the influence of temperature on active uptake mechanisms or biotransformation. The observed temperature effects on toxicokinetics may be particularly relevant in non-equilibrated systems, such as exposure peaks in summer as exemplified by the exposure modelling of a field measured pesticide peak where the internal concentrations increased by up to fourfold along the temperature gradient. The results provide novel insights into the mechanisms of chemical uptake, biotransformation and elimination in different climate scenarios and can improve environmental risk assessment.

Applicability of an on-line solid-phase extraction liquid chromatography – tandem mass spectrometry for the wastewater-based assessment of human exposure to chemicals from personal care and household products

Wastewater-based epidemiology (WBE) can be a useful complementary approach to assess human exposure to potentially harmful chemicals, including those from personal care and household products. In this work, a fully automated multiresidue method, based on on-line solid-phase extraction liquid chromatography – tandem mass spectrometry, was developed for the determination of 27 biomarkers of human exposure to selected chemicals from personal care and household products, including parabens, UV filters, phthalates and alternative plasticizers, phosphorous flame retardants/plasticizers (PFRs), and bisphenols. These biomarkers include both the parent compounds and their human metabolites. In addition, two oxidative stress biomarkers, 8-epi-prostaglandin F2α and 4-hydroxy nonenal mercapturic acid, were also considered in the study. The method was carefully optimized to tackle the challenges of analyzing compounds with different physico-chemical properties in a highly complex raw wastewater matrix, while model experiments were performed to investigate filtration losses and analyte stability. The applicability of the developed method was tested by analyzing raw wastewater from four European cities: Antwerp, Brussels (Belgium), Girona (Spain), and Zagreb (Croatia). Twenty-one biomarkers (10 parent compounds and 11 metabolites) were detected in all analyzed wastewater samples. The parent compounds with the highest mass loads were PFRs, parabens, and bisphenol S, while phthalate monoesters were the most prominent metabolites. The mass loads of most compounds were quite similar across cities, but geographic differences were observed for some biomarkers, such as metabolites of phthalates and alternative plasticizers. Exposure was then assessed for seven substances for which quantitative urinary excretion data are known. Our results indicate that safe reference values were exceeded for several contaminants, including butylated phthalates, bisphenol A, and tris(2-butoxyethyl) phosphate, particularly for toddlers. With this relatively simple method, which requires less sample manipulation, it is possible to promptly identify and monitor exposure to harmful chemicals at the population level using the WBE approach.

Pharmaceutical pollution of hospital effluents and municipal wastewaters of Eastern Canada

Quantification of drugs residues in wastewaters of different sources could help better understand contamination pathways, eventually leading to effluent regulation. However, limited data are available for hospital-derived wastewaters. Here, an analytical method based on automated on-line solid-phase extraction liquid chromatography tandem mass spectrometry (on-line SPE – UPLC-MS/MS) was developed for the quantification of multi-class pharmaceuticals in wastewaters. Filtrate phase and suspended solids (SPM) were both considered to evaluate the distribution of targeted analytes. Experimental design optimization involved testing different chromatographic columns, on-line SPE columns, and loading conditions for the filtrate phase, and different organic solvents and cleanup strategies for suspended solids. The selected methods were validated with suitable limits of detection, recovery, accuracy, and precision. A total of 30 hospital effluents and 6 wastewater treatment plants were sampled to evaluate concentrations in real field-collected samples. Certain pharmaceuticals were quantified at high levels such as caffeine at 670,000 ng/L in hospital wastewaters and hydroxyibuprofen at 49,000 ng/L in WWTP influents. SPM samples also had high contaminant concentrations such as ibuprofen at 31,000 ng/g in hospital effluents, fluoxetine at 529 ng/g in WWTP influents or clarithromycin at 295 ng/g in WWTP effluents. Distribution coefficients (Kd) and particle-associated fractions (Φ) indicate that pharmaceuticals tend to have better affinity to suspended solids in hospital wastewater than in municipal wastewaters. The results also bring arguments for at source treatment of these specific effluents before their introduction into urban wastewater systems.

Association of genetic polymorphisms with mercapturic acids in the urine of young healthy subjects before and after exposure to outdoor air pollution

ABSTRACT We aimed to identify the relationship between variations in metabolic genes and human urinary changes in mercapturic acids (MAs), including CEMA, HMPMA, SPMA, HPMA and HEMA, before and after air pollution exposure. Genotype detection for 47 relevant single nucleotide polymorphisms (SNPs) collected by literature research was performed. Five MAs expression levels in the urinary samples of 50 young healthy individuals with short-term exposure to clean, polluted and purified air at five time points were detected by targeted online solid-phase extraction liquid chromatography tandem mass spectrometry (SPE-LC-MS/MS), followed with associations of SNPs with MAs changes. Difference in MAs between polluted and clean/purified air was significantly associated with 21 SNPs mapped into 9 genes. Five SNPs in GSTP1 showed the most prominent association with the changes in SPMA expression, indicating that those SNPs in GSTP1 and SPMA might serve as biomarkers for susceptibility and the prognosis of lung cancer.

Biochar for the removal of detected micropollutants in South African domestic wastewater: a case study from a demonstration-scale decentralised wastewater treatment system in eThekwini

The presence of micropollutants, such as pharmaceuticals and personal care products, in surface and ground water has escalated globally, leading to adverse effects on aquatic organisms in receiving waters. Untreated or inadequately treated wastewater is the main source of micropollutants entering the environment. In South Africa, the consumption of antibiotics and antiretroviral drugs is relatively higher than other nations; however, little data exists on the identification and remediation of micropollutants in domestic wastewater. In this study, a novel method to detect and measure 71 micropollutants using online solid phase extraction liquid chromatography coupled to tandem mass spectrometry was developed. To test the method in the South African context, grab samples of the influent and anaerobically treated effluent (AF effluent) from a demonstration-scale decentralised wastewater treatment system in eThekwini (Durban) were taken over 3 consecutive days at 2 time points. The presence of 24 micropollutants was detected in the raw wastewater, with analgesics/anti-inflammatory drugs, antiretrovirals, and antibiotics showing the highest concentrations and with the majority of compounds still present in the AF effluent. One antibiotic, ciprofloxacin, exceeded its predicted no-effect concentration in all influent and AF effluent samples. This suggests that the anaerobic treatment of the raw wastewater was not effective in removing micropollutants. Preliminary data from lab-scale adsorption experiments using biochar produced from a set of 4 feedstocks – olive residues, tomato residues, rice husks, and the African palm tree Raphia farinifera – showed average removal rates for 4 compounds of up to 62%. The application of biochar is thus recommended as a secondary treatment step in decentralised wastewater treatment for the removal of micropollutants in South Africa.

Development an automated and high-throughput analytical platform for screening 39 glucocorticoids in animal-derived food for doping control

For the purpose of doping control, increasing demand has been highlighted for the determination of glucocorticoids in animal derived foods. Although several methods have been established, the barrier of low throughput still exists for doping control. Herein, we report an on-line purification and high throughput platform for fast screening of 39 glucocorticoids in animal-derived food (pork, chicken, milk and eggs) using on-line solid-phase extraction (SPE) technology and liquid chromatography-tandem high-resolution mass spectrometry (LC-HRMS). An in-house developed, low-cost monolithic column was applied in this work which prevented the requirement of laborious and costly off-line solid-phase extraction columns. With one-step extraction and replacement of solvent, the sample can be directly and automatically injected as well as purified to screen 39 glucocorticoids in a single run time. The overall recoveries ranged from 62.0%–116.3% with intraday and inter-day relative standard deviation lower than 10.9% and 12.4%, respectively. The limits of quantitation for different matrices were between 0.84 and 4.94 μg/kg. Compared to the previous methods, the platform developed in this study shows excellent performance for rapid analysis of large numbers of samples and a wide variety of compounds with respect to short running time, analytical specificity and sensitivity as well as overall method accuracy and precision. In conclusion, this platform can function as a high-throughput tool in the field of doping analysis and contribute to a better safety assurance of animal-derived food.

Online Turbulent Flow Extraction and Column Switching for the Confirmatory Analysis of Stimulants in Urine by Liquid Chromatography-Mass Spectrometry.

Stimulants are often used to treat attention deficit disorders and nasal congestion. As they can be misused and overdosed, the detection of stimulants is relevant in the toxicological field as well as in the doping control field. The effects of stimulants can indeed be beneficial for athletes. Therefore, their in-competition use is prohibited by the World Anti-Doping Agency (WADA). As stimulants represent one of the most detected categories of prohibited substances, automation of methods to detect and confirm their presence is desirable. Previous work has shown the advantages of using turbulent flow online solid-phase extraction liquid chromatography-tandem mass spectrometry (online SPE LC-MS-MS) for the detection and confirmation of diuretics and masking agents. Hence, a turbulent flow online SPE LC-MS-MS method, compliant with the WADA's identification criteria, was developed and validated for the detection and confirmation of 80 stimulants or metabolites with limits of identification varying between 10 (or possibly lower) and 100 ng/mL. As several metabolites are common metabolites for multiple administered stimulants, this means that with this method, misuse of well over 100 compounds can be detected. As the developed method uses the same columns and mobile phases as our turbulent flow online SPE LC-MS-MS method for the confirmation of diuretics and masking agents, there is no need to change the configuration of the instrument when switching between the diuretics method and the developed stimulants method.

Quantification of ultra-trace organolead species in environmental water by inductively coupled plasma mass spectrometry with online solid-phase extraction and high performance liquid chromatographic separation

Quantification of organolead compounds in environmental water is an essential task considering much higher toxicity and bioavailability of organolead species than inorganic plumbic ions. However, the speciation of ultra-trace organolead compounds at sub ng L−1 levels is challengeable for current instruments incorporating high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) and even offline enrichment that offer detection limits around several to tens of ng L−1. In this paper, an online solid-phase extraction (SPE) coupled HPLC-ICP-MS method was developed for speciation analysis of trace lead in water. Graphene oxide bounded silica particles (GO@SiO2) was utilized as the SPE adsorbent because of its superior performance over graphene bounded silica particles and commercial C18 packing particles. High enrichment factors (1603 for TML and 1376 for TEL) were obtained when lead species in 10 mL sample was adsorbed by 1 mM sodium dodecyl benzene sulfonate (SDBS) preconditioned GO@SiO2 at 10 mL min−1 and then eluted by 5 μL of 5 mM SDBS. Because of the highly efficient preconcentration, detection limits were downscaled to be 0.018 for TML and 0.023 ng L−1 for TEL with relative standard deviations below 5%. Additionally, the proposed method also yielded rapid separation of Pb(II), TML and TEL (8 min) by using green mobile phases (aqueous solutions of 5 mM sodium 1-pentanesulfonate at pH 2.5 with/without 4 mM tetrabutylammounium hydroxide). Upon successful application to fresh water, TML and TEL were only presented in the river water whereas Pb(II) was only existed in the tap water, along with accuracy validation by good spiked recoveries (93–106%).

On-line Solid-Phase Extraction-Liquid Chromatographic Method for the Determination of Carbofuran and 7-Phenolcarbofuran in Cervical-Uterine Epithelial Tissue

A method for the trace level determination of carbofuran and 7-phenolcarbofuran in cervical-uterine epithelial tissue samples is proposed. The finely chopped tissue is methanol extracted in an ultra- sonic bath; the extract is evaporated, diluted with water and acidified to eliminate hydrophobic impurities by precipitation. Precon- centration and additional cleanup are carried out in a polymeric (PLRP-S) precolumn by loading the filtrated extract and successively washing with acetonitrile-water 5:95 (v/v) and 0.01 M aqueous ammonia. The precolumn is finally on-line eluted and analysed by reverse-phase HPLC with UV detection at 280 nm. Recoveries >90% and relative standard deviation of ∼12% were obtained in the analysis of non-contaminated tissue samples spiked at 0.2 μg/g of the pesti- cide and metabolite. Absolute limits of detection were 20 ng of ana- lyte in a cervical biopsy (150-950 mg of epithelial tissue). Application to the analysis of three samples from countrywomen exposed to carbofuran revealed the probable presence of 7-phenolcar- bofuran in two of them.

Selective Determination of Acidic Drugs in Water Samples Using Online Solid Phase Extraction Liquid Chromatography with Alginate Incorporated Multi-Walled Carbon Nanotubes as Extraction Sorbent

A rapid and effective method is developed for selective determination of five selected acidic drugs (salicylic acid, naproxen, diclofenac, ibuprofen and mefenamic acid) in water samples by using online solid phase extraction (Online-SPE) prior to liquid chromatography diode array detector (LC-DAD) analysis. In this study, Alginate incorporated multi-walled carbon nanotubes (Alg-MWCNT) beads were prepared and utilized as solid phase extraction sorbent. Optimization of online SPE-LC operating parameters such as valve switching time, composition of acetonitrile and buffer pH was conducted using Box-Behnken Design of Response Surface Methodology (RSM) to evaluate the interactive effects of these three variables. Under the optimized conditions (valve switching time: 1.5 min, composition of acetonitrile: MSA, 60:40 and buffer pH: pH 2), the method showed good linearity (1–500 μg L−1) with coefficient of determination (R2) of 0.9971–0.9996 and low limits of detection ≤ 0.018 µg L–1. The method showed high relative recoveries in the range of 75–110% for river water and tap water samples, respectively with RSDs of ≤ 7.8 (n = 3). This method was successfully applied to the determination of acidic drugs in river and tap water samples. In addition, Alg-MWCNT sorbent offered high degree of selectivity and efficiency for online SPE-LC-DAD analysis.

Methodology for Analysis of UV Filters in Tilapia Using Off-line MSPD Followed by On-line SPE–LC/UV

A sensitive method was developed and validated for the determination of UV filters (oxybenzone, octocrylene, 4-methyl-benzylidene camphor, 2-ethylhexyl-4-methoxycinnamate and avobenzone) in tilapia muscle using matrix solid-phase dispersion followed by on-line solid-phase extraction–liquid chromatography/UV. The validation showed good linearity from 100 to 3600 ng g−1 with r2 values > 0.98. Precision values with relative standard deviations were < 24% for all analytes. The accuracy was evaluated with the recovery of spiked muscle samples, and it ranged between 89 and 96% for most analytes, except 2-ethylhexyl-4-methoxycinnamate. A positive matrix effect was observed for oxybenzone, so a matrix-matched calibration curve was used for quantitation purposes. This methodology was applied to incurred samples of fish exposed to the analytes for 3 days (100 μg L−1 each). Residual quantities of the contaminants were measured after 24, 48 and 72 h of exposure, and concentrations ranged between 400 and 2900 ng g−1. The developed method was able to quantify all of the target compounds at trace levels.

Assessing accuracy, precision and selectivity using quality controls for non-targeted analysis

The benchmarks to assess reproducibility are not well defined for non-target analysis. Parameters to evaluate analytical performance, such as accuracy, precision and selectivity, are well defined for target analysis, but remain elusive for non-target screening analysis. In this study, quality control (QC) guidelines are proposed to assure reliable data in non-target screening methodologies using a simple set of standards. Workflow reproducibility was assessed using an in-house QC mixture containing selected compounds with a wide range of polarity that can be detected either by electrospray ionization (ESI) in positive or negative mode. The analysis was performed by online solid phase extraction (SPE) liquid chromatography coupled to high resolution mass spectrometry (LC-HRMS). Data processing was done by a commercially available software, Compound Discoverer v. 3.0 using an environmental working template, which searched a multitude of databases, including Chemspider, EPA Toxcast, MzCloud among others. We have specifically evaluated method specificity, precision, accuracy and reproducibility in terms of peak area and retention time variability, true positive identification rate, intraday (within days) and interday (consecutive days) variations and the use of QC samples to reduce false positives. The method showed a satisfactory accuracy with an identification rate of ≥70% for most of the QC compounds. Precision estimated based on peak area relative standard deviation (RSD) ranged between 30 and 50% for most of the compounds. Data normalization to a single internal standard did not improve peak area variability. Retention time precision showed great repeatability and reproducibility (RSD ≤ 5%). In addition, a simple model of RT vs log Kow was designed based on our QC mixtures to efficiently reduced false positives by an average of 49.1%.

Automated online solid-phase extraction liquid chromatography tandem mass spectrometry investigation for simultaneous quantification of per- and polyfluoroalkyl substances, pharmaceuticals and personal care products, and organophosphorus flame retardants in environmental waters

This work describes development of a quick and accurate online solid-phase extraction (SPE) liquid chromatography tandem mass spectrometry method for simultaneous determination of 87 emerging organic compounds, including 22 per- and polyfluoroalkyl substances, 58 pharmaceuticals and personal care products, and 7 organophosphorus flame retardants, in diverse water matrices. Considering the wide range of physicochemical properties for the target contaminants, efficient analysis in one injection is challenging. Thus, key extraction and analytical parameters, including online SPE sorbent, mobile phase additives, sample pH, loading solvent pH and composition, injection volume, and valve-switching time, were systematically optimized. The final conditions, namely a polymeric reversed-phase column with alkaline samples and an acidic loading solvent, provided satisfactory results for all target analytes compared to conventional methods that employ acidic samples for multi-residue analysis. The method detection limits (MDLs) ranged from 0.16 to 5.13 ng L−1 with 85% of MDLs lower than 2 ng L−1 for sample volumes of just 1.8 mL. The method also demonstrated satisfactory accuracy with 82% of analytes exhibiting 70–130% recovery. Importantly, only 30 min was required per sample. The optimized method was successfully applied to investigate the removal efficiency of emerging contaminants in a drinking water treatment plant and to analyze the environmental occurrence of target analytes. The method is sensitive, reliable, labor-saving, and cost effective, and therefore has the potential to advance large-scale environmental monitoring programs.

Online solid-phase extraction liquid chromatography–mass spectrometry of hair cortisol using a surrogate analyte

Online SPE LC–MS with 13C3-cortisol as a surrogate analyte was developed, validated and applied for obtaining hair cortisol levels of 114 healthy volunteers. The first 3 cm from a posterior vertex position were analyzed as three individual segments resulting in 310 hair cortisol levels, which were used, after log transformation, to predict a range of values observed in future. The median value of hair cortisol was 4.76 pg/mg. The employed method allowed simple processing, high throughput and may be readily expanded to analyze additional steroid compounds in hair.

Per- and polyfluoroalkyl substances and fluorinated alternatives in urine and serum by on-line solid phase extraction–liquid chromatography–tandem mass spectrometry

Per- and polyfluoroalkyl substances (PFAS), man-made chemicals with variable length carbon chains containing the perfluoroalkyl moiety (CnF2n+1–), are used in many commercial applications. Since 1999–2000, several long-chain PFAS, including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), have been detected at trace levels in the blood of most participants of the National Health and Nutrition Examination Survey (NHANES)—representative samples of the U.S. general population—while short-chain PFAS have not. Lower detection frequencies and concentration ranges may reflect lower exposure to short-chain PFAS than to PFOS or PFOA or that, in humans, short-chain PFAS efficiently eliminate in urine. We developed on-line solid phase extraction–HPLC–isotope dilution–MS/MS methods for the quantification in 50 μL of urine or serum of 15 C3-C11 PFAS (C3 only in urine), and three fluorinated alternatives used as PFOA or PFOS replacements: GenX (ammonium salt of 2,3,3,3,-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-propanoate, also known as HFPO-DA), ADONA (ammonium salt of 4,8-dioxa-3H-perfluorononanoate), and 9Cl-PF3ONS (9-chlorohexadecafluoro-3-oxanonane-1-sulfonate), main component of F53-B. Limit of detection for all analytes was 0.1 ng/mL. To validate the method, we analyzed 50 commercial urine/serum paired samples collected in 2016 from U.S. volunteers with no known exposure to the chemicals. In serum, detection frequency and concentration patterns agreed well with those from NHANES. By contrast, except for perfluorobutanoate, we did not detect long-chain or short-chain PFAS in urine. Also, we did not detect fluorinated alternatives in either urine or serum. Together, these results suggest limited exposure to both short-chain PFAS and select fluorinated alternatives in this convenience population.

Graphene oxide-based composite monolith as new sorbent for the on-line solid phase extraction and high performance liquid chromatography determination of ß-sitosterol in food samples

A composite monolithic column was prepared by redox initiation method for the on-line purification and enrichment of β-sitosterol, in which graphene oxide (GO) was embedded. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherm measurement, which indicated that the monolith possessed characteristics of porous structure and high permeability. Under the optimum conditions for extraction and determination, the calibration equation was y = 47.92 × −0.1391; the linear range was 0.008–1.0 mg mL−1; the linear regression coefficient was 0.998; the limit of detection (LOD) is 2.4 μg mL−1; the limit of quantitation (LOQ) was 8 μg mL−1; precisions for intra-day and inter-day assays presented as relative standard deviations were less than 4.3% and 6.8%, respectively. Under the selective conditions, the enrichment factor of the method was 119. The recovery was in the range of 80.40–98.00%. Moreover, the adsorption amount of the monolith was compared with silica gel-C18 adsorbent and the monolith without graphene oxide being embedded. The polymerization monolithic column showed high selectivity and good permeability, and it was successfully used as on-line solid-phase extraction (SPE) column for determination of β-sitosterol in edible oil.