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In this work, the determination of different metals (i.e., Al, Cr, Cu, Mn, Ni and V) in engine lubricating oils by microwave plasma atomic emission spectrometry (MP AES) has been revisited. For this purpose, a new multinebulizer in combination with the standard dilution analysis (SDA) calibration methodology has been used. The microwave plasma is very unstable and may even extinguish when organic solvents are directly introduced. This problem can be avoided by the synergetic combination of the SDA calibration and the new multinebulizer since it allows the determination of analytes in complex matrices due to the simultaneous introduction of organic and aqueous solutions, favoring the plasma stabilization. Furthermore, the SDA calibration also corrects the matrix effects associated with complex matrices. For the purpose of comparison, the same study has been performed using conventional calibration methodologies (i.e., external calibration (EC), internal standard calibration (IS) and standard addition calibration (SA)). To compare the analytical performances, the analytical figures of merit (i.e., limit of detection and limit of quantification) and the accuracy (i.e., trueness and precision) of the results have been evaluated. The results obtained show very similar values for the SDA calibration compared to the other calibrations with a much lower consumption of reagents, resources and with a higher easiness of operation. In addition, the total analysis time has also been evaluated, which has emphasized the great advantage of the synergetic association of SDA calibration with the multinebulizer in chemical analysis. The authors would like to thank the Spanish Ministry of Science and Innovation (PID2021-126155OB-I00) and the Regional Government of Valencia (Spain) (CIPROM/2021/062, INVEST/2022/70) for the financial support.

A new natural deep eutectic solvent (NADES)-based analytical method for mercury speciation in water samples is presented. A NADES (i.e., decanoic acid:DL-menthol in a molar ratio of 1:2) is used as an environmentally friendly extractant for separation and preconcentration using dispersive liquid–liquid microextraction before LC-UV–Vis. Under optimal extraction conditions (i.e., NADES volume, 50 µL; sample pH, 12; volume of the complexing agent, 100 µL; extraction time, 3 min; centrifugation speed, 3000 rpm; and centrifugation time, 3 min), the limit of detection values were 0.9 µg L−1 for the organomercurial species and 3 µg L−1 for Hg2+, which had a slightly higher value. The relative standard deviation (RSD, n = 6) has been evaluated at two concentration levels (25 and 50 µg L−1) obtaining values for all the mercury complexes within the range of 6–12% and 8–12%, respectively. The trueness of the methodology has been evaluated using five real water samples from four different sources (i.e., tap, river, lake, and wastewater). The recovery tests have been performed in triplicate obtaining relative recoveries between 75 and 118%, with RSD (n = 3) between 1 and 19%, for all the mercury complexes in surface water samples. However, wastewater sample showed a significant matrix effect (recoveries ranged between 45 and 110%), probably due to the high amount of organic matter. Finally, the greenness of the method has also been evaluated by the analytical greenness metric for sample preparation (i.e., AGREEprep). Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The Spanish Ministry of Science and Innovation (PID2021-126155OB-I00) and the Regional Government of Valencia (Spain) (CIPROM/2021/062) provided financial support for this study.

A simple, sensitive and matrix-effect free analytical method for simultaneous determination of Cd, Hg and Pb in drug samples (i.e., commercial dosage tablets) by inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to the United States Pharmacopeia (USP) Chapter 232, those metals are considered elemental impurities from class 1 and they must be assessed in pharmaceutical production as well as in quality control evaluation. In order to increase the sensitivity of the analysis, dispersive liquid–liquid microextraction (DLLME) was performed and seven factors affecting analyte extraction were optimized by multivariate analysis. A microvolume of analyte enriched phase was directly introduced into the plasma using a multi-nebulizer, providing a high enrichment factor. When compared to conventional ICP OES analysis, DLLME improves the limit of quantitation (LOQ) values on average 40-fold for all analytes. Consequently, LOQ values were significantly lower than their permissible daily exposure limits for oral drugs. Accuracy was evaluated by addition and recovery experiments following USP recommendations in eight commercial drug samples. Recovery and RSD values were within the range of 90–108% and 1–9%, respectively. The authors are grateful to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, process no. 141634/2017-0, 202722/2019-8, 305201/2018-2 and 428558/2018-6), the Regional Government of Valencia (Spain) (PROMETEO/2018/087) for the financial support, Agilent Technologies Inc. for the loan of the ICP OES spectrometer, and Ingeniatrics for the MultiNeb® provided. This study was financed in part by the Coordenaçao de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001. The authors extend their appreciation to Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T). This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society.

In this work a green and fast sample preparation method based on reversed-phase dispersive liquid–liquid microextraction (RP-DLLME) was developed for the separation and preconcentration of several elements (i.e., Ag, As, Ba, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb, S, Se, Sn and V) in gasoline samples before determination by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). The extraction procedure was carried out in a reverse mode, since a small volume of the aqueous phase (i.e., 8 M HCl) is used to extract a relatively high volume of the organic phase (i.e., gasoline sample). Unlike conventional DLLME, in RP-DLLME the analytes were extracted from the organic phase into the aqueous phase. The experimental conditions for the microextraction procedure were: 5 g of sample, 8 M HCl as the extractant phase, mechanical agitation by vortex as the dispersion system, 115 μL of extractant volume, and 2 min extraction and 5 min centrifugation time. Under optimized extraction conditions the enrichment factor ranged between 3 and 53, and the limits of detection ranged between 0.02 and 50 μg kg−1. The proposed analytical method was validated and successfully used to analyze three gasoline samples. All gasoline samples were spiked at 100 μg kg−1 for all analytes, except sulfur (in this case at 1000 μg kg−1), obtaining recovery and RSD values within the range of 88–109% and 2–9%, respectively. The authors would like to thank the Regional Government of Valencia (Spain) (PROMETEO/2018/087) for the financial support, Agilent Technologies Inc. for the loan of the ICP-OES spectrometer, and Ingeniatrics for the OneNeb® provided. Financial support from Universidad Nacional del Sur is gratefully acknowledged. A. S. Lorenzetti, E. Vidal and C. E. Domini wish to thank Consejo Nacional de Investigaciones Científicas y Técnicas for the financial support received. The authors extend their appreciation to the Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T). This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society.

Introduction: Population-based fecal tests for colorectal cancer (CRC) screening have shown to reduce mortality thanks to the early detection of the disease. However, currently available fecal tests are limited in their sensitivity and specificity. Our aim is to look for volatile organic compounds in fecal samples as biomarkers for CRC detection. Material and Methods: Eighty participants were included; 24 had adenocarcinoma, 24 had adenomatous polyps and 32 presented no neoplasms. Fecal samples were collected 48 h preceding the colonoscopy from all participants, except CRC patient samples that were collected after 3–4 weeks from the colonoscopy. Magnetic headspace adsorptive extraction (Mag-HSAE) followed by thermal desorption-gas chromatography-mass spectrometry (TD-GC–MS) was performed on stool samples to identify volatile organic compounds as biomarkers. Results: p-Cresol was significantly more abundant in the cancer samples (P < 0.001) with an area under the curve (AUC) of 0.85 (CI 95%; 0.737–0.953), having a sensitivity and specificity of 83% and 82%, respectively. In addition, 3(4H)-dibenzofuranone,4a,9b-dihydro-8,9b-dimethyl- (3(4H)-DBZ) was also more abundant in the cancer samples (P < 0.001) with an AUC of 0.77 (CI 95%; 0.635–0.905), sensitivity of 78% and specificity of 75%. When combined (p-cresol and 3(4H)-DBZ), the AUC was 0.86, sensitivity 87% and specificity 79%. p-Cresol also appeared to be promising as a biomarker for pre-malignant lesions with an AUC of 0.69 (CI 95%; 0.534–0.862), sensitivity 83% and specificity 63%, P = 0.045. Conclusions: Volatile organic compounds emitted from feces and determined by a sensitive analytical methodology (Mag-HSAE-TD-GC–MS), employing a magnetic graphene oxide as extractant phase, could be used as a potential screening technology for CRC and pre-malignant lesions. Miren Alustiza would like to thank ISABIAL for her pre-doctoral grant (UGP-16-138/2016/45). This work was supported by the Instituto de Salud Carlos III (PI17/01756, PI20/01527); by Vicerrectorado de Investigación y de Transferencia de Conocimiento (UAUSTI18-04, UAUSTI19-05, UAUSTI20-04), and Conselleria d’Innovació, Universitats, Ciència i Societat Digital (Generalitat Valenciana) (PROMETEO/2018/087; CIPROM/2021/062). The authors extend their appreciation to the Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T).

Magnetic deep eutectic solvents (MDESs) have recently produced a torrent of pioneering applications in endless areas of sample preparation. By including a magnetic nanomaterial (e.g., magnetic nanoparticles) or a paramagnetic anion (e.g., [FeCl4]-) in their structure, MDESs exhibit a strong response under the application of an external magnetic field. Furthermore, the use of MDESs, as a sorbent or solvent in extraction techniques, have been scarcely employed to develop green analytical methods, characterized by the avoid of time-consuming steps and the use of toxic organic solvents, as well as the application of small amounts of MDESs, for the determination of organic and inorganic contaminants, drugs, proteins, among others in environmental, food and biological matrices. This review highlights the application of MDESs in sample preparation in analytical chemistry. Challenges and future outlooks of new MDESs are also presented. The authors would like to thank the Regional Government of Valencia (PROMETEO/2018/087) for the financial support. The authors extend their appreciation to Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T). This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society.

A novel approach is presented to determine four bisphenols in water and urine samples, employing magnetic dispersive solid‐phase extraction combined with liquid chromatography and diode array detection. A modified zeolite‐based magnetic composite was used as an efficient sorbent, combining the advantages of magnetic materials with the remarkable properties of zeolites. A multivariate optimization design was employed to optimize some experimental factors affecting magnetic dispersive solid‐phase extraction. The method was evaluated under optimized conditions (i.e., amount of sorbent, 50 mg; sample pH, unadjusted; NaCl concentration, 1.25%; extraction and elution time, 2 min; eluent solvent, ethanol; eluent solvent volume, 400 µL), obtaining good linearity with correlation coefficients ranging between 0.995 and 0.999 (N = 5) (from 2 to 250 µg/L for bisphenol A, bisphenol AP, and bisphenol P and from 5 to 250 µg/L for bisphenol AF). Method repeatability was assessed obtaining coefficients of variation between 3 and 11% (n = 6). Finally, the method was applied to spiked real samples, obtaining for water samples relative recoveries between 83 and 105%, and for urine samples between 81 and 108% for bisphenol A, bisphenol AP, and bisphenol AF, and between 47 and 59% for bisphenol P. The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project no. CTQ2016-79991-R) and Generalitat Valenciana (Spain) (project no. PROMETEO/2018/087) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).

A new concept of a nebulizer (i.e., multinebulizer) has been employed for trace element (e.g., Cd, Cu, Hg, Ni, Pb, and Zn) determination in marine biota samples (e.g., fish sample). To this end, an analytical methodology based on the combination of a multinebulizer with an isotope dilution (ID) calibration strategy and inductively coupled plasma mass spectrometry (ICP-MS) has been proposed. In this way, the on-line isotope dilution (OID) is accomplished by the simultaneous introduction of the liquid samples/standard and the isotopic reference solution (i.e., spike) into the plasma with an efficient mixing between them, which takes place at the inner cavity of the multinebulizer tip. The proposed OID-ICP-MS analytical methodology allows the fast determination of Cd, Cu, Hg, Ni, Pb and Zn in a biota sample certified reference material (CRM) (e.g., IAEA-476) with limits of detection of 0.006, 0.4, 0.09, 30, 0.2 and 4 ng g−1, respectively, and recovery values ranging from 97 to 103%. The primary advantage offered by the proposed analytical methodology is that the time-consuming spiking step in the conventional ID analysis is avoided. This yields savings in both the total time and cost of the analysis per sample. Hence, it has been proved that OID-ICP-MS using a multinebulizer is a promising solution for the trace element analysis of samples with a high matrix content, which simplifies operation and significantly increases sample throughput and productivity. The authors would like to thank the Ministry of Economy and Competitiveness of Spain (Project no. CTQ2016-79991-R, AEI/FEDER,UE) for the financial support, the Vice-Rectorate for Research and Knowledge Transfer of the University of Alicante for the funds to cover the expenses of the use of Research Technical Services (UAUST119-05), and Ingeniatrics for the MultiNeb® provided. The IAEA is grateful for the support provided to its Environment Laboratories by the Government of the Principality of Monaco.

This study is the first to use a new ZSM-5 zeolite-based composite decorated with iron oxide magnetic nanoparticles and modified with hexadecyltrimethylammonium bromide surfactant (i.e., HDTMA-ZSM-5/Fe2O3) as an efficient sorbent for magnetic dispersive solid-phase extraction (MDSPE) of nonsteroidal anti-inflammatory drugs in water and urine samples with subsequent measurement by liquid chromatography diode array detection. Experimental factors affecting MDSPE were optimized using a multivariate optimization strategy. The optimum experimental conditions were: amount of sorbent, 40 mg; sample pH, 2.2; NaCl concentration, 2.5%; extraction time, 2 min; eluent solvent, methanol; eluent solvent volume, 424 μL; and elution time, 2 min. The linearity of the method was studied from 3.3 to 400 μg L−1 (N = 8) for ketoprofen, from 1.7 to 400 μg L−1 (N = 8) for felbinac, from 6.6 to 400 μg L−1 (N = 7) for diclofenac and from 9.9 to 400 μg L−1 (N = 6) for ibuprofen. Method repeatability was evaluated at 10 and 200 μg L−1 spiking levels, obtaining coefficients of variation between 2 and 5% (n = 6). Limits of detection, determined empirically, were 1.0 μg L−1 , 0.5 μg L−1, 2.0 μg L−1 and 3.0 μg L−1 for ketoprofen, felbinac, diclofenac and ibuprofen, respectively. Tap water, reservoir water, wastewater and five urine samples were selected to assess method applicability. Recovery values ranged between 86–107% and 80–112% for water and urine samples, respectively, showing negligible matrix effects. Finally, this method was employed to monitor ibuprofen excretion in real urine samples. The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project n. CTQ2016-79991-R) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).

A new portable and simple 3D printed device was designed for free chlorine determination in water samples. The analytical method was based on the quenching caused by free chlorine on the fluorescence emission of the carbon dots (CD) synthesized from citric acid and urea. The fluorescence was captured through the camera of a smartphone, which was coupled to the 3D printed device, and the images were processed using the RGB system by the ImageJ 1.51q software. The proposed method was selective and precise (RSD% 4.6, for n = 6), and the trueness of the results was evaluated by comparing the results obtained with those recovered by the spectrophotometric method 4500-Cl G (standard method), with good agreement between them. Moreover, the remarkable correlation between the CD signal and the free chlorine concentration resulted in a determination with low detection limits (limit of detection of 6 μg L−1 and limit of quantification of 20 μg L−1). Therefore, the new method and the related portable device could be considered a fast, economical and reliable alternative for the on-site determination of free chlorine in water samples. The authors wish to thank the financial support received from Universidad Nacional del Sur (PGI 24/Q099 and 24/Q086) and the ANPCyT (PICT-201-0659). The authors also thank Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) particularly for the doctoral grant of D. Uriarte.

The advantages of the microwave plasma atomic emission spectrometry (MP-AES) for hydride generation (HG) by means of modified Multi Mode Sample Introduction System (MSIS®) have been revealed for analysis of As and Sb in complex real samples. Two main outcomes have been achieved: (i) reliable analysis and higher tolerability to less diluted matrices and (ii) a multifold reduction in the methodological limits of detection (MLOD). For the first time in real samples analysis the HG is assisted by silica-coated magnetic nanoparticles (MNPs) (∼2 mg mL−1 MnFe2O4@SiO2) added to the hydrogenation reagent stream (1.5% NaBH4). This innovative approach provides smooth hydrides generation from problematic matrices, better gas–liquid separation and steady gas transport from the MSIS chamber. The effect is due to the elimination of NaBH4 delivery interruptions, the foam suppression in the reactor and levelling the carbon amount carried to the MP. The used inert MNPs could be collected from the drain with a permanent magnet and appear to be recyclable and reusable without memory effect or efficiency loss. The achieved benefits are demonstrated in the determination of As and Sb in three types of complex matrices: industrial electrolyte with high dissolved solids content, human urine prone to intensive foam creation, and sparkling mineral water releasing CO2. The work was supported by NSF of Bulgaria, Project DN19/9 2017–2021 (INISA).

Magnetic nanomaterials and their applications on chemical analysis are active research topics during the past few years. In this review, a broad and deep overview of these interesting and promising materials is presented on forensic chemistry. The main topics discussed are fingerprinting, explosives, chemical and biological warfare, illicit drugs, anticounterfeiting, and the detection of DNA, RNA, and protein. Challenges and future outlooks of bringing the magnetic nanomaterial–based technology in forensic chemistry are also presented.

In this study, a sensitive and matrix-effect free analytical method for Cd determination in engine oils and fuel samples by dispersive liquid-liquid microextraction with electrothermal atomic absorption spectrometry has been successfully developed. The extractant solvent used for the microextraction procedure was a magnetic ionic liquid (MIL) (i.e., bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate (II) [Emim]2[Co(SCN)4]), which presents a paramagnetic property, and allows an easy phase separation using a magnet. In order to eliminate the well-known drawbacks of direct introduction of MIL in the graphite furnace, a back-extraction procedure was performed to transfer the analyte into an aqueous phase. The main experimental factors affecting the extraction of Cd (i.e., amount of sample and MIL, extraction and back-extraction time and concentration and amount of nitric acid) were optimized using a multivariate analysis consisting in two steps: a Plackett-Burman design followed by a circumscribed central composite design. Under optimum conditions (i.e., amount of sample: 6.2 g; amount of MIL: 119 mg; extraction time: 1 min; amount of nitric acid: 200 mg; nitric acid concentration: 1 mol L-1 and back-extraction time: 1 min), the proposed analytical method was validated and successfully used to analyze three real-world samples (i.e., used engine oil, gasoline and diesel). The three samples were spiked at two levels (i.e., 10 and 20 μg kg-1 of Cd for used engine oil and 1 and 3 μg kg-1 of Cd for gasoline and diesel). RSD and recovery values were within the range of 6–11% and 95–110%, respectively. The authors would like to thank the Spanish Government (projects n. CTQ2016-79991-R and PGC 2018-098363-100), Fundación Séneca (Project n. 19888/GERM/15) and European Union (FEDER funds) for the financial support.

A new, inexpensive and easy to use 3D printable device was developed for nephelometric and fluorimetric determination. Its applicability was tested for the quantification of quinine in tonic drinks and sulfate in natural water with good analytical accuracy. In this way, sulfate determination was carried out by nephelometry using a red LED, while quinine was determined using a blue LED by fluorimetry. A smartphone camera was used to take the pictures and afterwards transform them into the RGB color space using the software ImageJ by a personal computer. The linear range was 2.0-50.0 mg L-1for sulfate with a LOD of 0.13 mg L-1, and the corresponding quantification limit (LOQ) was 0.43 mg L-1. The linear range for quinine was from 0.42 to 3.10 mg L-1. The LOD and LOQ were 0.11 mg L-1and 0.38 mg L-1, respectively. Fil: Vidal, Ezequiel Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina Fil: Lorenzetti, Anabela Silvana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Biología Agrícola de Mendoza. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Instituto de Biología Agrícola de Mendoza; Argentina Fil: Aguirre, Miguel Ángel. Universidad de Alicante; España Fil: Canals, Antonio. Universidad de Alicante; España Fil: Domini, Claudia Elizabeth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; Argentina

A new, fast, simple, and environmentally friendly analytical method has been developed to determine six siloxanes in water samples: octamethyltrisiloxane, octamethylcyclotetrasiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, dodecamethylpentasiloxane and dodecamethylcyclohexasiloxane. The analytical method consists of magnetic solid‐phase extraction employing graphene oxide/Fe3O4 as sorbent for the separation and preconcentration of siloxanes prior to GC–MS determination. The extraction procedure was optimized by means of a Plackett‐Burman design. Under the optimized extraction conditions (graphene oxide/Fe3O4, 20 mg; extraction time, 10 min; eluent volume, 0.5 mL ACN; elution time, 2.5 min; sample volume, 20 mL), the method rendered repeatability levels with a relative standard deviation between 9 and 20% (n = 6, 10 μg/L). Methodological limits of detection ranged from 0.003 to 0.1 μg/L. The linearity of the method was studied between the methodological limit of quantification and 100 μg/L, obtaining correlation coefficient values between 0.990 and 0.999. The applicability of the method was assessed by analyzing drinking, river and wastewater samples. Relative recovery values ranged between 70 and 120% (1 and 60 μg/L spiking level) showing that the matrix had a negligible effect on extraction. Finally, the greenness of this method was confirmed by the semiquantitative Eco‐Scale metrics. The authors would like to thank “Vicerrectorado de Investigación y Transferencia de Conocimiento” of the University of Alicante (UAUSTI16-04), the Ministry of Science and Innovation of Spain (project no. CTQ2011-23968), the Ministry of Economy, Industry and Competitiveness of Spain (project no. CTQ2016-79991-R, AEI/FEDER, UE) for the financial support. L. Costa thanks the Capes Foundation within the Ministry of Education in Brazil (Process 99999.012013/2013-07).

A new portable electrochemical sensor based on 4-aminobenzoic acid-modified herringbone carbon nanotubes (hCNTs-4ABA/Au-IDA) has been developed for the simultaneous determination of ascorbic acid (AA) and uric acid (UA) in physiological fluids. AA and UA were quantified by chronoamperometry at 0.1 and 0.32 V, respectively, in phosphate buffer solution (PBS 0.25 M, pH 7.0). Significant results were obtained for the separate quantification of AA and UA, with a limit of detection (LOD) of 0.65 μM for both analytes, and sensitivities of (9.0 ± 0.4) A g−1 mM−1 and (8.8 ± 0.3) A g−1 mM−1 for AA and UA, respectively. Repeatability was studied at 50 μM for AA and UA, providing relative standard deviations (RSD) lower than 9%. Additions of glucose, dopamine and epinephrine did not interfere with the AA and UA determination. Furthermore, UA did not interfere with AA determination at 0.1 V, although AA additions increased the current recorded at 0.32 V. The method has been successfully applied to human urine, perspiration and serum samples, without significant matrix effects, which allows for the use of an external calibration and the analysis of all the matrices investigated. This work is supported by the Generalitat Valenciana (Prometeo2013/038) and by the Ministerio de Economia y Competitividad (MAT2016–76595-R). A. Abellán also thanks the Generalitat Valenciana for her fellowship.

A simple, fast, sensitive and green pretreatment method for determination of Cd, Co, Hg, Ni, Pb and V in oral and parenteral drug samples using inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. According to United States Pharmacopoeia (USP), those metals must be reported in all pharmaceutical products for quality control evaluation (i.e., elemental impurities from classes 1 and 2A of USP Chapter 232). To improve the analytical capabilities of ICP OES, a dispersive liquid-liquid microextraction (DLLME) has performed using a safe, cheap and biodegradable deep eutectic solvent (DES) as extractant solvent (a mixture of 2:1 molar ratio of DL-menthol and decanoic acid). Seven parameters affecting the microextraction efficiency have carefully optimized by multivariate analysis. Under optimized conditions, the DES-based DLLME-ICP OES procedure improved limit of quantitation (LOQ) values on range from 12 to 85-fold and afforded an enrichment factor on average 60-times higher than those obtained to direct ICP OES analysis. Consequently, LOQ values for Cd, Co, Hg, Ni, Pb and V have been on average 10-times lower than target limits recommended for drugs from parenteral route of administration. Trueness has evaluated by addition and recovery experiments following USP recommendations for three oral drug samples in liquid dosage form and three parenteral drugs. Recovery and RSD values have been within the range of 90-109% and 1-6%, respectively. All analytes were below the repectives LOQ values, hence, lower than the limits proposed by USP Chapter 232. The authors are grateful to the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, grants no. 141634/2017-0, 202722/2019-8, 305201/2018-2 and 428558/2018-6), the Ministry of Economy and Competitiveness of Spain (PGC2018-096616-B-I00) the Regional Government of Valencia (Spain) (PROMETEO/2018/087, ACIF/2020/186), and University of Alicante (VIGROB-316FI) for the financial support, Agilent Technologies Inc. for the loan of the ICP OES spectrometer, and Ingeniatrics for the OneNeb® Series 2 provided. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001. The authors extend their appreciation to Ministry of Science, Innovation and Universities for granting the Spanish Network of Excellence in Sample Preparation (RED2018-102522-T). This article is based upon work from the Sample Preparation Study Group and Network, supported by the Division of Analytical Chemistry of the European Chemical Society.

Complexation-mediated electromembrane extraction (EME) of highly polar basic drugs (log P < −1) was investigated for the first time with the catecholamines epinephrine, norepinephrine, and dopamine as model analytes. The model analytes were extracted as cationic species from urine samples (pH 4), through a supported liquid membrane (SLM) comprising 25 mM 4-(trifluoromethyl)phenylboronic acid (TFPBA) in bis(2-ethylhexyl) phosphite (DEHPi), and into 20 mM formic acid as acceptor solution. EME was performed for 15 min, and 50 V was used as extraction voltage across the SLM. TFPBA served as complexation reagent, and selectively formed boronate esters by reversible covalent binding with the model analytes at the sample/SLM interface. This enhanced the mass transfer of the highly polar model analytes across the SLM, and EME of basic drugs with log P in the range −1 to −2 was shown for the first time. Meanwhile, most matrix components in urine were unable to pass the SLM. Thus, the proposed concept provided highly efficient sample clean-up and the system current across the SLM was kept below 50 μA. Finally, the complexation-mediated EME concept was combined with ultra-high performance liquid chromatography coupled to tandem mass spectrometry and evaluated for quantification of epinephrine and dopamine. Standard addition calibration was applied to a pooled human urine sample. Calibration curves using standards between 25 and 125 μg L−1 gave a high level of linearity with a correlation coefficient of 0.990 for epinephrine and 0.996 for dopamine (N = 5). The limit of detection, calculated as three times signal-to-noise ratio, was 5.0 μg L−1 for epinephrine and 1.8 μg L−1 for dopamine. The repeatability of the method, expressed as coefficient of variation, was 13% (n = 5). The proposed method was finally applied for the analysis of spiked pooled human urine sample, obtaining relative recoveries of 91 and 117% for epinephrine and dopamine, respectively. The authors would like to thank the Spanish Ministry of Science and Innovation (project n. CTQ2011-23968) and Generalitat Valenciana (Spain) (projects n. GVA/2014/096 and PROMETEO/2013/038) for the financial support. E. Fernández thanks Spanish Ministry of Education for her FPU grant (FPU13/03125) and mobility grant (EST15/00074).

Magnetic dispersive solid-phase extraction (MDSPE) is combined with electrochemical detection by using a screen-printed carbon electrode modified with gold nanoparticles to determine lead(II). A zeolite-based magnetic composite was used as sorbent during sample preparation, thus combining the unique properties of zeolites as sorbent materials with the remarkable advantages provided by magnetic materials. Three different zeolite-based magnetic composites were initially investigated and characterized. ZSM-5/Fe2O3 treated with HNO3 (ZSM-5/Fe2O3(tr)) was finally selected as sorbent. Lead was extracted from urine samples using ZSM-5/Fe2O3(tr). After extraction, the phases were separated by using an external magnet. Subsequently, the magnetic composite carrying the analyte was directly deposited onto the working electrode of a modified screen-printed carbon electrode for final electrochemical detection. Thereby, the elution and detection of Pb(II) were carried out in a single step. A multivariate approach was employed to optimize the experimental parameters affecting extraction. Under optimized conditions and at a typical working potential of −0.23 V (vs. Ag pseudo-reference electrode), response is linear in the 0 to 25 μg L−1 Pb(II) concentration range. The empirical limit of detection ranged from 1.0 to 2.0 μg L−1. The method was used to analyze Pb(II)-spiked urine samples, and apparent recoveries ranged between 99 and 107%, with coefficients of variation of

A new multinebulizer has been employed for wear metal (e.g., Cd, Cr, Cu, Fe, Mn, Ni, and Pb) determination in used lubricating oils. To this end, a multinebulizer-based analytical methodology combined with on-line standard dilution analysis (on-line SDA) and inductively coupled plasma optical emission spectrometry (ICP OES) (multinebulizer/SDA/ICP OES) has been proposed, which is able to overcome typical limitations related to organic sample analysis by ICP-based techniques. This is accomplished by the simultaneous introduction of organic samples and aqueous calibration standards, with a minimal sample pretreatment (i.e., dilution). The multinebulizer/SDA/ICP OES combination allows the determination of Cd, Cr, Cu, Fe, Mn, Ni and Pb in used lubricating oils with a limit of detection of 20, 10, 6, 20, 4, 30 and 200 ng g−1, respectively. The subsequent analysis of spiked commercial lubricating oil samples has led to recovery values which range from 91 to 108%. The efficiency of the proposed methodology has been checked by comparing its results with values obtained with conventional standard addition calibration and both limits of detection and recovery values were of the same order of magnitude. The proposed analytical methodology has the main advantage of ease of operation, as time and cost of analysis are reduced and the use of organic calibration standards is also avoided. Hence, the synergistic association multinebulizer/SDA is a simple, fast, relatively economic, environmentally friendly, direct and reliable method of wear metal monitoring in used lubricating oils by ICP OES. The authors would like to thank the Ministry of Economy and Competitiveness of Spain (project no. CTQ2016-79991-R, AEI/FEDER, UE) for the financial support, Agilent Technologies Inc. for the loan of the ICP OES spectrometer, and Ingeniatrics for the MultiNeb® provided.

The continuous release of anthropogenic pollutants into marine environment increases the needs for the development of analytical procedures for their accurate determination in many sample types. Sound strategies for seafood safety monitoring call for measurement systems capable of producing comparable analytical results with demonstrated quality. Method validation, traceability, and uncertainty of analytical results are the three milestones to assess data quality. Some trace elements are essential for biological structures, but they can become toxic at concentrations beyond those necessary for their functions; others are toxic even at very low levels. Their accurate determination in reference samples serves as an important step in seafood safety control and pollution monitoring. Isotope dilution inductively coupled plasma-mass spectrometry (ID ICP-MS) has been applied for the determination of the total mass fractions of five trace elements (Cd, Cu, Hg, Pb, and Zn) and methyl mercury (MeHg) in marine biota candidate reference material IAEA-476. Because of the complex matrix of the sample and the expected spectral interferences, special care was taken for the validation of the applied methodology, particularly for its measurement step. Reference isotopic measurements were carried out by sector field inductively coupled plasma-mass spectrometer (ICP-SFMS). The entire ID ICP-SFMS measurement procedure was described by mathematical modeling and the combined uncertainty of measurement results was estimated. All factors influencing the final results and isotopic equilibrium were systematically investigated. This included the procedural blank, the moisture content in biota samples, and all factors affecting the blend ratio measurements (i.e., instrumental background, spectral interferences, dead time, mass discrimination effects, and the repeatability of measured isotope ratios). Modeling of the entire measurement procedure and the use of appropriate certified reference materials (CRM) enable to assure the traceability of obtained values to the International System of Units (SI). Finally, the developed procedure has been successfully applied in the process of the certification of the International Atomic Energy Agency (IAEA) certified reference material for trace elements and MeHg mass fractions in fish homogenate sample. The excellent agreement between obtained results in the present study and those derived from the IAEA certification campaign for trace elements and MeHg in the same sample matrix further validated the reference methods developed in the IAEA.

This review focuses on the combination of elemental detection techniques with liquid-phase microextraction (LPME), namely, single drop microextraction, hollow fiber based liquid-phase microextraction, dispersive liquid-liquid microextraction, and related techniques. General features of different microextraction procedures, historical overview and automation of LPME are described and compared, along with examples of new developments and applications presented to demonstrate its potential for trace and ultra-trace metal analysis. Furthermore, potential applications and an outlook on the combination of LPME and elemental detection techniques for inorganic analysis are presented. The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project n. CTQ2016-79991-R) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).

Gold interdigitated microelectrodes (Au-IDA) modified with either graphene flakes exfoliated using flavin mononucleotide (FMN) (Gr-FMN) or graphene flakes and platinum nanoparticles (Pt-Gr-FMN) have been studied in the oxidation of uric acid (UA). An electrochemical method for the detection and quantification of UA in phosphate buffer solution at physiological pH (PBS, 0.25 M, pH 7) in the absence and presence of ascorbic acid (AA) has been studied by cyclic voltammetry. The quantification of UA was investigated by cyclic voltammetry, presenting an oxidation peak at 0.99 V with both modified electrodes. Linearity range of 60–578 μM and 60–345 μM has been found for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA electrodes, respectively. Limits of detection of 18 μM were obtained for both electrodes, and the repeatability was studied at 177 μM providing 4% and 8% for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA, respectively. AA interference has been studied by cyclic voltammetry, showing two clearly separated oxidation peaks, at 0.99 V for UA oxidation and at 0.74 V for Gr-FMN/Au-IDA and 0.70 V for Pt-Gr-FMN/Au-IDA for AA oxidation. Linearity range has been studied in presence of 250 μM AA obtaining a working range of 60–578 μM for Gr-FMN/Au-IDA electrode and of 60–288 μM with Pt-Gr-FMN/Au-IDA electrode. Limits of detection remain at 18 μM for both electrodes and the repeatability was studied at 177 μM providing 8% and 14% for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA electrodes respectively. This work is supported by the Generalitat Valenciana (Prometeo2013/038) and by the Spanish Ministerio de Economía y Competitividad (MAT2013-42007-P). We also acknowledge partial funding of this work by Ministerio de Economía y Competitividad and the European Regional Development Fund (ERDF) through projectMAT2015-69844-R aswell as by Plan de Ciencia, Tecnología e Innovación 2013–2017 del Principado de Asturias and ERDF (project GRUPIN14-056). A. Abellán-Llobregat also thanks the Generalitat Valenciana for her fellowship and M. Ayán-Varela acknowledges his predoctoral contract (FPI) from Ministerio de Economía y Competitividad.

A novel and environment friendly analytical method is reported for total chromium determination and chromium speciation in water samples, whereby tungsten coil atomic emission spectrometry (WCAES) is combined with in situ ionic liquid formation dispersive liquid–liquid microextraction (in situ IL-DLLME). A two stage multivariate optimization approach has been developed employing a Plackett–Burman design for screening and selection of the significant factor involved in the in situ IL-DLLME procedure, which was later optimized by means of a circumscribed central composite design. The optimum conditions were complexant concentration: 0.5% (or 0.1%); complexant type: DDTC; IL anion: View the MathML sourcePF6−; [Hmim][Cl] IL amount: 60 mg; ionic strength: 0% NaCl; pH: 5 (or 2); centrifugation time: 10 min; and centrifugation speed: 1000 rpm. Under the optimized experimental conditions the method was evaluated and proper linearity was obtained with a correlation coefficient of 0.991 (5 calibration standards). Limits of detection and quantification for both chromium species were 3 and 10 µg L−1, respectively. This is a 233-fold improvement when compared with chromium determination by WCAES without using preconcentration. The repeatability of the proposed method was evaluated at two different spiking levels (10 and 50 µg L−1) obtaining coefficients of variation of 11.4% and 3.6% (n=3), respectively. A certified reference material (SRM-1643e NIST) was analyzed in order to determine the accuracy of the method for total chromium determination and 112.3% and 2.5 µg L−1 were the recovery (trueness) and standard deviation values, respectively. Tap, bottled mineral and natural mineral water samples were analyzed at 60 µg L−1 spiking level of total Cr content at two Cr(VI)/Cr(III) ratios, and relative recovery values ranged between 88% and 112% showing that the matrix has a negligible effect. To our knowledge, this is the first time that combines in situ IL-DLLME and WCAES. The authors would like to thank the Spanish Ministry of Science and Innovation (Project no. CTQ2011-23968), Spanish Ministry of Education, Culture and Sport (Project no. PHB2010-0018-PC), Generalitat Valenciana (Spain) (Project no. ACOMP/2013/072), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior in Brazil (Grant CAPES-DGU n. 243/11). L. Vidal also thanks the Spanish Ministry of Education, Culture and Sport for her travel Grant (HBP-2010-0030) and S.G. Silva is grateful to the Grant 2011/13288-7, São Paulo Research Foundation (FAPESP).

A novel, simple, fast, sensitive and environmentally friendly approach is presented to determine cadmium in urine samples, combining magnetic dispersive solid-phase extraction (MDSPE) for sample preparation and screen-printed carbon electrodes (SPCEs) for square-wave anodic stripping voltammetry. This association involves the miniaturization of sample preparation and measurement process. Firstly, cadmium was extracted directly from urine samples employing a ZSM-5/Fe2O3, then, the composite enriched with cadmium was deposited onto the SPCE and finally covered with a suitable electrolyte for electrochemical detection. Thereby, the elution and detection of cadmium were carried out in a single step. To optimize experimental parameters affecting MDSPE, a two-step multivariate strategy has been employed. The method has been evaluated under optimized extraction/elution conditions (i.e., type of sorbent, ZSM-5/Fe2O3; amount of sorbent, 10 mg; sample pH, 6.8; extraction time, 5.5 min; and HCl concentration, 0.5 M) using standard addition calibration. Standard addition calibration curves gave a good linearity in the range from 0 to 30 μg L−1 with correlation coefficients ranging from 0.997 to 0.998 (N = 7). The limit of detection, evaluated empirically and statistically, ranged from 0.5 to 1.0 μg L−1 and from 0.4 to 0.8 μg L−1, respectively, which are lower than the threshold level established by the Ministry of Labour and Social Affairs (Spain) and World Health Organization for normal cadmium content in urine (i.e., 3.4 and 4.0 μg L−1, respectively). The repeatability of the proposed method was evaluated at 5 and 20 μg L−1 spiking levels obtaining coefficients of variation ranged between 12 and 15% (n = 6). A certified reference material (REC-8848/Level II) was analyzed to assess method accuracy finding 92% and 1.3 μg L−1 as the recovery (trueness) and standard deviation values, respectively. Finally, the method was applied to spiked urine samples, obtaining good agreement between spiked and found concentrations (recovery ranged from 89 to 98% and CV values ranged from 7% to 14%). Therefore, this is a new and successful contribution to the portable total analytical systems. The authors would like to thank the Generalitat Valenciana (Spain) (project n. PROMETEO/2018/087) and the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project n. CTQ2016-79991-R) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).

Zeolites are ordered crystalline materials with a promising performance for a wide range of applications such as catalysis, petrochemistry, environmental remediation, and medicine, but have scarcely been evaluated in Analytical Chemistry. Their unique and fascinating properties such as their high surface area, high adsorption capacity and molecular selectivity, chemical and thermal stability, ion-exchange capacity, low cost extraction and synthesis, and their easy modification, which provides a wide range of zeolite-based materials, make zeolites potential sorbents for extraction procedures. Therefore, in this review, we provide an overview of the current status of zeolites and zeolite-based materials used in extraction and microextraction techniques with reference to recent applications and highlight some of the novel advances. The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project no. CTQ2016-79991-R) for financial support. P. Baile also thanks the Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589).

In this work, the combination of dispersive micro solid-phase extraction (DµSPE) with laser-induced breakdown spectroscopy (LIBS) was evaluated for simultaneous preconcentration and detection of Zn, Cd, Mn, Ni, Cr and Pb in aqueous samples. Two adsorbent materials were tested in the microextraction step, namely graphene oxide and activated carbon. In both cases, the microextraction process consisted in the dispersion of a small quantity of adsorbent in the sample solution containing the analytes. However, while the use of activated carbon required a previous chelation of the metals, this step was avoided with the use of graphene oxide. After extraction, the analytes retained in the adsorbents were analysed by LIBS. Several experimental factors affecting the extraction of the metals (adsorbent amount, pH and extraction time) were optimized by means of the traditional univariate approach. Under optimum microextraction conditions, the analytical features of the proposed DµSPE-LIBS methods were assessed, leading to limits of detection below 100 µg kg−1 and 50 µg kg−1 with the use of activated carbon and graphene oxide, respectively, as adsorbents in the DµSPE process. Trueness evaluation of the most sensitive procedure was carried out by spike and recovery experiments in a real sample of tap water, leading to recovery values in the range 98–110%. This work was supported by the Spanish Ministry of Economy and Competitiveness, (Spain) (Project no. CTQ2016-79991-R and fellowship number BES-2012-058759 (FPI-MICINN)); the Regional Government of Valencia (Spain) (Project no. PROMETEO/2013/038); and the University of Alicante, (Spain) (Grant no. UAUSTI16-04).

A rapid and portable analytical methodology has been developed for ascorbic acid (Vitamin C) quantification from aqueous samples using a spectrometric smartphone-based system for the first time. The method employs point-of-use approaches both for sample preparation and sample measurement, demonstrating the capability for mobile quality control of pharmaceutical and food products. Our approach utilizes an oxidation–reduction reaction between ascorbic acid and methylene blue, followed by a dispersive liquid–liquid microextraction (DLLME) to extract the aqueous-phase methylene blue into organic media. Then, a back-extraction procedure is employed to transfer the methylene blue to aqueous media, followed by analysis of the sample’s absorption spectrum using the spectrometric smartphone-based system. The DLLME and back-extraction procedures are optimized by use of a two-step multivariate optimization strategy. Finally, vitamin C supplements and orange juice are used as real-world samples to assess the applicability of the smartphone-based method, which is successfully compared with the standard laboratory-based approach. We would like to acknowledge the National Science Foundation for their support of this work via Grant no. CBET 12-64377. M.A.A. is grateful to Generalitat Valenciana (Spain) (APOSTD/2016/076) for his Post-Doctoral fellowship and the financial support from the European Social Fund (ESF). K.D.L. is supported by a Ruth L. Kirschstein Pre-Doctoral Fellowship (NIH F30AI122925).

The purpose of this work is to present a simple, fast, cost effective and environmentally friendly magnetic dispersive solid-phase microextraction (MDSPME) method, employing a composite based on ZSM-5 zeolite decorated with iron oxide magnetic nanoparticles (i.e., ZSM-5/Fe2O3) as a valuable sorbent, for the simultaneous separation and preconcentration of cadmium (Cd), mercury (Hg) and lead (Pb) from urine samples for subsequent measurement by inductively coupled plasma optical emission spectrometry. The composite was first saturated with zinc and then modified with a hexadecyltrimethylammonium bromide surfactant and sodium diethyldithiocarbamate trihydrate chelating agent. A two-step multivariate strategy, using Plackett–Burman and circumscribed central composite designs, has been employed to optimize experimental parameters affecting MDSPME. The method has been evaluated under optimized extraction conditions (i.e., amount of sorbent, 50 mg; sample pH, 4.0; extraction time, 3 min; eluent solvent, nitric acid; eluent solvent volume, 432 μL; eluent solvent concentration, 11.8 M and elution time, 2 min) using standard addition calibration. Calibration curves using standards between 0 and 100 μg L−1 gave a good linearity with correlation coefficient values ranging from 0.998 to 0.9997 for Cd, from 0.998 to 0.9998 for Hg and from 0.9996 to 0.9999 for Pb (N = 8). The repeatability of the method has been evaluated at 3 and 50 μg L−1 obtaining coefficients of variation between 2 and 5% (n = 6). The limit of detection values ranged from 0.15 to 0.20 μg L−1 for Cd, from 0.42 to 0.73 μg L−1 for Hg and from 0.23 to 0.39 μg L−1 for Pb. These values satisfy the threshold limit (3.4 μg L−1 for Cd, 10.0 μg L−1 for Hg and 85.0 μg L−1 for Pb) established by the Ministry of Labour and Social Affairs (Spain) for normal content of these metals in human urine and by the World Health Organization for normal mercury content in urine (i.e., 10 μg L−1). Finally, three urine samples were used to assess the applicability of the developed procedure. Recovery values ranged between 87 and 107% showing negligible matrix effects. The authors would like to thank the Spanish Ministry of Science and Innovation (project n. CTQ2011-23968) and the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project no. CTQ2016-79991 R) for the financial support, and Agilent Technologies Inc. for the loan of the ICPOES spectrometer. P. Baile also thanks the Ministry of Education for her FPU grant (FPU14/04589).

A microwave-assisted extraction (MAE) procedure to isolate phenolic compounds from almond skin byproducts was optimized. A three-level, three-factor Box–Behnken design was used to evaluate the effect of almond skin weight, microwave power, and irradiation time on total phenolic content (TPC) and antioxidant activity (DPPH). Almond skin weight was the most important parameter in the studied responses. The best extraction was achieved using 4 g, 60 s, 100 W, and 60 mL of 70% (v/v) ethanol. TPC, antioxidant activity (DPPH, FRAP), and chemical composition (HPLC-DAD-ESI-MS/MS) were determined by using the optimized method from seven different almond cultivars. Successful discrimination was obtained for all cultivars by using multivariate linear discriminant analysis (LDA), suggesting the influence of cultivar type on polyphenol content and antioxidant activity. The results show the potential of almond skin as a natural source of phenolics and the effectiveness of MAE for the reutilization of these byproducts. We acknowledge the Spanish Ministry of Economy and Competitiveness for financial support (MAT-2011-28468-C02-01). A.V. thanks Conselleria de Educación (Spain) for ACIF/2010/172 Predoctoral Research Training Grant.

An array of gold interdigitated microelectrodes (Au-IDA) has been modified by casting herringbone carbon nanotubes (hCNTs) producing a new electrochemical sensor suitable for the simultaneous determination of ascorbic acid (AA) and uric acid (UA) in PBS (0.25 M, pH 7.0). The sensor showed good electrocatalytic properties for both analytes with low working potentials, linear ranges between 0 and 600 μM for AA, and between 0 and 420 μM for UA. The empirical limits of detection (LODs) and the limits of quantification (LOQs) for both analytes were 15 μM and 50 μM, respectively. Moreover, UA does not interfere in the measurement of AA and vice versa. Furthermore, the presence of common analytes in physiological fluids as glucose, dopamine and epinephrine do not interfere in the quantification neither AA nor UA. This work is supported by the Ministerio de Economía y Competitividad (MAT2016-76595-R) and FEDER. A. Abellán also thanks the Generalitat Valenciana for her fellowship.

A new, fast, easy to handle, and environmentally friendly magnetic headspace single-drop microextraction (Mag-HS-SDME) based on a magnetic ionic liquid (MIL) as an extractant solvent is presented. A small drop of the MIL 1-ethyl-3-methylimidazolium tetraisothiocyanatocobaltate(II) ([Emim]2[Co(NCS)4]) is located on one end of a small neodymium magnet to extract nine chlorobenzenes (1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,4,5-tetrachlorobenzene, and pentachlorobenzene) as model analytes from water samples prior to thermal desorption-gas chromatography-mass spectrometry determination. A multivariate optimization strategy was employed to optimize experimental parameters affecting Mag-HS-SDME. The method was evaluated under optimized extraction conditions (i.e., sample volume, 20 mL; MIL volume, 1 μL; extraction time, 10 min; stirring speed, 1500 rpm; and ionic strength, 15% NaCl (w/v)), obtaining a linear response from 0.05 to 5 μg L−1 for all analytes. The repeatability of the proposed method was evaluated at 0.7 and 3 μg L−1 spiking levels and coefficients of variation ranged between 3 and 18% (n = 3). Limits of detection were in the order of nanograms per liter ranging from 4 ng L−1 for 1,4-dichlorobenzene and 1,2,3,4-tetrachlorobenzene to 8 ng L−1 for 1,2,4,5-tetrachlorobenzene. Finally, tap water, pond water, and wastewater were selected as real water samples to assess the applicability of the method. Relative recoveries varied between 82 and 114% showing negligible matrix effects. The authors would like to thank Vicerrectorado de Investigación y Transferencia del Conocimiento of the University of Alicante (UAUSTI16-04), Generalitat Valenciana (project nos. GVA/2014/096 and PROMETEO/2013/038), and Ministerio de Economía, Industria y Competitividad (project no. CTQ2016-79991-R, AEI/FEDER, UE) for the financial support. E. Fernández thanks Ministerio de Educación for her FPU grant (FPU13/03125).

In this study, an analytical methodology based on a combination of dispersive liquid–liquid microextraction with laser-induced breakdown spectrometry was evaluated for simultaneous pre-concentration, speciation and detection of Cr. The microextraction procedure was based on the injection of appropriated quantities of 1-undecanol and ethanol into a sample solution containing the complexes formed between Cr(VI) and diethyldithiocarbamate (DDTC). The main experimental factors affecting the complexation and the extraction of metal (pH, DDTC concentration, extractant and volume of disperser solvents) were optimized using a multivariate analysis consisting of two steps: a Plackett–Burman design followed by a Circumscribed Central Composite Design (CCCD). Under optimum microextraction conditions, the analytical figures of merit of the proposed methodology were assessed. The method was finally applied to the analysis of a certified reference material hard drinking water (ERM® CA011a), yielding results in good agreement with the certified value. National Council for Scientific and Technological Development (Brazil) (CNPq - Science without Borders project no. 245782/2012-5) and São Paulo Foundation Research (FAPESP project no. 2011/19730-3) are acknowledged. This study has been supported by the Government of Spain (CTQ2011-23968) and the Regional Government of Valencia (Spain) (ACOMP/2013/072).

In this work, a new and simple analytical methodology based on in-chamber chemical vapor generation has been developed for the spectrochemical analysis of commercial fuel samples. A multiple nebulizer with three nebulization units has been employed for this purpose: One unit was used for sample introduction, while the other two were used for the necessary reagent introduction. In this way, the aerosols were mixed inside the spray chamber. Through this method, analyte transport and, therefore, sensitivity are improved in inductively coupled plasma-optical emission spectrometry. The factors (i.e., variables), influencing chemical vapor generation, have been optimized using a multivariate approach. Under optimum chemical vapor generation conditions ([NaBH4] = 1.39%, [HCl] = 2.97 M, total liquid flow = 936 μL min−1), the proposed sample introduction system allowed the determination of arsenic, selenium, and mercury up to 5 μg g−1 with a limit of detection of 25, 140, and 13 μg kg−1, respectively. Analyzing spiked commercial fuel samples, recovery values obtained were between 96 and 113%, and expanded uncertainty values ranged from 4 to 16%. The most striking practical conclusion of this investigation is that no carbon deposit appears on the plasma torch after extended periods of working. The authors would like to thank the Spanish Ministry of Science and Innovation (project n. CTQ2011-23968), the Spanish Ministry of Economy, Industry and Competitiveness (project n. CTQ2016-79991-R) (AEI/FEDER, UE) and Generalitat Valenciana (Spain) (project n. PROMETEO/2013/038) for the financial support, and Agilent Technologies Inc. for the loan of the ICP OES spectrometer.

A novel approach is presented to determine hydrophilic phenols in olive oil samples, employing vortex-assisted reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) for sample preparation and screen-printed carbon electrodes for voltammetric analysis. The oxidation of oleuropein, hydroxytyrosol, caffeic acid, ferulic acid and tyrosol was investigated, being caffeic acid and tyrosol selected for quantification. A matrix-matching calibration using sunflower oil as analyte-free sample diluted with hexane was employed to compensate matrix effects. Samples were analyzed under optimized RP-DLLME conditions, i.e., extractant phase, 1 M HCl; extractant volume, 100 µL; extraction time, 2 min; centrifugation time, 10 min; centrifugation speed, 4000 rpm. The working range showed a good linearity between 0.075 and 2.5 mg L−1 (r = 0.998, N = 7) for caffeic acid, and between 0.075 and 3 mg L−1 (r = 0.999, N = 8) for tyrosol. The methodological limit of detection was empirically established at 0.022 mg L−1 for both analytes, which is significantly lower than average contents found in olive oil samples. The repeatability was evaluated at two different spiking levels (i.e., 0.5 mg L−1 and 2 mg L−1) and coefficients of variation ranged from 8% to 11% (n = 5). The applicability of the proposed method was tested in olive oil samples of different quality (i.e., refined olive oil, virgin olive oil and extra virgin olive oil). Relative recoveries varied between 83% and 108% showing negligible matrix effects. Finally, fifteen samples were analyzed by the proposed method and a high correlation with the traditional Folin-Ciocalteu spectrophotometric method was obtained. Thereafter, the concentrations of the fifteen oil samples were employed as input variables in linear discriminant analysis in order to distinguish between olive oils of different quality. The authors would like to thank Spanish Ministry of Science and Innovation (Project no. CTQ2011-23968), Spanish Ministry of Economy, Industry and Competitiveness (Project no. CTQ2016-79991-R, AEI/FEDER, UE) and Generalitat Valenciana (Spain) (Projects n. GVA/2014/096 and PROMETEO/2013/038) for the financial support. E. Fernández also thanks Spanish Ministry of Education for her FPU grant (FPU13/03125).

This study presents a new, user-friendly, cost-effective and portable headspace solid-phase extraction technique based on graphene oxide decorated with iron oxide magnetic nanoparticles as sorbent, located on one end of a small neodymium magnet. Hence, the new headspace solid-phase extraction technique has been called Magnetic Headspace Adsorptive Extraction (Mag-HSAE). In order to assess Mag-HSAE technique applicability to model analytes, some chlorobenzenes were extracted from water samples prior to gas chromatography-mass spectrometry determination. A multivariate approach was employed to optimize the experimental parameters affecting Mag-HSAE. The method was evaluated under optimized extraction conditions (i.e., sample volume, 20 mL; extraction time, 30 min; sorbent amount, 10 mg; stirring speed, 1500 rpm, and ionic strength, non-significant), obtaining a linear response from 0.5 to 100 ng L−1 for 1,3-DCB, 1,4-DCB, 1,2-DCB, 1,3,5-TCB, 1,2,4-TCB and 1,2,3-TCB; from 0.5 to 75 ng L−1 for 1,2,4,5-TeCB, and PeCB; and from 1 to 75 ng L−1 for 1,2,3,4-TeCB. The repeatability of the proposed method was evaluated at 10 ng L−1 and 50 ng L−1 spiking levels, and coefficients of variation ranged between 1.5 and 9.5% (n = 5). Limits of detection values were found between 93 and 301 pg L−1. Finally, tap, mineral and effluent water were selected as real water samples to assess method applicability. Relative recoveries varied between 86 and 110% showing negligible matrix effects. The authors would like to thank the Spanish Ministry of Science and Innovation (project n. CTQ2011-23968), Generalitat Valenciana (project n. PROMETEO/2013/038) for the financial support. M. Ahmadi would like to thank Iranian Ministry of Science, Research, and Technology for the travel grant. E. Fernández thanks Spanish Ministry of Education for her FPU grant (FPU13/03125).

A fast, simple, economical, and environmentally friendly magnetic solid-phase extraction (MSPE) procedure has been developed to preconcentrate 2,4,6-trinitrotoluene (TNT) from water samples prior to determination by liquid chromatography-UV-Vis employing graphene oxide/Fe3O4 nanocomposite as sorbent. The nanocomposite synthesis was investigated, and the MSPE was optimized by a multivariate approach. The optimum MSPE conditions were 40 mg of nanocomposite, 10 min of vortex extraction, 1 mL of acetonitrile as eluent, and 6 min of desorption in an ultrasonic bath. Under the optimized experimental conditions, the method was evaluated to obtain a preconcentration factor of 153. The linearity of the method was studied from 1 to 100 μg L−1 (N = 5), obtaining a correlation coefficient of 0.994. The relative standard deviation and limit of detection were found to be 12% (n = 6, 10 μg L−1) and 0.3 μg L−1, respectively. The applicability of the method was investigated, analyzing three types of water samples (i.e., reservoir and drinking water and effluent wastewater) and recovery values ranged between 87 and 120% (50 μg L−1 spiking level), showing that the matrix had a negligible effect upon extraction. Finally, the semiquantitative Eco-Scale metrics confirmed the greenness of the developed method. The authors would like to thank the Ministry of Science and Innovation of Spain (project no. CTQ2011-23968) for the financial support and L. Costa thanks the Capes Foundation within the Ministry of Education in Brazil (Process 12013/13-7).

An electrochemical sensor based on graphene oxide decorated with gold nanoparticles has been prepared for the simultaneous quantification of uric acid (UA) and ascorbic acid (AA) in urine samples. The gold interdigitated microelectrodes array (Au-IDA) has been modified using graphene oxide doped with gold nanoparticles (AuNPs-GO/Au-IDA), which was characterized by TEM, FE-SEM, XPS and cyclic voltammetry. Excellent results were obtained for the separate quantification of UA and AA by chronoamperometry. The electrochemical sensor exhibits limits of detection (LODs) of 1.4 μM and 0.62 μM for AA and UA, respectively, limits of quantification (LOQs) of 4.6 μM (AA) and 2.0 μM (UA), and the working ranges obtained were between 4.6 μM and 193 μM for AA and between 2 μM and 1.05 mM for UA. The repeatability was studied at 20 μM providing coefficients of variation of 16% for AA and 13% for UA. Moreover, UA does not interfere in the measurement of AA and viceversa (provided that the concentration of UA is equal to or higher than 450 μM in the latter case). For lower concentrations of UA, an easy and fast strategy to quantify both analytes is presented. The good electrocatalytic activity achieved with this material makes it useful for the quantification of AA and UA in biological fluids. Other analytes like glucose, dopamine and epinephrine have been investigated. The results allow us to conclude that they do not interfere in the quantification of AA and UA in PBS (0.25 M, pH 7.0). Human urine samples have been analyzed using the method proposed, contaning AA and UA concentration levels of (0.588 ± 0.002) mM and (1.43 ± 0.02) mM, respectively, which are in the concentration range of these analytes in urine samples for healthy people. This work is supported by the Generalitat Valenciana (Prometeo2013/038 and PROMETEOII/2014/010) and by the Ministerio de Economia y Competitividad (MAT201676595-R). A. Abellán-Llobregat also thanks the Generalitat Valenciana for her fellowship.

Here we present two types of all-printable, highly stretchable, and inexpensive devices based on platinum (Pt)-decorated graphite for glucose determination in physiological fluids. Said devices are: a non-enzymatic sensor and an enzymatic biosensor, the latter showing promising results. Glucose has been quantified by measuring hydrogen peroxide (H2O2) reduction by chronoamperometry at −0.35 V (vs pseudo-Ag/AgCl) using glucose oxidase immobilized on Pt-decorated graphite. The sensor performs well for the quantification of glucose in phosphate buffer solution (0.25 M PBS, pH 7.0), with a linear range between 0 mM and 0.9 mM, high sensitivity and selectivity, and a low limit of detection (LOD). Thus, it provides an alternative non-invasive and on-body quantification of glucose levels in human perspiration. This biosensor has been successfully applied on real human perspiration samples and results also show a significant correlation between glucose concentration in perspiration and glucose concentration in blood measured by a commercial glucose meter. This work is supported by the Generalitat Valenciana (Prometeo2013/038), by the Ministerio de Economia y Competitividad (MAT2016-76595-R), and the U.S. National Institute of Biomedical Imaging and Bioengineering of NIH (R21EB019698). A. Abellán also thanks the Generalitat Valenciana for her fellowship and the Universidad de Alicante for her fellowship for a research stay in University of San Diego, California.