Apple Juice Samples Research Articles

Synergistic SERS enhancement of NiCo-LDHs microurchins and silver nanoparticles for ultra-sensitive and reusable detection of thiabendazole

Two-dimensional layered semiconductor materials as a distinctive class of materials are comprehensively explored for widespread applications due to narrow bandgap, controllable morphology, and tunable metal cation composition. Herein, we constructed a sensing platform of surface enhanced Raman spectroscopy (SERS) by combination of nickel‑cobalt layered double hydroxide (NiCo-LDH) microurchins and plasmonic silver nanoparticles (Ag NPs) for fungicide detection of thiabendazole (TBZ). The NiCo-LDHs/Ag-NPs microcomposites consist of NiCo-LDHs microurchins having a large number of nanoneedles deposited with photoreduced Ag NPs. The SERS platform with NiCo-LDHs/Ag-NPs shows an excellent SERS performance for TBZ detection, including an ultra-low detection limit of 1.49 × 10−11 M, a sublime enhancement factor of 1.71 × 109, high uniformity, good reproducibility, and long-term storage stability. The ultrahigh SERS activity of NiCo-LDH/Ag-NPs can be attributed to strong electromagnetic enhancement in the nanoscale gaps between Ag NPs, massive charge transfer through large-area NiCo-LDH/Ag-NPs interfaces, and the synergistic action of electromagnetic and charge transfer mechanisms. Besides, the unique morphology of NiCo-LDHs/Ag-NPs microcomposite provides a broad surface area for adsorption of TBZ molecules for further Raman signal enhancement. The practicability of the proposed SERS platform is confirmed by detecting TBZ in the real samples of apple juice and river water. The exceptional self-cleaning capability of the NiCo-LDHs/Ag-NPs microcomposite with an retention rate of 81.97 % even after the fifth degradation cycle underscores its impressive sustainable reusability and cost-effectiveness. The findings in this work lay the foundation for the development of high-performance SERS platforms to ensure food safety and environmental protection.

Highly sensitive determination of trace arsenic(III) onto carbon paste electrode modified with graphitic carbon nitride decorated Fe-MOF

An effective electrochemical sensor was developed to detect and determine of the As(III) by modifying the carbon paste electrode (CPE) with graphitic carbon nitride decorated with iron-based metal-organic frameworks (Fe-MOF/g-C3N5). The differential pulse anodic stripping voltammetry (DPASV) method was used to analyze As(III) ions in a phosphate buffer solution (0.10 M, pH = 5). Fe-MOF/g-C3N5/CPE showed high sensitivity (4.24 μA μg−1 L), satisfactory linear range (0.50 μg L−1–5.00 μg L−1 and 5.00 μg L−1–30.00 μg L−1), and low detection limit (LOD, 0.013 μg L−1). The prepared sensor was showed an excellent repeatability and selectivity, and successfully used for determination of the As(III) ion in ambient waters and apple juice samples.

Enrichment of apple juice with antioxidant-rich elderberry (Sambucus nigra L) pomace extract

AbstractElderberry pomace, a by-product generated by elderberry processing industries, may be a favourable resource for further utilisation due to its components of high nutritional quality. In our research, elderberry pomace extract (EP) was added to apple juice as natural food additive for controlling microbial spoilage and enriching antioxidant components.During the 8-week storage period of enriched apple juice (EPA) and control apple juice samples antioxidant properties were evaluated using the FRAP assay, Folin–Ciocalteu method, and pH differentiation method. The amount of polyphenols components was quantified using an RP-HPLC method. The microbiological status of samples was studied by determining the total viable and yeast/mould counts. The EPA is an important source of polyphenol components and other bioactive compounds, and the results suggest that extract of elderberry pomace could be a promising natural preservative to improve microbiological stability during refrigerated storage and increase the quality of apple juice.

A smartphone-based sensor for detection of iron and potassium in food and beverage samples

A novel approach for simultaneous detection of iron and potassium via a smartphone-based potentiometric method is proposed in this study. The screen printed electrodes were modified with carbon black nanomaterial and ion selective membrane including zinc (II) phtalocyanine as the ionophore. The developed Fe3+-selective electrode and K+-selective electrode exhibited detection limits of 1.0 × 10−6 M and 1.0 × 10−5 M for Fe3+ and K+ ions, respectively. The electrodes were used to simultaneously detect Fe3+ and K+ ions in apple juice, skim milk, soybean and coconut water samples with recovery values between 90%–100.5%, and validated against inductively coupled plasma-optical emission spectrometry. Due to the advantageous characteristics of the sensors and the portability of Near Field Communication potentiometer supported with a smartphone application, the proposed method offers sensitive and selective detection of iron and potassium ions in food and beverage samples at the point of need.

Synergistic Sb2S3-NiS2 heterostructure: A robust electrocatalyst for electrochemical sensing of Hg (II), As (III) ions and carbendazim fungicide

We developed a novel modified electrode based on Sb2S3-NiS2 heterostructure for the electrochemical detection of carbendazim, mercury (Hg2+), and arsenic (As3+). XRD, FESEM, HRTEM, and XPS characterization techniques were employed to confirm the formation of Sb2S3-NiS2 heterostructures. In comparison to other electrodes, the Sb2S3-NiS2 modified electrode has a strong electrocatalytic performance towards carbendazim, Hg2+, and As3+ detection. The Sb2S3-NiS2 nanocomposite's superior electrocatalytic activity is ascribed to its high conductivity, charge capacitance, synergistic effect, substantial number of active sites, and metal trap centres. Electrochemical studies such as cyclic voltammetry, LSV, and DPV depict excellent sensing capacity of Sb2S3-NiS2 for carbendazim, Hg2+, and As3+ with an ultralow detection limit calculated as 0.42 nM, 8.3 nM, and 92 nM, respectively. This is much below the upper limit established by the World Health Organization and the US Environmental Protection Agency. The chronoamperometry response and reusability up to weeks suggest excellent and superior stability. Furthermore, the modified electrode successfully detected carbendazim in real samples of apple and tomato juices and Hg2+ ions in the water of the Dal Lake. As far as we know, this is the first report on the Sb2S3-NiS2 heterostructure's electrocatalytic capability. Hopefully, this study will provide new insight into the future fabrication and development of novel electrocatalyst materials.

An Electrochemical Strategy for Detection of Trace‐Level Binapacryl Using Square‐Wave Cathodic Stripping Voltammetry

AbstractBinapacryl is a fungicide and miticide from the dinitrophenol group and is used to control fungi and mites in agricultural areas. Since even trace amounts of pesticides can be highly toxic to humans and the environment, accurate and sensitive analytical methods are needed for their determination. Therefore, the electrochemical behavior of binapacryl fungicide on the glassy carbon electrode (GCE) was investigated using square wave cathodic stripping voltammetry (SWCSV) and cyclic voltammetry (CV). Some parameters such as accumulation potential, accumulation time, pulse amplitude, frequency, and step potential were optimized on GCE. From the plotted calibration graph, the linear operating range was found to be 0.16–6.20 μM (0.06–2.0 mg/L), and accordingly the limit of detection (LOD) and limit of quantification (LOQ) for the first and second peak were 0.060 μM/0.201 μM and 0.0627 μM/0.209 μM, respectively. The proposed method was applied for spiked tap water, apple juice and grape juice samples. An electroreduction mechanism has also been proposed for binapacryl with the participation of 2e−/2H+ via the nitro group of the molecule. Also, the selectivity of the method was demonstrated by investigating the interference effects of some pesticides on the determination of binapacryl.

A Novel Molecularly Imprinted Quartz Crystal Microbalance Sensor Based on Erbium Molybdate Incorporating Sulfur-Doped Graphitic Carbon Nitride for Dimethoate Determination in Apple Juice Samples.

Dimethoate (DIM) as an organophosphorus pesticide is widely utilized especially in the cultivation of vegetables and fruits due to its killing effect on harmful insects. However, unconscious use of DIM in large amounts can also cause serious health problems. For these reasons, rapid and reliable detection of DIM from food samples is significant. In this study, a novel quartz crystal microbalance (QCM) sensor based on erbium molybdate incorporating sulfur-doped graphitic carbon nitride (EM/S-g-C3N4) and a molecularly imprinting polymer (MIP) was designed for DIM detection in apple juice samples. Firstly, an EM/S-g-C3N4 nanocomposite with high purity was prepared under hydrothermal conditions at high temperatures over a long period of time. After the modification of the EM/S-g-C3N4 nanocomposite on a QCM chip, the polymerization solution including N,N'-azobisisobutyronitrile (AIBN) as an initiator, ethylene glycol dimethacrylate (EGDMA) as a cross-linker, methacryloylamidoglutamic acid (MAGA) as a monomer, and DIM as an analyte was prepared. Then, the polymerization solution was dropped on an EM/S-g-C3N4 nanocomposite modified QCM chip and an ultraviolet polymerization process was applied for the formation of the DIM-imprinted polymers on the EM/S-g-C3N4 nanocomposite modified QCM chip. After the polymerization treatment, some characterization studies, including electrochemical, microscopic, and spectroscopic methods, were performed to illuminate the surface properties of the nanocomposite and the prepared QCM sensor. The values of the limit of quantification (LOQ) and the detection limit (LOD) of the prepared QCM sensor were as 1.0 × 10-9 M and 3.3 × 10-10 M, respectively. In addition, high selectivity, stability, reproducibility, and repeatability of the developed sensor was observed, providing highly reliable analysis results. Finally, thanks to the prepared sensor, it may be possible to detect pesticides from different food and environmental samples in the future.

Polycaprolactone/polyacrylic acid/graphene oxide composite nanofibers as a highly efficient sorbent to remove lead toxic metal from drinking water and apple juice

Due to the characteristics of electrospun nanofibers (NFs), they are considered a suitable substrate for the adsorption and removal of heavy metals. Electrospun nanofibers are prepared based on optimized polycaprolactone (PCL, 12 wt%) and polyacrylic acid (PAA, 1 wt%) polymers loaded with graphene oxide nanoparticles (GO NPs, 1 wt%). The morphological, molecular interactions, crystallinity, thermal, hydrophobicity, and biocompatibility properties of NFs are characterized by spectroscopy (scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis), contact angle, and MTT tests. Finally, the adsorption efficacy of NFs to remove lead (Pb2+) from water and apple juice samples was determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). The average diameter for PCL, PCL/PAA, and PCL/PAA/GO NFs was 137, 500, and 216 nm, respectively. Additionally, the contact angle for PCL, PCL/PAA, and PCL/PAA/GO NFs was obtained at 74.32º, 91.98º, and 94.59º, respectively. The cytotoxicity test has shown non-toxicity for fabricated NFs against the HUVEC endothelial cell line by more than 80% survival during 72 h. Under optimum conditions including pH (= 6), temperature (25 °C), Pb concentration (25 to 50 mg/L), and time (15 to 30 min), the adsorption efficiency was generally between 80 and 97%. The adsorption isotherm model of PCL/PAA/GO NFs in the adsorption of lead metal follows the Langmuir model, and the reaction kinetics follow the pseudo-second-order. PCL/PA/GO NFs have shown adsorption of over 80% in four consecutive cycles. The adsorption efficacy of NFs to remove Pb in apple juice has reached 76%. It is appropriate and useful to use these nanofibers as a high-efficiency adsorbent in water and food systems based on an analysis of their adsorption properties and how well they work.

Levan modified patulin specific impedimetric aptasensor with its application in food and biological fluids

In this study, a label-free impedimetric aptasensor was developed for the determination of patulin (PAT) mycotoxin. The pencil graphite electrode (PGE) surface was modified with the levan and then PAT-specific aptamer was immobilized onto the PGE surface. After the interaction of PAT with aptamer EIS measurements were performed. Under optimum conditions, the limit of detection (LOD) in buffer medium was calculated as 0.095 pg/mL in the concentration range of 10−1–105 pg/mL. The selectivity of the developed label-free impedimetric aptasensor was investigated against fumonisin B1 (FB1), ochratoxin A (OTA), and deoxynivalenol (DON) in buffer medium. The implementation of label-free impedimetric aptasensor to patulin determination was performed in apple juice samples as well as in fetal bovine serum (FBS) medium. Accordingly, the LOD of PAT was estimated as 3.27 pg/mL in apple juice and 0.41 pg/mL in the FBS medium. The selectivity of the aptasensor was also investigated in both mediums. It is predicted that the developed aptasensor will have an important place in the fields of food safety and health monitoring in the literature. Also, it is anticipated that the electrochemical determination of mycotoxins, especially in biological fluids, will be a role model for future studies.

Core-satellite nanoassembly system with aptamer-conjugated Au@Ag nanoparticles for SERS detection of patulin in apples

Patulin (PAT), a major contaminant in apples, poses a huge threat to human health as well as the economic sector. There is an urgent need to develop a sensitive, selective, and fast-responsive method to detect PAT in apples. However, one of the main challenges is overcoming the interferences of complex food matrices. In this study, we developed a highly sensitive competitive SERS sensor based on plasmonic nanoparticles modified by aptamers. The study utilized the formation of nanocomposites through aptamer-modified Au@Ag nanoparticles (NPs) and gold nano-stars (AuNSs) to induce high-intensity Raman signals from the SERS tag. Subsequently, in the presence of PAT, the nanocomposites underwent decomposition, evident through the significant decrease in SERS intensity. According to the standard curve established in this study, the detection limit was 0.0281 ng/mL. The competitive sensor was applied to spiked apple fruit and juice samples, indicating a recovery rate ranging from 91.98% to 102.94%. The excellent analytical performances and high sensitivity observed suggest the potential of the plasmonic nanocomposite sensing strategy in detecting PAT in real matrices.

Ternary solvent based homogeneous liquid-liquid microextraction for the preconcentration of organochlorine pesticides from water and apple juice samples.

In the present study, the optimal experimental conditions were determined by optimizing the effect of extraction solvent types and volume, salt types and concentration, centrifugation speed and time using one variable at a time. Under optimal experimental conditions, calibration curves were constructed separately using water and apple juice samples as representative matrices, and good linearities were achieved over a wide concentration range of 0.2-1600 ng L-1 with a coefficient of determination (r2) ≥ 0.998. The limits of detection (LOD) and limits of quantification (LOQ), determined to be 3 and 10 times the signal-to-noise ratios (S/N), were between 0.07-3.9 and 0.2-12.0 ng L-1 for water samples and 2.6-10.0 and 8.0-30.0 ng L-1 for the apple juice sample respectively. The precisions study showed %RSD values of ≤6% for both matrices, indicating satisfactory precisions. The enrichment factors and recoveries of the proposed method ranged from 41.4-74.5 and 86-109% respectively. The proposed method could be used as a simple and environmentally friendly alternative for the analysis of OCPs from environmental and food matrices. This method potentially offers a more sustainable and effective approach to monitoring OCPs in environmental and food products. Its use in the analysis of apple juice samples is particularly novel and can provide valuable insights into pesticide contamination in fruit juices.

Etched stainless steel wire modified with conjugated microporous polymers-F6 for jacket-free stir bar sorptive extraction of benzoylureas in juice sample.

Benzoylurea (BU) insecticides have been widely used for pest control as third-generation insecticides. Considering that their residues in food may cause adverse effects on human health, the upper limits of BUs remaining in food have been set by the administration. Therefore, it is essential to develop a sensitive and efficient analytical method to determine the residues of BUs in food. Stir bar sorptive extraction (SBSE) is a novel sample preparation technique, and stainless steel wire (SSW) is an ideal substrate for an SBSE device. In this work, a novel SBSE device of SSW jacket-free stir bar with a dumbbell shape was designed and prepared. The conjugated microporous polymer CMP-F6, which possesses a porous structure, high hydrophobicity and rich fluorine-containing functional groups, was immobilized on the surface of SSW by the method of polyacrylonitrile glue adhesion. Compared with previous studies, which used SSW as a substrate, the method of etching partial SSW with hydrochloric acid, on the one hand, made the surface of SSW rough and easy to modify the extraction coating, and on the other hand, converted itself into a dumbbell-shaped structure, which is conducive to improving the extraction efficiency and stability of the SBSE device. The method of SBSE-HPLC-UV was established for determining five BUs. Owing to the hydrophobic interaction and F-F interaction between CMP-F6 and analytes, this method showed good extraction efficiency and had good linearity (R2 ≥ 0.9945) and high sensitivity (LODs in the range of 0.1-0.2 ng mL-1). It was used for the analysis of benzoylurea in an apple juice sample, and the recoveries were 74.3-117.9%.

Antibacterial activity of Ricinus communis plant extract against antibiotic resistant Helicobacter pylori and Gluconobacter oxydans isolated from fresh apple juices samples.

Bacteria were isolated from samples of Fresh Apple juices from shops of three different localities of Lahore. Analysis of samples from Liberty, Anarkali and Yateem khana Markets show different levels of contamination. There were pathogenic and non-pathogenic bacteria in all samples and were identified by the morphological and biochemical tests. Most of the plasmids of pathogenic bacteria were 4kb in their molecular size. Ribotyping of 16S ribosomal RNA gene sequencing was done to confirm Helicobacter pylori strain and Gluconobacter oxydans. The highest sensitivity of 210mm was shown by Enterobacter sp. against Aztheromysine disk (15µg) while Micrococcus sp. was highly resistant against all of the Antibiotics applied. The antibiotic resistance of pathogenic bacteria was also checked against Ricinus communis plant's extracts, all isolated bacterial pathogens were resistant but only, E.coli was inhibited at 300µl of the extracts. Presence of pathogenic bacteria in Apple juice samples was due to contamination of sewage water in drinking water while some of these pathogenic bacteria came from Apple's tree and other from store houses of fruits.

Application of gas chromatography-stable isotope mass spectrometry to determine the oxygen isotope ratio of water in concentrated fruit juice

In this study, we developed a method to determine the authenticity of concentrated fruit juice using the δ18O ratio of water. We utilized the gas chromatography-isotope ratio mass spectrometry (GC-IRMS) technique along with the offline isotope exchange equilibrium method to pretreat and measure the oxygen isotopes in water in concentrated apple juice. This innovative approach uses anhydrous ethanol as a solvent to dissolve concentrated juices, thereby facilitating a more comprehensive reaction between the water in the sample and the CO2 standard gas. Additionally, the reaction vessel exhibits excellent air tightness, ensuring rapid equilibrium time and enabling accurate determination of δ18O in the water content of concentrated juice. The reaction vessel had excellent air tightness and rapid equilibration time, enabling accurate measurement of δ18O of water in concentrated fruit juice. The reaction vessel used had excellent air tightness and rapid equilibration time, ensuring accurate measurement of the δ18O of water in concentrated fruit juice. We analyzed 40 samples of concentrated apple juice and found that the range of δ18O values in the water of concentrated apple juice was between 1.29 ‰ and 7.59 ‰. Additionally, we used prepared sucrose syrup as a simulated sample and found that the δ18O distribution range was between −10.43 ‰ and −10.53 ‰. Furthermore, we conducted adulteration simulation experiments on randomly selected real samples and discovered a linear negative correlation between the adulteration ratio and the δ18O value of water in the samples.

An Aptamer-Based Lateral Flow Biosensor for Low-Cost, Rapid and Instrument-Free Detection of Ochratoxin A in Food Samples.

In this work, a simple and cost-efficient aptasensor strip is developed for the rapid detection of OTA in food samples. The biosensor is based on the lateral flow assay concept using an OTA-specific aptamer for biorecognition of the target analyte. The strip consists of a sample pad, a conjugate pad, a nitrocellulose membrane (NC) and an absorbent pad. The conjugate pad is loaded with the OTA-specific aptamer conjugated with gold nanoparticles (AuNPs). The test line of the NC membrane is loaded with a specific OTA-aptamer probe and the control line is loaded with a control probe. The assay is based on a competitive format, where the OTA present in the sample combines with the OTA aptamer-AuNP conjugate and prevents the interaction between the specific probe immobilized on the test line and the OTA aptamer-AuNP conjugates; therefore, the color intensity of the test line decreases as the concentration of OTA in the sample increases. Qualitative detection of OTA is performed visually, while quantification is performed by reflectance colorimetry using a commercial scanner and image analysis. All the parameters of the assay are investigated in detail and the analytical features are established. The visual limit of detection (LOD) of the strip is 0.05 ng mL-1, while the LOD for semi-quantitative detection using reflectance colorimetry is 0.02 ng mL-1. The lateral flow strip aptasensor is applied to the detection of OTA in wine, beer, apple juice and milk samples with recoveries in the range from 91 to 114%. The assay exhibits a satisfactory selectivity for OTA with respect to other mycotoxins and lasts 20 min. Therefore, the lateral flow strip aptasensor could be useful for the rapid, low-cost and fit-for-purpose on-site detection of OTA in food samples.

Dispersive solid phase extraction using a hydrophilic molecularly imprinted polymer for the selective extraction of patulin in apple juice samples

A molecularly imprinted polymer with a specific selectivity for patulin was successfully synthesized. The molecularly imprinted material was prepared using the two functional monomers dopamine and melamine and formaldehyde as the cross-linker. The resulting material possessed a large number of hydrophilic groups, such as hydroxyls, imino groups, and ether linkages. For the first time, uric acid was used as a dummy template for its structural similarity to patulin. Comprehensive characterization and detailed studies of the adsorption process were carried out via adsorption isotherms, while the rate-limiting steps were investigated using adsorption kinetics. Separation, determination, and quantification of patulin were achieved by ultra-high performance liquid chromatography coupled with both photodiode array detection and tandem mass spectrometry. The latter was applied to patulin confirmation in the analysis of real samples. The methodology was validated in 20 apple juice samples. The results showed that the developed hydrophilic molecularly imprinted polymer had high selectivity and specific adsorption towards patulin, with mean recoveries ranging between 85 and 90% and a relative standard deviation lower than 15%. The developed molecularly imprinted polymer exhibited good linearity in the range 1–100 ng mL−1 with coefficient of determination (R2) > 0.99. The limit of detection was 0.5 ng mL−1, and the limit of quantification was 1 ng g−1. The developed method showed a good purification capacity for apple juices due to its hydrophilic nature and the polar interactions established with the target analyte.Graphical abstract

Disposable Voltammetric Determination of Celestine Blue at a Pencil Graphite Electrode

The proposed study describes a novel and disposable voltammetric sensor that designed for the sensitive determination of celestine blue (CelsB) using a pencil graphite electrode (PGE). The electrochemical characterization study of the designed sensor was performed by recording the cyclic voltammograms (CVs) and electrochemical impedance (EI) curves in 5.0 mM of Fe(CN)63-/4- including 0.10 M of KCl, and compared with the other carbon-based electrodes such as carbon paste (CPE) and glassy carbon (GCE) electrodes. The electrochemical behaviour of CelsB was examined at different carbon-based electrodes including PGE, CPE, and GCE by the cyclic voltammetric (CV) method. The recorded CVs showed that the remarkable response obtained at PGE toward oxidation of CelsB. Moreover, the PGE shows a wide linear range (4.0 − 150 μM) and detects the CelsB with a notable limit of detection (1.21 μM). In addition, the results from the interference studies proved that the PGE enables selective voltammetric determination of CelsB in presence of various species. A feasibility study for CelsB sensor was also tested on tap water and cherry apple juice samples and the recovery values obtained between 96.2 − 103 % with high precision and accuracy indicated that the PGE shows an acceptable and good applicability to real samples.

3D/1D heterostructure of p-BiOBr nanoflowers modified n-TiO2 nanorod arrays for highly sensitive photoelectrochemical determination of hydrogen peroxide

Hydrogen peroxide (H2O2) is a major transmitter of redox signals during chemical processes. Cost-effective and easy-to-operate sensors for H2O2 are in high demand in a variety of fields. A novel photoelectrochemical (PEC) sensor for H2O2 detection was investigated, using BiOBr/TiO2NAs/FTO (BiOBr/TNAs) as a PEC electrode which is obtained by successive ionic layer adsorption and reaction (SILAR) method. This non-enzymatic PEC BiOBr/TNAs electrode shows excellent selectivity, stability, and reproducibility for H2O2 detection in optimizing modes. The linear relationship is in a broad range from 4 to 1800 μM (R2 = 0.994) and a detection limit of 0.65 μM (S/N = 3). In the detection of H2O2 in apple juice and milk real samples, the BiOBr/TNAs show outstanding recovery ranging from 98.0 % to 102.0 %, indicating great potential in practical applications. Meanwhile, the p-n heterojunction formed between BiOBr and TiO2 improves the utilization of visible light and effectively promotes the separation of photogenerated electrons and holes. This work provides a new strategy for the non-enzymatic detection of hydrogen peroxide in PEC mode.

A dual action electrochemical molecularly imprinted aptasensor for ultra-trace detection of carbendazim

Carbendazim is often used in agriculture to prevent crop diseases, even though it has been associated with health concerns. To ensure the safety of food products and comply with environmental regulations, an ultrasensitive method for carbendazim determination must be developed. In this study, a new electrochemical molecularly imprinted polymer-aptasensor based on hemin-Al-metal organic framework@gold nanoparticles (H-Al-MOF@AuNPs) was developed for sensitive and selective carbendazim detection. Hemin linked to the surface of the Al-metal organic framework also possesses outstanding peroxidase-like qualities that can electrocatalyse the reduction of H2O2. Thus, H-Al-MOF functions as an in-situ probe. Additionally, AuNPs offer many binding sites to load carbendazim aptamers and create an imprinted polymer-aptasensing interface. Dopamine is the chemical functional monomer in the electropolymerised film, while carbendazim is the template molecule. Thus, compared to the molecularly imprinted polymer or aptasensor alone, the molecularly imprinted polymer-aptasensor showed greater selectivity due to the synergistic action of the polymer and carbendazim aptamer towards carbendazim. A decrease in peak current was observed by differential pulse voltammetry (DPV) and chronoamperometry (CA) as the concentration of carbendazim increased. This possibly resulted from carbendazim connecting to the carbendazim aptamer and simultaneously blocking the imprinted polymer cavities on the surface of the modified electrode, which reduced the transfer of electrons. Signals were observed for hemin DPV and H2O2 catalytic reduction CA. DPV and CA showed that the linear ranges for carbendazim were 0.3 fmol L-1-10 pmol L-1 and 0.7 fmol L-1-10 pmol L-1, respectively, with limits of detection of 80 and 300 amol L-1. Satisfactory recoveries were obtained with tap water, apple juice, and tomato juice samples, demonstrating that the proposed sensor has potential for food and environmental analysis.

Design and development of second-generation fabric phase sorptive extraction membranes: Proof-of-concept for the extraction of organophosphorus pesticides from apple juice prior to GC-MS analysis.

In this work, different sol-gel sorbent-coated second-generation fabric phase sorptive extraction (FPSE) membranes were synthesized using titania-based sol-gel precursors. The proposed membranes were tested for their efficiency to extract eleven selected organophosphorus pesticides (OPPs) from apple juice samples. Among the examined materials, sol-gel C18 coated titania-based FPSE membranes showed the highest extraction efficiency. These membranes were used for the optimization and validation of an FPSE method prior to analysis by gas chromatography-mass spectrometry. The detection limits for OPPs ranged between 0.03 and 0.08ngmL-1. Moreover, the relative standard deviation was<8.2% and 8.4% for intra-day and inter-day studies, respectively. The relative recoveries were 91-110% (intra-day study) and 90-106% (inter-day study) for all the target analytes, demonstrating good overall method accuracy. Moreover, the novel membranes were reusable at least 5 times. The titania-based membranes were compared to the conventional silica-based membranes and their utilization resulted in higher extraction recoveries.