Analysis of benzo[a]pyrene in vegetable oils using molecularly imprinted solid phase extraction (MISPE) coupled with enzyme-linked immunosorbent assay (ELISA)

A surface-enhanced Raman scattering sensor for the detection of benzo[a]pyrene in foods based on a gold nanostars@reduced graphene oxide substrate

In this study, a simple and sensitive surface-enhanced Raman scattering (SERS) sensor based on gold nanostars@reduced graphene oxide (AuNS@rGO) was successfully developed for the detection of benzo[a]pyrene in foods. The detection strategy involved benzo[a]pyrene adsorption on reduced graphene oxide, followed SERS detection of adsorbed molecules. Owing to the large electric fields generated by the gold nanostars under laser irradiation, which greatly amplified the Raman signals of benzo[a]pyrene, very high sensitivity for the target analyte was achieved. Under optimized conditions, the SERS sensor exhibited a wide linear detection range for benzo[a]pyrene (from 0.1 μg L^-1 to 10000 μg L^-1), with a low limit of detection of 0.0028 μg L^-1. Chicken samples spiked with benzo[a]pyrene were assayed using the sensor, with recoveries ranging from 89.20% to 100.80%. The benzo[a]pyrene content in roasted mutton sample was quantified using the SERS sensor and a reversed-phase high-performance liquid chromatography method, with similar results being obtained.

Preparation of Monoclonal Antibody against Pyrene and Benzo [a]pyrene and Development of Enzyme-Linked Immunosorbent Assay for Fish, Shrimp and Crab Samples

Polycyclic aromatic hydrocarbons (PAHs) are significant environmental and food pollutants that can cause cancer. In this work, a specific monoclonal antibody (mAb) to identify pyrene (PYR) and benzo [a]pyrene (BaP) was prepared, and an indirect competitive enzyme-linked immunoassay (ic-ELISA) was established to detect PYR and BaP residues in living aquatic products for the first time. The effects of complete antigens with different coupling ratios on the production of high-sensitivity mAb was explored. Under the optimal conditions, the IC₅₀ value was 3.73 ± 0.43 µg/L (n = 5). The limits of detection (LODs) for PYR and BaP in fish, shrimp, and crab ranged from 0.43 to 0.98 µg/L. The average recoveries of the spiked samples ranged from 81.5–101.9%, and the coefficient of variation (CV) was less than 11.7%. The validation of the HPLC-FLD method indicated that the ELISA method set up in this experiment provided a trustworthy tool for PAHs residues detection in aquatic products.

Green synthesis of phloroglucinol-urotropine porous polymer: Ingenious miniaturized solid phase extraction for efficient purification and determination of polycyclic aromatic hydrocarbons in lotus roots

Polycyclic aromatic hydrocarbons (PAHs) posed a serious threat to food safety and human health due to long-term emission. In this work, a new method was established using phloroglucinol-urotropine porous polymer (PU-PP) in a pipette tip for solid phase extraction (PT-SPE) for the first time and used prior to determination of four PAHs (phenanthrene, anthracene, fluoranthene, and pyrene) in lotus roots. Synthesis of the PU-PP adsorbent was green compared with alternatives; urotropine was used as a cross-linker and ethanol-water as the solvent. PU-PP-based PT-SPE had the advantages of low solvent consumption, good purification, practicability, stability, and low-cost. The proposed pre-purification method offered low limits of detection (0.09-0.28 ng/g) and good recoveries (84.6-114.3 %, RSDs ≤ 5.6 %) for determination of the four PAHs, which were detected at trace concentrations in samples. This new method provides an alternative for monitoring trace pollutants in aquatic plant ingredients.

Simultaneous Determination of Aflatoxins and Benzo(a)pyrene in Vegetable Oils Using Humic Acid-Bonded Silica SPE HPLC–PHRED–FLD

In the present work, a rapid, accurate, and cost-effective method was developed for the simultaneous quantification of aflatoxins and benzo(a)pyrene in lipid matrices, using solid-phase extraction (SPE) via humic acid-bonded silica (HAS) sorbents, followed by high-performance liquid chromatography coupled with photochemical post-column reactor fluorescence spectroscopy (HPLC–PHRED–FLD) analysis. The major parameters of extraction efficiency and HPLC–PHRED–FLD analysis were investigated and this method was fully validated. The limits of quantification and the limits of detection were 0.05–0.30 and 0.01–0.09 µg kg⁻¹, respectively. The recoveries were 66.9%–118.4% with intra-day and inter-day precision less than 7.2%. The results of 80 oil samples from supermarkets indicated a high occurrence of BaP, and most of concentrations were within the requirements of EU and China food safety regulations. This is the first utilization of HAS–SPE HPLC–PHRED–FLD to simultaneously analyze the occurrence of aflatoxins and benzo(a)pyrene in vegetable oils.

Label-free SERS strategy for rapid detection of capsaicin for identification of waste oils

Identification of waste oils is challenging in the field of food safety due to the lack of common markers and straightforward analytical methods. Herein, we developed a novel label-free surface-enhanced Raman spectroscopy (SERS) strategy to identify waste oils using Ag nanoparticles solution (Ag NPs sol.) as a SERS substrate to significantly enhance the Raman signal of capsaicin marker molecule usually contained in the waste oils. The enhanced signal was directly detected by a portable Raman spectrometer with the limit of detection (LOD) of 2.9 μg L^-1 within 10 min. Concentration-dependent SERS investigation showed the linear relationship between the SERS signal intensity of the characteristic peaks and the concentrations of capsaicin in the range of 10-2500 μg L^-1 and the correlation coefficient was 0.9895. Our findings show the sensitivity, accessibility, and reliability of this method for the rapid identification of waste oils and furthermore for the practical applications in the field of food safety.

A gold-based strip sensor for the detection of benzo[a]pyrene in edible oils

This report describes the development of a sensitive and broadly specific indirect competitive enzyme-linked immunosorbent assay (icELISA) and a gold nanoparticle-based immunochromatographic strip (GNP-ICS) assay for the detection of benzo[a]pyrene (B[a]P), using an anti-B[a]P monoclonal antibody (mAb). A broad-specific anti-B[a]P mAb (4E8) was raised from two types of haptens, with half maximal inhibitory concentrations and limits of detection (LOD) values of 2.51 and 0.54 ng mL-1, respectively. In addition, the cross-reactivity was up to 390% with structurally related compounds. The GNP-ICS assay based on a GNP-labeled mAb showed broad specificity in the detection of B[a]P and its analogues, with cut-off and visual LOD values of 100 and 10 ng mL-1, respectively. Furthermore, the recoveries from the developed icELISA and GNP-ICS assay in edible oil samples spiked with B[a]P were validated by high-performance liquid chromatography-fluorescence detection. The results revealed that the icELISA could reliably detect B[a]P in edible oils.

A Review on the Occurrence and Analytical Determination of PAHs in Olive Oils

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental and processing contaminants, which may contaminate vegetable oils due to atmospheric fall-out or bad production practices. Due to their carcinogenic and toxic effects, surveillance schemes and mitigation strategies are needed to monitor human exposure to PAHs. In particular, due to the lipophilic nature of these substances, edible oils may present unsafe levels of these compounds. Among these, olive oil, and in particular extra virgin olive oil, is a high-value commodity, also known for its health benefits. Therefore, the occurrence of contaminants in this product is not only of health concern but also causes economic and image damage. In this review, an overview of the occurrence of PAHs in all categories of olive oil is provided, as well as a description of the official methods available and the analytical developments in the last 10 years.

Determination of benzo[α]pyrene in edible oil using tetraoxocalix[2]arene[2]triazine bonded silica SPE sorbent

Benzo[α]pyrene (BaP) is a well-known carcinogen in edible oil. In this study, a method combined solid-phase extraction (SPE) with fluorescent detection was developed using tetraoxocalix[2]arene[2]triazine sorbent (SiO₂-OCA) for the clean-up and enrichment of BaP. The interaction between SiO₂-OCA and BaP involves a donor-acceptor complex mechanism. The experimental procedure was as follows: BaP was extracted from edible oil with DMF/H₂O (9:1, v/v). Then, the ratio of DMF/H₂O was adjusted to 1:2 prior to SPE. The final concentrate was analysed using a fluorescence detector at excitation and emission wavelengths of 255 and 420 nm. The method was fully validated. The linearity was in the range of 0.1-100 μg kg^-1 with a coefficient of 0.999. The limits of detection and quantification were 0.03 and 0.1 μg kg^-1, respectively. The average recoveries were in the range of 88.0 - 122.3%. The intraday and interday precisions were 6.8% and 9.2%, respectively. Compared with other methods, the method reported in this article shows a good detection limit, high reproducibility and recovery and linearity over a broad concentration range. This established method was also applied to evaluate real samples. The concentration of six tested samples was below 5 μg kg^-1.

Ultrasensitive Detection of Capsaicin in Oil for Fast Identification of Illegal Cooking Oil by SERRS

Discrimination of illegal cooking oil is a conundrum in the fields of analytical chemistry and food safety due to complicated sample systems, lack of common targets, and stringent demand of ultrahigh detection sensitivity for corresponding analytical methods. Capsaicin, one of the exogenous molecules that is subsistent in recycled kitchen waste oils, can be regarded as a target for illegal cooking oil identification. Nowadays, tracing capsaicin in oils is implemented mainly by high-performance liquid chromatography-mass spectrometry, which displays shortcomings in high costs and incapableness for field test. Here, we established a surface-enhanced resonance Raman scattering approach to detect capsaicin and identify illegal cooking oils by means of the molecular derivatization treatment of capsaicin. This method features high detection sensitivity with the detection limit of 1.0 × 10^-8 M, rapid response (<7 min detection duration), and simplicity in sample pretreatment, which is available for fast field test of illegal cooking oils.

Rapid, efficient and selective preconcentration of benzo[a]pyrene (BaP) by molecularly imprinted composite cartridge and HPLC

In this study, cryogel-based molecularly imprinted composite cartridges were designed for the rapid, efficient, and selective preconcentration of benzo[a]pyrene (BaP) from water samples. First, a BaP-imprinted poly(2-hydroxyethyl methacrylate-N-methacryloyl-(L)-phenylalanine) composite cartridge was synthesized under semi-frozen conditions and characterized by scanning electron microscopy, elemental analysis, Fourier transform infrared spectroscopy, and swelling tests. After the optimization of preconcentration parameters, i.e., pH and initial BaP concentration, the selectivity and preconcentration efficiency, and reusability of these cartridges were also evaluated. In selectivity experiments, BaP imprinted composite cartridge exhibited binding capacities 3.09, 9.52, 8.87, and 8.77-fold higher than that of the non-imprinted composite cartridge in the presence of competitors, such as benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), indeno[1,2,3-cd]pyrene (IcdP), and 1-naphthol, respectively. The method detection limit (MDL), relative standard deviation (RSD) and preconcentration efficiency (PE) of the synthesized composite cartridge were calculated as 24.86μg/L, 1.60%, and 349.6%, respectively.

Biomimetic receptors for bioanalyte detection by quartz crystal microbalances - from molecules to cells

A universal label-free detection of bioanalytes can be performed with biomimetic quartz crystal microbalance (QCM) coatings prepared by imprinting strategies. Bulk imprinting was used to detect the endocrine disrupting chemicals (EDCs) known as estradiols. The estrogen 17β-estradiol is one of the most potent EDCs, even at very low concentrations. A highly sensitive, selective and robust QCM sensor was fabricated for real time monitoring of 17β-estradiol in water samples by using molecular imprinted polyurethane. Optimization of porogen (pyrene) and cross-linker (phloroglucinol) levels leads to improved sensitivity, selectivity and response time of the estradiol sensor. Surface imprinting of polyurethane as sensor coating also allowed us to generate interaction sites for the selective recognition of bacteria, even in a very complex mixture of interfering compounds, while they were growing from their spores in nutrient solution. A double molecular imprinting approach was followed to transfer the geometrical features of natural bacteria onto the synthetic polymer to generate biomimetic bacteria. The use of biomimetic bacteria as template makes it possible to prepare multiple sensor coatings with similar sensitivity and selectivity. Thus, cell typing, e.g., differentiation of bacteria strains, bacteria growth profile and extent of their nutrition, can be monitored by biomimetic mass sensors. Obviously, this leads to controlled cell growth in bioreactors.

Biomimetic receptors and sensors

In biomimetics, living systems are imitated to develop receptors for ions, molecules and bioparticles. The most pertinent idea is self-organization in analogy to evolution in nature, which created the key-lock principle. Today, modern science has been developing host-guest chemistry, a strategy of supramolecular chemistry for designing interactions of analytes with synthetic receptors. This can be realized, e.g., by self-assembled monolayers (SAMs) or molecular imprinting. The strategies are used for solid phase extraction (SPE), but preferably in developing recognition layers of chemical sensors.