Determination of pesticide residues in olives and olive oil by matrix solid-phase dispersion followed by gas chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry

Fluorometric Assay of Tyrosinase and Atrazine Based on the Use of Carbon Dots and the Inhibition of Tyrosinase Activity

Sensitive and convenient strategy of tyrosinase (TYR) and its inhibitor atrazine is in pressing demand for essential research as well as pragmatic application. In this work, an exquisite label-free fluorometric assay with high sensitivity, convenience and efficiency was described for detecting TYR and the herbicide atrazine on the basis of fluorescent nitrogen-doped carbon dots (CDs). The CDs were prepared via one-pot hydrothermal reaction starting from citric acid and diethylenetriamine. TYR catalyzed the oxidation of dopamine to dopaquinone derivative which could quench the fluorescence of CDs through a fluorescence resonance energy transfer (FRET) process. Thus, a sensitive and selective quantitative evaluation of TYR can be constructed on the basis of the relationship between the fluorescence of CDs and TYR activity. Atrazine, a typical inhibitor of TYR, inhibited the catalytic activity of TYR, leading to the reduced dopaquinone and the fluorescence was retained. The strategy covered a broad linear range of 0.1-150 U/mL and 4.0-80.0 nM for TYR and atrazine respectively with a low detection limit of 0.02 U/mL and 2.4 nM/mL. It is also demonstrated that the assay can be applied to detect TYR and atrazine in spiked complex real samples, which provides infinite potential in application of disease monitoring along with environmental analysis.

Hydrophobic carboxymethyl cellulose as a clean-up sorbent in the determination of nitrofuran metabolites in animal-fat samples

Hydrophobic carboxymethyl cellulose (CMC) biopolymers were fabricated for the removal of fat from food sample matrices. The hydrophobic CMCs were synthesised via the esterification of CMC with three alcohols with carbon chains of different lengths, methanol, butanol, and octadecanol, in the presence of sulfuric acid. The structure of the three synthesised hydrophobic CMCs was verified using FT-IR, and the physicochemical properties were investigated by TGA, SEM, and X-ray. Characterization confirmed the successful synthesis of the hydrophobic CMCs and that the hydrophobic groups are embedded in the sorbent biopolymer to interact with fat and reduce the fat content of the sample extract. Moreover, the performance of the fabricated hydrophobic CMCs was studied in two applications: fat removal and the determination of nitrofuran (NF) metabolites in fat samples. In the first application, excellent results were observed for fat removal; the highest percentage of fat removed from food sample extracts was 94.2% and the lowest was 88.5%. Successful results were also observed in the determination of NF metabolites in fat samples, as the final extract was clear and pure using the hydrophobic CMCs, while it was turbid for the control sample. In addition, the recovery of four NF metabolites was in the range of 97-117%. In general, the hydrophobic CMCs showed promising and satisfactory results, with CMC-C18 exhibiting the best results. The NF detection method was validated using CMC-C18 in three spiking levels; 0.5, 1.0 and 1.5 μg kg-1. The average recoveries of NF range between 83.3 to 104.3%, and the intra-day precision was determined by coefficient of variation, which was below 10% for all NF. The limit of detection and limit of quantification were between 0.6 to 0.9 and 0.20 to 0.28 μg kg-1 respectively. For linearity, the correlation coefficient (r2) was higher than 0.99 for NF metabolites. Overall, the hydrophobic CMCs can be further developed and safely used as green sorbents in food analysis applications.

Effects of additives on the performance of a laser-induced graphene sensor modified with ZrO2 nanoparticles for OP detection

In this study, a simple and portable electrochemical sensor based on laser-induced graphene (LIG) has been developed to systematically investigate the feasibility of LIG as an electrode to detect organophosphorus pesticides (OPs). It proves that the LIG-based electrode has a relatively high electrochemically active surface area (ECSA) and heterogeneous electron transfer (HET) of 0.100 cm2 and 0.000825 cm s-1, respectively. In addition, zirconium dioxide nanoparticles (ZrO2 NPs) have been modified on the electrode with three different binders, β-cyclodextrin (β-CD), chitosan (CS) and Nafion, to improve the adsorption capacity of the electrode toward OPs, and the effect of the binders on the performance of the as-fabricated sensor has been investigated in detail. The results show that β-CD increases not only the electrochemically active surface area of the electrode but also the redox peak current of methyl parathion (MP). To evaluate the sensitivity of the sensor, differential pulse voltammetry (DPV) curves have been tested in solutions containing different concentrations of MP using ZrO2-β-CD/LIG as an electrode, which shows a detection range of 5-200 ng ml-1 and a detection limit of 0.89 ng ml-1. In summary, the LIG-based sensor has a low detection limit, high sensitivity and good interference resistance, and thus has tremendous potential for the detection of pesticides in the environment.

Quantitative analysis of the minimum days of dietary survey to estimate dietary pesticide exposure: Implications for dietary pesticide sampling strategy

Populations are exposed to pesticides through diet on a daily basis. However, there is no research guiding how to evaluate dietary pesticide exposure, and researchers used 1-day, 3-days, 7-days or even longer dietary survey to evaluate without any consensus. It is important for dietary pesticide evaluation to identify the minimum survey days. To increase knowledge of this, a data combination was applied between a two-wave consecutive repeated-measures study in Baoding City and the Fifth China Total Diet Study. Further policy consistency on pesticides were evaluated to explain its credibility. We computed the sensitivity and specificity to evaluate how well different days of dietary survey classify participants with high exposure, and calculated the minimum days required to estimate the participant-specific mean at different acceptable error range. With 1 day of dietary survey, the classification sensitivity was low (<0.6) for total HCH, endosulfan, chlordane, cyhalothrin, allethrin, and prallethrin; that for the other pesticides was high sensitivity (≥0.6). Sensitivity increased as the number of days increased, and the maximum marginal sensitivity increase (≥0.039) occurred from 1 to 2 days for all pesticides except phenothrin, whose maximum marginal sensitivity increase (0.042) occurred from 2 to 3 days. The specificity increased gradually from 0.8 to 0.9 from 1 to 7 days. Under the acceptable error range of 0.5%, 3-28 days were required for participant-specific mean estimation and 1-7 days were required when acceptable error range was shrunk in 1%. Only 1 day was enough if 5% error range was acceptable. In conclusion, 3 days in the study period was cost-effective to distinguish high exposure group, and it rose to 7 when estimating participant-specific mean from a conservative perspective. This study can serve as a reference to determine the minimum survey days for epidemiological studies employing dietary surveys.

Organochlorine pesticides in vegetable oils: An overview of occurrence, toxicity, and chromatographic determination in the past twenty-two years (2000-2022)

Organochlorine pesticides (OCPs) are used globally to control pests in the food industry. However, some have been banned due to their toxicity. Although they have been banned, OCPs are still discharged into the environment and persist for long periods of time. Therefore, this review focused on the occurrence, toxicity, and chromatographic determination of OCPs in vegetable oils over the last 22 years (2000-2022) (111 references). Literature search shows that OCPs kill pests by destroying endocrine, teratogenic, neuroendocrine, immune, and reproductive systems. However, only five studies investigated the fate of OCPs in vegetable oils and the outcome revealed that some of the steps involved during oil processing introduce more OCPs. Moreover, direct chromatographic determination of OCPs was mostly performed using online LC-GC methods fitted with oven transfer adsorption desorption interface. While indirect chromatographic determination was favored by QuEChERS extraction technique, gas chromatography frequently coupled to electron capture detection (ECD), gas chromatography in selective ion monitoring mode (SIM), and gas chromatography tandem mass spectrometry (GC-MS/MS) were the most common techniques used for detection. However, the greatest challenge still faced by analytical chemists is to obtain clean extracts with acceptable extraction recoveries (70-120%). Hence, more research is still required to develop greener and selective extraction methods toward OCPs, thus improving extraction recoveries. Moreover, advanced techniques like gas chromatography high resolution mass spectrometry (GC-HRMS) must also be explored. OCPs prevalence in vegetable oils varied greatly in various countries, and concentrations of up to 1500 µg/kg were reported. Additionally, the percentage of positive samples ranged from 1.1 to 97.5% for endosulfan sulfate.

Application of Fe3O4@CNFs combined with deep eutectic solvent-based dual microextraction: a novel and green strategy for rapid determination of pesticides in edible oil samples

A novel, green, and effective strategy employing Fe₃O₄-modified carbon nanofibers (CNFs) combined with deep eutectic solvent (DES) is proposed as an extraction agent to extract five pesticides in edible oil samples via dual microextraction modes, followed by high-performance liquid chromatography for determination. The Fe₃O₄@CNFs nanomaterial and a sequence of hydrophilic DES were prepared at first and then characterized by multiple techniques. Subsequently, the extraction performance of DES and Fe₃O₄@CNFs-DES was compared and Fe₃O₄@CNFs-DES exhibited better extraction ability. After that, several influencing parameters such as the composition of DES, the amount of Fe₃O₄@CNFs-DES, the dispersion methods, and the extraction time were investigated and optimized. Eventually, Fe₃O₄@CNFs as the solid adsorbent combined with tetrabutylammonium chloride-lactic acid-based DES as the extraction solvent were selected to extract target pesticides from oil samples. The established method received good linearity in the range 25-1000 ng·g^-1. The limits of detection for all analytes were in the range 2.25-7.50 ng·mL^-1. Satisfactory recoveries of target pesticides were obtained (ranging from 82 to 117%) with a relative standard deviation of 0.26-9.46%. The proposed method has been successfully applied to the rapid detection of target pesticides in oil samples, demonstrating its great potential for quick screening and analysis.

Geographical Origin Assessment of Extra Virgin Olive Oil via NMR and MS Combined with Chemometrics as Analytical Approaches

Geographical origin assessment of extra virgin olive oil (EVOO) is recognised worldwide as raising consumers’ awareness of product authenticity and the need to protect top-quality products. The need for geographical origin assessment is also related to mandatory legislation and/or the obligations of true labelling in some countries. Nevertheless, official methods for such specific authentication of EVOOs are still missing. Among the analytical techniques useful for certification of geographical origin, nuclear magnetic resonance (NMR) and mass spectroscopy (MS), combined with chemometrics, have been widely used. This review considers published works describing the use of these analytical methods, supported by statistical protocols such as multivariate analysis (MVA), for EVOO origin assessment. The research has shown that some specific countries, generally corresponding to the main worldwide producers, are more interested than others in origin assessment and certification. Some specific producers such as Italian EVOO producers may have been focused on this area because of consumers’ interest and/or intrinsic economical value, as testified also by the national concern on the topic. Both NMR- and MS-based approaches represent a mature field where a general validation method for EVOOs geographic origin assessment could be established as a reference recognised procedure.

Comparison of Different d-SPE Sorbent Performances Based on Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) Methodology for Multiresidue Pesticide Analyses in Rapeseeds

Pesticide extraction in rapeseed samples remains a great analytical challenge due to the complexity of the matrix, which contains proteins, fatty acids, high amounts of triglycerides and cellulosic fibers. An HPLC-MS/MS method was developed for the quantification of 179 pesticides in rapeseeds. The performances of the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method were evaluated using different dispersive solid-phase extraction (d-SPE) sorbents containing common octadecylsilane silica/primary-secondary amine adsorbent (PSA/C18) and new commercialized d-SPE materials dedicated to fatty matrices (Z-Sep, Z-Sep+, and EMR-Lipid). The analytical performances of these different sorbents were compared according to the SANTE/12682/2019 document. The best results were obtained using EMR-Lipid in terms of pesticide average recoveries (103 and 70 of the 179 targeted pesticides exhibited recoveries within 70-120% and 30-70%, respectively, with low RSD values). Moreover, the limits of quantification (LOQ) range from 1.72 µg/kg to 6.39 µg/kg for 173 of the pesticides. Only the recovery for tralkoxydim at 10 μg/kg level was not satisfactory (29%). The matrix effect was evaluated and proved to be limited between -50% and 50% for 169 pesticides with this EMR-Lipid and freezing. GC-Orbitrap analyses confirmed the best efficiency of the EMR-Lipid sorbent for the purification of rapeseeds.

Quantification of pharmaceuticals in the sealant fluids of actively used waterless urinals

Prior measurements at bench scale revealed that waterless urinal cartridges containing oily sealant fluids are capable of partitioning pharmaceuticals from urine and therefore reducing their concentration in wastewater. We sought to measure pharmaceutical removal from in-use waterless urinals. We developed a method to quantify pharmaceuticals in the sealant phase, which resulted in 79 ± 30% and 71 ± 30% recovery of eight pharmaceuticals from two sealant fluids, respectively. The method was applied to sealant samples collected over three weeks from in-use waterless urinals on a university campus. Six of eight pharmaceuticals were present in the sealant samples from 1.4 µg/L to 241 µg/L. Loads of the six pharmaceuticals detected in the sealants were removed from the receiving wastewater from 0.02 µg/day to 3.4 µg/day across the sampling period. The concentration of the pharmaceuticals were similar over time, indicating rapid saturation and washout of the sealant. We also observed relatively rapid loss of sealant at maintenance intervals consistent with the manufacturer's instructions. These findings indicate that while waterless urinals do remove some pharmaceuticals from the wastewater stream, meaningful changes to wastewater concentrations will only result if the sealant fluid and/or the urinal cartridge are significantly modified. PRACTITIONER POINTS: We developed a quantification method for pharmaceuticals in oily waterless urinal sealants. Pharmaceuticals were present at relatively low concentrations in the sealant phase of two in-use waterless urinals. We identify engineering challenges that must be overcome to meaningfully reduce pharmaceutical loads in wastewater with waterless urinals.

Magnetic Ionic Liquids in Sample Preparation: Recent Advances and Future Trends

In the last decades, a myriad of materials has been synthesized and utilized for the development of sample preparation procedures. The use of their magnetic analogues has gained significant attention and many procedures have been developed using magnetic materials. In this context, the benefits of a new class of magnetic ionic liquids (MILs), as non-conventional solvents, have been reaped in sample preparation procedures. MILs combine the advantageous properties of ionic liquids along with the magnetic properties, creating an unsurpassed combination. Owing to their unique nature and inherent benefits, the number of published reports on sample preparation with MILs is increasing. This fact, along with the many different types of extraction procedures that are developed, suggests that this is a promising field of research. Advances in the field are achieved both by developing new MILs with better properties (showing either stronger response to external magnetic fields or tunable extractive properties) and by developing and/or combining methods, resulting in advanced ones. In this advancing field of research, a good understanding of the existing literature is needed. This review aims to provide a literature update on the current trends of MILs in different modes of sample preparation, along with the current limitations and the prospects of the field. The use of MILs in dispersive liquid–liquid microextraction, single drop microextraction, matrix solid-phase dispersion, etc., is discussed herein among others.

Photocatalytic Detoxification of Some Insecticides in Aqueous Media Using TiO2 Nanocatalyst

The present study was performed to fabricate a titanium dioxide (TiO2) nanocatalyst with proper characteristics for the removal of some insecticides (dimethoate and methomyl) from aqueous media. A TiO2 catalyst of regular (TiO2-commercial-/H2O2/UV) or nano (TiO2-synthesized-/H2O2/UV) size was employed as an advanced oxidation process by combining it with H2O2 under light. Moreover, the total detoxification of insecticides after treatment with the most effective system (TiO2(s)/H2O2/UV) was also investigated through exploring the biochemical alterations and histopathological changes in the liver and kidneys of the treated rats. Interestingly, the present study reported that degradation rates of the examined insecticides were faster using the TiO2 catalyst of nano size. Complete degradation of the tested insecticides (100%) was achieved under the TiO2(s)/H2O2/UV system after 320 min of irradiation. The half-life values of the tested insecticides under H2O2/TiO2(c)/UV were 43.86 and 36.28 for dimethoate and methomyl, respectively, whereas under the H2O2/TiO2(c)/UV system, the half-life values were 27.72 and 19.52 min for dimethoate and methomyl, respectively. On the other hand, no significant changes were observed in the biochemical and histopathological parameters of rats administrated with water treated with TiO2(s)/H2O2/UV compared to the control, indicating low toxicity of the TiO2 nanocatalyst-. Altogether, the advanced oxidation processes using TiO2 nanocatalyst can be considered as a promising and effective remediation technology for the complete detoxification of methomyl and dimethoate in water. However, further future research is needed to identify the possible breakdown products and to verify the safety of the used nanomaterials.

Facile and Low-Cost SPE Modification Towards Ultra-Sensitive Organophosphorus and Carbamate Pesticide Detection in Olive Oil

Despite the fact that a considerable amount of effort has been invested in the development of biosensors for the detection of pesticides, there is still a lack of a simple and low-cost platform that can reliably and sensitively detect their presence in real samples. Herein, an enzyme-based biosensor for the determination of both carbamate and organophosphorus pesticides is presented that is based on acetylcholinesterase (AChE) immobilized on commercially available screen-printed carbon electrodes (SPEs) modified with carbon black (CB), as a means to enhance their conductivity. Most interestingly, two different methodologies to deposit the enzyme onto the sensor surfaces were followed; strikingly different results were obtained depending on the family of pesticides under investigation. Furthermore, and towards the uniform application of the functionalization layer onto the SPEs’ surfaces, the laser induced forward transfer (LIFT) technique was employed in conjunction with CB functionalization, which allowed a considerable improvement of the sensor’s performance. Under the optimized conditions, the fabricated sensors can effectively detect carbofuran in a linear range from 1.1 × 10⁻⁹ to 2.3 × 10⁻⁸ mol/L, with a limit of detection equal to 0.6 × 10⁻⁹ mol/L and chlorpyrifos in a linear range from 0.7 × 10⁻⁹ up to 1.4 × 10⁻⁸ mol/L and a limit of detection 0.4 × 10⁻⁹ mol/L in buffer. The developed biosensor was also interrogated with olive oil samples, and was able to detect both pesticides at concentrations below 10 ppb, which is the maximum residue limit permitted by the European Food Safety Authority.

Nanomaterial-based immunosensors for ultrasensitive detection of pesticides/herbicides: Current status and perspectives

The increasing level of pesticides and herbicides in food and water sources is a growing threat to human health and the environment. The development of portable, sensitive, specific, simple, and cost-effective sensors is hence in high demand to avoid exposure or consumption of these chemicals through efficient monitoring of their levels in food as well as water samples. The use of nanomaterials (NMs) for the construction of an immunosensing system was demonstrated to be an efficient and effective option to realize selective sensing against pesticides/herbicides. The potential of such applications has hence been demonstrated for a variety of NMs including graphene, carbon nanotubes (CNTs), metal nanoparticles, and nano-polymers either in pristine or composite forms based on diverse sensing principles (e.g., electrochemical, optical, and quartz crystal microbalance (QCM)). This article evaluates the development, applicability, and performances of NM-based immunosensors for the measurement of pesticides and herbicides in water, food, and soil samples. The performance of all the surveyed sensors has been evaluated on the basis of key parameters, e.g., detection limit (DL), sensing range, and response time.

Dissipation and safety evaluation of afidopyropen and its metabolite residues in supervised cotton field

The novel insecticidal mechanism of afidopyropen can be substituted for traditional pesticides to control sap-sucking pests in cotton field. The data of residue amounts of afidopyropen and its metabolite M440I007 in cotton matrix and the environment soil are important to evaluate the safe use of the target compound and establish maximum residue limit (MRL). In this work, the dissipation and residue of afidopyropen and its metabolite M440I007 in cotton and field soils were investigated. The analytical methods of the target compound in cotton plants, cottonseed, crude cottonseed oil, cottonseed oil and soil were developed and quantified by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS), which satisfied the rules of pesticide residue determination. The dissipation half-lives of afidopyropen in cotton plants and soil ranged from 1 to 3 days and 4-13 days, respectively. After 14 days from the last application, the residues of afidopyropen were below 0.01 mg/kg in cottonseed and were <0.005-0.0099 mg/kg in soil, and the residues of M440I007 were below 0.02 mg/kg in cottonseed and below 0.01 mg/kg in soil. The total national estimated daily intake (NEDI) of afidopyropen was 1.41 mg and the risk quotient (RQ) was 28.0%. The results showed that the risk of application of afidopyropen with the recommended dosage was acceptable.

Electrochemical biosensor for methyl parathion based on single-walled carbon nanotube/glutaraldehyde crosslinked acetylcholinesterase-wrapped bovine serum albumin nanocomposites

Semiconducting single-walled carbon nanotubes (s-SWCNTs) have been demonstrated as an excellent material for transistors, miniaturized devices and sensors due to their high carrier mobility, stability, scattering-free ballistic transport of carriers etc. Herein, we have designed a biosensor to selectively detect methyl parathion (MP, organophosphorus pesticide) using glutaraldehyde (Glu) cross-linked with acetylcholinesterase (AChE) immobilized on s-SWCNTs wrapped with bovine serum albumin (BSA). The fabricated biosensor was characterized and confirmed by Fourier-transform infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV). In the presence of MP, the effective interaction between AChE and MP favours the accumulation of MP-AChE complex on the glassy carbon electrode (GCE) surface which reduces the electron transfer property. Based on this interaction, detection of various concentration of MP was demonstrated by SWV using BSA/AChE-Glu-s-SWCNTs composite modified electrode. The proposed biosensor exhibited a wide linear range (WLR) for MP target in 100 mM phosphate buffered saline solution (PBS) (pH 7.4) from 1 × 10^-10 M to 5 × 10^-6 M with a limit of detection (LOD) of 3.75 × 10^-11 M. In addition, the BSA/AChE-Glu-s-SWCNTs/GCE biosensor showed good repeatability and reproducibility for MP detection. Moreover, the proposed biosensor showed better electrode stability when stored at 4 °C. This new electrochemical biosensor is also exhibited high selectivity and sensitivity for MP, which made it possible to test MP in real strawberry and apple juices. Furthermore, the BSA/AChE-Glu-s-SWCNTs/GCE offered a favourable electron transfer between the acetylthiocholine chloride (ATCl) and electrode interface than BSA/AChE-s-SWCNTs/GCE, s-SWCNTs/GCE and bare GCE.

Vortex-assisted deep eutectic solvent reversed-phase liquid-liquid microextraction of triazine herbicides in edible vegetable oils

In this study, four triazine herbicides-namely, simazine, ametryn, prometryn and terbuthylazine-were separated and determined using high-performance liquid chromatography coupled with ultraviolet detector (HPLC-UVD). The deep eutectic solvent (DES) formed by tetrabutylammonium chloride ([N₄₄₄₄]Cl, TBA) and ethylene glycol (EG) was selected as the extraction solvent of vortex-assisted reversed-phase liquid-liquid microextraction (VA-RPLLME). The application of the hydrophilic DES expands the range of choice for LLME. The experimental parameters affecting the extraction recoveries, including the amount of the DES, the sample volume and the vortex time, were investigated and optimized by the design of experiments (DoE) methodology. A quadratic model, namely central composite face-centered (CCF) design featuring 20 runs was used instead of the conventional trial and error approach. Under optimum conditions, the limits of determination (LODs) of the method were 0.60-1.50 μg L^-1. The enrichment factors for the analytes ranged from 27 to 31. The extraction recoveries were in the range of 84.1-104.9%, and the intra-day, inter-day and intermediate relative standard deviations (RSDs) were less than 8.4%. Finally, the method was applied for the determination of triazine herbicides in vegetable oil samples. The obtained recoveries were in the range of 60.1-107.2% and RSDs were lower than 8.1%. In general, VA-RPLLME can be complementary to the present available methods for the determination of triazine herbicides in vegetable oil samples.

Ultrasensitive electrochemical detection of methyl parathion pesticide based on cationic water-soluble pillar[5]arene and reduced graphene nanocomposite

We report a rapid, sensitive and selective electrochemical sensor based on pillar[5]arene (CP5) reduced graphene (rGO) nanohybrid-modified glassy carbon electrode CP5-rGO/GCE for the trace detection of methyl parathion (MP) by differential pulse voltammetry (DPV) for the first time. Compared to beta-cyclodextrin (β-CD)-functionalized reduced graphene (rGO)-modified GCE β-CD-rGO/GCE, the proposed CP5-rGO/GCE sensor exhibits excellent electrochemical catalytic activity, rapid response, high sensitivity, good reproducibility and anti-interference ability towards MP. The recognition mechanism of β-CD/MP and CP5/MP was studied by 1H NMR. The results indicate a higher supramolecular recognition capability between CP5 and MP compared to that between β-CD and MP. The β-CD-rGO and CP5-rGO nano-composites were prepared via a wet chemistry approach. The resulting nano-composites have been characterized by thermogravimetric analysis (TGA), fourier transform infrared spectrometry (FTIR), charge transfer resistance (R ct) and zeta potential. The CP5-rGO/GCE combines the merits of CP5 and rGO, and is used for quantitative detection of MP. It has a low detection limit of 0.0003 μM (S/N = 3) and a linear response range of 0.001-150 μM for MP. This method has been used to detect MP in soil and waste water samples with satisfactory results. This study provides a promising electrochemical sensing platform and is a promising tool for the rapid, facile and sensitive analysis of MP.

Characterization and evaluation of phenolic profiles and color as potential discriminating features among Spanish extra virgin olive oils with protected designation of origin

Changes in phenolic profiles and color parameters can help to differentiate between extra virgin olive oils (EVOOs) with protected designation of origin (PDO). Phenolic profile characterization and CIELAB parameters determination of 9 PDO EVOOs from Spain were developed. Both properties of EVOOs are very relevant to their commercialization and increase the product value. The Serrana de Espadán olive cultivar was characterized for the first time and showed the highest pinoresinol concentrations and clarities in these olive oils, which are important values for the product image. To detect fraudulent instrumental work and implement quality control, principal component analysis (PCA) and linear discriminant analysis (LDA) were performed. EVOO geographical origin and cultivar distributions were achieved with cumulative variances of 93.4% and 92.4%, respectively. A categorization of PDO EVOOs was proposed using the following 7 phenolic compounds: phenolic alcohols (tyrosol and hydroxytyrosol), 3,4-DHPEA-EDA, 3,4-DHPEA-EA, p-HPEA-EDA, pinoresinol and total phenolic compounds.

Determination of ∆-9-Tetrahydrocannabinol (THC), 11-hydroxy-THC, 11-nor-9-carboxy-THC and Cannabidiol in Human Plasma using Gas Chromatography-Tandem Mass Spectrometry

Two marijuana compounds of particular medical interest are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). A gas chromatography-tandem mass spectrometry (GC-MS-MS) method was developed to test for CBD, THC, hydroxy-THC (OH-THC) and carboxy-THC (COOH-THC) in human plasma. Calibrators (THC and OH-THC, 0.1 to 100; CBD, 0.25 to 100; COOH-THC, 0.5-500 ng/mL) and controls (0.3, 5 and 80 ng/mL, except COOH-THC at 1.5, 25 and 400 ng/mL) were prepared in blank matrix. Deuterated (d3) internal standards were added to 1-mL samples. Preparation involved acetonitrile precipitation, liquid-liquid extraction (hexane:ethyl acetate, 9:1), and MSTFA derivatization. An Agilent 7890 A GC was interfaced with an Agilent 7000 MS Triple Quadrupole. Selected reaction monitoring was employed. Blood samples were provided from a marijuana smoking study (two participants) and a CBD ingestion study (eight participants). Three analytes with the same transitions (THC, OH-THC and COOH-THC) were chromatographically separated. Matrix selectivity studies showed endogenous chromatographic peak area ratios (PAR) at the analyte retention times were <20% of the analyte limit of quantitation PAR. The intra-assay accuracy ranged from 83.5% to 118% of target and the intra-run imprecision ranged from 2.0% to 19.1%. The inter-assay accuracy ranged from 90.3% to 104% of target and the inter-run imprecision ranged from 6.5% to 12.0%. Stability was established for 25 hours at room temperature, 207 days at -20°C, after three freeze-thaw cycles and for 26 days for rederivatized processed samples. After smoking marijuana predictable concentrations of THC, OH-THC and COOH-THC were seen; low concentrations of CBD were detected at early time points. In moderate users who had not smoked for at least 9 hours before ingesting an 800 mg oral dose of CBD, the method was sensitive enough to follow residual concentrations of THC and OH-THC; sustained COOH-THC concentrations over 50 ng/mL validated its higher analytical range.

Detection of trace levels of organophosphate pesticides using an electronic tongue based on graphene hybrid nanocomposites

Organophosphate (OP) compounds impose significant strains on public health, environmental/food safety and homeland security, once they have been widely used as pesticides and insecticides and also display potential to be employed as chemical warfare agents by terrorists. In this context, the development of sensitive and reliable chemical sensors that would allow in-situ measurements of such contaminants is highly pursued. Here we report on a free-enzyme impedimetric electronic tongue (e-tongue) used in the analysis of organophosphate pesticides comprising four sensing units based on graphene hybrid nanocomposites. The nanocomposites were prepared by reduction of graphene oxide in the presence of conducting polymers (PEDOT:PSS and polypyrrole) and gold nanoparticles (AuNPs), which were deposited by drop casting onto gold interdigitated electrodes. Impedance spectroscopy measurements were collected in triplicate for each sample analyzed, and the electrical resistance data were treated by Principal Component Analysis (PCA), revealing that the system was able to discriminate OPs at nanomolar concentrations. In addition, the electronic tongue system could detect OPs in real samples, where relations between the principal components and the variation of pesticides in a mixture were established, proving to be useful to analyze and monitor mixtures of OP pesticides. The materials employed provided sensing units with high specific surface area and high conductivity, yielding the development of a sensor with suitable stability, good reproducibility, and high sensitivity towards pesticide samples, being able to discriminate concentrations as low as 0.1nmolL^-1. Our results indicate that the e-tongue system can be used as a rapid, simple and low cost alternative in the analyses of OPs pesticide solutions below the concentration range permitted by legislation of some countries.

Pesticide residues in chicken eggs - A sample preparation methodology for analysis by gas and liquid chromatography/tandem mass spectrometry

A sample preparation method was developed for the analysis of chicken eggs to determine 97 GC and 81 LC amenable residues, including organophosphates, organochlorines, pyrethroids, triazoles, carboxyl-containing compounds, and the indicator PCBs. Hereby, considerations were given to the recoveries of the analytes, the method's suitability for routine analysis, and the assessment of the clean-up effect, for which a simple thin layer chromatography was implemented to visualize the most important lipid classes. The procedure consisted of (I) the extraction by matrix solid phase dispersion, and the clean-up by means of (II) small-scale gel permeation chromatography (GPC) and (III) two different solid phase extractions (SPE) for GC and LC amenable analytes, as well as (IV) the quantification using GC-MS/MS and LC-MS/MS. Cyclohexane/ethyl acetate was chosen as extraction solvent due to its suitability for extracting strong non-polar but also more polar analytes. The classical GPC was scaled down to ensure a 50% lower solvent consumption. The comprehensive investigation of conventional and modern zirconium-oxide-coated SPE materials resulted in the selection of octadecyl-modified silica (C18) combined with primary secondary amine using acetonitrile as elution solvent for GC amenable analytes and pure C18 in combination with acidified methanol for LC amenable pesticides. Compared to the currently established EN 1528 method the sample preparation proposed offered a higher sample throughput and a lower solvent consumption. Furthermore, for the first time the clean-up effectiveness of the sample preparation steps was documented as shown by means of thin-layer chromatography. The validation of chicken eggs proved the fulfillment of the quality control criteria for 164 of the 178 analytes tested, mostly at the lowest validated level of 5μg/kg for pesticides and 0.5μg/kg for the single indicator PCBs. However, the analysis of strongly polar analytes was still problematic, which could be attributed to the extraction and the GPC step. Nevertheless, the successful investigation of EU proficiency test materials (EUPT AO 07-09) confirmed the comparability of the results with the currently established sample preparation procedures and demonstrated the potential of the applicability of the presented method to other matrices as exemplified for lean poultry meat and fatty liquid cream.

Dispersive micro-solid-phase extraction of herbicides in vegetable oil with metal-organic framework MIL-101

Dispersive microsolid-phase extraction based on metal-organic framework has been developed and applied to the extraction of triazine and phenylurea herbicides in vegetable oils in this work. The herbicides were directly extracted with MIL-101 from diluted vegetables oils without any further cleanup. The separation and determination of herbicides were carried out on high performance liquid chromatography. The effects of experimental parameters, including volume ratio of n-hexane to oil sample, mass of MIL-101, extraction time, centrifugation time, eluting solvent, and elution time were investigated. The Student's t test was applied to evaluate the selected experimental conditions. The limits of detection for the herbicides ranged from 0.585 to 1.04 μg/L. The recoveries of the herbicides ranged from 87.3 to 107%. Our results showed that the present method is rapid, simple, and effective for extracting herbicides in vegetable oils.