Salt-assisted Liquid-liquid Extraction Research Articles

Assessing the potentialities of an easy-to-use sample treatment strategy: Multivariate investigation on “Moka extraction” of typical ingredients from dietary supplements

Mr. Bialetti invented Moka in 1933 and it still represents the most common way to prepare coffee at home. The process through which Mokas extract components from the ground coffee is a solid-liquid extraction which occurs at high pressure and temperature. These features are desirable in simple sample treatment strategies, since they allow good extraction efficiencies in a short time. Herein, for the first time, Moka-pot extraction was considered as an alternative processing protocol to extract polar compounds from dietary supplements. The effect of four experimental variables on extraction efficiency was evaluated through a fractional factorial design of experiments applied to a pooled matrix. In particular, solvent pH and its content of organic modifier, heating temperature and sample mass (reflecting the ratio to the amount of solvent which has to be kept fixed due to practical needs) were considered. The performances of the best conditions were then validated by determining recoveries (between 52 and 134 %, except for acetylsalicylic acid) and matrix effects (resulting always negligible or moderate at 100-fold dilution) of a spiked matrix which did not present any of the target analytes. They were finally applied to real samples, allowing to quantify some compounds, including artificial sweeteners, methylxanthines and taurine. Results were then compared with the quantities declared on the labels and those obtained with a Salt-Assisted Liquid-Liquid Extraction (SALLE), previously developed. Interestingly, the two methods were comparable for most compounds, but Moka extraction allowed to quantify taurine, which was not recovered with the SALLE. This promising result encourages further work to extend the use of the simple Moka device to other analytes and further matrices.

Salt-assisted liquid-liquid extraction and on-column concentration for chromatographic determination of phenolic compounds in beer

Salt-assisted liquid-liquid extraction (SALLE) and on-column concentration were evaluated to simplify the chromatographic determination of phenolic compounds in beer. Resveratrol, flavonoids (quercetin and kaempferol), and phenolic acids (caffeic, p-coumaric, and trans-ferulic acids) were used as model compounds based on their concentrations reported in craft beers. SALLE with acetonitrile was effective for sample cleanup, with recoveries ranging from 84 % to 112 %. The on-column concentration was carried out in high performance liquid chromatography by starting the gradient elution with acidified water (sample carrier stream) in a reversed-phase mode. Consequently, the analytes were retained in a narrow band, and highly polar/ionic potentially interfering species were flushed from the column. The effectiveness of the approach was demonstrated by linear correlations between the peak areas and the injected volumes from 10 to 200 µL (r ≥ 0.999), without significant variations in peak width (< 10 %), retention times (< 0.7 %), and peak symmetry (tailing factors within the range of 0.8–1.1). For all analytes, a linear response was achieved from 100 to 1000 µg L−1 (r > 0.999), with limits of detection within the range of 9–82 µg L−1. The approach was also effective for on-column concentrations of resveratrol, quercetin, and kaempferol in sequential injection chromatography (SIC), with injected volumes up to 750 µL and linear responses within 100–1000 µg L−1 (r > 0.997). The proposal reduced consumption of organic solvents (with only 770 µL required per determination in SIC) and avoided solid-phase extraction cartridges for analyte preconcentration.

Sample preparation for suspect screening of persistent, mobile and toxic substances and their phase II metabolites in human urine by mixed-mode liquid chromatography

Persistent, mobile and toxic substances have drawn attention nowadays due to their particular properties, but they are overlooked in human monitorization works, limiting the knowledge of the human exposome. In that sense, human urine is an interesting matrix since not only parent compounds are eliminated, but also their phase II metabolites that could act as biomarkers. In this work, 11 sample preparation procedures involving preconcentration were tested to ensure maximum analytical coverage in human urine using mixed-mode liquid chromatography coupled with high-resolution tandem mass spectrometry. The optimized procedure consisted of a combination of solid-phase extraction and salt-assisted liquid-liquid extraction and it was employed for suspect screening. Additionally, a non-discriminatory dilute-and-shoot approach was also evaluated. After evaluating the workflow in terms of limits of identification and type II errors (i.e., false negatives), a pooled urine sample was analysed. From a list of 1450 suspects and in-silico simulated 1568 phase II metabolites (i.e. sulphates, glucuronides, and glycines), 44 and 14 substances were annotated, respectively. Most of the screened suspects were diverse industrial chemicals, but biocides, natural products and pharmaceuticals were also detected. Lastly, the complementarity of the sample preparation procedures, columns, and analysis conditions was assessed. As a result, dilute-and-shoot and the Acclaim Trinity P1 column at pH = 3 (positive ionization) and pH = 7 (negative ionization) allowed the maximum coverage since almost 70 % of the total suspects could be screened using those conditions.

Multiclass Determination of Endocrine-Disrupting Chemicals in Meconium: First Evidence of Perfluoroalkyl Substances in This Biological Compartment.

Major concerns have been raised about human exposure to endocrine-disrupting chemicals (EDCs) during pregnancy. Effective methodologies for the assessment of this exposure are needed to support the implementation of preventive measures and the prediction of negative health effects. Meconium has proven a valuable non-invasive matrix for evaluating cumulative exposure to xenobiotics during the last two trimesters of pregnancy. The study objective was to develop a novel method to determine the presence in meconium of perfluoroalkyl substances (PFASs), bisphenols, parabens, and benzophenones, EDCs that are widely used in the manufacture of numerous consumer goods and personal care products, including cosmetics. Ten PFASs, two bisphenols, four parabens, and four benzophenones were measured in meconium samples prepared by using a combination of Captiva Enhanced Matrix Removal (EMR) lipid cartridges with salt-assisted liquid-liquid extraction (SALLE) and dispersive liquid-liquid microextraction (DLLME) before the application of liquid chromatography-tandem mass spectrometry (LC-MS/MS). Experimental parameters were optimized by applying different chemometric techniques. Limits of detection ranged from 0.05 to 0.1 ng g-1, and between-day variabilities (relative standard deviations) ranged from 6.5% to 14.5%. The method was validated by matrix-matched standard calibration followed by a recovery assay with spiked samples, obtaining percentage recoveries of 89.9% to 114.8%. The method was then employed to measure compounds not previously studied in this matrix in 20 meconium samples. The proposed analytical procedure yields information on cumulative in utero exposure to selected EDCs.

A Highly Selective Analytical Method Based on Salt-Assisted Liquid-Liquid Extraction for Trace-Level Enrichment of Multiclass Pesticide Residues in Cow Milk for Quantitative Liquid Chromatographic Analysis.

In this study, a simple, inexpensive, selective, and fast salting-out assisted liquid-liquid extraction (SALLE) technique coupled with high-pressure liquid chromatography-diode array detection (HPLC-DAD) was developed for the extraction, preconcentration, and analysis of trace level seven multiclass pesticide residues in pasteurized and raw cow milk samples. The significant factors that affect the extent to which the target analytes are extracted, such as the type of extraction solvent and its volume, the type and concentration of salting-out salts, the pH of the solution, and the extraction time, have been investigated. Under optimum conditions, the correlation coefficient (r2) was obtained within a range of 0.9982-0.9997 for a broad linear range concentration of 2-1500 ng·mL-1. Reliable sensitivity was achieved with limits of detection (LODs) and limits of quantification (LOQs) ranging from 0.58-2.56 ng·mL-1 and 1.95-8.51 ng·mL-1, respectively. While precision with interday and intraday in terms of relative standard deviations (RSDs) was observed in the range of 1.97 - 7.88% and 4.52 - 8.04%, respectively. The results of the precision studies reveal that good repeatability and reproducibility (RSDs <9) were achieved, thus showing a low variability extraction of the developed method. Finally, the proposed and validated approach was effectively used to extract and determine pesticide residues in real milk matrices; however, the target analytes were not detected in all samples.

The role of sample preparation in suspect and non-target screening for exposome analysis using human urine

The use of suspect and non-target screening (SNTS) for the characterization of the chemical exposome employing human biofluids is gaining attention. Among the biofluids, urine is one of the preferred matrices since organic xenobiotics are excreted through it after metabolization. However, achieving a consensus between selectivity (i.e. preserving as many compounds as possible) and sensitivity (i.e. minimizing matrix effects by removing interferences) at the sample preparation step is challenging. Within this context, several sample preparation approaches, including solid-phase extraction (SPE), liquid-liquid extraction (LLE), salt-assisted LLE (SALLE) and dilute-and-shoot (DS) were tested to screen not only exogenous compounds in human urine but also their phase II metabolites using liquid-chromatography coupled to high-resolution tandem mass spectrometry (LC-HRMS/MS). Additionally, enzymatic hydrolysis of phase II metabolites was evaluated. Under optimal conditions, SPE resulted in the best sample preparation approach in terms of the number of detected xenobiotics and metabolites since 97.1% of the total annotated suspects were present in samples extracted by SPE. In LLE and SALLE, pure ethyl acetate turned out to be the best extractant but fewer suspects than with SPE (80.7%) were screened. Lastly, only 52.5% of the suspects were annotated in the DS approach, showing that it could only be used to detect compounds at high concentration levels. Using pure standards, the presence of diverse xenobiotics such as parabens, industrial chemicals (benzophenone-3, caprolactam and mono-2-ethyl-5-hydroxyhexyl phthalate) and chemicals related to daily habits (caffeine, cotinine or triclosan) was confirmed. Regarding enzymatic hydrolysis, only 10 parent compounds of the 44 glucuronides were successfully annotated in the hydrolysed samples. Therefore, the screening of metabolites in non-hydrolysed samples through SNTS is the most suitable approach for exposome characterization.

High-Purity Bioactive Ingredient-3S,3'S-Astaxanthin: A New Preparation from Genetically Modified Kluyveromyces marxianus without Column Chromatography and Gel Filtration.

A highly efficient methodology for bioactive ingredient 3S,3'S-astaxanthin (3S,3'S-AST) preparation from genetically modified yeast (Kluyveromyces marxianus) with a combination of enzyme-assisted extraction and salt-assisted liquid-liquid extraction (SALLE) was achieved. The highest yield of 3S,3'S-AST indicated that FoodPro® CBL for yeast cell walls hydrolysis could significantly enhance extraction and obtain, with the help of SALLE procedure, quantified 3S,3'S-AST over 99% in purity through cation chelation. In the oxygen radical antioxidant capacity (ORAC) assay, the antioxidant capacity of high-purity 3S,3'S-AST products were 18.3 times higher than that of the original raw material extract. This new combination preparation may replace previous methods and has the potential to be scaled up in the manufacture of high-purity 3S,3'S-AST from low-value bioresources of raw materials to high-value products in the food and/or drug industries with lower cost and simple equipment.

SAMHSA drug panel screening in oral fluid: Development of screening method at 8 seconds per sample using LDTD-MS/MS

In 2019, the US Department of Health and Human Services (via the SAMHSA agency) has established scientific and technical guidelines for federal workplace drug testing programs in oral fluids (Federal Register/Vol. 84, No. 207, 2019). Screening various drug classes requires several different immunoassay reagents or an LC-MS/MS method with a longer analysis time per sample. LDTD-MS/MS technology combines the speed and the analysis of different drug classes with a single method. The goal of this presentation is to use an automated sample preparation method for LDTD-MS/MS screening of all compounds in a single operation. Quantisal collection devices were used in this method. Drug-free oral fluids of different volunteers were collected using the Quantisal device. After the collection of the oral fluid, the pad is transferred into a tube containing an extraction buffer. During this process, oral fluids are diluted by a factor of 3. The SAMHSA drug panel for an Oral fluid screen was spiked in extracts at a concentration around the decision point cut-off (Amphetamine: 50 ng/mL, Methamphetamine: 50 ng/mL, MDA: 50 ng/mL, MDMA: 50 ng/mL, PCP: 100 ng/mL, Morphine: 30 ng/mL, Hydromorphone: 30 ng/mL, Codeine: 30 ng/mL, Hydrocodone: 30 ng/mL, Cocaine: 30 ng/mL, Oxymorphone: 30 ng/mL, Oxycodone: 30 ng/mL, 6-AM: 4 ng/mL and THC: 4 ng/mL). Samples were extracted using the Azeo automated extraction system. The robot scans the barcode of the sample, generates a batch file for the LDTD-MS/MS system, extracts the sample and spots the LazWell plate. Salt assisted liquid-liquid extraction (SALLE) was used as the sample preparation method. LDTD (Phytronix Luxon) uses a carrier gas (air) flow rate of 6 L/min with water infusion at 20 uL/sec. Samples were desorbed from the surface of the plate using a laser ramp of 6 seconds to 65% power and 2 seconds hold at 65% power. Mass spectrometer (Shimadzu 8060) operates in positive MRM mode with a specific transition for the following drugs: Amphetamine, Methamphetamine, MDA, MDMA, PCP, Morphine, Hydromorphone, Codeine, Hydrocodone, Cocaine, Oxymorphone, Oxycodone, 6-AM and THC. Data acquisition systems of mass spectrometers were not designed to deal with signals of only a few seconds per sample. The synchronization sequence adds 6 to more than 15 seconds between each sample. To bypass this, all samples are acquired in a single file. To allow the analysis of such data, Cascade™ software is designed to detect, split, and integrate every sample peak acquired in a single file. Spiked samples around the decision point and blank solutions are used to validate the precision of the method. Each concentration must not exceed 20% CV and the mean concentration ± 2 times the standard deviation must not overlap with other concentrations at the decision point. The peak area against the IS ratio was used to normalize the signal. Replicate extractions are deposited on a LazWell plate and dried before analysis. No overlapping at the decision point is observed for all curves and the CV% was below 15% for within-run experiments. A dry and wet stability of sample extracts were performed. Precision criteria were applied. All results are within the acceptable criteria range. Oral fluids are collected from eight different volunteers. Samples are screened to verify the presence of each analyte (all samples were negative). Drugs are spiked at 50% cut-off (QC-L) and 200% cut-off (QC-H) and screened as unknown to verify the method sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy. A percentage of 100% was obtained for all validation parameters of all drugs. Luxon Ion Source® combined to a Shimadzu 8060 mass spectrometer system allows ultra-fast (8 seconds per sample) screening of a SAMHSA drug panel in oral fluid using a simple and automated sample preparation method.

Front Cover: Determination of 2,4‐dichlorophenoxyacetic acid in environmental and food samples using salt‐assisted liquid‐liquid extraction coupled with micro‐channel and high‐performance liquid chromatography

DOI: 10.1002/sscp.202200010 The cover picture shows a salt-assisted liquid-liquid extraction in a micro-channel as a simple and fast method was applied determination of 2,4-dichlorophenoxyacetic acid in environmental and vegetables samples. Micro-channels due to small inside diameter are appropriate candidates to enhance the contact between the organic phase and the aqueous phase in liquid-liquid extraction methods. The 2,4-dichlorophenoxyacetic acid can lead to serious damage to humans and animals. The maximum contaminant levels of the 2,4-dichlorophenoxyacetic acid for finished drinking water according to guidelines of the United State Environmental Protection Agency and World Health Organization are 0.07 and 0.03 mg/L, respectively.

Extraction strategies of PAHs from grilled meat for their determination by HPLC–DAD

Strategies have been used in this work for rapid and precise extraction of polycyclic aromatic hydrocarbons (PAHs) from grilled meat. Samples were pre-extracted with acetonitrile/potassium hydroxide under microwave irradiation, and after dilution with water subjected to two alternative pre-concentration and clean-up methods. In the first method, the extract was treated with hydrophilic deep eutectic solvent (DES) of choline chloride:phenol (1:2, molar ratio), and the extract phase separated by salt-assisted liquid–liquid extraction (SALLE) with acetonitrile. This method was found better than the conventionally used emulsification with tetrahydrofuran. In the other method, a methanolic solution of 1,4-dichlorobenzene (DCB) was injected into the extract when a cloudy solution was obtained due to dispersion of DCB particles. The sorbent with extracted PAHs was collected on bare Fe3O4 nanoparticles; a modification which was faster than the usually opted centrifugation in dispersive solid phase extraction. Matrix polar compounds and proteins were excluded due to low polarity of DES-SALLE combination and non-polar surface of DCB. Linear calibration graphs are obtained in HPLC–DAD in the range 0.1–1000 µg kg−1 of PAHs in both extraction methods (using 10 mL of standard extract). The limits of detection (S/N = 3) of PAHs (determined on tenfold diluted standard extract) were in the range 11–25 ng kg−1 by the DES method and 14–30 ng kg−1 by the DCB method, which were better than obtained by many of currently used extraction methods. The enrichment factors ranged 75–115 in DES extraction method, 60–95 in DCB method. The methods have been applied to the real samples of grilled meat, and the results found by the present methods agreed together and with those found by the standard methods. DES method in combination with SALLE was found more convenient to operate.

High throughput method for quantifying androstenone and skatole in adipose tissue from uncastrated male pigs by laser diode thermal desorption-tandem mass spectrometry

The study aims at developing a rapid and robust mass spectrometric method capable of measuring the malodorous boar taint compounds androstenone and skatole in fat samples from male pig carcasses. The developed method is suited for use in commercial abattoirs as an at-line method to detect the presence of these compounds in carcasses or as a high-speed analysis in laboratories with high sample turnover. The chemical assay is based on salt-assisted liquid-liquid extraction and direct measurement with Laser Diode Thermal Desorption-Tandem Mass Spectrometry (LDTD-MS/MS). When fully automated as an at-line method, a single LDTD-MS/MS system will have a measuring capacity of >420 male pig carcasses per hour. The limit of quantification (LOQ) is 0.05 µg/g and 0.10 µg/g for skatole and androstenone, respectively, which is well below the expected sorting thresholds. The reproducibility of the method (%RSD) meets the industry requirement for an RSD of below 10%.

Determination of 2,4-Dichlorophenoxyacetic Acid in Water and Edible Seeds Samples Using Salt-Assisted Liquid-Liquid Extraction Coupled with High-Performance Liquid Chromatography

A simple, fast, and effective salt-assisted liquid-liquid extraction (SALLE) technique coupled with high-performance liquid chromatography (HPLC) was developed for determination of 2,4-dichlorophenoxyacetic acid (2,4-D) in water and edible seeds samples. Due to the polar nature of the 2,4-D molecules, LC analysis was performed on a CN stationary phase by using acetonitrile and acidic water as mobile phase. Extraction was achieved based on salting-out phenomenon. Affecting variables on the extraction efficiency of the 2,4-D, such as the solvent type and its volume, type of salt and its concentration, vortex time, and sample pH, have been investigated and optimized. The target analyte was successfully extracted by acetonitrile and sodium chloride as extracting solvent and salting-out agent, respectively. Under the optimized experimental conditions, calibration curve shows good linearity (r2 > 0.9957) and precision (RSD < 6.5%) in the concentration ranges of 1.0–10,000 ng/mL. The limit of detection (LOD) and limit of quantification (LOQ) were 0.3 and 1.0 ng/mL, respectively. The recoveries were in the range of 82.0–95.0 % with RSD values less than 7.2%. The method was successfully applied for the extraction and determination of 2,4-D in several edible seeds and water samples.

HPLC-MS/MS method for the determination of perfluoroalkyl substances in breast milk by combining salt-assisted and dispersive liquid-liquid microextraction.

The widespread use of perfluoroalkyl substances has resulted in the universal exposure of humans to these endocrine-disrupting chemicals, including the exposure of neonates through breastfeeding. The objective of this study was to develop a method to determine 10 perfluoroalkyl substances in breast milk (1-mL aliquot) by combining salt-assisted liquid-liquid extraction with dispersive liquid-liquid microextraction and using high-performance liquid chromatography-tandem mass spectrometry. Chemometric strategies were applied to optimize experimental parameters. The limit of quantification was 20pgmL-1 for all analytes, and inter-day variability (evaluated as relative standard deviation) ranged from 8.2 to 13.8%. The method was validated by a recovery assay with spiked samples. Percentage recoveries ranged from 85.9 to 110.8%. The method was satisfactorily applied to assess target compounds in 20 breast milk samples from donors. Perfluorooctanoic acid, perfluorooctane sulfonate, and perfluorohexanoic acid were the most frequently detected analytes. This analytical procedure can provide useful information on newborn's exposure to these xenobiotics.

Assessment of perfluoroalkyl substances in placenta by coupling salt assisted liquid-liquid extraction with dispersive liquid-liquid microextraction prior to liquid chromatography-tandem mass spectrometry

The widespread use of perfluoroalkyl substances (PFAS) is resulting in a broad human exposure to these endocrine disrupting chemicals (EDCs), prompting biomonitoring research to evaluate its magnitude and impact, especially during critical windows of exposure such as fetal and perinatal periods. This study was focused on developing a method to determine 10 PFAS in placental tissue by combining salt-assisted liquid-liquid extraction with dispersive liquid-liquid microextraction and using liquid chromatography-tandem mass spectrometry. Chemometric strategies were applied to optimize the experimental parameters. The limit of quantification was 0.02 ng g−1 for all analytes, and the inter-day variability (as relative standard deviation) ranged from 7.9% to 13.8%. Recoveries ranged from 88.2% to 113.9%. The suitableness of the procedure was demonstrated by assessing the targeted compounds in 20 placenta samples. The highest concentrations were recorded for perfluorooctanoic acid and perfluorooctane sulfonate, with maximum concentrations of 0.62 and 1.02 ng g−1 and median concentrations of 0.13 and 0.53 ng g−1, respectively. Median concentrations of the other PFAS ranged from detected values to 0.08 ng g−1. This analytical procedure yields useful data on fetal exposure to PFAS.

Development of a human biomonitoring method for assessing the exposure to ethoxyquin in the general population.

Ethoxyquin (EQ) is commonly used as an antioxidant in animal feeds. Although EQ is not permitted for usage in food products for humans within the EU, residues of EQ and its transformation products could be determined in food of animal origin. Despite its widespread use and concerns on its toxicological profile, no information about the systemic exposure to EQ in the general population is available. Hence, we developed a human biomonitoring (HBM) method for EQ. Our approach included a metabolism study with five subjects, who were administered an oral dose of 0.005mg EQ/kg body weight. Unchanged EQ and the major metabolite 2,2,4-trimethyl-6(2H)-quinolinone (EQI) were identified as urinary excretion products of EQ. While small amounts of EQ could be determined in high concentrated samples from the metabolism study only, 28.5% of the orally applied EQ dose could be recovered as EQI. Toxicokinetic parameters were determined for EQI, the potential biomarker of exposure. In addition, an analytical method for EQI (LOQ = 0.03µg/L) in urine based on UHPLC-MS/MS comprising enzymatic glucuronide hydrolysis and salt-assisted liquid-liquid extraction was developed, validated and applied to 53 urine samples from the general population. EQI could be quantified in 11 (21%) of the samples in levels up to 1.7µg/L urine, proving the suitability of the developed method for the intended purpose.

Trace Analysis of 61 Emerging Br-, Cl-, and I-DBPs: New Methods to Achieve Part-Per-Trillion Quantification in Drinking Water.

Disinfection byproducts (DBPs) are a ubiquitous source of chemical exposure in drinking water and have been associated with serious health impacts in human epidemiologic studies. While toxicology studies have pinpointed DBPs with the greatest toxic potency, analytical methods have been lacking for quantifying complete classes of most toxic DBPs at sufficiently low quantification limits (ng/L). This new method reports the parts-per-trillion quantification for 61 toxicologically significant DBPs from 7 different chemical classes, including unregulated iodinated haloacetic acids (HAAs) and trihalomethanes (THMs), haloacetaldehydes, haloketones, haloacetonitriles, halonitromethanes, and haloacetamides, in addition to regulated HAAs and THMs. The final optimized method uses salt-assisted liquid-liquid extraction in a single extraction method for a wide range of DBPs, producing the lowest method detection limits to-date for many compounds, including highly toxic iodinated, brominated, and nitrogen-containing DBPs. Extracts were divided for the analysis of the HAAs (including iodinated HAAs) by diazomethane derivatization and analysis using a GC-triple quadrupole mass spectrometer with multiple reaction monitoring, resulting in higher signal-to-noise ratios, greater selectivity, and improved detection of these compounds. The remaining DBPs were analyzed using a GC-single quadrupole mass spectrometer with selected ion monitoring, utilizing a multimode inlet allowed for lower injection temperatures to allow the analysis of thermally labile DBPs. Finally, the use of a specialty-phase GC column (Restek Rtx-200) significantly improved peak shapes, which improved separations and lowered detection limits. Method detection limits for most DBPs were between 15 and 100 ng/L, and relative standard deviations in tap water samples were mostly between 0.2 and 30%. DBP concentrations in real samples ranged from 40 to 17 760 ng/L for this study.

Dual stir bar sorptive extraction coupled to thermal desorption-gas chromatography-mass spectrometry for the determination of endocrine disruptors in human tissues

The validation of a procedure for the determination of six alkylphenols (APs), 4-tert-butylphenol, 4-pentylphenol, 4-tert-octylphenol, 4-hexylphenol, 4-octylphenol and 4-nonylphenol, and three bisphenols (BPs), bisphenol A, bisphenol F and bisphenol Z, in seven human organs and tissues (kidney, liver, heart, lung, spleen, brain and abdominal fat) obtained from eight autopsies is presented. Previously ground samples were treated by salt-assisted liquid-liquid extraction (SALLE) for isolation of the analytes and then pre-concentrated using dual stir bar sorptive extraction (SBSE), allowing two different extraction conditions for the same sample. Finally, thermal desorption was used as the injector system in combination with gas chromatography coupled to mass spectrometry (GC-MS). To determine BPs, derivatization using acetic anhydride was required, although this step was not necessary for the APs. Two parallel extractions of the contaminants with the stir bars were performed, followed by thermal desorption and chromatographic analysis. The procedure provided quantification limits between 0.050 and 4.0 ng g−1 for APs and from 0.26 to 2.6 ng g−1 for BPs. Repeatability and reproducibility values were lower than 15% in all cases. The accuracy of the procedure was established by a recovery study, which provided values in the 85.8–115% range for APs and 83.6–120% for BPs. Samples were analyzed with the proposed methodology and data were processed by ANOVA tests to study the behaviour and bioaccumulation of these compounds in human tissues or organs. In addition, discriminant analysis detected age- and sex-dependent differences in bioaccumulation.

Salt-assisted liquid-liquid extraction in microchannel.

In this study, for the first time, salt-assisted liquid-liquid extraction was performed in a microchannel system. The proposed design is based on the increase of contact surface area between target analytes and extracting phase during the sample and extracting phase transfer in microchannel. In this method, first sample solution, extracting solvent, and salt were mixed by stirrer and simultaneously delivered into a microchannel using a syringe pump. In order to optimize the influential parameters on the extraction efficiency of the proposed method, zidovudine and tenofovir disoproxil fumarate were selected as model analytes. The main parameters such as extracting solvent and its volume, salt amount, pH of sample solution, and microchannel shape, length, and its inner diameter were investigated and optimized. Under the optimized conditions, the proposed method was linear in the range of 0.1-30µg/mL and R2 coefficients were equal to 0.9922 and 0.9947 for zidovudine and tenofovir disoproxil fumarate, respectively. Extraction efficiency of the proposed method was compared with conventional salt-assisted liquid-liquid extraction. The results show that the proposed design has higher extraction efficiency than conventional salt-assisted liquid-liquid extraction. Finally, the proposed method was successfully applied for the determination of zidovudine and tenofovir disoproxil fumarate in plasma samples.

Determination of paraquat in environmental samples using salt-assisted liquid-liquid extraction coupled with microchannel and HPLC

ABSTRACT For the first time a new sample preparation method namely salt-assisted liquid-liquid extraction in microchennel (SALLE-MC) was developed for the determination of paraquat (PQ) in environmental samples. In the proposed method, the mixture of aqueous sample, miscible organic solvent (extracting solvent) and salting-out agent were mixed by a magnetic stirrer and simultaneously delivered into a microchannel using a syringe pump. Quantitative analysis was achieved using a high-performance liquid chromatography system. Effective parameters on the extraction efficiency of PQ such as extracting solvent and its volume, salt amount, pH of sample solution, microchannel shape, length and its inner diameter were investigated and optimised. Under the optimised conditions, calibration curve of the proposed method was linear in the range of 0.02–30 µg/mL with R 2 coefficient of 0.9954. Extraction recovery data were in the range of 90.0–94.0% with relative standard deviation less than 6.0%. The results show that the proposed method has higher extraction efficiency than conventional SALLE. Finally, the proposed method was successfully applied for the determination of PQ in environmental samples.

Bioaccumulation of Polycyclic Aromatic Hydrocarbons for Forensic Assessment Using Gas Chromatography-Mass Spectrometry.

Polycyclic aromatic hydrocarbons (PAHs) are considered xenobiotics of a potentially carcinogenic nature, being accumulated in the fatty tissue of the body. The objective of this work was the development and validation of a new analytical method to check the bioaccumulation of these toxic compounds in human organs obtained from autopsies. The contaminants were first isolated from the tissues by salt-assisted liquid-liquid extraction in acetonitrile. Because of the low concentrations of these compounds in the human body, a dispersive liquid-liquid microextraction procedure was included. The preconcentrated samples were analyzed by gas chromatography-mass spectrometry to identify the compounds. Principal component analysis was applied to show the natural clustering of forensic samples and orthogonal partial least-squares discriminant analysis to develop a multivariate regression method, which permitted the classification of samples. The quantification limits for the 13 PAHs (acenaphthylene, fluorene, phenanthrene, anthracene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene, benzo(g,h,i)perylene, and indeno(1,2,3-cd)pyrene) analyzed were in the 0.06-0.44 ng g-1 range, depending on the compound, while the mean intraday relative standard deviation of about 7% demonstrated the high precision of the method. Linearity was verified in the 0.5-200 ng g-1 range, and the enrichment factors were between 55 and 122. The results provided by the analysis of seven different human organs (brain, liver, kidney, lung, heart, spleen, and abdominal fat) from eight autopsies confirmed the PAH-bioaccumulation capacity of human body, fat showing the highest degree of bioaccumulation. The present work is the first study on PAH contamination in different organs obtained from autopsies, being PAH detected in most human samples at values ranged from 0 to 19 ng g-1.